Paradrillia

Paradrillia patruelis, from Joop Trausel and Frans Slieker.

Paradrillia is a genus of conoid gastropods found in the Indo-Pacific region, with a fossil record going back to the Miocene (Powell 1966; previous CoO posts on conoids can be found here, here, here and here). Species of Paradrillia are small shells, about one to three centimetres in length, with a relatively tall spire and short siphonal canal. The sculpture on the outside of the shell usually consists of nodular spirals; the operculum is leaf-like, with a terminal nucleus. The long, awl-shaped radular teeth are trough-shaped in cross-section (Kilburn 1988).

Paradrillia regia, from G. & Ph. Poppe.

The classification of Paradrillia has shifted around over the years, like most of the less differentiated conoids that were lumped by Powell (1966) under the heading of 'Turridae'. Powell (1966) classed them as Turriculinae, Kilburn (1988) transferred them to the Stictispirinae. Kilburn also synonymised Powell's separate genera Paradrillia and Vexitomina. Powell had distinguished them on the basis that Paradrillia supposedly had an operculum with a mediolateral nucleus instead of the terminal nucleus of Vexitomina. However, this was based on a single specimen that Kilburn regarded as teratological after he found terminal nuclei in Paradrillia melvilli. Most recently, Paradrillia was placed by by Bouchet et al. (2011) on the basis of molecular data in their new family Horaiclavidae.

REFERENCES

Bouchet, P., Yu. I. Kantor, A. Sysoev & N. Puillandre. 2011. A new operational classification of the Conoidea (Gastropoda). Journal of Molluscan Studies 77: 273-308.

Kilburn, R. N. 1988. Turridae (Mollusca: Gastropoda) of southern Africa and Mozambique. Part 4. Subfamilies Drilliinae, Crassispirinae and Strictispirinae. Annals of the Natal Museum 29 (1): 167-320.

Powell, A. W. B. 1966. The molluscan families Speightiidae and Turridae: An evaluation of the vaid taxa, both recent and fossil, with lists of characteristic species. Bulletin of the Auckland Institute and Museum 5: 1-184.

Beetle Flies

Unidentified celyphid, photographed by Giovzaid85.

Those of you who follow me on Twitter (@CatofOrg) may have already seen these guys, but I thought it worth putting them up here as well. Because sometimes you come across an animal that just makes you stop, blink, and exclaim, "What the creeping jayzus is that!". Ladies and gentlemen, the Celyphidae.

Another celyphid, photographed by Melvyn Yeo.

Celyphids are flies that are doing their damnedest to look like a beetle (and are hence, unsurprisingly, commonly known as beetle flies). The scutellum, which in most flies is a relatively small lobe of the thorax sitting behind and between the wings, has become massively enlarged and overtops the abdomen. The wings (which are full-sized and fully functional) slip in underneath the scutellum when folded back. Just to add to the overall beetle-osity of the thing, celyphids can be very shiny and metallic (check out the blue-black item here). The function of this giant scutellum is unknown; protection is the first thing that comes to my mind, but I don't know if the scutellum is any more sclerotised than the rest of the animal. One suggestion that has apparently been made is that the scutellum may provide extra buoyancy in flight (Tenorio 1972), to which I ask, is it hollow or something?

Photo by Meng Foo Choo.

Celyphids are found in tropical Asia and Africa (all the photos on this page except the last were taken in Singapore). They are closely related to the more widespread family Lauxaniidae, and have been treated by at least some authors as a derived subgroup of the latter (some lauxaniids also show a degree of enlargement of the scutellum). The larvae of celyphids feed on rotting vegetation.

Celyphus koannanius, from here.

REFERENCE

Tenorio, J. M. 1972. A revision of the Celyphidae (Diptera) of the Oriental Region. Trans. R. Ent. Soc. Lond. 123 (4): 359-453.

Yponomeutoids and their Boring Larvae

...because some puns will never die.

Larvae of the bird-cherry ermine moth Yponomeuta evonymella, from here.

As noted in an earlier post, most people's perception of Lepidoptera, 'butterflies and moths', is heavily skewed towards the larger members of the group while the greater diversity is actually to be found among the smaller species (this sentence, offhand, could be repurposed for just about any animal group). The subject of today's post, the Yponomeutoidea, are a clade of about 1800 species of the much-overlooked smaller Lepidoptera. Yponomeutoids have been recognised as a group primarily on the basis of a single synapomorphy, the presence of posterior lobes on the eighth abdominal pleura (a 'pleuron' being a sclerite on the side of the body wall). This character has been secondarily lost in some subgroups of the Yponomeutoidea, but the clade is also supported by molecular data (Sohn et al. 2013). The larvae of yponomeutoids are plant-feeders, with the clade including some species that feed internally as leaf-miners or stem-borers, and others that feed externally on leaves though they do conceal themselves within a silk webbing. A number of species are effectively both, starting out as internal leaf borers then changing to external leaf webbers as they grow larger. Some species are notable horticultural pests, such as the diamondback moth Plutella xylostella that attacks brassicas*.

