Porcelain Fans

Mature specimen of Rhapydionina deserta, from Loeblich & Tappan (1964).

Calcareous foraminiferans have been featured on this site before: planktic floaters, living stars, microscopic jelly moulds and gigantic reef-formers. All these forms have belonged to the group of calcareous forams known as the rotaliids. Today's subject is another group of forams, the Rhapydionininae, belonging to a different calcareous group, the Miliolida. Miliolids may have shell walls made of calcite like the rotaliids, but differ in the wall structure: while the walls of rotaliids are glass-like and porous, those of miliolids are structured like porcelain. Phylogenetic studies of forams have not placed the miliolids close to the rotaliids, and the two groups seem to have evolved their secreted shells independently (Sen Gupta 2002).

Rhapydionina liburnica, from Loeblich & Tappan (1964).

The Rhapydionininae were defined by Loeblich & Tappan (1964) as a group of miliolids with a conical test composed of broad chambers stacked one on top of another (the overall shape being kind of like a fan or an ice-cream cone), with each of these chambers subdivided by internal septa into multiple chamberlets (the difference between a 'chamber' and a 'chamberlet' being that the latter are not completely divided from each other by the walls). The opening of the test took the form of a sieve-like array of pores at the top end. However, subsequent researchers have discovered that Loeblich & Tappan's definition was inadequate. Rhapydioninines start life growing as a flat spiral, with growth becoming linearised at maturity. However, it turns out that not all Rhapydionininae become linear; some retain their juvenile coiling into maturity (Vicedo et al. 2011). At least some species are believed to have both a linear megalospheric form and a coiled microspheric form. To explain, forams can be divided between microspheric forms, in which the first chambers of a new test are much smaller, and megalospheric forms with larger initial chambers. In those relatively few forams whose life cycles have been studied in detail, these two forms correspond to an alternation of generations, with a mostly microspheric asexually-reproducing generation giving rise to the generally megalospheric sexually-reproducing phase. Loeblich & Tappan's (1964) concept of rhapydionines, therefore, would have potentially placed members of a single species into separate families.

Diagram of internal structure of two adult chambers of Cuvillierinella, from Vicedo et al. (2011). Key to abbreviations: ap f = apertural face, c chl = cortical chamberlets, flo = floor, m chl = medullar chamberlet, prp = preseptal space, rpi = residual pillars, s = septum, sl = septulum.

Rhapydionines are best known as fossils, with a definite range from the Upper Cretaceous to the mid-Eocene (Loeblich & Tappan 1984). Believe it or not, whether there are still rhapydioninines in the world is something of an open question. Loeblich & Tappan (1964) listed two Recent genera in the Rhapydionininae, each represented by only a single known specimen. Ripacubana conica was originally described from sand deposits in Cuba; however, Loeblich & Tappan (1964) suggested that Ripacubana may actually represent what has been referred to as a 'zombie taxon'. Some of you may be familiar with the palaeontological concept of a 'Lazarus taxon', where a species disappears from the fossil record only to reappear at a later date. What has actually happened in these cases is that the species had only become locally extinct, but survived in some other locality that has not been preserved, subsequently recolonising its old range. A 'zombie taxon', however, is one that has genuinely become extinct at the earlier date, but its fossilised remains have since been transported into a younger sediment deposit, giving the impression that it survived later than it did*. In the case of Ripacubana, it is difficult to know just how long a foram shell buried in sand has been lying there.

*Identifications of Lazarus taxa also have to be on the look-out for 'Elvis taxa': where the more recent population does not in fact represent the same species, but a different species that has convergently evolved similar features.

Craterites rectus, from Loeblich & Tappan (1964).

Loeblich & Tappan (1964) did not express the same reservations about Craterites rectus, described from a beach on Lord Howe Island east of Australia. Craterites was later separated as its own subfamily by Loeblich & Tappan (1984) on the basis of its being attached to the substrate, and so differing from other free-living Rhapydionininae. Nevertheless, they kept the two subfamilies together as the family Rhapydioninidae, so Craterites may still be the only known survivor of the rhapydioninine lineage. However, with only one known specimen, the details of the internal structure of Craterites remain unknown.

