Chilostomellidae: Deep Forams

Holotype of Chilostomella serrata, from the Smithsonian National Museum of Natural History.

The specimen in the figure above is a fairly typical representative of the Chilostomellidae, a cosmopolitan family of forams known from the Jurassic to the present day. Members of this family have a translucent calcareous test with chambers arranged in a trochospiral (broad conical) or planispiral (flat spiral) pattern. The chambers of each spiral are expanded to cover over the prior spirals so only the outermost spiral is generally visible. The aperture of the test in the final chamber is a narrow slit along the margin with the underlying chamber (Loeblich & Tappan 1964).

Despite their long history and wide distribution, I get the general impression that chilostomellids are not usually abundant. They are generally restricted to deeper waters, more than 100 m below the surface (Cushman et al. 1954). Members of the genus Chilostomella, at least, have commonly been regarded as associated with low-oxygen environments. However, it has also been suggested that their favoured conditions are not so much a question of low oxygen as high organic flux (Jorissen 2002). Perhaps the best location to find chilostomellids would be around sites where dead animals and seaweeds have fallen to the deeper waters below.

REFERENCES

Cushman, J. A., R. Todd & R. J. Post. 1954. Recent Foraminifera of the Marshall Islands. Bikini and nearby atolls, part 2, oceanography (biologic). Geological Survey Professional Paper 260-H: 319–384, pls 82–93.

Jorissen, F. J. 2002. Benthic foraminiferal microhabitats below the sediment-water interface. In: Sen Gupta, B. K. (ed.) Modern Foraminifera pp. 161–179. Kluwer Academic Publishers: Dordrecht.

Loeblich, A. R., Jr & H. Tappan. 1964. Treatise on Invertebrate Paleontology pt C. Protista 2. Sarcodina: chiefly "thecamoebians" and Foraminiferida vol. 2. The Geological Society of America, and The University of Kansas Press.

Digging for Tellina

When I was a child, a large part of my extended family would gather over the Christmas period to park their tents and caravans alongside the estuary downhill from my great-grandparents' house (in the usual way of these things, my memory has these summer camping periods lasting for ages, but I don't think they could have been longer than a week or so). While we were there, I would spend a fair chunk of the day looking for the wildlife that inhabited the slightly muddy estuary beach. Among these were various bivalves whose shells could be found littering the shoreline, or which might be found by digging in the sand at low tide. Close to the surface were New Zealand cockles Austrovenus stutchburyi (not actually a direct relative of the English cockle but a member of the Veneridae family that has adopted a similar body form). A little deeper were pipis and tuatuas. And a little deeper again were the flat, slender shells of Tellina.

Thin tellin Tellina tenuis, copyright S. Rae.

I should note that Tellina species are not really deep burrowers in the grand scheme of things, generally only embedding themselves about one to three centimetres below the surface, but again I must ask that you make allowances for childhood memories. Their low profile and weakly inflated shells also make them fast diggers so they were probably able to elude most casual explorations. Like most subsurface bivalves, Tellina species are sediment feeders. Their usual aspect is lying horizontally beneath the sediment, extending their long, unfused siphons to the surface to gather detritus (Ujino & Matuskuma 2010; the shells of Tellina are usually twisted slightly to one side at the end to facilitate the siphons' passage). Even if you've not seen the Tellina animals themselves, you may have seen the radiating trails made by the siphons as they extend along the top of the sediment.

Sunrise tellin Tellina radiata, copyright James St. John.

Tellina is an extremely diverse genus, with species found worldwide and recognised through the entirety of the Mesozoic (Moore 1969). These species vary greatly in appearance, with shells varying from almost completely smooth to strongly ornamented, and from subcircular to quite elongate. It should therefore come as little surprise that numerous attempts have been made to divide Tellina between various subgenera and genera but issues such as homoeomorphy in Tellina's evolution (where distinct lineages have converged on similar body forms) have lead to disagreement over the best system to adopt. In 1934, the malacologist A. E. Salisbury complained that, "The number of genera, subgenera, and sections into which the Tellinidae has been cut up is getting somewhat appalling; the list of names is still increasing every year, and, if every variation of form is magnified, it is quite possible to go on until at last each species becomes the representative of a different genus and each variety that of a subgenus" (of course, as seems almost inevitable when one encounters complaints of this kind, Salisbury himself then proceeds to add to the tally of generic names in that same paper). Though I suspect most modern malacologists would probably disagree with the extremely broad concept of Tellina advocated by Salisbury, the question of how best to handle the genus taxonomically remains an open one.

