Flower-tails

The patterned anthurid Mesanthura astelia, from Museum Victoria.

Anthuroidea (or Anthuridea, depending on where you look) are small marine isopods that get up to a couple of centimetres in length. Anthuroids are distinguished from other isopods by their particularly narrow, elongate body form, as well as (in most species) their tail-fans with the component uropods arranged in a manner reminiscent of a 'five-petalled flower' (hence the name of the group, 'flower-tails'). The one exception is the recently described Leipanthura casuarina in which the uropod branches are cylindrical rather than flattened; Leipanthura is a very small species (less than 3 mm long) and probably represents a neotenous form retaining a juvenile tail morphology into adulthood (Poore 2009).

The question of whether this group should be called Anthuridea or Anthuroidea relates to different proposals on their phylogenetic position. The name 'Anthuridea' is older (replacing an even earlier name, Aberrantia, that does not appear to have any recent usage) but was changed to Anthuroidea by Brandt & Poore (2003) when they reclassified anthuroids from a separate 'suborder' of isopods to a 'superfamily' within the suborder Cymothoida. In a more recent analysis by Wilson (2009), the monophyly of Cymothoida was supported by morphological data alone, but not by molecular data or combined analysis (in particular, several parasitic 'cymothoid' families such as Gnathiidae and Bopyridae formed a clade in the latter analyses that was sister to all other isopods). As the composition of the anthuroids has never altered under either name, the question of orthography is largely academic.

Individual of Paranthura elegans, photographed by Peter J. Bryant. Paranthura belongs to a separate family (Paranthuridae) from Mesanthura (Anthuridae); the families are distinguished by the mouthparts of Paranthuridae being modified into piercing stylets, as opposed to the chewing mouthparts of Anthuridae.

Anthuroids live hidden among sponges, corals, seaweeds, etc. or burrowed into sand, where they are active hunters of smaller invertebrates (as evidenced by their raptorial forelimbs). They have most commonly been recorded from shallow waters, but are also known from the deep sea (Kensley 1982). It is unclear whether their supposed rarity in deep-sea collections reflects poorer investigation, or whether the morphological conservatism of anthuroids compared to other isopod groups has restricted their ecological diversity. At least some species are protogynous sequential hermaphrodites (Brusca et al. 2001), that is, they begin life as females and transform later into males.

REFERENCES

Brandt, A., & G. C. B. Poore. 2003. Higher classification of the flabelliferan and related Isopoda based on a reappraisal of relationships. Invertebrate Systematics 17 (6): 893-923.

Kensley, B. 1982. Deep-water Atlantic Anthuridea (Crustacea: Isopoda). Smithsonian Contributions to Zoology 346: 1-60.

Poore, G. C. B. 2009. Leipanthura casuarina, new genus and species of anthurid isopod from Australian coral reefs without a “five-petalled” tail (Isopoda, Cymothoida, Anthuroidea). ZooKeys 18: 171–180.

Wilson, G. D. F. 2009. The phylogenetic position of the Isopoda in the Peracarida (Crustacea: Malacostraca). Arthropod Systematics and Phylogeny 67 (2): 159-198.

Name the bug # 52

Does this look familiar to anyone?

Attribution to follow.

Update: Identity now available here. Photo from here.

Origins - A Day in the Broom Room

Welcome to something rather special: after nearly four years, this is Catalogue of Organisms' first ever guest post. Ted MacRae usually writes about tiger beetles and other insects at his own excellent site, Beetles in the Bush, but he has provided a post for this site after winning at 'Name the Bug'. For it, he has selected a topic with a history arguably far more complicated than it should have ever needed to be: human evolution. I hope you all enjoy, and anyone who isn't familiar with Ted's own site already should check it out.--Christopher Taylor.

I may be better known for my interest in entomology, having studied insects all of my adult life and much of my childhood. Entomology, however, was only one of many subjects that piqued my interest as a child, the other big ones being evolution and paleontology, and - especially - human evolution. Obviously, Insecta won out over Australopithecus as the focus of my career pursuits, but I've remained a bit of a closet paleoanthropologist ever since and try to stay abreast of the ever-increasing pace of significant fossil finds that the field enjoys. For the most part, staying abreast has, for me, involved reading both primary journal articles and popular books on the subject. I could rattle off the names and numbers of paleoanthropology’s most famous hominid fossils as easily as I could the genera of Buprestidae. Little did I realize that one day I would have the opportunity to behold, with my own eyes, some of the very fossils that I had read about for so many years.

