Field of Science

The Coutoubeines

Members of the family Gentianaceae, the gentians, are for the greater part associated with cooler climes. Residents of areas subject to heavy snowfalls have often commented on the appearance of their showy flowers with warming weather in the spring. But not all subgroups of the gentians are so temperate: some, such as the Coutoubeinae, are inhabitants of the tropics.

Schultesia guianensis, copyright João de Deus Medeiros.


The Coutoubeinae are a group of about thirty known species divided between five genera found in Central and South America (Struwe et al. 2002). A single species, Schultesia stenophylla, is found in western Africa but, as it is also found in Brazil alongside related species, it can be reasonably presumed to be a recent immigrant to that region. Like most other members of the Gentianaceae, species of the Coutoubeinae are low herbs, often found growing in open habitats. With the exception of the genus Deianira, most lack a basal rosette of leaves. Flowers are usually white or pink, and are quadrimerous (with four corolla lobes) in the majority of species (one species, Schultesia pachyphylla, has blue pentamerous flowers; Guimarães et al. 2013). Perhaps the most characteristic feature of the group is that pollen is released in tetrads (clumps of four). I haven't come across any specific comments on the functional significance (if any) of this feature in coutoubeines but it has been suggested that pollen clumping in plants may correlate with visits from pollinators being relatively uncommon (and getting a decent amount of pollen transported at a time becomes more important than increasing the chance of pollen being transported to multiple targets).

Coutoubea spicata, copyright Alex Popovkin.


T The largest genus of coutoubeines is Schultesia, including about twenty species. Schultesia species are annual herbs with long-lanceolate leaves and tube-shaped, usually pink (occasionally yellow or blue) flowers with the calyx tube at least as long as the lanceolate corolla lobes. The species Xestaea lisianthoides, sometimes included in Schultesia, differs from Schultesia in the arrangement of stamens (inserted unevenly in the corolla rather than in the upper part of the tube) and the shape of the stigmatic lobes (oblong rather than rounded). Coutoubea species have white, salver-shaped flowers with triangular corolla lobes. Symphyllophyton caprifolium, a rare species restricted to southern Brazil, is a short-lived perennial with perfoliate leaves and yellow to cream salver-shaped flowers with the calyx tube shorter than the corolla lobes. Finally, Deianira includes suffrutescent herbs with a basal rosette of leaves and salver-shaped flowers with a short calyx tube.

REFERENCES

Guimarães, E. F., V. C. Dalvi & A. A. Azevedo. 2013. Morphoanatomy of Schultesia pachyphylla (Gentianaceae): a discordant pattern in the genus. Botany 91: 830–839.

Struwe, L., J. W. Kadereit, J. Klackenberg, S. Nilsson, M. Thiv, K. B. von Hagen & V. A. Albert. 2002. Systematics, character evolution, and biogeography of Gentianaceae, including a new tribal and subtribal classification. In: Struwe, L., & V. A. Albert (eds) Gentianaceae: Systematics and Natural History pp. 21–309. Cambridge University Press: Cambridge.

The Model Tetrahymenidans

Ciliates have long been one of the most (if not the most) confidently recognised groups of unicellular eukaryotes owing to their distinctive array of features, in particular locomotion by means of more or less dense tracts of small cilia that often run the length of the organism. And of all ciliates, perhaps none have been more extensively studied than species of the genus Tetrahymena such as T. thermophila. Being easily cultured in the laboratory, Tetrahymena species have become model organisms for the study of a great many genetic and cellular systems such as cell division and gene function. At least two Nobel prizes have been awarded for work based on Tetrahymena that established the functions of telomeres and ribozymes. But Tetrahymena is just one genus of larger group of ciliates, the Tetrahymenida.

Tetrahymena thermophila, from Robinson 2006.


In general, tetrahymenidans are more or less 'typical'-looking ciliates with an ovoid body form and a well-developed 'mouth' at one end. The name Tetrahymena, meaning 'four membranes', refers to the presence of four membrane-like structures inside the oral cavity, a larger, ciliated undulating membrane on the left and three membranelles (formed from polykinetids, complex arrays of cilia and associated basal bodies and fibrils). Most tetrahymenidans possess some variation of this arrangement with the exception of Curimostoma, a genus of parasites of freshwater flatworms and molluscs that lack oral structures (Lynn & Small 2002). Life cycles may contain a number of morphologically differentiated stages. A more mobile theront stage will seek out food sources then transform into a feeding trophont. Mature trophonts may divide asexually or reproduce through conjugation. Cellular multiplication often involves successive divisions so a single parent cell may give rise to four daughter cells. In a number of species, resistant resting cysts may form under adverse conditions.

Glaucoma scintillans, another well-studied tetrahymenidan, copyright Proyecto Agua.


Tetrahymenidans are also ecologically diverse, occupying a range of freshwater habitats. They may be free-living, feeding on bacteria, or they may be parasitic or histophagous, feeding on the tissues of invertebrates. Some species may switch between one or the other depending on circumstances. A few Tetrahymena species have even been cultured in the laboratory axenically: that is, absorbing nutrients directly from a culture broth without requiring a bacterial food supply. Recently, the first confirmed case of a tetrahymenidan containing endosymbiotic algae was described by Pitsch et al. (2016). The species Tetrahymena utriculariae inhabits the bladders of the carnivorous bladderwort Utricularia reflexa. Endosymbiotic green algae provide it with oxygen, allowing the ciliate to survive within the anoxic environment of the bladders.

REFERENCES

Lynn, D. H., & E. B. Small. 2002. Phylum Ciliophora Doflein, 1901. In: Lee, J. J., G. F. Leedale & P. Bradbury (eds) An Illustrated Guide to the Protozoa: Organisms traditionally referred to as Protozoa, or newly discovered groups 2nd ed. vol. 1 pp. 371–656. Society of Protozoologists: Lawrence (Kansas).

Pitsch, G., L. Adamec, S. Dirren, F. Nitsche, K. Šimek, D. Sirová & T. Posch. 2016. The green Tetrahymena utriculariae n. sp. (Ciliophora, Oligohymenophorea) with its endosymbiotic algae (Micractinium sp.), living in traps of a carnivorous aquatic plant. Journal of Eukaryotic Microbiology 64: 322–335.

The Age of the Ceratites

The ammonites are unquestionably one of the most famous groups of fossil mollusks, indeed of fossil invertebrates in general. Even those who have little consciousness of the fossil world might be expected to have a vague mental picture of a coiled shell housing a squid-like beast. But ammonites are far from being the only group of shelled cephalopod known from the fossil record. And though ammonites may have dominated the marine environment during the Jurassic and Cretaceous periods, during the preceding Triassic period they were overshadowed by another such group, the ceratites.

Reconstruction of Ceratites spinosus, from Klug et al. (2007).


The ceratites of the order Ceratitida (or suborder Ceratitina, depending on how you've tuned your rank-o-meter today) were close relatives of the ammonites, each deriving separately from an earlier cephalopod group known as the prolecanitids. The earliest forms regarded as ceratites appeared during the mid-Permian, though the exact dividing line between prolecanitid and ceratite seems to be somewhat arbitrary (as, indeed, is only to be expected with a well-known historical lineage). During the remainder of the Permian their diversity remained fairly subdued. When marine life was hit with the cataclysmic upheaval that was the end-Permian extinction, two lineages of ceratites managed to squeak through, together with a single other prolecanitid lineage that would give rise to the ammonites during the ensuing Triassic. With most of their competitors thus eliminated, ceratite diversity expanded rapidly.

Externally, the shells of ceratites and ammonites were very similar, and without knowing their evolutionary context one would be hard-pressed to tell one from the other. Most ceratite shells formed the typical flat spiral one associates with ammonoids, with different species being variously evolute (with successive coils lying alongside the previous one) to involute (outer coils overlapping and concealing the inner ones), and cross-sections varying from narrow and lenticular to broad and low (Arkell et al. 1957). One later Triassic family, the Choristoceratidae, had shells that began as an evolute coil but became uncoiled or straightened in later stages. Another Upper Triassic group, the Cochloceratidae, had turreted shells that might externally be mistaken for those of a gastropod.

Ceratites dorsoplanus, showing ceratitic sutures, copyright Hectonichus.