REFERENCES

Moore, R. C. (ed.) 1969. Treatise on Invertebrate Paleontology pt N. Mollusca 6. Bivalvia vol. 2. The Geological Society of America, Inc., and The University of Kansas.

Salisbury, A. E. 1934. On the nomenclature of Tellinidae, with descriptions of new species and some remarks on distribution. Proceedings of the Malacological Society of London 21: 74–91.

Ujino, S., & A. Matsukuma. 2010. Inverse life positions of three species in the genus Cadella (Bivalvia: Tellinidae). Molluscan Research 30 (1): 25–28.

Agenioideus: Average Spider Hawks

I have commented in earlier posts on the challenges of identifying spider hawks of the family Pompilidae, resulting from this wasp family's combination of high species diversity with a mostly conservative body plan. As a result of this conservatism, pompilid classification has tended to drift towards a situation where the majority of species are included in a relatively small number of somewhat vaguely defined genera. Each of the species included in one of these genera can be associated with other species in the genus, and groups of species approach each other closely enough that clear lines cannot be settled upon, but identifying features shared by all members of the genus can prove difficult. A good example of one such genus is Agenioideus.

Female Agenioideus birkmanni, from the University of Texas at Austin.

Species assigned to Agenioideus can be found pretty much worldwide though the greatest diversity occurs in warmer parts of the Holarctic. Though there does not seem to be a great deal of disagreement over which species should be placed in this genus, it seems a little difficult to say exactly what makes an Agenioideus. If anything, Agenioideus species seem to be associated by how relentlessly average they are, possessing a unique combination of characters that are none of them individually unique. They have wings with three submarginal cells, a broad metapostnotum in front of the propodeum, and legs ending in a small arolium with a weak comb of setae between a pair of long claws, mostly with a single small ventral tooth (Krogmann & Austin 2012). If you don't know exactly what those terms mean, just know that they are all quite unspecialised features for pompilids. Males often have asymmetrical claws on the forelegs, with the inner claw strongly bent and bifid while the outer claw is like those on the other legs, and the pterostigma (the dark node at the front of the fore wings) is relatively large compared to other genera. Females often have a comb of longer spines on the inner margin of the fore tarsi. But these last, more derived, features may not be universally present across all species of the genus.

Female Agenioideus nigricornis with redback spider Latrodectus hasselti as prey, copyright Mark Newton.

As befits their unspecialised appearance, most Agenioideus species (as far as we know) are relatively unspecialised in their nesting behaviour (Shimizu 1997). Like other pompilids, they lay their eggs on paralysed spiders that will provide food for the larva when it hatches. Most Agenioideus species construct simple nests with a single brood cell containing a single spider for each nest. One European species, A. nubecula, is known to produce slightly more extensive nests with up to four cells. The nest may be made by digging in loose soil or by using a pre-existing cavity; whether the wasp is more likely to do one or the other is correlated with whether she possesses a well-developed tarsal comb. A Japanese species, A. ishikawai, is known to at least partially dig a nest before capturing a spider, completing construction after bringing it back. The most specialised provisioning behaviour known for the genus, however, is found in another European species, A. coronatus. This species hunts jumping spiders which she paralyses with her sting as is standard. The paralysis, however, is only temporary, lasting just a few minutes, just long enough for the female to deposit an egg near the base of the spider's abdomen where it cannot easily remove it. The spider is then freed to go about its business without being placed in a nest, until the wasp larva hatches and feeds on its host in the manner of a parasitoid.

REFERENCES

Krogmann, L., & A. D. Austin. 2012. Systematics of Australian Agenioideus Ashmead (Hymenoptera: Pompilidae) with the first record of a spider wasp parasitizing Latrodectus hasselti Thorell (redback spider). Australian Journal of Entomology 51: 166–174.

Shimizu, A. 1997. Taxonomic studies on the Pompilidae occurring in Japan north of the Ryukyus: the genus Agenioideus Ashmead (Hymenoptera). Japanese Journal of Entomology 65 (1): 143–167.