In 1999, I had the opportunity to travel to South Africa to spend some time in the field with my friend and colleague, Chuck Bellamy, who at the time was serving as Senior Curator in the Coleoptera Department at the Transvaal Museum (now the Ditsong National Museum of Natural History) in Pretoria. During my visit, and learning of my interest in paleoanthropology, Chuck arranged for me a private tour of the 'Broom Room' with its curator, Dr. Heidi Fourie. The Broom Room houses some of the most important fossils of early hominids in the world, including the famous Sterkfontein (STS) 5 'Mrs Ples' and Swartkrans (SK) 48 crania. The bulk of the fossils were discovered by Robert Broom, Raymond Dart, and their successors at the famous Sterkfontein and Swartkrans hominid sites in the northeastern part of the country. Australopithecus africanus, Paranthropus robustus, and some of the earliest known members of the genus Homo (recently described as H. gautangensis) are represented among the fossils, which range from 1.5 to 2.8 million years in age.

When Robert Broom first arrived in South Africa in 1936 and saw Raymond Dart's recently discovered 'Taung child" - the first known Australopithecus fossil, he is said to have knelt at the edge of the table containing the fossil and exclaimed, "I behold my ancestor!" Such was the feeling I had when I first entered the Broom Room and saw the rich wooden cabinets and rows of fossils neatly arrayed on its red felt-lined shelves. I knew which fossil I wanted to see first - Mrs. Ples, the most complete Australopithecus africanus cranium known, discovered at Sterkfontein in 1947 by Robert Broom and John Robinson. Originally named Plesianthropus transvaalensis, it was subsequently regarded to be conspecific with the Taung Child and thought to represent an adult female (most researchers now regard it to represent a sub-adult male). As Dr. Fourie held the cranium for me to look at, I noticed the fossil was about 3.5 feet off the floor - about the presumed height for the species. I suddenly saw Mrs. Ples standing before me in life - a living, breathing being, not an animal, yet not quite human either. I may not have used Broom's precise words, but I whispered something along those lines to myself as the slender, hairy virtual creature stood before me. The Museum Gift Shop was selling plaster replicas of Mrs. Ples, one of which now sits on the desk in my office. I think about that experience at the Transvaal Museum almost everytime I look at it.

Among the other A. africanus fossils I noticed was a partial cranium, also discovered by Broom at Sterkfontein in 1947. While not as complete as Mrs. Ples (missing portions of its left side), it was subsequently associated with a mandible found in the same layer (STS 36) by matching wear patterns on the teeth - making it one of the most complete A. africanus skulls to have been found. Originally classified as a female, this 2.5 million year old cranium is smaller and less prognathous (forward projecting mouth) than other known A. africanus crania. However, its large post-canine teeth and indications of massive chewing muscles suggest it is a male.

Skulls are not the only cranial fossils represented in the collection. Endocranial casts as well have been found in the same deposits from which the crania were taken, and I actually got to hold STS 60 in my own hands! With a chimp-like volume of 428 cubic centimeters, it's a bit on the small side of normal for A. africanus (nearly 60 cc less than the brain capacity of Mrs. Ples, though equaling that of STS 71). Holding it in my hands, I mentally compared its size with that of my own brain and tried to imagine the cognitive differences implied by such difference (okay, no jokes here!).

Broom recognized that the australopithecine fossils he was finding in South Africa represented two distinct morphs - a "gracile" form now encompassed by A. africanus, and a more "robust" form that he described in 1938 as Paranthropus robustus. The fossils from Swartkrans conform to this latter type, with the most complete cranium being SK 48, discovered by Broom and Robinson in 1952 and dated to between 1.5 and 2.0 million years in age. It should be noted that the term "robust" refers not to the size of the body, but rather the characters of the skull that include a more prominent sagittal crest in males, greater sexual dimorphism in body size, and robust zygomatics and mandible with large, thickly enameled post-canine dentition. The Museum Shop had a plaster replica of SK48 as well, which also now sits on the desk in my office.