REFERENCES

Loeblich, A. R., Jr & H. Tappan. 1964. Treatise on Invertebrate Paleontology pt C. Protista 2. Sarcodina, chiefly "thecamoebians" and Foraminiferida, vol. 1. The Geological Society of America and The University of Kansas Press.

Loeblich, A. R., Jr & H. Tappan. 1984. Suprageneric classification of the Foraminiferida (Protozoa). Micropaleontology 30 (1): 1-70.

Sen Gupta, B. K. 2002. Modern Foraminifera. Springer.

Vicedo, V., G. Frijia, M. Parente & E. Caus. 2011. The Late Cretaceous genera Cuvillierinella, Cyclopseudedomia, and Rhapydionina (Rhapydioninidae, Foraminiferida) in shallow-water carbonates of Pylos (Peloponnese, Greece). Journal of Foraminiferal Research 41 (2): 167-181.

The Wool Plants

Vegetable lamb, as illustrated in The Travels of Sir John Mandeville (ca 1360).

Medieval legend in Europe spoke of a strange animal that could supposedly be found far off in central Asia: the vegetable lamb. According to legend, this was an animal much like an ordinary sheep except that it grew directly from a plant, to which it remained attached by the umbilical cord. The vegetable lamb would sustain itself by grazing on nearby vegetation but when this was depleted, as the lamb could not move away from the plant to which it was attached, the lamb would die. How such a pointlessly self-defeating organism was supposed to persist does not appear to have concerned the medieval lexicographers; presumably it was supposed to be allegorical of something.

Opening fruit of Gossypium hirsutum, photographed by B. P. Schuiling.
Part of the reason for the legend's persistence, however, was that there was indeed a form of 'wool' that came from a plant: cotton. The cotton genus Gossypium comprises about fifty species found in tropical and subtropical regions around the world (Wendel et al. 2010). Members of the genus vary from herbaceous perennials to small trees. The genus is divided into four subgenera, most of which are geographically distinct. The subgenus Gossypium is found in Africa and Arabia, subgenus Sturtia in Australia, and subgenus Houzingenia in the Americas. These three subgenera between them include the diploid cotton species; the fourth subgenus Karpas is also found in the Americas but differs in containing tetraploid species. Genetic evidence indicates that the subgenus Karpas arose at some point in the very recent past (within the last one or two million years) from a single hybridisation event between a species of subgenus Gossypium and one of Houzingenia, probably as a result of some chance dispersal event from Africa. Gossypium seeds seem well suited to dispersal: seeds of the Hawaiian Island species G. tomentosum have apparently germinated after being kept immersed in artificial seawater for three years (Wendel et al. 2010)! This same predicection for dispersal has resulted in the tetraploid species rapidly becoming widespread despite their recent origin, and in producing two species in remote locales: the Hawaiian G. tomentosum is directly related to the mainland G. hirsutum, while the Galapagos G. darwinii is sister to the mainland G. barbadense.

Levant cotton Gossypium herbaceum, photographed by H. Zell.

Commercial cotton is grown from four species of Gossypium, which may have each been domesticated independently in prehistoric times. All Gossypium species produce seeds with a covering of fuzzy hairs, but seeds of the two Old World diploid species G. herbaceum and G. arboreum also possess an outer layer of longer, flatter hairs that can be woven into thread. It was one of these two species, or possibly some now-extinct close relative, that made the crossing over the Atlantic to become one ancestor of the tetraploid species; as a result, the tetraploid species also possess these long outer hairs. Two of the tetraploid species, G. barbadense and G. hirsutum, were also domesticated, and the latter of these is now by far the most abundant cotton species in cultivation*.

*In case you were wondering, no-one seems to have suggested that the island species related to the two American domesticates might have been human-dispersed.

Sturt's desert rose Gossypium sturtianum, from here.

Other diploid Gossypium species do not possess this longer outer hair layer, only the inner short layer, and are not sources of commercial cotton (though hybrids with some of these species have been used to breed desirable genetic traits into the commercial species). In one group of Australian species (the section Grandicalyx) found in the Kimberley region of northern Western Australia, the hair layer has become very sparse and the seeds are almost hairless. These seeds also possess fatty bodies called eliosomes that are attractive to ants, and the plants are dispersed by having hungry ants carry their seeds away. Grandicalyx species are seasonal herbs, dying off above ground during droughts only to resprout from their thick root-stock. Other Australian species include the Sturt's desert rose Gossypium sturtianum, the floral emblem of Australia's Northern Territory.