Internally, ceratites and ammonites often differed in the structure sutures, the lines formed by the join between the outer shell and the septa dividing the internal chambers. In ammonoids as a whole, the sutures are variously curved back and forth on the inside of the shell, with those parts of the suture going forwards (towards the shell opening) forming what are called saddles and those going backwards (away from the opening) forming lobes. In most ceratites, the sutures more or less form a pattern that is known (appropriately enough) as ceratitic: the saddles are simple and not future divided, but the lobes have multiple smaller digitations. In some later taxa, the sutures became goniatitic (with both saddles and lobes simple, secondarily similar to those found in earlier ammonoids) or ammonitic (with both saddles and lobes subdivided, the pattern more commonly associated with ammonites).

Our knowledge of the soft anatomy of ceratites remains limited. We know that they possessed an anaptychus (a leathery plate at the front of the body that may have functioned as an operculum, as I described in an earlier post). Known radulae have fairly simple, slender, undifferentiated teeth (Kruta et al. 2015) so they were probably micro-predators or planktivores in the manner of most ammonites. A black, bituminous layer sometimes preserved against the inside of the shell in the body cavity may represent the remains of the dorsal mantle. Similarity between this layer and the dorsal mantle of nautilids lead Klug et al. (2007) to infer the presence of a non-mineralised hood in ceratites, though I wonder how the presence of a hood would relate to an anaptychus. Conversely, Doguzhaeva et al. (2007) interpreted the black layer as the remains of ink from a ruptured ink sac.

Assemblage of Arcestes leiostracus, copyright Lubomír Klátil.


Ceratites were to remain the ecological upper hand throughout the course of the Triassic. Though ammonites (represented by the phylloceratidans) were not uncommon during this period, their diversity remained consistently lower. However, the end of the Triassic was marked by a spike in global temperatures and ocean acidification, generally regarded as connected to the volcanic rifting activity that marked the beginning of formation of the Atlantic Ocean (Arkhipkin & Laptikhovsky 2012). Of the two ammonoid lineages, only the ammonites survived into the Jurassic; the ceratites were wiped out. Whether some aspect of ammonite biology made them better suited to survive the stresses of global climate change, or whether their survival was a question of simple dumb luck, seems to be an open question. Nevertheless, with the ceratites out of the picture, the way was open for the ammonites to become the lords of the Mesozoic ocean.

REFERENCES

Arkell, W. J., B. Kummel & C. W. Wright. 1957. Mesozoic Ammonoidea. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt L. Mollusca 4. Cephalopoda: Ammonoidea pp. L80–L465. Geological Society of America, and University of Kansas Press.

Arkhipkin, A. I., & V. V. Laptikhovsky. 2012. Impact of ocean acidification on plankton larvae as a cause of mass extinctions in ammonites and belemnites. Neues Jahrbuch für Geologie und Paläontologie—Abhandlungen 266 (1): 39–50.

Doguzhaeva, L. A., R. H. Mapes, H. Summesberger & H. Mutvei. 2007. The preservation of body tissues, shell, and mandibles in the ceratitid ammonoid Austrotrachyceras (Late Triassic), Austria. In: Landman, N. H., R. A. Davis & R. H. Mapes (eds) Cephalopods Past and Present: New Insights and Fresh Perspectives pp. 221–238. Springer.

Klug, C., M. Montenari, H. Schulz & M. Urlichs. 2007. Soft-tissue attachment of Middle Triassic Ceratitida from Germany. In: Landman, N. H., R. A. Davis & R. H. Mapes (eds) Cephalopods Past and Present: New Insights and Fresh Perspectives pp. 205–220. Springer.

Kruta, I., N. H. Landman & K. Tanabe. 2015. Ammonoid radula. In: Klug, C., et al. (eds) Ammonoid Paleobiology: From Anatomy to Ecology pp. 485–505. Springer: Dordrecht.

The Life and Times of Diaulomorpha

Diaulomorpha is a fairly typical genus of the diverse micro-wasp family Eulophidae. Like most other eulophids, members of this genus are slender with a relatively soft metasoma. The mesosoma, on the other hand, is tougher, weakly vaulted, and conspicuously reticulate dorsally. Members of the genus are known from Australasia and South America (Bouček 1988).

Body of female Diaulomorpha itea, from Bouček (1988).


Diaulomorpha species are parasitoids of insect larvae that live as miners in leaves. They are known to feed on both Lepidoptera and Hymenoptera larvae; it seems that it is not the identity of the host that attracts them but the lifestyle. They are multivoltine, that is they can go through multiple generations in the course of a year. The breeding cycle and behaviour of a Diaulomorpha species was described by Mazanec (1990) as a parasitoid of the jarrah leafminer Perthida glyphopa, a moth whose larvae attack the leaves of jarrah Eucalyptus marginata.

Mating between males and females occured after a brief courtship ritual in which the pair each extended their wings upwards and beat them up and down. Females located host larvae by running across the leaf surface and drumming the outside of prospective mines with their abdomen. They would then drill into the mine with their ovipositor, though of course the host larva would generally be trying to escape the wasp's attentions; a female might have to drill several holes before successfully piercing the caterpillar. The ovipositor would then be 'stirred' into the host to cause haemolymph and other fluids to leak out of its skin, and the wasp would feed on this fluid through the hole formed by the ovipositor. Egg laying would begin shortly after the wasp had finished feeding. Egg production was relatively slow, with only five or six eggs able to develop within the mother at a time, and the female wasp would lay through a newly created hole into the mine near the selected host. Usually only one egg would be laid in a mine but sometimes multiple eggs would be laid and the emerging larvae would share the host individual. After laying an egg, the female would tap around the laying hole with the tip of her metasoma, presumably depositing some chemical that would signal to other Diaulomorpha females that the mine had already been attacked. The host, meanwhile, would stop feeding after being stabbed with the female's ovipositor and would finally die after about a day and a half. It was around this time that the larva(e) would hatch and commence feeding on its remains.

Though healthy hosts would obviously be preferable, female Diaulomorpha were not above attacking hosts that had already died or had already been parasitised by other wasps. Such hosts were particularly likely to be attacked by young females that had not yet learnt to deal with the defensive actions of a healthy host. Deceased hosts could present a problem in that their bodily fluid pressure had been lost, and the female might have to stab them with her ovipositor several times before she had ingested enough fluid to begin laying. Pre-parasitised hosts were less of a problem as endoparasitic wasp larvae within the host would die after the Diaulomorpha's stab along with the host.

Mazarec (1990) found parasitism levels by Diaulomorpha within the host population to be low. What is more, as host populations increased the level of parasitism would plateau, so the proportion of parasitised hosts was far lower in dense host populations. This presumably resulted from the wasp's low rate of egg production: as host populations increased, the population of wasps did not keep up with it. As such, the role of Diaulomorpha in pest control is probably limited.

REFERENCES

Bouček, Z. 1988. Australasian Chalcidoidea (Hymenoptera): A biosystematic revision of genera of fourteen families, with a reclassification of species. CAB International: Wallingford (UK).

Mazanec, Z. 1990. The immature stages and life history of Diaulomorpha sp. (Hymenoptera: Eulophidae), a parasitoid of Perthida glyphopa Common (Lepidoptera: Incurvariidae). Journal of the Australian Entomological Society 29: 147–159.

The Mirines

Every profession has its quirks, tricks of the trade that are difficult to learn and appreciate except through direct experience. One quirk of entomology is that specimens of each distinct type of insect will have their own nuances for the best method to preserve and present them. And there are some particular types of insect that can be particularly challenging in that regard. Which is a roundabout way of saying: I am not a great fan of mirids.

Green mirid Creontiades dilutus, copyright CSIRO.


Mirids are the largest recognised family of the true bugs in the Heteroptera, with over 11,000 species known worldwide and presumably many more remaining undescribed. They can be distinguished from most (though not, it should be stressed, all) other bug families by the presence of the cuneus, a distinct cross-fold near the outer tip of the hemelytron (the toughened basal part of the fore wing). Most mirids can be further recognised by the absence of ocelli. They are mostly smaller bugs, generally somewhat soft-bodied, and mostly plant feeders though there are some notable exceptions. They also (and this is the reason why they have sometimes been the object of my animus in the past) have a tendency to be what I can only describe as weirdly flimsy. Most insect specimens, at least while stil fresh and relaxed, hold together reasonably well when subject to basic handling. Mirids, on the other hand, will throw off legs if you so much as look at them too hard.