It should be noted that not everyone in the field accepts Paranthropus as a valid genus distinct from Australopithecus. There is little doubt that the included species represent a derived and specialized form, but whether P. robustus from South Africa and the two east African species P. aethiopicus and P. boisei form a monophyletic clade is still an open question. There is some evidence to suggest that P. robustus is descended from A. africanus because of similarity of some derived features with the latter, which if correct would render Paranthropus paraphyletic and not a valid taxon (Conry 1997). This view, necessarily, suggests also that the hyper-masticatory adaptations of robust australopithecines evolved independently in eastern and southern Africa. While this certainly could have happened, (Strait et al., 1997) argue that a more parsimonious interpretation of multiple morphological traits suggests Paranthropus is indeed monophyletic and that it should be retained as a valid genus. Either way, Paranthropus certainly represents a distinct “grade” of australopithecines, and until more convincing data to the contrary are produced I prefer to recognize it as a valid genus.

The massive mandibles that distinguish P. robustus from the gracile australopithecines are richly represented among the Swartkrans material (one can imagine that these robust bony structures are prone to preservation), including SK23 (discovered at the same time and dated to the same age as the SK 48 cranium) and SK 12 and the SK 52 partial skull (see photos). Presumably these morphological adaptations of the mandible/maxilla and associated musculature are related to a more specialized diet of tough plant material that required considerable chewing to process, compared to the more omnivorous A. africanus that pre-date them.



Also amongst the P. robustus fossils is SK 1585, the only endocranial cast known for the species with a volume of 530 cc. Combined with SK 48 and other partial and cranial remains that have been recovered for the species, it appears that the brain of P. robustus averaged slightly larger than that of the earlier A. africanus. Whether this translates to increased cognitive function is open for debate, although there are some structural differences in SK 1585 compared to A. africanus endocranial casts that suggest this could be the case.

Perhaps the most contentious fossil in the Broom Room is SK 847, a highly fragmentary partial cranium discovered at Swartkrans in 1969 by Ronald Clarke and dated to between 1.5 and 1.8 million years. Originally thought to represent P. robustus due to its association with other fossils of that species, it was eventually associated with a maxilla (SK 80) originally described as Telanthropus capensis and later included in Homo erectus. The affinities of the composite specimen were contentious, and at the time of my visit its classification remained unresolved (Johanson and Edgar 1996). More recent studies have suggested that this and other South African specimens represent a species not previously sampled in east Africa, and the specimen was eventually included as a paratype in the description of a new species, Homo gautangensis, the newest member and earliest representative of its - our - genus (Curnoe 2010).



REFERENCES:

Conroy, G. C. 1997. Reconstructing human origins: a modern synthesis. New York, Norton.

Curnoe, D. 2010. A review of early Homo in southern Africa focusing on cranial, mandibular and dental remains, with the description of a new species (Homo gautengensis sp. nov.). Journal of Comparative Human Biology 61(3):151–77.

Johanson, D. and B. Edgar. 1996. From Lucy to Language. New York: Simon and Schuster Editions.

Strait, D. S., F. E. Grine and M. A. Moniz. 1997. A reappraisal of early hominid phylogeny. Journal of Human Evolution 32:17-82.

Copyright © Ted C. MacRae 2011

A Vision of Thrips

The giant thrips Idolothrips spectrum, drawn by Geoff Thompson.

The thrips are one of the more undeservedly obscure groups of insects, largely because of their generally small size. When they do get attention, it is usually as horticultural pests, living amongst fresh growth of garden plants, and causing unsightly blemishes to form on flowers and fruit due to their feeding. However, the thrips are more than just nuisances, and include many forms for which the gardener's ire would be unwarranted. For instance, consider today's subject, the Idolothripini, which do not feed on young shoots but on fungal spores, hunting them down amongst leaf litter and under bark.