Gossypium gossypioides, from here.

As with other plant groups, hybridisation appears to have been a recurring factor in the evolution of Gossypium. The diploid Gossypium species have been divided between eight genome groups, hybrids between which are generally not viable (though not unknown: the parents of the tetraploid lineage, for instance, belonged to separate groups). However, genetic studies of some Gossypium species have identified discrepancies where a species may possess the nuclear genome of one group, but the chloroplast genome of another. For instance, the North American species G. gossypioides resembles other New World species in its nuclear genome, but has chloroplasts related to those of G. herbaceum or G. arboreum (which it may have acquired as a result of the same hybridisation event that produced the tetraploid species*). This phenomenon, which has been called cytoplasmic introgression, may have arisen in cotton through a process called semigamy. Semigamy is a particular form of apomixis (reproduction without fertilisation) in which sperm and egg cells fuse cytoplasmically, but their nuclei remain distinct (Curtiss et al. 2011). These nuclei will eventually be segregated by cell division, resulting in offspring that are mosaics of male- and female-line genomes. Over time, selection or drift may produce a homogenous population that retains the nuclear genome of one ancestor, but the cytoplasmic heritage of the other.

*The American parent of the tetraploids has more usually been identified as G. raimondii, a South American species, but G. raimondii is the direct sister species of G. gossypioides. It may be that G. gossypioides is the true parent of the tetraploids, or it may be that it too is derived from G. raimondii or its parent stock).

REFERENCES

Curtiss, J., L. Rodriguez-Uribe, J. McD. Stewart & J. Zhang. 2011. Identification of differentially expressed genes associated with semigamy in Pima cotton (Gossypium barbadense L.) through comparative microarray analysis. BMC Plant Biology 11: 49.

Wendel, J. F., C. L. Brubaker & T. Seelanan. 2010. The origin and evolution of Gossypium. In: Stewart, J. McD., D. Oosterhuis, J. J. Heitholt & J. R. Mauney (eds) Physiology of Cotton pp. 1-18. Springer.

Riroriro

The grey warbler or riroriro Gerygone igata, photographed by Peter Bray.

The eighteen recognised species of the genus Gerygone are an assemblage of small, drab-coloured birds found mostly in the Australo-Papuan region, with G. sulphurea found in the Malay Peninsula, Indonesia and the Philippines, and G. flavolateralis found in New Caledonia and Vanuatu. These are another group of birds that have tended to draw the short straw in the vernacular name stakes: G. igata, one of the most abundant of New Zealand's native birds, is usually identified by the uninspiring 'grey warbler'. Personally, I prefer the more onomatopoeiac Maori name for these lively little birds: 'riroriro' (it has been suggested in some circles that it could possibly be referred to as the 'grey gerygone'; this proposition shall be treated with the scorn that it deserves). The riroriro and its congeners feed on small insects that they mostly glean from leaves or small branches, generally in the middle to upper canopies (Ford 1985). A certain amount of their prey is caught in the air, while the riroriro and the brown warbler G. mouki of eastern Australia also forage in lower vegetation than other species. The riroriro is also the only Gerygone species known to forage on the ground (Keast & Recher 1997).

Gerygone species build hanging purse-shaped nests; this is a brown warbler Gerygone mouki photographed by Peter.

Somewhat unusually for a decently-speciose passerine genus, the circumscription of Gerygone has been fairly stable in recent years, and the genus has mostly been supported as monophyletic. The only exception of recent times has been the New Guinean G. cinerea, recently reclassified by Nyári & Joseph (2012) as a species of Acanthiza. In the early 1900s, some authors divided Gerygone species between smaller genera (for instance, the Australian ornithologist Gregory Mathews, who never met a genus he couldn't break down). One species so separated was the Chatham Island warbler G. albofrontata, which is something of an island giant compared to other Gerygone species, weighing about 12 g while other species are about 6 to 7 g (Keast & Recher 1997). Unfortunately, the Chatham Island warbler was not included in the phylogenetic analysis of Gerygone by Nyári & Joseph (2012), but it was not identified as significantly separate from other Gerygone species in the morphological analysis by Ford (1985).