An ant-mimicking mirid, Dacerla inflata, copyright Judy Gallagher.


Mirids are divided between several subfamilies, with the type subfamily Mirinae including well over 4000 species (Kim & Jung 2019). Mirines tend to be relatively large compared to other mirids (up to a bit over half a centimetre in length) and are characterised by features of the genitalia, together with a pair of lamellate, divergent parempodia (fleshy structures that may help in gripping onto things) at the end of the legs between the claws. Other notable features (shared with the closely related Deraeocorinae) include a deeply punctate pronotum, and a relatively long beak that extends beyond the mid coxae at rest. Several species of Mirinae are notable pests. The green mirid Creontiades dilutus is one of the more significant bug pests of crops in Australia, attacking a wide range of hosts including cotton, stone fruit, potatoes, legumes and many more (Malipatil & Cassis 1997). It generally feeds from growing points, killing new buds and inhibiting the production of flowers and new growth. Other polyphagous pests causing similar damage include the tarnished plant bugs of the genus Lygus, whose vernacular name is somewhat self-explanatory, and the alfalfa bug Adelphocoris lineolatus.

Tarnished plant bug Lygus pratensis, copyright Hectonichus.


Six tribes have been recognised within the Mirinae, distinguished by their overall habitus. The Mirini, the largest tribe, have a more or less ovoid body shape with a distinct, raised pronotal collar and opaque hemelytra. The Hyalopeplini have a similar body shape to Mirini but transparent hemelytra. The Restheniini have a reduced evaporative area on the abdomen. The Stenodemini and Mecistoscelini are long and slender with long appendages, with the head directed forward in the Stenodemini. The Herdoniini are ant mimics, presumably for defence from predators. The appearance of an ant waist is achieved by a narrowing of the mirid's own body and wings, and/or an appropriately placed white triangular marking across the hemelytron. Despite the superficial distinctiveness of the tribes, however, a phylogenetic study of the Mirinae by Kim & Jung (2019) found at least two of them to be paraphyletic, with Mecistoscelini being nested within Stenodemini, and Hyalopeplini and Restheniini within Mirini. The affinities of the Herdoniini, unsampled by Kim & Jung, remain to be established.

REFERENCES

Kim, J., & S. Jung. 2019. Phylogeny of the plant bug subfamily Mirinae (Hemiptera: Heteroptera: Cimicomorpha: Miridae) based on total evidence analysis. Systematic Entomology 44: 686–698.

Malipatil, M. B., & G. Cassis. 1997. Taxonomic review of Creontiades Distant in Australia (Hemiptera: Miridae: Mirinae). Australian Journal of Entomology 36: 1–13.

The Concilitergans: Sitting Next to Trilobites

The last few decades have seen a vast increase in our understanding of life during the early Cambrian. Long one of the most famous groups of invertebrates of the Palaeozoic, the trilobites are now known to have shared their early environment with a number of related lineages that bore some resemblance in overall appearance but lacked their mineralisation of the exoskeleton. One such group was labelled by Hou & Bergström (1997) as the Conciliterga.

Reconstruction of the concilitergan Kuamaia lata from Hou & Bergström (1997). Note that the reconstructed appearance of the eyes is probably erroneous, as explained below.


Concilitergans are a group of flattened marine arthropods known from the early and middle Cambrian of a number of parts of the world, including North America, China and Australia. Most species were ovoid in shape (like a typical trilobite), tapering somewhat towards the rear and often ending in a point. An Australian species, Australimicola spriggi, was more elongate in form and ended in a pair of terminal spines. Some were quite sizable; one species, Tegopelte gigas, reached nearly a foot in length and was one of the largest known animals of its time. Concilitergans also resembled trilobites in possessing a more or less semi-circular head shield followed by a series of regular segments and often a final larger pygidial segment. Towards the front of the body, the segment boundaries were anteriorly reflexed (Paterson et al. 2012). In a number of species, the body segmentation was more prominent medially than laterally with the tergites overlapping slightly down the mid-line but not along the edges. A pair of antennae arose from the underside of the head near the front. In most species, with the exception of Australimicola, a pair of prominent teardrop-shaped bulges was also present dorsally near the front of the head. These bulges were interpreted as a pair of dorsal eyes by Hou & Bergström (1997) but re-interpreted by Edgecombe & Ramsköld (1999) as raised areas of the exoskeleton that provided accomodation for the actual eyes located on the underside of the head.

Reconstruction of Tegopelte gigas, copyright Marianne Collins.


Phylogenetic analyses have confirmed a close relationship between concilitergans and trilobites (Edgecombe & Ramsköld 1999) and the two groups probably resembled each other in life-style. With their ovoid shape, flattened body and down-cast eyes, concilitergans were also not dissimilar in overall conformation to modern cockroaches and a comparison is tempting. Study of trackways attributed to Tegopelte, owing to their size and structure, indicated that it mostly walked with a slow, low gait but was also capable of adopting a higher, faster gait for quickly skimming across the sediment surface (Minter et al. 2012). It should be noted that while news reports on the latter study (like this one) repeatedly refer to Tegopelte as a predator, the original paper consistently describes it as a "predator or scavenger". One can imagine concilitergans crawling along the sea-bed, picking up fragments of organic matter and scavenging on the remains of the less fortunate. Eventually, though, their lack of armament compared to their longer-surviving allies might have been their downfall as they were less prepared to deal with the diversification of active predators as the Cambrian progressed.

REFERENCES

Edgecombe, G. D., & L. Ramsköld. 1999. Relationships of Cambrian Arachnata and the systematic position of Trilobita. Journal of Paleontology 73 (2): 263–287.

Hou X. & J. Bergström. 1997. Arthropods of the Lower Cambrian Chengjiang fauna, southwest China. Fossils and Strata 45: 1–116.

Minter, N. J., M. G. Mángano & J.-B. Caron. 2012. Skimming the surface with Burgess Shale arthropod locomotion. Proceedings of the Royal Society of London Series B—Biological Sciences 279: 1613–1620.

Paterson, J. R., D. C. García-Bellido & G. D. Edgecombe. 2012. New artiopodan arthropods from the Early Cambrian Emu Bay Shale Konservat-Lagerstätte of South Australia. Journal of Paleontology 86 (2): 340–357.

Tuskfish

The reefs of the Indo-west Pacific Oceans are one of the most species-rich regions of the entire marine environment. A complex geological history and high geographical complexity have contributed to drive speciation, resulting in a number of local radiations. One such radiation is the tuskfishes of the genus Choerodon.

Orange-dotted tuskfish Choerodon anchorago, copyright Bernard Dupont.


Choerodon is a genus of the wrasse family Labridae, most diverse around the islands of south-east Asia and northern Australasia where they inhabit coastal reefs or sea-grass beds. A revision of the genus by Gomon (2017) recognised 27 species, varying in size from a little over ten centimetres in length to half a metre or more. LIke other members of the wrasse family, they are often brightly coloured, with juveniles in particular of a number of species being patterned with bold vertical stripes. The vernacular name of 'tuskfish', as well as the zoological name of the genus (which translates as 'pig-tooth'), refers to the possesion of a pair of prominent, protruding incisors at the front of each of the upper and lower jaws. Other characteristic features of Choerodon include a dorsal fin with twelve spiny rays and eight soft rays, or thirteen spines and seven soft rays, and a lack of scales on the lower part of the cheek and lower jaw. Choerodon species, like most other wrasses, are protogynous hermaphrodites, starting their lives as females before eventually transforming into males.

Baldchin groper Choerodon rubescens, copyright Katherine Cure.


Diet-wise, tuskfishes are predators, feeding on animals such as crustaceans or mollusks. Larger species may even take other vertebrates. A kind of tool use has been observed for the genus, with difficult prey such as clams (Jones et al. 2011) or young turtles (Harborne & Tholan 2016) being grasped in the mouth and hammered against rocks to subdue them and/or break open shells. Multiple species of tuskfish may be found in close proximity though they will often differ in their preferred habitat. A study of five Choerodon species found around Shark Bay in Western Australia by Fairclough et al. (2008) found that the baldchin groper C. rubescens was found only on exposed marine reefs whereas the other four species preferred more sheltered habitats further inside the bay. The blue tuskfish C. cyanodus and blackspot tuskfish C. schoenleinii were both found in a range of habitats in this region but C. cyanodus was most abundant along rocky shores whereas C. schoenleinii preferred coral reefs (C. schoenleinii also differed from other species in the region in constructing burrows at the base of reefs that it used as a retreat). The purple tuskfish C. cephalotes was almost exclusively found among seagrass meadows. Finally, the bluespotted tuskfish C. cauteroma spent the early part of its life among seagrasses but moved onto reefs as it matured to adulthood.