Morion Revisited

In an earlier post, I introduced you to the carabid beetle genus Morion, currently recognised as including about forty species from tropical and subtropical regions around the world. In that post, I mentioned how Will (2003) had questioned the monophyly of this genus, owing to its lack of derived features in comparison with closely related genera. In this post, I'll take the opportunity to dive a little further into ways the genus may be divided.

Just to remind you what we're looking at: Morion monilicornis, copyright Robert Webster.

As noted by Will (2003), many authors have recognised two subgenera within Morion, Morion sensu stricto and Neomorion. These subgenera were first established by Jeannel (1948) who identified a distinction between species he examined from the Old World (Africa and Asia) and the Americas. The Old World species, to which Jeannel gave the name Neomorion, had a number of setae along the rear margin of the last ventrite of the abdomen. In males, the basal segment of the fore tarsus had the inner apex drawn out into a tooth. The aedeagus bears a large dorsoapical orifice; in Old World Morion examined by Jeannel, this orifice was covered over by a large bilobed lamella. In the New World species of Morion sensu stricto, in contrast, the rear margin of the last ventrite bore only two setae, and males lacked a medioapical tooth on the basal fore tarsomere. The opening of the aedeagus lacked a covering lamella. In his key to Morion and related genera, Will (2003) referred only to the state of the male fore tarsus as distinguishing the subgenera. It may be that this indicates that the significance of the other characters described by Jeannel had been subject to question, but I suspect that they may have omitted by Will because their state in a number of Morion species remains unknown.

Aedeagi of Morion in lateral and dorsal view from Jeannel (1948). On the left is an Old World species (Morion orientale), on the right a South American species (M. georgiae).

A particular notable lacuna in Jeannel's brief survey of Morion was that he didn't look at any Australian species. In his description of M. crassipes*, a species found in the vicinity of Cairns in Queensland, Sloane (1904) noted that the male fore tarsi differed from those of other Australian species in having the "basal joints rounded and not produced at inner apical angle", implying that most Australian Morion have tarsi resembling those of the New World species. Moore (1965), in a review of Australian genera of Pterostichinae, describes Morion as having an aedeagus with an orifice on the dorsum, with no mention of a covering lamella, again also suggesting a resemblance to New World rather than Old World species (unfortunately, Moore did not specify exactly which species his description of the genitalia was based on). Moore (1965) also noted that Australian species were distinctive among Morion in having a pronotum with more than the two setae along each lateral margin found in species from elsewhere. One species which is found in New Guinea and northern Australia, M. longipennis, does have only two pairs of marginal setae on the pronotum, and Darlington (1962) suggested that it was probably more closely related to Asian species than to other Australian Morion. The aforementioned M. crassipes differs from other Australian species in a number of significant features, including large size (it grows to a full inch in length) and modified legs, and Sloane (1904) did briefly wonder whether it should even be regarded as a Morion, but it does share the plurisetose pronotal margins. I should note that I've found no reference to the pilosity of the last ventrite in any Australian species.

*Under the name 'Morio crassipes'; confusion about whether this genus should be called Morion or Morio lingered for a long time in the early 20^th century.

So overall, there is the suggestion of three distinct groups within Morion, for the Old World, American, and Australian species, with the last two more similar to each other than to the first. The New World species of Morion are more diverse in South America than in North America, and one might be tempted to line up the relationship between the three groups with the division of Gondwana. The Old World species group may have diverged first with the separation of Africa and/or India, followed by the South American and Australian lineages diverging as their own continents became isolated. The South American species group may have spread into North America with the formation of the Central American land bridge, and the increased proximity of Australasia to Asia may have allowed members of the Old World group such as M. longipennis to invade from the northwest. However, I've based this scenario on some pretty weak assumptions based on very incomplete data, and it would require a more detailed investigation before we could say if there's any merit to it.

REFERENCES

Darlington, P. J., Jr. 1962. The carabid beetles of New Guinea. Part I. Cicindelinae, Carabinae, Harpalinae through Pterostichini. Bulletin of the Museum of Comparative Zoology 126 (3): 319–564, 4 pls.

Jeannel, R. 1948. Faune de l'Empire Français. X. Coléoptères Carabiques de la Région Malgache (deuxième partie). Office de la Recherche Scientifique Coloniale: Paris.

Moore, B. P. 1965. Studies on Australian Carabidae (Coleoptera). 4.—The Pterostichinae. Transactions of the Royal Entomological Society of London 117 (1): 1–32.