The Chatham Island warbler Gerygone albofrontata, from here.

REFERENCES

Ford, J. 1985. Phylogeny of the acanthizid warbler genus Gerygone based on numerical analyses of morphological characters. Emu 86: 12-22.

Keast, A., & H. F. Recher. 1997. The adaptive zone of the genus Gerygone (Acanthizidae) as shown by morphology and feeding habits. Emu 97: 1-17.

Nyári, Á. S., & L. Joseph. 2012. Evolution in Australasian mangrove forests: multilocus phylogenetic analysis of the Gerygone warblers (Aves: Acanthizidae). PLoS One 7(2): e31840.

Into the Labyrinth

Climbing perch Anabas testudineus emerging from water, as illustrated by Richard Lydekker.

Amongst the unholy mess that is the Percomorpha, one group that has long been recognised is the labyrinth fishes of the Anabantoidei. The anabantoids are a group of freshwater fishes found in southern Asia and Africa (but not Madagascar) that get their vernacular name from their possession of a distinctive respiratory organ called the labyrinth. This organ, found in a cavity above the gills, is derived from part of the first gill arch; the bone has become expanded and much-folded, and is covered with a layer of respiratory epithelium. So long as the gills do not actually dry out, the labyrinth allows these fish to take in oxygen directly from the air, and they can survive in warm, low-oxygen waters. They can even survive for limited periods entirely out of water (a feature that has helped make some of the larger species popular food fish, due to the greater ease of keeping them fresh in a tropical environment). Recent phylogenetic studies (e.g. Li et al. 2009) have agreed in placing labyrinth fishes as related to a number of other freshwater Indo-Australian fishes, such as the snakeheads of the Channidae and the swamp eels of the Synbranchidae, many of which are also tolerant of air-breathing.

Kissing gouramis Helostoma temminckii, from Peter Bus.

Labyrinth fishes can be divided between three families (Rüber et al. 2006). One of these contains a single species, the kissing gourami Helostoma temminckii of south-east Asia. Kissing gouramis are primarily specialised filter feeders, though they may also graze on algae or insects. The vernacular name refers to their enlarged lips, making them look permanently puckered up. Kissing gouramis even 'kiss', pressing their smackers against one another, though this is regarded as an act not of affection but of aggression (kind of like a 1930s Hollywood melodrama) as the fish push against one another.

A rather unfortunate Cape kurper Sandelia capensis, photographed by Darryl Lampert.

The climbing perches of the Anabantidae include the south Asian Anabas and the African Ctenopominae. These short-bodied carnivores have serrated edges to their gill covers that the Asian species use to pull themselves over land when travelling between water bodies (imagine lying on your stomach and pulling yourself along with your chin). You can see video of some climbing perch Anabas testudineus emerging from water here.

Giant gourami Osphronemus goramy, photographed by E. Naus.

The most diverse subgroup of the Anabantoidei is the gouramis of the Osphronemidae, another south Asian group. The largest of the Osphronemidae, the giant gourami Osphronemus goramy, grows up to 70 cm, but most species are quite a bit smaller. A number of gourami species (as well as the kissing gourami) are popular aquarium fishes; the most popular by far is the Siamese fighting fish Betta splendens, males of which have been bred to exhibit much longer and more ornamental fins than found in the wild. The gouramis are generally omnivorous, with species varying in the extent to which they prefer plant or animal food. The most specialised carnivore of the Osphronemidae is the pikehead Luciocephalus pulcher, a small but elongate species that has been described as having the most protrusible mouth of any fish (and that, by the way, is no small claim). You can see the pikehead in action below:

The pikehead is so divergent from other labyrinth fishes that past authors have regarded it as its own family, possibly the sister taxon to all other anabantoids, or even questioned whether it was a labyrinth fish at all. However, as confirmed by Rüber et al. (2006), Luciocephalus is not only a true anabantoid but nested well within the Osphronemidae as sister to the chocolate gouramis of the genus Sphaerichthys. These and two other genera, Ctenops and Parasphaerichthys, form what is known as the 'spiral egg' clade, named after the presence of spiraling ridges on the egg leading to the micropyle, that have been suggested to act as guides for the sperm.