Tuskfish and other wrasses are highly prized as eating fishes. However, it would be remiss to refer to the reefs of the Indo-west Pacific without mentioning that many of them are highly endangered. Heavy fishing, often using destructive methods, have combined with the effects of changing climate to cause a dramatic reduction in reef cover in recent decades. Should the decline continue at current rates, the lives of millions of people stand to be dangerously impacted.

REFERENCES

Fairclough, D. V., K. R. Clarke, F. J. Valesini & I. C. Potter. 2008. Habitat partitioning by five congeneric and abundant Choerodon species (Labridae) in a large subtropical marine embayment. Estuarine, Coastal and Shelf Science 77: 446–456.

Gomon, M. F. 2017. A review of the tuskfishes, genus Choerodon (Labridae, Perciformes), with descriptions of three new species. Memoirs of Museum Victoria 76: 1–111.

Harborne, A. R., & B. A. Tholan. 2016. Tool use by Choerodon cyanodus when handling vertebrate prey. Coral Reefs 35: 1069.

Jones, A. M., C. Brown & S. Gardner. 2011. Tool use in the tuskfish Choerodon schoenleinii? Coral Reefs 30 (3): 865.

Australasian Mistletoes

Australia is home to a fair diversity of parasitic mistletoes, nearly ninety species in all. In a previous post, I described one of our most remarkable species, the terrestrial Nuytsia floribunda. But, of course, the remaining species occupy the more typical aerial mistletoe habitat, growing directly attached to the branches and trunk of their host. And within Australia, the most diverse mistletoe genus is Amyema.

Amyema pendula growing on Acacia, copyright Groogle.


Species of Amyema are found in southeast Asia, Australia, and islands of the Pacific as far east as Samoa. A revision of the genus by Barlow (1992) recognised 92 species with the greatest diversity in the Philippines, Australia and New Guinea. They are found in a range of habitats, from wet rainforests to arid woodlands. Some species (particularly in arid habitats) grow from a single central haustorium (the structure by which a parasitic plant attaches to and draws nutrients from its host); others (particularly rainforest species) produce numerous haustoria from runners stretching along the outside of the host. Most rainforest species tend to have low host specificity but those growin in arid habitats may be more likely to restrict themselves to a small number of host species. Those species which restrict themselves to a single host may have leaves closely resembling that host, making them difficult to spot within the host canopy.

Amyema species are mostly characterised by their flowers which are typical borne in triads with the triads often then being clustered in loose umbels. In some species, the triads are reduced to pairs or single flowers. The flowers themselves are bird-pollinated and have four to six long petals that are generally separated right to the base, at most forming only a very short tube at the base of the flower. The flowers are hermaphroditic though a study of some Australian species by Bernhardt et al. (1980) found a tendency for anthers to mature before the stigma, presumably to prevent self-pollination.

Flowers of Amyema miquelii, copyright Kevin Thiele.


Not surprisingly, attention on mistletoes in Australia has commonly been focused on their effect on host trees. Mistletoe infestations may be heavy and have commonly been blamed for tree mortalities. However, one might legitimately question whether mistletoes themselves cause fatalities: does mistletoe infestation cause a host tree to become unhealthy, or are unhealthy trees more vulnerable to infestation by mistletoes? A study by Reid et al. (1992) on Amyema preissii infesting Acacia victoriae found that, though there was a relationship between mistletoe volume and host mortality, they were unable to demonstrate that mistletoe removal improved host survival. Conversely, such a positive effect was found by Reid et al. (1994) for removal of Amyema miquelii growing on two Eucalyptus species (the methods of this latter study also include the great line, "the highest mistletoes had to be shot down with a .22 rifle"). However, the authors remained conservative when it came to advocating mistletoe removal. Not only do a number of native birds and other animals depend on mistletoes for food and nesting sites, mistletoe removal can be an expensive process and may not itself be devoid of adverse effects on the host tree. Where rates of infestation are not extreme, it may still be better to just live and let live.

REFERENCES

Barlow, B. A. 1992. Conspectus of the genus Amyema Tieghem (Loranthaceae). Blumea 36: 293–381.

Bernhardt, P., R. B. Knox & D. M. Calder. 1980. Floral biology and self-incompatibility in some Australian mistletoes of the genus Amyema (Loranthaceae). Australian Journal of Botany 28: 437–451.

Reid, N., D. M. Stafford Smith & W. N. Venables. 1992. Effect of mistletoes (Amyema preissii) on host (Acacia victoriae) survival. Australian Journal of Ecology 17: 219–222.

Reid, N., Z. Yan & J. Fittler. 1994. Impact of mistletoes (Amyema miquelii) on host (Eucalyptus blakelyi and Eucalyptus melliodora) survival and growth in temperate Australia. Forest Ecology and Management 70: 55–65.

Moles, Tortoises, Calves and Cowries

The cowries of the family Cypraeidae are one of the most readily recognisable groups of tropical and subtropical shells. Their distinctive shape (with no spire and a long narrow aperture running the length of the shell) and highly polished appearance are guaranteed to catch the eye (to the extent that one species, the money cowry Monetaria moneta, famously has a history of being used as a form of currency in many regions around the Indian Ocean). Though there are a large number of cowry species found around the world, they tend to be similar enough to each other that, until relatively recently, many authors would place all within a single genus Cypraea. This approach has fallen out of fashion in more recent years and, indeed, the current favoured approach divides the family between several subfamilies. One such subgroup is the subfamily Luriinae.

Live mole cowry Talparia talpa, copyright Juuyoh Tanaka.


In a phylogenetic analysis of the cowries, Meyer (2003) recognised the Luriinae as including two tribes, the Luriini and Austrocypraeini. This concept of Luriinae was essentially based on molecular phylogenetic analysis though it was also corroborated by radular morphology (with a reduced shaft on all teeth). The underside of the shell in luriines is mostly smooth with the 'teeth' being restricted to alongside the aperture. As in other cowries, the mantle is widely extended and mostly covers the shell in life (this is how cowry shells stay so shiny). In most luriines, the mantle is covered by warty papillae. In species of the genus Luria these warts are obsolete (Schilder 1939) but they are particularly prominent in the Indo-west Pacific mole cowry Talparia talpa. Members of the Luriinae vary greatly in size: the Pacific Annepona mariae is only a centimetre or two in length but the tortoise cowry Chelycypraea testudinaria of the Indian and western Pacific Oceans grows to ten centimetres or more. Species of Luriini have shells that are banded in coloration, with three or four broad dark bands divided by narrower light bands. The Austrocypraeini are most commonly marked with brown speckles or blotches on a pale background; these blotches may be irregular as in Chelycypraea testudinaria or more regularly rounded as in Annepona mariae. The calf cowry Lyncina vitellus of the Indo-Pacific is marked with white spots on a brown background, and some species or forms of Austrocypraeini may have coloration patterns more like the banded arrangement of Luriini.

Lynx cowry Lyncina lynx, copyright Patrick Randall.


My impression is that species of Luriinae tend to be mostly nocturnal, sheltering in crevices in coral reefs during the day before emerging to feed at dusk (the name of the aforementioned mole cowry is, I suspect, more likely to refer to its appearance in some way than to any actual burrowing habit). Though I haven't (though a cursory search, at least) found any reference to species of Luriinae in particular being endangered, a number of cowries in general have been threatened by overcollecting for their shells. Certainly, luriines would be subject to the broad range of threats that currently hang over coral reefs and their inhabitants anywhere in the world.

REFERENCES

Meyer, C. P. 2003. Molecular systematics of cowries (Gastropoda: Cypraeidae) and diversification patterns in the tropics. Biological Journal of the Linnean Society 79: 401-459.

Schilder, F. A. 1939. Die Genera der Cypraeacea. Archiv für Molluskenkunde 71 (5–6): 165–201.