*Horticulture is the only human endeavour in which you will hear something described as 'attacking' a cabbage.

Apple leaf miner Lyonetia clerkella, photographed by Jeff Higgott.

The most recent review of the clade's systematics by Sohn et al. (2013) recognised eleven families within the Yponomeutoidea, but this was not the first re-organisation of the yponomeutoids and it will probably not be the last. Many of the families have few distinct synapomorphies, and a few recognised by Sohn et al. lack recognised morphological synapomorphies altogether and are united by molecular analysis only. Most yponomeutoids follow the usual microlepidopteran pattern of being small and generally brown, but there are some exceptions. The 'mega-plutellids' of New Zealand and Tasmania (placed by Sohn et al. in the family Glyphipterygidae rather than Plutellidae) are relatively large, with the Tasmanian Proditrix nielseni having a wingspan of over six centimetres (McQuillan 2003). The adult of the ailanthus webworm Atteva pustulella has a fairly striking array of black-ringed white patches on an orange background.

Galapagos bitterbush moth Atteva hysginiella, photographed by Rich Hoyer.

Though the clade is diverse in its habits overall, feeding habits tend to be conserved within each of the constituent families. It is not entirely clear whether internal or external feeding represents the original lifestyle of the yponomeutoids, though there may be a slight tip towards internal feeding. If this is the case, then external feeding has arisen within the yponomeutoids on a number of occasions, and the pine needle miners of the genus Zelleria in the family Yponomeutoidea probably represent at least one case of a internal feeder derived from externally feeding ancestors. Some families show a bias towards particular plant hosts: the Attevidae are primarily found on Simaroubaceae, while the Bedeliidae show a preference for Convolvulaceae. Others are more diverse in their selection.

REFERENCES

McQuillan, P. B. 2003. The giant Tasmanian ‘pandani’ moth Proditrix nielseni, sp. nov. (Lepidoptera: Yponomeutoidea: Plutellidae s. l.) Invertebrate Systematics 17: 59-66.

Sohn, J.-C., J. C. Regier, C. Mitter, D. Davis, J.-F. Landry, A. Zwick & M. P. Cummings. 2013. A molecular phylogeny for Yponomeutoidea (Insecta, Lepidoptera, Ditrysia) and its implications for classification, biogeography and the evolution of host plant use. PLoS One 8(1): e55066. doi:10.1371/journal.pone.0055066.

Majids: Crabs with Stylish Hats

Aggregation of large spider crabs Leptomithrax gaimardii, photographed by Peter Fuller.

The subjects of today's post, the Majidae, commonly go by the names of spider crabs or decorator crabs. The first of those names might sound like some people's ultimate nightmare, but I doubt that anyone could complain about the latter. Majids are characterised by having a carapace longer than wide, often with a covering of bristly hooked setae and relatively long legs (hence the name 'spider crab'). They get their alternate name of 'decorator crab' from the habit of many species of using the aforementioned hooked setae to attach algae and other bits of organic matter to themselves. The primary purpose of this adornment is to provide camouflage, and a decorated spider crab can be inordinately difficult to see when not moving. A secondary use of the crab's organic covering, however, is that they will also feed on material from it in times of need*.

*It is perhaps fortunate for Gaga that the question was never raised of her doing the same.

Triangle crab Eurynolambrus australis, from here.

The circumscription of the Majidae is more than a little fluid: at times, it has been used to include all the spider crabs of the superfamily Majoidea, but the more common practice these days is to divide the majoids between a number of families. Unfortunately, authors have disagreed about what those families should be. Ng et al. (2008) united the subfamilies Majinae and Mithracinae within the Majidae on the basis of shared features such as a well-developed protective orbit around the eyestalk. However, a direct relationship between majines and mithracines is not currently supported by molecular (Hultgren & Stachowicz 2008) or larval (Marques & Pohle 1998) data, though both these latter data sources are themselves limited by the relatively small number of studied taxa. Two smaller subfamilies included by Ng et al. (2008) in the Majidae, the Planoterginae and the isolated species Eurynolambrus australis, have not yet been analysed molecularly. Eurynolambrus australis is a particularly unusual little majid, so much so that it looks more like a parthenopid than a majid. Eurynolambrus also lacks hooked setae and so does not decorate itself; instead, it relies for disguise on its resemblance in colour to the coralline algae amongst which it lives (and on which it primarily feeds, though it is omnivorous overall—Woods & McLay 1996). Ng et al. placed it in the Majidae nevertheless owing to the resemblance of its larval stages to those of Majinae.