Siamese fighting fish Betta splendens mating below a bubble-nest, photographed by Stephen & John Downer.

The anabantoids are also known for the bubble-nests constructed by a number of species, in which the eggs are contained within a floating nest of bubbles that is guarded by the male parent (both parents in the Ceylonese combtail Belontia signata). Bubble-nesting has evolved at least twice among the anabantoids: once in the Osphronemidae, and once in the ctenopomine genus Microctenopoma (other anabantids and Helostoma are free spawners that do not construct nests or guard their eggs; the ctenopomine Sandelia capensis digs a nest in the bottom substrate) (Rüber et al. 2006). Though bubble-nesting is probably the ancestral behaviour for Osphronemidae, it has been modified in a number of sublineages. Osphronemus species build submerged nests from vegetation, while members of the 'spiral egg' clade (except Parasphaerichthys) and a number of Betta species are mouthbrooders. Usually the male broods the fry in these species, but the female is the brooder in a couple of Sphaerichthys species.

REFERENCES

Li, B. A. Dettaï, C. Cruaud, A. Couloux, M. Desoutter-Meniger & G. Lecointre. 2009. RNF213, a new nuclear marker for acanthomorph phylogeny. Molecular Phylogenetics and Evolution 50: 345-363.

Rüber, L., R. Britz & R. Zardoya. 2006. Molecular phylogenetics and evolutionary diversification of labyrinth fishes (Perciformes: Anabantoidei). Systematic Biology 55 (3): 374-397.

The Kellyclams

Ruddy lasaeas Lasaea adansoni photographed in a rock crevice by David Fenwick.

Members of the family Lasaeidae, commonly known as kellyclams, are small thin-shelled bivalves that often live in close association with larger invertebrates such as crustaceans, worms or cnidarians. The clam may be directly attached to its host or share a burrow with it; one genus, Entovalva, includes associates of sea cucumbers that live within their host's esophagus (you can find some more details of this particular relationship here). Though the clam's presence may not be entirely without physical effect on its host, such effects are usually minor and kellyclams are generally regarded as commensals rather than parasites. Other species live independently and may live nestled among rocks or buried in sediment; these free-living forms may possess a relatively large muscular foot for mobility. Like most bivalves, kellyclams are filter feeders; the invertebrate-commensal species are believed to take advantage of water currents created by the host to increase the effectiveness of their own feeding currents.

Commensal Pseudopythina rugifera attached to a ghost shrimp Upogebia pugettensis, photographed by Arthur Anker.

The family-level classification of the kellyclams has been fairly turbulent. The family has variously been known as the Lasaeidae, Erycinidae or Leptonidae, owing to confusion over which of these names has priority, while some authors have regarded them as separate families and/or recognised further segregate families Kelliidae or Montacutidae. With their small size, kellyclams have simplified a number of the characters used in classifying other bivalves, and a number of the commensal species have become modified in order to co-exist with their host. The Peregrinamor species, for instance, live attached longitudinally underneath the thorax of the ghost shrimp Upogebia; they have accordingly become low and elongate, and were until recently misclassified as mussels of the Mytilidae (note that the Lasaeidae and Mytilidae represent evolutionary lineages that first diverged some time in the Ordovician). In the broad sense, the Lasaeidae have been separated from the closely related family Galeommatidae by the fact that members of the latter have the soft body enlarged so that the shell becomes internal. However, Goto et al. (2012) established that even this distinction is not reliable, with the Galeommatidae nested and probably polyphyletic within the Lasaeidae. Also, while Goto et al. did not support recognition of the Lasaeidae as a holophyletic group, nor did they support any of the segregate families. Commensal species are scattered phylogenetically among free-living species, and host-switching has apparently happened numerous times within commensal lineages.

The Lasaeidae are hermaphrodites, and often brooders. Rather than being released as eggs, young are retained within their parent until they are released as veligers (later-stage larvae that have begun to develop a shell) or as miniature versions of the adults.