Aidanosagitta

If you've ever spent time, as I certainly did back in my undergraduate days, thumbing through textbooks of animal diversity, then you may be familiar with the so-called 'minor phyla'. These are those isolated subgroups of the animal kingdom that are phylogenetically remote from other such taxa but which, owing to low diversity and/or low exposure, are commonly not regarded as warranting more than a cursory summary in the end-papers of some other more prominent group. One such group is the arrow worms (Chaetognatha), and for this post I'm focusing on the arrow worm genus Aidanosagitta.

Arrow worms are marine micropredators, slender-bodied animals mostly growing to a bit less than a centimetre in length but generally not seen without the aid of a microscope due to being mostly transparent. The greater number of arrow worm species are planktonic and could be described as superficially fish-like with paired fins running down the side of the body. The front of the head forms a flexible hood within with the mouth is flanked by elongate spines, used for grasping prey.

Two Aidanosagitta species: A. bella (above) and A. venusta (below), from Kasatkina & Selivanova (2003).


A review of the arrow worms by Tokioka (1965) recognised fifteen genera within the phylum. Aidanosagitta is one of the planktonic genera; currently, about thirty species are recognised within this genus. Distinguishing features of the genus include a firm, muscular body, diverticula arising from the gut, and the posterior pair of fins being located on the 'tail' section of the body (behind the anus) (Kasatkina & Selivanova 2003).

The majority of Aidanosagitta species are found in tropical and subtropical waters, most commonly in inlets and lakes. An exception is provided by a number of species found in colders waters adjoining the north-west Pacific, in the Sea of Okhotsk and the Sea of Japan (Kasatkina & Selivanova 2003). Species are distinguished by features such as the sizes of the fins, the size and position of the large subenteric ganglion, and the presence and extent of a layer of spongy tissue that may partially cover the outside of the body. Particular species of arrow worms may be associated with particular bodies of water (such as particular currents) and changes in their distribution may indicate changes in the greater environment.

REFERENCES

Kasatkina, A. P., & E. N. Selivanova. 2003. Composition of the genus Aidanosagitta (Chaetognatha), with descriptions of new species from shallow bays of the northwestern Sea of Japan. Russian Journal of Marine Biology 29 (5): 296–304.

Tokioka, T. 1965. The taxonomical outline of Chaetognatha. Publications of the Seto Marine Biological Laboratory 12 (5): 335–357.

Apiocera: Flower-Loving Flies that Don't Particularly Care for Flowers

The insect world is full of animals that may be striking in appearance but about which we know relatively little. Such, for instance, are the flies of the genus Apiocera.

Male Apiocera, copyright Chris Lambkin.


Apiocera is a genus of a bit over 130 known species of relatively large flies, about half an inch to an inch in length, that are found in hot, arid habitats in disparate parts of the world: western North America, southern South America, southernmost Africa and Australia. Records of Apiocera from Borneo and Sri Lanka were regarded by Yeates and Irwin (1996) as probably errors. They are similar in their overall appearance to the robber flies of the family Asilidae, differing lacking the piercing mouthparts of robber flies or the moustache of bristles below the antennae. The venation of their wings is more similar to that of the mydas flies of the Mydidae, but they differ from most mydids in having shorter antennae and the regular triangle of three round ocelli on top of the head (Woodley 2009).

Observations of Apiocera species have been fairly few. A study of North American species by Toft & Kimsey (1982) found them to be restricted to sandy habitats with a fair amount of subsurface moisture, such as the shores of lakes and rivers or among sand dunes. The larvae, so far as we know, are similar to those of robber flies and are probably burrowing predators in the sand. Adults emerge from holes in the ground late in the growing season. In some places (such as Wikipedia), you may find Apiocera referred to as 'flower-loving flies' but visits to flowers are few. Toft & Kimsey (1982) found that the species they observed emerged after most plants had finished flowering and, indeed, questions have been raised historically as to whether adult Apiocera feed at all. Nevertheless, they may take honeydew from plant-sucking insects, and I will direct you to the photo below by Jean & Fred Hort that seems to show at least one Apiocera individual feeding at a flower. Males may congregate at certain locations, seemingly to form leks, though it is unclear whether they maintain territories. Toft & Kimsey (1982) noted that tussels between males of A. hispida were common, observing that "two males would make rapid contact in mid-flight, and stay together in a buzzing, tumbling ball for several seconds".


There seems to be little question that Apiocera and mydas flies are closely related. In fact, an analysis of Apiocera's phylogenetic relationships by Yeates & Irwin (1996) lead to a number of other genera that had previously been classified with Apiocera in the family Apioceridae being reassigned to the Mydidae (I suspect that it is the behaviour of these other 'apiocerids' that is behind the erroneous association of Apiocera with the 'flower-loving' moniker). Apioceridae is still maintained as a distinct family for Apiocera alone but, as noted by Woodley (2009), one could be forgiven for questioning whether Apiocera would be better treated as a very basal mydid. But that, of course, is simply a question of categories.

REFERENCES

Toft, C. A., & L. S. Kimsey. 1982. Habitat and behavior of selected Apiocera and Rhaphiomidas (Diptera, Apioceridae), and descriptions of immature stages of A. hispida. Journal of the Kansas Entomological Society 55 (1): 177–186.

Woodley, N. E. 2009. Apioceridae (apiocerid flies). In: Brown, B. V., A. Borkent, J. M. Cumming, D. M. Wood, N. E. Woodley & M. A. Zumbado (eds) Manual of Central American Diptera vol. 1 pp. 577–578. NRC Research Press: Ottawa.

Yeates, D. K., & M. E. Irwin. 1996. Apioceridae (Insecta: Diptera): cladistic reappraisal and biogeography. Zoological Journal of the Linnean Society 116: 247–301.

The Running of the Crabs

There are many varieties of spider in the world that, while not necessarily uncommon, tend to be little known to the general public owing to their cryptic and retiring nature. As an example, meet the genus Philodromus.

Philodromus cespitum, copyright R. Altenkamp.


Philodromus is the largest genus recognised in the family Philodromidae, commonly referred to as the running crab spiders or small huntsman spiders. About 250 species have been assigned to this genus from various parts of the world (Muster 2009), mostly in the Holarctic region. Like the huntsman spiders of the Sparassidae and the crab spiders of the Thomisidae, philodromids are an example of what old publications often referred to as 'laterigrade' spiders, in which the legs are arranged to extend sideways from the body more than forwards and backwards. They have eight eyes arranged in two recurved rows of four. Philodromids differ from crab spiders in having scopulae (clusters of hairs that can look a bit like little booties) on the leg tarsi, and having secondary eyes that lack a tapetum (reflective layer). They differ from huntsmen in that the junction between the tarsi and metatarsi is restricted to movement in a single plane, rather than the tarsus being able to move freely (Jocqué & Dippenaar-Schoeman 2007). Philodromids do not build a web to capture prey but instead seize prey directly.

The distinction between Philodromus and other genera in the family has historically been imprecise (Muster 2009) which goes some way to explaining the large number of species it has encompassed. In general, though, the eye rows of Philodromus are relatively weakly recurved, and its body form is less slender than that of the genera Tibellus and Thanatus. These may well be primitive features for the family, and a phylogenetic analysis of philodromids by Muster (2009) indicated that at least one group of species historically included in Philodromus (the P. histrio group) may be more closely related to the slender-bodied genera. The great French arachnologist Eugene Simon recognised several species groups in Philodromus, distinguished by features such as eye arrangement and leg spination, but recent authors feel that the status of these groups requires further investigation before we could consider treat?ing them as distinct genera.

Philodromus dispar, copyright Judy Gallagher.


Most species of Philodromus live on vegetation, flattening themselves against stems and foliage to avoid detection. As with other laterigrade spiders, the arrangement of their legs allows for rapid sideways movement, perfect for avoiding predators or turning up where prey do not expect them. At least one species group found in the Mediterranean region (including P. pulchellus and its relatives) differs in being ground-living, with a predilection for salt flats (Muster et al. 2007). Bites to humans from Philodromus appear to be vanishingly rare: a report on such a bite by Coetzee et al. (2017) appears to be the first record of one (the bite was painful, causing swelling and some ulceration, but without long-term effects following treatment). Philodromus species are much more likely to have a net positive value to humans, as they may act as control agents for insect pests among crops and orchards.