Channel clinging crab Mithrax spinosissimus, photographed by Nick Hobgood.

The two main subfamilies, the Majinae and Mithracinae, can be distinguished by the development of the orbit around the eyestalk. In the Mithracinae, the orbit is broadly expanded both above and below (with the lower margin formed from an expansion of the basal antennal segment), almost entirely enclosing the eyestalk and giving the front of the carapace a distinctly broad appearance in dorsal view. In the Majinae, the basal antennal segment is not expanded to form an underside to the orbit, so the eyestalks are contained from above only (Davie 2002). The Majinae are most diverse in the Indo-West Pacific, with only a handful of genera found outside this region. Some majines are quite large: the Australian Leptomithrax gaimardii reaches a leg-span of about 70 cm. The Mithracinae are more pantropical inhabitants of shallow water reefs.

REFERENCES

Davie, P. J. F. 2002. Zoological Catalogue of Australia vol. 19.3B. Crustacea: Malacostraca: Eucarida (part 2): Decapoda—Anomura, Brachyura. CSIRO Publishing: Collingwood (Australia).

Hultgren, K. M., & J. J. Stachowicz. 2008. Molecular phylogeny of the brachyuran crab superfamily Majoidea indicates close congruence with trees based on larval morphology. Molecular Phylogenetics and Evolution 48: 986-996.

Marques, F., & G. Pohle. 1998. The use of structural reduction in phylogenetic reconstruction of decapods and a phylogenetic hypothesis for 15 genera of Majidae: testing previous larval hypotheses and assumptions. Invertebrate Reproduction and Development 33 (2-3): 241-262.

Ng, P. K. L., D. Guinot & P. J. F. Davie. 2008. Systema brachyurorum: part I. An annotated checklist of extant brachyuran crabs of the world. Raffles Bulletin of Zoology 17: 1-286.

Woods, C. M. C., & C. L. McLay. 1996. Diet and cryptic colouration of the crab Eurynolambrus australis (Brachyura: Majidae) at Kaikoura, New Zealand. Crustacean Research 25: 34-43.

The Legacy of Rhampsinitus

According to the Histories of Herodotus, Rhampsinitus was a pharaoh of Egypt who ordered the construction of a secure storehouse for his wealth. However, the architect in charge of the storehouse's construction installed a secret entrance into it without the pharaoh's knowledge. The architect later told his two sons about the secret entrance, which they then used to help themselves to a share of the pharaoh's treasure. Unable to detect how the thieves were getting in, Rhampsinitus ordered a man-trap to be placed inside the storehouse, and the next time the thieves got in, one of them was caught by the trap. As there was no chance of escape, the remaining thief cut off his brother's head to prevent identification. Nevertheless, Rhampsinitus held onto the headless body and ordered his soldier's to look out for anyone showing signs of recent bereavement.

Through a ruse involving a pair of donkeys, a cartload of wine and some arguably irresponsible guards, the thief was able to recover his brother's body from the pharaoh, escaping both capture and his mother's complaints about his brother's mistreatment. Rhampsinitus therefore came up with another scheme to catch the thief: he ordered his daughter to offer herself up in a brothel to whoever would tell her the greatest misdeed he had committed. The thief did indeed confess his crimes to the daughter, who was apparently just that enticing. But when she attempted to grab hold of him and call for the guards, he escaped by palming a hand cut from a body that he had hidden up her sleeve. When he was told how the thief had eluded him again, Rhampsinitus was so impressed by the man's audacity and cunning that he ordered him pardoned. When the man came forward, Rhampsinitus gave him his daughter for a wife.

Male Rhampsinitus hispidus, from Roewer (1923). This would appear to be a species that lives up to its name; others are not quite so flagrantly spinose.

Modern historians agree that Rhampsinitus probably never existed, at least not as he was portrayed by Herodotus (while the accusation that Herodotus was the 'father of lies' is more than a little unfair, it must be admitted that he was not always one to let a little thing like historical accuracy stand in the way of a good story). Nevertheless, his name lives on today in southern Africa: in 1879, the French arachnologist Eugene Simon gave the name Rhampsinitus to a genus of long-legged harvestmen. Simon did not give any explanation for his choice, and it is possible that there was no direct reason: many authors gave random classical names to genera. Alternatively, it may be that the crown of denticles on the eyemound of this genus inspired Simon to give it a suitably regal name.