REFERENCES

Goto, R., A. Kawakita, H. Ishikawa, Y. Hamamura & M. Kato. 2012. Molecular phylogeny of the bivalve superfamily Galeommatoidea (Heterodonta, Veneroida) reveals dynamic evolution of symbiotic lifestyle and interphylum host switching. BMC Evolutionary Biology 12: 172.

"Anatomy of Mollusca": A Case of Plagiarism

Whilst researching material for an upcoming post, I came across this book on Google Books, published in 2010 by the International Scientific Publishing Agency, New Delhi:

Anatomy of Mollusca, by Rita Rawat

Looking at the section previewed through Google Books, I couldn't help feeling that it seemed a little... familiar. Take a look at this screenshot from Google Books:

Now take a look at this screenshot, taking from a page written by my erstwhile associates at Palaeos.com, last modified in 2006:

I can only go by what was available in the Google Books preview, of course, without direct access to the actual book, but I can confirm that most if not all of the material in pages 15 to 72 at least of the "Anatomy of Mollusca" appears to have been copied directly from Palaeos.com (unfortunately, a large part of Palaeos.com is currently offline as the site gets revamped). A quick Google search failed to uncover anything indicating whether the International Scientific Publishing Agency has a reputation for publishing lifted material, so I can't say if this is part of a broader issue.

Amazon currently has the "Anatomy of Mollusca" on sale for just over $75. Not that expensive by the standards of technical publications, but a fair chunk of change by the standards of books in general. Certainly a lot more than the cost of reading the same stuff on Palaeos.com, which carries no extra cost beyond that of the ISP charges.

Dung Beetles

Flat-headed dung beetles Pachylomerus femoralis with a ball of the good stuff, photographed by Guido Coza.

The dung beetles of the Scarabaeini include 146 species found in Africa and Asia, classified by Forgie et al. (2006) into three genera: Pachysoma, Pachylomerus and Scarabaeus, with the last including the vast majority of species. The Scarabaeus species are perhaps the most famous of all dung beetles, renowned since ancient history when Egyptians saw a dung beetle rolling a ball of dung along the ground as a metaphor for the movement of the sun through the heavens*. Dung beetles collect their turd balls to use as food for themselves or for their larvae. Ball-rolling is not unique to the Scarabaeini as a method of transporting dung, however (it is also done by members of other dung beetle tribes), nor do all Scarabaeini species engage in ball-rolling.

*It probably does not say much for the standard of ancient Egyptian public sanitation that they were apparently so willing to believe that the ultimate source of all life on the planet was a giant mass of burning poop.

Flightless orange dung beetle Pachysoma denticolle, photographed by Alex Dreyer.

The flightless dung beetles of the genus Pachysoma, for instance, transport their food by dragging it along between their hind legs. Pachysoma species are also less choosy than other Scarabaeini, feeding not just on dung but all manner of organic detritus. They have specialisations allowing them to feed on drier food particles than other Scarabaeini, suitable for their arid habitats in southern Africa. In contrast, species of the subgenus Sceliages within Scarabaeus are the epicures of the scarabaein world: they feed entirely on dead millipedes, which they push along in front of themselves bulldozer-style (Forgie et al. 2005). Relatively few species of Scarabaeini feed by burrowing directly alongside piles of dung where they lay, but this may be done by Pachylomerus and Scarabaeus galenus (both of which may also transport food).

Individual of Sceliages transporting a millipede, photographed by Shaun Forgie.

Most Scarabaeini are active during the day, but a small number such as Scarabaeus satyrus are nocturnal in habit. In the phylogenetic analyses conducted by Forgie et al. (2005), these nocturnal species usually formed a single clade. Had the ancient Egyptians observed the nocturnal dung beetles as well, they could have presented us with a sky full of poo at all hours.

REFERENCES

Forgie, S. A., U. Kryger, P. Bloomer & C. H. Scholtz. 2006. Evolutionary relationships among the Scarabaeini (Coleoptera: Scarabaeidae) based on combined molecular and morphological data. Molecular Phylogenetics and Evolution 40: 662-678.

Forgie, S. A., T. K. Philips & C. H. Scholtz. 2005. Evolution of the Scarabaeini (Scarabaeidae: Scarabaeinae). Systematic Entomology 30: 60-96.