REFERENCES

Coetzee, M., A. Dippenaar, J. Frean & R. H. Hunt. 2017. First report of clinical presentation of a bite by a running spider, Philodromus sp. (Araneae: Philodromidae), with recommendations for spider bite management. South African Medical Journal 107 (7): 576–577.

Jocqué, R., & A. S. Dippenaar-Schoeman. 2007. Spider Families of the World. Royal Museum for Central Africa: Tervuren (Belgium).

Muster, C. 2009. Phylogenetic relationships within Philodromidae, with a taxonomic revision of Philodromus subgenus Artanes in the western Palearctic (Arachnida: Araneae). Invertebrate Systematics 23: 135–169.

Muster, C., R. Bosmans & K. Thaler. 2007. The Philodromus pulchellus-group in the Mediterranean: taxonomic revision, phylogenetic analysis and biogeography (Araneae: Philodromidae). Invertebrate Systematics 21: 39–72.

Stilts and Avocets

Visit a healthy wetland in many parts of the world and you may be able to see boldly patterned, lightly built birds with remarkably long legs and bills wading through the shallows. These are the members of the Recurvirostridae, commonly known as the stilts and avocets.

American avocets Recurvirostra americana, from here.


About a dozen species of recurvirostrid are currently recognised, depending on the exact classification scheme in play. They are divided between three genera with the avocets forming the genus Recurvirostra and the stilts divided between Himantopus and Cladorhynchus. The most obvious distinction between the two subgroups is in the shape of the bill: that of stilts is straight but avocets have a distinct upwards curve towards the end of theirs. A fourth genus has often been included in the Recurvirostridae for the ibisbill Ibidorhyncha struthersii, a striking-looking inhabitant of the upland rivers of the Himalayan plateau, but uncertainty about this bird's phylogenetic position has led most recent authors to exclude it from the family.

The recurvirostrids feed mostly on small aquatic invertebrates such as brine shrimp or insect larvae. Their long legs, among the longest relative to body size of any bird, allow them to wade in deeply in search of prey. Stilts actively probe the waters and underlying sediment whereas avocets tend to forage by sweeping their bill through the water side to side. Avocets and the banded stilt Cladorhynchus leucocephalus of Australia prefer brackish waters such as lagoons and estuaries, with the banded stilt congegrating around the great salt lakes of inland Australia. Breeding is conducted by monogamous pairs that share the duty of incubating their simple nest on the ground near water. These nests may be gathered into loose colonies; the banded stilt forms particularly large colonies in which the chicks are herded into communal creches of several hundred.

Pied stilt Himantopus leucocephalus, copyright JJ Harrison.


The majority of recurvirostrids are patterned with black or dark brown and white. The red-necked avocet Recurvirostra novaehollandiae has the head and neck coloured reddish-brown as does the American avocet R. americana during the breeding season. The banded stilt has a broad reddish-brown band across the top of the breast. There is also the black stilt Himantopus novaezelandiae of New Zealand, which is somewhat self-explanatory. Beaks are black in all species; the legs are grey in avocets and red in stilts.

Four geographically distinct species of avocet occupy the modern world: the American avocet in North America, the red-necked avocet in Australia, the pied avocet Recurvirostra avosetta in Eurasia and Africa, and the Andean avocet R. andina in South America. The Andean avocet is a bird of high altitudes, occupying shallow, alkaline lakes in the upper Andes. Cladorhynchus includes only the banded stilt. The most varied taxonomy concerns the genus Himantopus. Historically, all the black-and-white stilts (and sometimes also the black stilt) have been recognised as a single near-cosmopolitan species. In more recent years, the trend has been towards recognition of five or six distinct species in the genus. Most of these species are well separated geographically except for in New Zealand where the black stilt shares its range with the pied stilt Himantopus leucocephalus, a more recent immigrant from Australia. The breeding range of the black stilt is currently restricted to a relatively small area of New Zealand's South Island, and the species is considered endangered due to factors such as habitat alteration and the threat of hybridisation with the more abundant pied stilt*.

*It's worth spending some thought on the role of hybridisation as a conservation risk. Some observers may express concern that regarding hybridisation as a threat per se carries uncomfortable intonations of "racial purity", and that limiting the available gene pool may do more harm than good. After all, it's not as if the black stilt heritage of hybrid individuals is just gone (hybrids between the two species are, I believe, fully fertile and able to produce offspring of their own). The question is, I suppose, do the black stilt genes actually persist in the mixed population? Or does selection and/or drift winnow them out over time? This would be a difficult question to answer, and not without risk to find out.

Banded stilts Cladorhynchus leucocephalus and red-necked avocets Recurvirostra novaehollandiae, copyright Ed Dunens.


Phylogenetically, it is reasonably well established that recurvirostrids form a clade with the ibisbill and oystercatchers. This clade is in turn closely related to the plovers of the Charadriidae; indeed, many recent phylogenies have indicated that the recurvirostrid-oystercatcher clade may even be nested within the plovers as generally recognised. Considering the relatively small number of species in each clade, it might seem reasonable to suggest the recurvirostrids be reduced to a subfamily of the Charadriidae, but bird taxonomists being bird taxonomists, there seems to be more of a push to divide the Charadriidae up instead.

The fossil record of the Recurvirostridae is limited. A handful of species have been assigned to this family from the Eocene, but all are known from limited remains and their position is questionable. Coltonia recurvirostra is known from part of a wing from Utah; it was a relatively large bird, appearing to be more than one-and-a-half times the size of any living recurvirostrid. Fluviatilavis antunesi was described from a femur, humerus and radius from Portugal but was described as exhibiting some primitive features not found in modern recurvirostrids. It is also worth noting that its original description (Harrison 1983) compared it most favourably with the ibisbill, so if that species is not to be regarded as a recurvirostrid, probably neither is Fluviatilavis.

REFERENCE

Harrison, C. J. O. 1983. A new wader, Recurvirostridae (Charadriiformes), from the early Eocene of Portugal. Ciências da Terra 7: 9–16.

Taxocrinus

Below is an example of Taxocrinus, a genus of fossil crinoids known from the later Devonian and earlier Carboniferous of Europe and North America. It is a relatively plesiomorphic representative of the flexible crinoids, one of the major crinoid lineages of the Palaeozoic era.

Taxocrinus colletti, copyright James St. John.


Flexible crinoids are characterised by arms that lack pinnules, the small side-branches found on the arms of most other crinoids. As a result, the preserved arms have a somewhat tentacle-like appearance, and are commonly preserved coiled in over the oral surface of the central cup. In Taxocrinus, the arms were regularly and isotomously bifurcated: that is, they divided between two branches of more or less equal size. The central cup itself in flexible crinoids was (somewhat counter-intuitively) quite inflexible, with the plates of the aboral surface firmly jointed together. The oral surface bore a more flexible covering of small plates, and an anal tube (visible near the midline of the fossil above) directed waste away from the mouth. The stem was round in cross section and lacked lateral cirri (Moore 1978).

Flexible crinoids were around for a very long time but it is rare for them to be found in abundance. As such, they were probably specialised for particular habitats that were either uncommon or less likely to be preserved. It has been suggested that, because their pinnule-less arms would have been poorly suited for filtering particles from strong currents, flexible crinoids may have inhabited calm, low-energy waters (Breimer 1978) (though I do wonder if enlarged tube feet may have partially filled the role of pinnules; is it possible to estimate the size of the tube feet from the preserved skeleton?) Crinoids living in such habitats will often hold the arms in a bowl arrangement so they may capture particles settling from higher in the water column. In the case of the flexible crinoids, moving the arms in and out may have created local water movements to further draw such particles in.

Though Taxocrinus itself would disappear in the mid-Carboniferous, flexible crinoids as a whole would persist to the end of the Permian. In more derived forms, the branching of the arms was often unequal, with the smaller branches effectively replacing the missing pinnules. In the end, though, the specialised flexibles were yet another casualty of the end-Permian cataclysm that so shook the composition of life on this planet.

REFERENCES

Breimer, A. 1978. Autecology. In: Moore, R. C., & C. Teichert (eds) Treatise on Invertebrate Paleontology pt T. Echinodermata 2 vol. 1 pp. T331–T343. The Geological Society of America, Inc.: Boulder (Colorado), and The University of Kansas: Lawrence (Kansas).