As a whole, thrips have a very characteristic form that makes them readily distinguishable from other insects. Their wings (at least in those species that have them) are relatively long and strap-like, with few or no veins and a long fringe of hairs. The mouthparts are long and tubular, as well as asymmetrical with the mandible being developed on only one side, and feeding is down via a long pair of maxillary stylets that are retracted into the head when resting. Thrips are also one of the groups of insects that lead themselves most readily to anthropomorphisation, with the framing of the head by the forelegs when slide-mounted (the usual method of studying these small insects) often giving the impression of waving, shaking of fists, or other expressions. Such impressions are accentuated by the fact that the normal insect claws on each foot are replaced by an adhesive bladder. Idolothripini belong to the thrips family Phlaeothripidae, distinguished from other families by the complete absence of veins in the wings and the development of the final abdominal segment into a long tube, often used for the secretion of protective chemicals*. Large phlaeothripids (I can't say exactly which species) become very visible here in Perth when dispersing at certain times of year; when they land, their long mobile abdomens give them an almost reptilian appearance. Phlaeothripids are in turn divided between the Phlaeothripinae and Idolothripinae on the basis of the appearance of the maxillary stylets: very narrow in Phlaeothripinae, broader in Idolothripinae. Mound and Palmer (1983) expressed the view that the Phlaeothripinae are probably paraphyletic with regard to the Idolothripinae, and though the basis for this proposal was not clear it is consistent with the (admittedly limited) available molecular data (Mound & Morris 2007). Mound and Palmer (1983) divided the Idolothripinae into the tribes Idolothripini and Pygothripini, though Pygothripini was explicitly paraphyletic to Idolothripini.

*I've seen specimens of the phlaeothripine Gynaikothrips curl their abdomen above their thorax like miniature scorpions and move it back and forth in a manner suggesting that they were releasing some offensive spray that I was not sensitive enough to detect.


Head (antennae removed) and pronotum of Lasiothrips perplexus, showing the broad maxillary stylets outlined by dashes. Figure from Mound and Palmer (1983) via World Thysanoptera.

As defined by Mound and Palmer (1983), Idolothripini lacked sutures in the metathoracic sternopleuron, one of the plates of the exoskeleton on the underside of the thorax. Most Idolothripini also had at least two pairs of wing-retaining setae on each abdominal segment, specialised hooked setae on the backs of phlaeothripids that hold the wings back when at rest* (due to the absence of veins, phlaeothripid wings are very floppy), but Mound and Palmer also included some species with only single pairs of wing-retaining setae that they regarded as more generally similar to other Idolothripini. These single-paired taxa have been referred by Retana-Salazar (2009) to a new tribe Anactinothripini.

*The wing-retaining setae can make slide-mounting phlaeothripids a little trickier than other thrips, as the wings must often be unhooked from the setae before being spread on the slide. This can be even trickier than it sounds, because even once unhooked the wings have a definite tendency to simply reattach themselves to the setae like the opposing sides of a strip of velcro.


Head and pronotum of Hartwigia tumiceps. Figure from Mound and Palmer (1983), via World Thysanoptera.

Within the Idolothripini, a range of morphologies can also be found. Many species have the part of the head bearing the antennae protruding noticeably in front of the eyes. This is taken to its most extreme form in the Indian Tiarothrips subramanii, in which the preocular head process is nearly as long as the remainder of the head. Mecynothrips kraussi from the Solomon Islands has a comparable process, but with an apparently different derivation: in Tiarothrips, the process has mostly formed from the parts of the head in front of the ocelli, with the median ocellus only a little in front of the eyes, but in M. kraussi the median ocellus is located well in front of the eyes, more than half-way down the extended process. Another particularly notable species is the South African Hartwigia tumiceps, a thrips which has evolved into an ant-mimic. Hartwigia has a remarkably swollen head: in most phlaeothripids, the head is roughly oblong in shape and distinctly narrower than the pronotum (the first thoracic segment), but that of Hartwigia is almost globular and wider than the pronotum, as well as being covered by an abundance of small setae. It also has white markings on the bases of its legs that make the thorax appear narrower, and a raised section towards the end of the thorax that mimics the node of an ant's petiole (Stannard 1976).

REFERENCES

Mound, L. A., & D. C. Morris. 2007. The insect order Thysanoptera: classification versus systematics. Zootaxa 1668: 395-411.

Mound, L. A., & J. M. Palmer. 1983. The generic and tribal classification of spore-feeding Thysanoptera (Phlaeothripidae: Idolothripinae). Bulletin of the British Museum of Natural History 46 (1): 1-174.

Retana-Salazar, A. P. 2009. Monografía de los grupos genéricos: Anactinothrips - Zeugmatothrips (Tubulifera: Idolothripinae). ECIBRC: San Jose (Costa Rica).