The long-legged harvestman fauna of sub-Saharan Africa is dominated by members of the subfamily Phalangiinae, which largely have the region to themselves except a few relictual Neopilionidae restricted to the southernmost part of the continent. Rhampsinitus is currently the largest recognised genus of African phalangiines, with over forty species. The centre of diversity for the genus is in the southern region, but it extends north to Zaire, Uganda and Kenya (possibly to Somalia, though the assignment of the Somalian species to Rhampsinitus has been questioned—Staręga 2009). Rhampsinitus is one of a group of African phalangiines (including Guruia and Dacnopilio, but not Cristina) in which the males have enlarged chelicerae similar to those of Australasian 'monoscutids'*. In the absence of a formal phylogenetic study of the Phalangiinae, it remains an open question whether these large-chelicerate genera form a clade. Schönhofer (2008) looked briefly at variation in male chelicera length (which can be considerable) within one species, Rhampsinitus transvaalicus; his results suggest an allometric relationship between body size and chelicera length for this species at least.

*A few years back, I was sent a pile of 'monoscutids' from the California Academy of Sciences to identify. While they're still waiting for me in the cupboard (sorry, guys!), I could see when I unpacked them that many were in fact African phalangiines that had been misidentified due to this character.

Relationship between altitude and eyemound ornamentation, as illustrated by Kauri (1961).

A number of species in this genus have interesting distributions, often related to altitude. Thus, in South Africa, Rhampsinitus leighi is found in lowland habitat from sea level to 800 m, while R. transvaalicus inhabits montane forest above 1200 m (Staręga 2009). Kauri (1961) made a comparison of morphometrics and altitude in South African Rhampsinitus: montane species had much shorter legs relative to body size than the lowland R. leighi. There was also a difference in development of ornamentation: R. maculatus, collected at 10,000 feet above sea level, had the denticles on the eyemound reduced to mere spicules, in contrast to the ornate, almost antler-like outgrowths of R. leighi.

REFERENCES

Kauri, H. 1961. Opiliones. In: Hanström, B., P. Brinck & G. Rudebeck. South African Animal Life: Results of the Lund University Expedition in 1950–1951 vol. 8 pp. 9–197. Almqvist & Wiksell: Uppsala.

Schönhofer, A. L. 2008. On harvestmen from the Soutpansberg, South Africa, with description of a new species of Monomontia (Arachnida: Opiliones). African Invertebrates 49 (2): 109-126.

Staręga, W. 2009. Some southern African species of the genus Rhampsinitus Simon (Opiliones: Phalangiidae). Zootaxa 1981: 43-56.

Ceratium...er...Neoceratium...er...Tripos humilis

The dinoflagellate formerly known as Ceratium humile, from here.

Ceratium has long been a popular choice as a representative dinoflagellate genus for textbooks, because as micro-organisms go, they're fairly specky. The theca of Ceratium is characterised by protruding horns, with an elongate anterior horn and one to three posterior horns. The posterior horns may be directed back from the theca, or they may curve around towards the front to produce an anchor-like shape. These horns increase the cell's buoyancy, though they do make them fairly slow swimmers. The concept of Ceratium has been fairly stable since the early 1800s, but Gómez et al. (2010) found when conducting a molecular analysis of a number of 'Ceratium' species that there was a deep divide between freshwater and marine Ceratium species. As well as the molecular divide, there is also a morphological difference: freshwater species have six plates around the cingulum (the groove around the theca body in which sits one of the flagella), while marine species have five cingular plates. As a result, Gómez et al. proposed dividing the two clades between two genera, with the name Ceratium being restricted to the freshwater species. The marine species were all transferred into a new genus Neoceratium. However, Gómez (2013) later recognised that there were a number of older generic names floating about that had been given to marine taxa, and the marine species were moved again into a resurrected genus Tripos. Among the taxa affected by this double transfer was the species shown in the photo above, now known as Tripos humilis.

There are a large number of anchor-shaped Tripos species, and distinguishing them is apparently a difficult process. Tripos humilis has the anterior part of the theca in front of the cingulum (excluding the anterior horn) fairly low, the upper surface of the theca (i.e. the side away from the origin of the flagella) strongly convex, and the right-hand posterior horn much longer than the left, with the right horn tending to converge towards the anterior horn while the left horn diverges (Subrahmanyan 1968). The cingulum is also distinctly angled relative to the posterior margin of the theca. While other Tripos species are found in a range of habitats, T. humilis appears to be a more specifically tropical species. It is found pantropically, though seemingly nowhere abundantly.