Moore, R. C. 1978. Flexibilia. In: Moore, R. C., & C. Teichert (eds) Treatise on Invertebrate Paleontology pt T. Echinodermata 2 vol. 2 pp. T759–T812. The Geological Society of America, Inc.: Boulder (Colorado), and The University of Kansas: Lawrence (Kansas).

White by Evening in the American Southwest

Though various species of it may be found around the world, the evening primrose family Onagraceae reaches its highest diversity in the south-west of North America. For this post, I'm looking at a genus endemic to this region, Eremothera.

Eremothera boothii, copyright Kerry Woods.


Eremothera is one of several genera of evening primroses newly recognised by Wagner et al. (2007). The species included in this genus had previously been included in the broader genera Oenothera or Camissonia, but these genera were progressively broken down owing to polyphyly and poor definitions. Eremothera species are annual herbs with more or less erect stems. Leaves are arranged on the stem alternately; those near the base are carried on a long petiole of up to six centimetres. The genus is distinguished from its close relatives by having mostly white flowers that open in the evening (in rare cases they my be pink or red, fading as they age). Pollination is by moths when the flowers first open, with small bees visiting the flowers the following morning. The fruit is a long capsule that arises directly from the main stem without a subtending stalk.

Eremothera refracta with flowers and green fruits, copyright Stan Shebs.


Seven species of Eremothera were recognised by Wagner et al. (2007). Eremothera nevadensis is a specialist of clay soil that occupies a relatively small range in Nevada, around Reno. Eremothera refracta is a widespread species in the south-west United States with fruit that are of an even diameter along their length (Hickman 1993). Eremothera chamaenerioides is a self-pollinating derivative of E. refracta with smaller flowers in which the stigma is surrounded and overtopped by the anthers. Eremothera boothii and E. minor (both also widespread) have fruits that are wider at the base than at the tip. In E. minor the inflorescence is held erect; in E. boothii the flowers nod. Two localised species, E. gouldii and E. pygmaea, are self-pollinating derivatives of E. boothii. Eremothera minor is also self-pollinating, and may in some cases even be cleistogamous with pollen being transferred to the stigma without the flower even opening.

REFERENCES

Hickman, J. C. (ed.) 1993. The Jepson Manual: Higher Plants of California. University of California Press: Berkeley (California).

Wagner, W. L., P. C. Hoch & P. H. Raven. 2007. Revised classification of the Onagraceae. Systematic Botany Monographs 83: 1–240.

Slippers on the Coast

The 'limpet' form is something that has evolved numerous times among gastropods, as various lineages of marine snail converted to a more or less unwhorled shell and low profile. In many cases, the evolution of the limpet form is also associated with high energy environments, the ability to nestle against rocks helping the gastropod maintain its grip against the surge of the waves. In the modern world, the most diverse and familiar lineage of limpets is that including the common limpets of the genus Patella and their relatives, but there also many independent lineages to be found. One of these is the slipper limpets of the genus Crepidula.

Various views of shell of Crepidula onyx, copyright H. Zell.


Slipper limpets get their vernacular name from the shape of their shell, whose more or less oval shape together with a jutting internal horizontal shelf (the septum) at one end gives the overall impression of a carpet slipper. About forty species (including fossils) of Crepidula are currently recognised worldwide. Species recognition has historically been difficult owing to their simple form and tendency to vary according to the environment in which they mature, but Hoagland (1977) identified a number of key distinguishing features such as disposition and shape of the muscle scars, features of the septum, and conformation of the apical beak of the shell. In contrast to the grazing common limpets, slipper limpets are filter feeders using their gill to capture micro-algae from the water column. They are protandric hermaphrodites, beginning their life as males but maturing into females as they grow. Eggs are brooded under the shell when first produced; in some species, the eggs are subsequently released to hatch into planktonic larvae whereas other species produce fewer eggs but retain them until the young have developed to the crawling stage. For instance, two species found on the east coast of North America that are very similar in adult appearance and have been confused historically differ in that Crepidula ustulatulina, found around Florida and the Gulf of Mexico, produces free-living larvae whereas the more northerly C. convexa does not.

Mating stack of Crepidula fornicata, copyright Dendroica cerulea.


The most renowned species of slipper limpet is the northern Atlantic Crepidula fornicata. This species was originally native to the eastern coast of North America but was accidentally imported to Europe in the late 1800s in association with oysters being transported as stock for farming (Blanchard 1997). In the subsequent years, C. fornicata has become increasingly widespread on the shores of Europe, and is often a significant fouling pest for oyster farms. It has also been introduced to even further flung locations such as Japan and Washington State. Crepidula fornicata is famed for its habit of forming high mating stacks with several smaller males living permanently on the dorsal surface of larger females. If the female of a stack dies, the largest male may develop into a female. Not all Crepidula species form such stacks: in some, just two or three individuals may form a temporary cluster when mating.

Historically, Crepidula has been distinguished from other genera in the limpet family Calyptraeidae by their posterior shell apex and flat septum (other calyptraeid genera may have a cone-shaped shell and/or cup-shaped septum). However, a molecular analysis of the family by Collin (2003) found that species of Crepidula sensu Hoagland (1977) did not form a single clade within Calyptraeidae, and the genus' prior members are now divided between at least four genera. While these genera may be distinguishable using features of the soft anatomy, they are almost indistinguishable from the shells alone.

REFERENCES

Blanchard, M. 1997. Spread of the slipper limpet Crepidula fornicata (L. 1758) in Europe. Current state and consequences. Scientia Marina 61 (Suppl. 2): 109–118.

Collin, R. 2003. Phylogenetic relationship among calyptraeid gastropods and their implications for the biogeography of marine speciation. Systematic Biology 52 (5): 618–640.

Hoagland, K. E. 1977. Systematic review of fossil and recent Crepidula and discussion of evolution of the Calyptraeidae. Malacologia 16 (2): 353–420.

The Splanchnotrophidae: Comfy inside a Sea Slug

In previous posts, I've referred to the great significance of the minute crustaceans known as copepods to aquatic ecosystems. At the time, I was referring to free-living members of this group but the copepods also include a wide range of parasitic forms. Some of these parasitic copepods have evolved into forms so derived and bizarre that they are barely recognisable as crustaceans. One example of this is the family Splanchnotrophidae.

Sea slug Janolus fuscus with protruding egg sacs of a splanchnotrophid copepod, probably Ismaila belciki, copyright Michael D. Miller.


Splanchnotrophids are a group of copepods endoparasitic on two orders of shell-less marine gastropods (sea slugs), the Nudibranchia and Sacoglossa. They are characterised by reduced mouthparts and appendages though they retain a distinct pair of claw-like antennae. These antennae seem to be used to hold the copepod in place in their preferred location within the body cavity of their host. Though the exact means of feeding by splanchnotrophids is not certain, their rudimentary mouthparts, combined with a rarity of observations of actual tissue damage in parasitised hosts, indicate that they probably suck nutriment from their host's haemolymph. Females and males live in association within the host, the minute (and slightly more recognisably copepod-y) males holding close to their comparatively gigantic mates. As well as their size, female splanchnotrophids differ from males in the possession of elongate, tubular dorsal outgrowths of the thorax. These are most commonly presumed to function to provide more space for the female's enlarged ovaries, though some have suggested additional functions such as maintaining position within the host, respiration or absorbing nutrients (Anton & Schrödl 2013). The female's tubular egg-sacs extend through an opening in the host's body wall to release eggs into the water column. Usually, these egg-sacs will emerge close to some outgrowth of the host's own body, such as gills or papillae, and may be coiled if relatively long; these measures presumably help protect the egg-sacs from external damage. How the released larvae find and colonise new hosts remains unknown but it is possible the antennules (the smaller second pair of antennae possessed by most crustaceans) are used to locate hosts chemically, with their reduced condition in adults the result of a halt to development once their purpose has been fulfilled.

Female (left) and male Ismaila aliena dissected out from host, from Anton & Schrödl (2013).