Stannard, L. J., Jr. 1976. A synopsis of some ant-mimicking thrips, with special reference to the American fauna(Thysanoptera: Phlaeothripidae: Idolothripinae). Journal of the Kansas Entomological Society 49 (4): 492-508.

Name the Bug # 51

Only a part of the organism, I'm afraid. Is it enough for you to identify it?



Attribution (as always) to follow.

I'm currently out in the field, so I'm not sure how quickly I'll be able to reveal this one. Until then, good luck!

Update: Identity available here. Figure from here.

Gutless Wonders

Congregation of Symsagittifera roscoffensis, photographed by Patrick Le Mao (NB. The link for this photo is the one provided by Google Images, but I'm having trouble loading the source page).

The Acoela are a distinct assemblage of marine worms ranging in size from the microscopic to a little over a centimetre in length. The name 'Acoela' means 'without a cavity', and refers to the lack of a proper gut in these animals. Instead, the mouth (which is situated on the underside of the animal) leads to a central vacuole surrounded by a syncytium (a multinucleate mass that is not divided into individual cells) that takes in nutritive particles by phagocytosis (engulfment by membrane folding, like how an Amoeba feeds). In many of the larger acoels, feeding is supplemented (or even largely superseded) by the presence of endosymbiotic algae that provide nutrients for their host worm (it is the algae that give the worms in the photo above their bright green colour). One particular family of acoels, the Solenofilomorphidae, live in anoxic sulfide sands, an environment that until the late 1960s was thought inimicable to animal life.


The panther worm Hofstenia miamia, photographed by Andreas Wallberg.

Acoels have received most attention in recent years due to debate about their relationships to other animals. Long included among the Platyhelminthes (flatworms), recent studies have indicated that acoels are not close relatives of that group (which is now placed as a derived lineage of Lophotrochozoa). It is generally accepted that acoels are most closely related to a similar group of marine worms called Nemertodermatida, and a few recent studies have also connected them with another marine worm Xenoturbella (Philippe et al. 2011). All three groups lack a through-gut, and a relationship between them seems credible. As regards the connection between this total group and other animals (a subject that I've discussed in a previous post), there are three main options currently on the table: (1) Acoels and their relatives are the sister group (or, in some studies, successive sister groups) to all other bilaterians. This is perhaps the most popular position, and suggests that the simple morphology of acoels relative to other animals may be comparable to the ancestral morphology for bilaterians as a whole. (2) Some recent studies (e.g. Philippe et al. 2011) have recovered an alternative position for acoels within the deuterostomes, as sister to echinoderms + hemichordates. If so, the simple morphology of acoels would probably be derived from more complex ancestors. (3) Finally, there are still some studies (e.g. Dunn et al. 2008) whose results place acoels together with the Platyhelminthes among the Lophotrochozoa (generally as the sister to other Platyhelminthes). However, most current researchers seem to regard such results as due to long-branch attraction between the two groups.


Specimens of an unidentified species of acoel on coral, photographed by Teresa Zubi.

Within the Acoela themselves, recent studies have supported the association of larger species as a clade nested among the smaller species (Hooge & Tyler 2006). Many characters used in earlier classifications of the group, such as the presence of a pharynx or endosymbionts or the placement and numbers of genitalia*, have not always related well to recent molecular phylogenies, but other features such as the arrangement of muscles in the body wall have. One particularly notable feature has been the arrangement of microtubules in the spermatozoa, with successive reductions in the number of central microtubules (from the ancestral 9 + 2 arrangement, to 9 + 1, to 9 + 0) correlating strongly with molecular data (Hooge & Tyler 2006).

*I believe I've noted it before, but for all that organisms such as microscopic worms are usually regarded as morphologically 'simple' and 'conservative', you don't find much variation among more 'complex' animals like mammals in the number of penises they have.

REFERENCES

Dunn, C. W., A. Hejnol, D. Q. Matus, K. Pang, W. E. Browne, S. A. Smith, E. Seaver, G. W. Rouse, M. Obst, G. D. Edgecombe, M. V. Sørensen, S. H. D. Haddock, A. Schmidt-Rhaesa, A. Okusu, R. M. Kristensen, W. C. Wheeler, M. Q. Martindale & G. Giribet. 2008. Broad phylogenomic sampling improves resolution of the animal tree of life. Nature 452: 745-749.