Chain of Tripos, from here.

Dinoflagellates can sometimes form long chains when dividing individuals don't fully separate but continue to multiply. In Ceratium and Tripos species, the members of a chain remain connected through the apical horns. Chaining individuals may be somewhat morphologically distinct from isolated individuals; in T. humilis, the horns of chained individuals are relatively much shorter. Chains are apparently commoner when dinoflagellates form 'red tides' or algal blooms, and one suggested function is that a chain is able to swim faster overall than an individual, improving the dinoflagellates' ability to compete when moving to occupy suitable places in the water column for light or food.

REFERENCES

Gómez, F. 2013. Reinstatement of the dinoflagellate genus Tripos to replace Neoceratium, marine species of Ceratium (Dinophyceae, Alveolata). CICIMAR Oceánides 28(1): 1-22.

Gómez, F., D. Moreira & P. López-García. 2010. Neoceratium gen. nov., a new genus for all marine species currently assigned to Ceratium (Dinophyceae). Protist 161: 35-54.

Subrahmanyan, R. 1968. The Dinophyceae of the Indian Seas. Part I. Genus Ceratium Schrank. Marine Biological Association of India, Memoir 2: 1-129.

Pitchfork Mosses

Dicranum flagellare, photographed by Sue. The upright green stalks are the brood branches.

The subject of today's post is the cosmopolitan moss genus Dicranum, sometimes known as fork mosses or, apparently, wind-blown mosses. Dicranum species are characterised by elongate narrow leaves and an erect, often forked growth habit. In some habitats, Dicranum species may form reasonably extensive turfs. The genus name comes from the Greek word for a pitchfork and apparently refers to the teeth of the peristome (the ring of teeth around the opening of the spore capsule) though, if this is true, naming these mosses after a feature of the spore capsule may not necessarily have been the best idea. Many Dicranum populations produce sporophytes relatively rarely (a diagram of the moss life cycle was included in this post). Instead, these populations more commonly reproduce asexually through the production of vegetative propagules by the gametophyte. Once such species, the Holarctic Dicranum flagellare, produces terminal clusters of reduced branches, called 'brood branches'. If detached from the parent plant, these brood branches can grow into a new moss. A notable dispersal agent for brood branches, as it turns out, is slugs (Kimmerer & Young 1995). Brood branches break off the parent plant as the slug crawls past them, adhering to the slug by means of its slime. The trail of slime left by the slug also greatly improves the chance of a brood branch adhering to a suitable substrate once it becomes separated from its transport.


Dicranum scoparium, photographed by Li Zhang.

Because of the rarity of sporophytes, species of Dicranum are mostly distinguished by features of the leaves. Dicranum leaves may be straight or curved, the edge of the leaf may be smooth or toothed, and the blade of the leaf may be composed of one or two cell layers. Many species are characterised by the shape of the leaf in transverse section (Hedenäs & Bisang 2004). When sporophytes are produced, Dicranum species are dioicous: that is, they have separate male and female plants. However, in a number of species, the male plants are reduced in size and grow epiphytically on the leaves or rhizoids of the larger female plants. At least one species, Dicranum scoparium, has both dwarf and full-sized males (Hedenäs & Bisang 2004). Some Dicranum species have wide distributions, with a number found almost throughout Eurasia and North America, but others have more restricted distributions (D. transsylvanicum, for instance, is known from a single location in western Romania). Dicranum species are often very selective habitat-wise, with species differing in their choice of habitat, and they have been used as indicators of environmental conditions. This habitat selectivity can result in fragmented species distributions: for instance, Dicranum muehlenbeckii (which grows in dry, calcareous or mineral-rich environments) is found in central Europe, but is also known from a single locality in central Sweden. Dicranum scoparium, a more generalist species found in both humid and dry conditions, is widespread in Eurasia and North America, but is also known from New Zealand and a single region of Australia, near Mt Kosciuszko in New South Wales. As noted in a previous post, much ink has been spilled as regards the biogeographic processes underlying disjunct distributions in moss taxa. In that light, it should be pointed out that, while Australian and New Zealand specimens of Dicranum scoparium do tend to be less robust than the average Holarctic specimen, no molecular differences have yet been identified between the populations (Klazenga 2012).

REFERENCES

Hedenäs, L., & I. Bisang. 2004. Key to European Dicranum species. Herzogia 17: 179-197.

Kimmerer, R. W., & C. C. Young. 1995. The role of slugs in dispersal of the asexual propagules of Dicranum flagellare. The Bryologist 98 (1): 149-153.