Relatively few splanchnotrophids have been recognised to date, maybe about a dozen species divided between five genera. A few other species that had earlier been included in the family on little more grounds than that they were endoparasites of gastropods were excluded by Huys (2001)*. A sixth genus and species Chondrocarpus reticulosus is of uncertain relationships. If correctly associated with the splanchnotrophids, it is of interest in parasitising a different group of sea slugs (the pleurobranchids) and in its massive size (growing to twelve millimetres vs only a few millimetres for females of the other genera), but the only available description is inadequate for its proper characterisation. In some localities, splanchnotrophids have proven to be surprisingly abundant. A once-off survey of potential host species in Oregon found no less than 62% of individuals of one species to be infected (25 other potential host species were completely free of parasites), whereas a longer-term survey off the coast of Chile found an overall infection rate of 13% with some particular host species approaching 100% infection (Schrödl 2002). Host specificity seems to vary within the family: a study by Anton et al. (2018) found that species of the genus Ismaila tended to restrict themselves to a single host species, whereas species of Splanchnotrophus are more catholic and undiscriminating. Nevertheless, a lack of correlation between relationships of splanchnotrophid species and those of their host species suggests that, even in the more discriminating Ismaila, host changes may not have been uncommon.

*As a concise indication of just how sloppy some of the earlier work on 'splanchnotrophids' had been, one misattributed species was re-identified by Huys (2001) as having been based on the detached head of a pelagic amphipod.

The broader relationships of splanchnotrophids within copepods also remain poorly understood. A phylogenetic study by Anton & Schrödl (2013) suggested that Splanchnotrophidae may form a clade with another genus of copepods endoparasitic in gastropods, Briarella, with this clade being in turn derived from ectoparasitic ancestors. However, by the authors' own admission, this study was heavily biased in both taxon and character coverage to the Splanchnotrophidae, and may have been affected by insufficient scrutiny of non-splanchnotrophid taxa. Though derivation of the endoparasitic splanchnotrophids from ectoparasitic ancestors has a definite intuitive appeal, further study is required before we can feel confident about it.

REFERENCES

Anton, R. F., D. Schories, N. G. Wilson, M. Wolf, M. Abad & M. Schrödl. 2018. Host specificity versus plasticity: testing the morphology-based taxonomy of the endoparasitic copepod family Splanchnotrophidae with COI barcoding. Journal of the Marine Biological Association of the United Kingdom 98 (2): 231–243.

Anton, R. F., & M. Schrödl. 2013. The gastropod-crustacean connection: towards the phylogeny and evolution of the parasitic copepod family Splanchnotrophidae. Zoological Journal of the Linnean Society 167: 501–530.

Huys, R. 2001. Splanchnotropid systematics: a case of polyphyly and taxonomic myopia. Journal of Crustacean Biology 21 (1): 106–156.

Schrödl, M. 2002. Heavy infestation by endoparasitic copepod crustaceans (Poecilostomatoida: Splanchnotrophidae) in Chilean opisthobranch gastropods, with aspects of splanchnotrophid evolution. Organisms, Diversity & Evolution 2: 19–26.

The Ant-like Beetles

As I've commented before, the world is home to an overwhelming diversity of small brown beetles, most of them (for me, at least) inordinately difficult to distinguish. One group of tiny beetles that is quite recognisable, though, is the ant-like beetles of the genus Anthicus.

Anthicus cervinus, copyright Robert Webster.


Over a hundred species around the world have been attributed to this genus. Few of them grow more than a few millimetres in length. They are elongate with the elytra more or less rounded and often covered in short hair. The legs are relatively long. The prothorax is globular and generally narrower towards the base. The head is inclined and carried on a narrow neck (Ferté-Sénectère 1848). Many species have the elytra contrastingly patterned with bands or spots. As the vernacular name indicates, the overall appearance is reminiscent of a small ant though I'm not sure if this indicates a protective mimicry or is merely coincidence.

Anthicus antherinus, copyright Udo Schmidt.


The natural history of most Anthicus species is poorly known. The greater number of species are saprophages, found in association with rotting vegetation or scavenging on dead insects. One species, Anthicus floralis, is found worldwide as a storage pest, infesting seed and grain stores. One of the larger North American species, A. heroicus, has larvae that attack masses of dobsonfly eggs on midstream boulders (Davidson & Wood 1969). The larvae feed on the eggs from the inside, using them for shelter as well as nutrition, before emerging from the eggs to pupate.

REFERENCES

Davidson, J. A., & F. E. Wood. 1969. Description and biological notes on the larva of Anthicus heroicus Casey (Coleoptera: Anthicidae). Coleopterists Bulletin 23 (1): 5–8.

Ferté-Sénectère, M. F. de la. 1848. Monographie des Anthicus et genres voisins, coléoptères hétéromères de la tribu des trachélides. Sapia: Paris.

The Camisiids: Cryptic Inhabitants of Soil and Wood

Various views of Camisia biverrucata, copyright Pierre Bornand.


The animal in the above pictures is a typical representative of the Camisiidae, a widely distributed family of oribatid mites. Members of this family can be found in soil, on the trunks of trees, or hidden among mosses and lichens. They are slow-moving animals and are often concealed from potential predators by an encrusting layer of dirt and organic debris. Carrying this encrusting layer may be related to a reduction in the offensive chemical-producing glands that are used by many other oribatids for defense (Raspotnig et al. 2008). In members of the genus Camisia, the openings of these glands are completely covered by dirt, but in the genera Platynothrus and Heminothrus the openings still protrude above the encrustation. The recently described Paracamisia osornensis, which does not carry an encrusting layer, retains a large offensive gland (Olszanowski & Norton 2002).

Close to 100 species have been assigned to this family; though found in most parts of the world, camisiids are most diverse in the Northern Hemisphere. One species in particular, Platynothrus peltifer, is almost global in distribution and the range of habitats in which it has been found includes soil, litter, peat and even aquatic habitats (Norton & Behan-Pelletier 2009) When one is as small and metabolically undemanding as these animals are, there may be surprisingly little difference between being out in the air or immersed in water, and even primarily terrestrial oribatids may survive submersion almost indefinitely. Genetic studies of P. peltifer have identified a high level of within-species divergence and it has been calculated on this basis that this species may have survived almost unchanged in external appearance for some 100 million years (Heethoff et al. 2007).

The ubiquitous Platynothrus peltifer, copyright Centre for Biodiversity Genomics.


The Camisiidae are closely related to another oribatid family, the Crotoniidae, that is found in South America and Australasia. One of the more significant differences between the two families is that whereas the camisiids appear to be entirely parthenogenetic, crotoniids reproduce sexually. Recent analyses, both molecular and morphological, indicate that the 'camisiids' are paraphyletic with regard to the crotoniids, leading Colloff & Cameron (2009) to treat the latter as a subfamily, Crotoniinae, of the former. This re-classification has been accepted by other authors though the law of priority requires that the combined family should be known as the Crotoniidae, not Camisiidae. The nested position of the sexual crotoniines within the asexual 'camisiids', with other related oribatid families also being asexual, has led to the suggestion that the crotoniines have somehow re-evolved sexuality. This would be fascinating if true, seemingly violating the usual principle that complex features can't be re-evolved once lost. Personally, I tend to be sceptical of claims like this (see this old post, for instance). I would like to see evidence beyond simple phylogenetic position to indicate if this is a true re-evolution rather than an historical bias towards loss of sexuality giving a misleading image.

REFERENCES

Colloff, M. J., & S. L. Cameron. 2009. Revision of the oribatid mite genus Austronothrus Hammer (Acari: Oribatida): sexual dimorphism and a re-evaluation of the phylogenetic relationships of the family Crotoniidae. Invertebrate Systematics 23: 87–110.

Heethoff, M., K. Domes, M. Laumann, M. Maraun, R. A. Norton & S. Scheu. 2007. High genetic divergences indicate ancient separation of parthenogenetic lineages of the oribatid mite Platynothrus peltifer (Acari, Oribatida). Journal of Evolutionary Biology 20: 392–402.

Norton, R. A., & V. M. Behan-Pelletier. 2009. Suborder Oribatida. In: Krantz, G. W., & D. E. Walter (eds) A Manual of Acarology 3rd ed. pp. 430–564. Texas Tech University Press.

Olszanowski, Z., & R. A. Norton. 2002. Paracamisia osornensis gen. n., sp. n. (Acari: oribatida) from Valdivian forest soil in Chile. Zootaxa 25: 1–15.

Raspotnig, G., E. Stabentheiner, P. Föttinger, M. Schaider, G. Krisper, G. Rechberger & H. J. Leis. 2008. Opisthonotal glands in the Camisiidae (Acari, Oribatida): evidence for a regressive evolutionary trend. Journal of Zoological Systematics and Evolutionary Research 47 (1): 77–87.