Hooge, M. D., & S. Tyler. 2006. Concordance of molecular and morphological data: the example of the Acoela. Integrative and Comparative Biology 46 (2): 118-124.

Philippe, H., H. Brinkmann, R. R. Copley, L. L. Moroz, H. Nakano, A. J. Poustka, A. Wallberg, K. J. Peterson & M. J. Telford. 2011. Acoelomorph flatworms are deuterostomes related to Xenoturbella. Nature 470: 255-258.

Name the Bug # 50

This may be very easy or it may be very difficult. Can you recognise the subject of the photo below?



Attribution to follow.

Update: Identity now available here. Photo by Patrick Le Mao.

Milk-vetches, Liquorice and Locoweeds

Flowers of the weeping broom Carmichaelia stevensonii, from here.

Far in the distant past, I commented on a review of the New Zealand brooms of the genus Carmichaelia. The New Zealand brooms were placed by Wagstaff et al. (1999) in the tribe Galegeae, which includes more than 3000 species around the world. The vast majority of these are placed in the genus Astragalus, milk-vetches, which may itself have well over 2500 species and be the largest recognised genus of flowering plant. Other significant members of the Galegeae include the locoweeds (Oxytropis) and Glycyrrhiza, a small genus of less than twenty species that nevertheless deserves praise for being the source of liquorice*.

*I am reliably informed that there are people in this world who do not appreciate the flavour of liquorice. There is simply no accounting for taste.


Flowers of Astragalus monspessulanus, from here.

However, despite its wide recognition, phylogenetic studies of recent years have been unanimous in declaring the Galegeae polyphyletic. It is true that the vast majority of galegeans remain in a clade, with only a few relatively minor genera placed elsewhere (Wojciechowski et al. 2000). The problem is that one of those 'minor genera' happens to be Galega itself, the type genus and therefore sine qua non of the tribe, which is more closely related to the chickpeas of the genus Cicer. Wojciechowski et al. (2000) circumvented this issue by recognising a clade called Hologalegina, uniting the 'Galegeae' with other tribes such as Hedysareae, Trifolieae, Fabeae, Loteae and Robinieae. Within the Hologalegina, the taxa previously assigned to the Galegeae all belong to what is called the IRLC, the 'Inverted Repeat-Lacking Clade'. The name of this clade refers to the loss of a copy of the 25 kb inverted repeat in the chloroplast genome that is otherwise found in almost all other land plants. Members of the IRLC are largely herbaceous, and many of the most commercially significant legumes (such as peas, beans, lentils, clover and alfalfa) belong to this clade.


Liquorice, Glycyrrhiza glabra, photographed by J. C. Schou. The flavour comes from the roots.

With the exception of the aforementioned Glycyrrhiza (which is another phylogenetically distant genus from other galegeans), most of the 'Galegeae' are not commercially grown. They may be commercially eradicated: species of Oxytropis get their name of 'locoweed' from their toxic effects on grazing livestock, and various species of Astragalus and Swainsona are also known for their toxicity. Some species are cultivated as garden plants, such as the weeping broom Carmichaelia stevensonii shown in the top photo (though many places still list it under the older name of Chordospartium stevensonii) and the kaka beak Clianthus puniceus. One particular galegean is widely regarded as the stuff that gardeners' dreams are made of, despite being a notoriously difficult plant to grow. My partner tells me that when he lived in Kalgoorlie as a child, tourist buses would regularly appear outside his house just so that their passengers could see this plant flowering in the front yard. I speak, of course, of Swainsona formosa, Sturt's desert pea:


Photographed by Marj Kibby.

REFERENCES

Wagstaff, S. J., P. B. Heenan & M. J. Sanderson. 1999. Classification, origins, and patterns of diversification in New Zealand Carmichaelinae (Fabaceae). American Journal of Botany 86 (9): 1346-1356.

Wojciechowski, M. F., M. J. Sanderson, K. P. Steele & A. Liston. 2000. Molecular phylogeny of the “temperate herbaceous tribes” of papilionoid legumes: a supertree approach. In: Herendeen, P. S., & A. Bruneau (eds). Advances in Legume Systematics vol. 9, pp. 277–298. Royal Botanic Gardens, Kew.