Sloane, T. G. 1904. Studies in Australian entomology. No. XIV. New species of geodephagous Coleoptera from tropical Australia. Cicindelidae (3), and Carabidae (5) [Platysmatini, Morioni, Perigonini, Masoreini, and Physocrotaphini]. Proceedings of the Linnean Society of New South Wales 29 (3): 527–538.

Will, K. W. 2003. Review and cladistic analysis of the generic-level taxa of Morionini Brullé (Coleoptera: Carabidae). Pan-Pacific Entomologist 79 (3–4): 212–229.

Pseudogagrella: A Harvestman Torn

The Sclerosomatidae are one of the most diverse of the currently recognised harvestmen families, and one of the most problematic when it comes to classification. In various earlier posts, I have noted the challenges that bedevil sclerosomatid systematics, many reflecting a historical focus on superficial external features of questionable evolutionary significance. Perhaps no taxon more neatly exemplifies the problems with higher sclerosomatid classification than the eastern Asian genus Pseudogagrella.

Pseudogagrella sakishimensis, copyright Tomoya Suzuki.

Historically, the greater number of sclerosomatids have been divided between two major subfamilies, the Leiobuninae and Gagrellinae. The Leiobuninae have mostly been recognised as living in the northern temperate regions whereas the Gagrellinae were mostly tropical. The division between the two subfamilies has long been regarded as more than a little fuzzy, and has usually hinged on a single feature: the presence (Gagrellinae) or absence (Leiobuninae) of rings of flexible integument (noduli) in the femora of the legs. Pseudogagrella is a genus of sclerosomatid harvestmen recognised from Japan, Taiwan, China and Sumatra (Chen & Shih 2017). Members of this genus lack leg noduli so have historically been included in the Leiobuninae. The problem is that their overall appearance, with a tendency to bold coloration, a tall median spine rising from the hardened scute covering most of the abdomen, and legs that are not merely long but ludicrously so (even by harvestman standards), is extremely similar to species of Gagrellinae. So much so, in fact, that some species currently placed in Pseudogagrella were long included in the archetypical gagrelline genus, Gagrella (Suzuki 1977).

With the distinction between the two subfamilies being so vague, I don't think it really came as that much surprise to anyone when molecular phylogenetics underlined the need for a thorough re-working of sclerosomatid systematics. Though the analysis conducted by Hedin et al. (2012) did not support the prior distinction between 'leiobunines' and 'gagrellines', it did suggest the existence of distinct lineages occupying distinct geographical regions. One species of Pseudogagrella included in the analysis (the southern Japanese P. amamiana) was placed in a cluster of eastern Asian species including other Asian 'gagrellines', but also the 'leiobunine' 'Leiobunum' japonicum. So it seems likely that, should subfamilies of Sclerosomatidae continue to be recognised, Pseudogagrella will indeed be a member of Gagrellinae, but Gagrellinae itself shall not quite be what people think of it as being.

Pseudogagrella dorsomaculata, copyright Tyus Ma.

There is also, of course, the question of whether Pseudogagrella itself is a coherent unit. Hedin et al. (2012) included only the one Pseudogagrella species in their analysis and the need for an extensive revision of the Asian sclerosomatid genera still remains. A study of Chinese species assigned to the genus Melanopa (Zhang & Zhang 2013), which is primarily distinguished from Gagrella by having relatively shorter legs, suggested the possibility of this 'genus' being divided between groups of Palaearctic and Indo-Malayan species, and I've wondered if this division might carry further (unfortunately, I'm not aware of any Indo-Malayan 'gagrellines' being included in molecular phylogenies; I think all the Asian species covered by Hedin et al. were Palaearctic). The majority of Pseudogagrella species, found in Japan and Taiwan, can be comfortably compared to other sclerosomatids from that region, but the Sumatran P. multimaculata, and possibly the southern Chinese species, might turn out to be closer to their own geographical peers. As always, a great deal of research remains to be done.

REFERENCES

Chen, S.-L., & H.-T. Shih. 2017. Descriptions of three new species of the harvestmen genus Pseudogagrella (Opiliones: Sclerosomatidae: Gagrellinae) from Taiwan, supported by morphological and molecular evidence. Zootaxa 4268 (1): 34–52.

