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.