Hedin, M., N. Tsurusaki, R. Macías-Ordóñez & J. W. Shultz. 2012. Molecular systematics of sclerosomatid harvestmen (Opiliones, Phalangioidea, Sclerosomatidae): geography is better than taxonomy in predicting phylogeny. Molecular Phylogenetics and Evolution 62 (1): 224–236.

Suzuki, S. 1977. Opiliones from Taiwan (Arachnida). Journal of Science of the Hiroshima University, Series B, Division 1 (Zoology) 27 (1): 121–157.

Zhang, C., & F. Zhang. 2013. Notes on some species of the genus Melanopa (Opiliones: Sclerosomatidae: Gagrellinae) from China, with description of a new species. Journal of Arachnology 41: 306–318.

Monkey Frogs

Following my last post, it looks like we're staying in the Neotropics for a while longer. The leaf frogs or monkey frogs of the Phyllomedusinae (a subfamily of the tree frog family Hylidae) are perhaps the most famous group of frogs to be found in South America. One particular species, the red-eyed tree frog Agalychnis callidryas, would for many people be the first image that comes to mind when they picture a frog, owing to its regular appearance in popular media.

The aforementioned red-eyed tree frog Agalychnis callidryas, copyright Carey James Balboa.

The phyllomedusines are a group of about sixty species of slender, arboreal frogs that live as ambush predators of invertebrates. The inner digits of the hands and feet are opposable and can be used to grasp slender twigs while adhesive pads at the ends of the digits allow the frog to grip onto flat surfaces such as leaves. Darren Naish at Tetrapod Zoology (Wayback Machine version; the current iteration of Tetrapod Zoology is at tetzoo.com) has described leaf frogs as superficially resembling "slow-climbing primates like lorises". Phyllomedusines will perch with all four hands and feet firmly grasping the substrate, waiting for suitable prey to inadvertently stray too close. Prey is captured by means of a highly protrusible tongue, not found in other hylids. In at least some species, light markings are present on the outer toes which may be drummed while in ambush to attract prey. Bertoluci (2002) suggested that the movement of these light patches in Phyllomedusa burmeisteri may resemble those of a worm or caterpillar but I would suggest that merely the appearance of the small moving points alone may pique a wandering arthropod's interest while the camouflaged remainder of the frog blends into the background.

Orange-legged tree frog Phyllomedusa oreades, copyright Danielvelhobio.

Though phyllomedusines begin their lives as aquatic tadpoles, their eggs are laid in clutches outside the water, in locations such as on leaves, tree trunks, rock crevices, etc. In some species, one or more leaves are folded together to construct a nest in which the eggs are laid. Some phyllomedusines in the genera Agalychnis and Cruziohyla are capable of gliding by means of extensive webbing on enlarged hands and feet and/or skin flaps on arms and legs. Interestingly, possession of gliding ability in phyllomedusines is correlated with explosive breeding patterns, suggesting that its main function is to facilitate synchronised movement of members of a population between their usual upper canopy habitat and suitable breeding locations near ground-level water bodies (Faivovich et al. 2009). Females of the two gliding genera (or sometimes a mating pair) may also spend time sitting in water prior to egg-laying; during this time, the female draws water into her bladder that she will then release over the eggs while laying them. In the majority of phyllomedusines (except Agalychnis) egg masses contain a mixture of eggs and empty, eggless capsules. In those species that construct nests from folded leaves, these extra capsules act as the glue holding the leaf surfaces together. Their function in other species is less obvious; they may help to protect the egg mass from drying out.

Upon hatching, the tadpoles will wriggle out of the egg mass to drop into a nearby body of water, whether a pond, a stream, or a pool of water collected in the hollow of a tree. After a childhood spent scraping algae for food, they will eventually transform into a new generation of frogs, ready to ascend once again into the trees above.

REFERENCES

Bertoluci, J. 2002. Pedal luring in the leaf-frog Phyllomedusa burmeisteri (Anura, Hylidae, Phyllomedusinae). Phyllomedusa 1 (2): 93–95.

Faivovich, J., C. F. B. Haddad, D. Baêta, K.-H. Jungfer, G. F. R. Álvares, R. A. Brandão, C. Sheil, L. S. Barrientos, C. L. Barrio-Amorós, C. A. G. Cruz & W. C. Wheeler. 2010. The phylogenetic relationships of the charismatic poster frogs, Phyllomedusinae (Anura, Hylidae). Cladistics 26: 227–261.

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.

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 2^nd 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.