Name the Bug # 11

What's this? Attribution to follow.

Update: Identification now available here. Photo by A. Staudt.

Taxon of the Week: Collonychium

Dorsal view of an unidentified Collonychium species. Photo by Abel & Ana.

Just a brief Taxon of the Week entry today because unfortunately I don't have a lot of info available on this taxon. The name Collonychium was recently revived from taxonomic limbo by Kury (2003) for two species of gonyleptid harvestmen found in south-east Brazil. Collonychium bicuspidatum is found in the provinces of Rio de Janeiro, São Paulo and Paraná while C. perlatum is found in Espírito Santo and Minas Gerais. Collonychium bicuspidatum had previously been included in the genus Paragonyleptes, of which it is the type species, before Kury (2003) recognised the type specimen of Collonychium bicuspidatum as a juvenile female of Paragonyleptes bicuspidatus (despite having the same species names, these two were originally described as separate species). A number of other southern Brazilian harvestman species had been assigned to Paragonyleptes, mostly by the famed creator of artificial classifications Carl-Friedrich Roewer and Cândido Firmino de Mello-Leitão (who, if anything, out-Roewered Roewer). These species were mostly listed by Kury (2003) as Gonyleptinae incertae sedis so they may or may not be Collonychium species.



I'm not entirely sure what's happening in this photo, again by Abel & Ana. Gonyleptids such as Collonychium have very powerful posterior-directed hindlegs, often with large spines pointing inwards on the retrolateral side (they're not as prominent in this individual, but in other species they may be very scary indeed). I think the individual in the photo above may be executing a handstand in order to bring the hindlegs into a better position to scissor with them at its intimidator (in this case, the photographer).

REFERENCE

Kury, A. B. 2003. Annotated catalogue of the Laniatores of the New World (Arachnida, Opiliones). Revista Ibérica de Aracnología, volumen especial monográfico 1: 1-337.

The Parrot of King Charles I

Yesterday, I asked people to identify this:



This specimen was originally illustrated in Frank Buckland's 1875 Log-book of a Fisherman and Zoologist. According to Buckland's account, he was presented with it by his servant while stationed at Windsor as an army surgeon, and told that the specimen had been found behind a chimney of the castle by some construction workers. One of the palace servants had then identified the skeleton as belonging to a favourite parrot of King Charles I.

Buckland confessed that, for a brief moment, the overall appearance of the specimen had him taken in. But it didn't take long for him to recognise it for what it was - the skeleton of a rabbit, cut in half with most of the thoracic skeleton removed, the neck and top part of the spine attached directly to the pelvis, and arranged in a position reminiscent of a bird. The construction workers and palace servants were themselves a complete fabrication. "King Charles I's parrot" became a favourite addition to Buckland's own collection.

Buckland himself was something of a character, a trait inherited from his equally eccentric father William Buckland (known as describer of one of the first known non-avian dinosaurs, Megalosaurus, and for his determination to eat a representative of every species of the animal kingdom). For more Bucklandery, you could start at his Wikipedia entry, while the Log-book is freely available from the Internet Archive at the link above.

Name the Bug: Sticholonche zanclea

Sticholonche zanclea (photo from here).

Sticholonche zanclea is a very unusual marine protist. In the past, it has been classified among the heliozoans, a group of organisms united by their generally radial arrangement of long cytoplasmic extensions called axopodia. However, both molecular and ultrastructural studies have established that the 'heliozoans' are a polyphyletic assemblage of a number of unrelated groups that have converged on a similar morphology. 'Heliozoans', in general, are passive trappers of other micro-organisms and food particles by means of their axopodia; the helizoan morphology provides for significant area coverage without massively increasing the cell cytoplasm. Compare this to the 'radiosa' form adopted by amoebae that become detached from their substrate and which serves a similar purpose (though in that case the aim is increasing the chance of recontacting the substrate). In the case of Sticholonche, molecular analysis has placed it among the also-axopod-bearing radiolarians with which it shares the production of siliceous spicules. Sticholonche differs from other radiolarians in lacking a central capsule dividing the cell into internal and external sectors; however, said molecular analyses place it nested among rather than sister to radiolarians. Indeed, it may be the sister to the spumellarid family Litheliidae (Kunimoto et al., 2006).

Sticholonche differs from other 'heliozoans' in being flattened with the axopodia concentrated laterally. The axopodia are rigid, reinforced by a central core of microtubules, and anchored on small cup-shaped depressions on the nuclear envelope (Cachon et al., 1977). By flexing the nuclear envelope, Sticholonche can move by rowing itself with the axopodia. If your day has so far provided insufficient awesomeness, follow this link, scroll down the page a bit, and you will find a video of a Sticholonche doing just that.

REFERENCES

Cachon, J., M. Cachon, L. G. Tilney & M. S. Tilney. 1977. Movements generated by interactions between the dense material at the ends of microtubules and non-actin-containing microfilaments in Sticholonche zanclea. Journal of Cell Biology 72: 314-338.

Kunimoto, Y., I. Sarashina, M. Iijima, K. Endo & K. Sashida. 2006. Molecular phylogeny of acantharian and polycystine radiolarians based on ribosomal DNA sequences, and some comparisons with data from the fossil record. European Journal of Protistology 42 (2): 143-153.

Name the bug # 10

I wonder if any of you are familiar with this animal:



Attribution to follow.

Update: Identification here. Image from Buckland (1875).

Name the Bug #9

I'm pretty sure you all know the drill by now. Attribution, as always, to follow.

Update: Identification now available here. Photo from here.

The Schizosphere (Taxon of the Week: Schizosphaerella)

Micrographs of Schizosphaerella from Perch-Nielsen (1989).

The dead are all around us. Large parts of the world's surface are made up by the remains of long-gone marine organisms who left their shells and skeletons, initially constructed for protection from predators and the elements, to form gigantic sedimentary graveyards. Over time, as with everything else, the identities of these unwitting benefactors have changed as new groups supplant the old.

During the Jurassic period, the predominant groups of biomineralising plankton were the calcareous coccoliths and Schizosphaerella (radiolarians were present but only important under certain conditions, planktic foraminiferans would not appear until the Cretaceous, while diatoms appeared in the Jurassic but remained marginalised until during the Cenozoic - Erba, 2004). Of these two, Schizosphaerella was particularly significant; at times, it accounted for nearly 100% of plankton-derived carbonate deposition (Mailliot et al., 2007). Schizosphaerella left its remains from the late Triassic to the end of the Jurassic in the form of globular to bell-shaped resting cysts, five to 30 μm in diameter, known as schizospheres. These are composed of two roughly hemispherical plates joined by a simple hinge. The two recognised species, S. punctulata and S. astraea, are distinguished by the presence or absence, respectively, of a subperipheral groove around the hinge and by the lattice arrangement of the elongate radiating elements that make up the wall (Perch-Nielsen, 1989). The nature of the Schizosphaerella organism during the active parts of its life cycle (assuming that the fossils are cysts) are unknown, as are its relationships to other organisms. The most common suggestion is that it represents some form of dinoflagellate - calcareous cysts are definitely produced by dinoflagellates of the subfamily Calciodinelloideae. However, Streng et al. (2004) have pointed out that the two-plated hinge arrangement of Schizosphaerella is unlike that known for any dinoflagellate, whose cysts normally open through an archeopyle at one end. That micropalaeontology is littered with examples of taxa of uncertain relationships (becoming more so the further back one goes in time) should come as no surprise to anyone - after all, it is often difficult enough to work out the relationships of modern unicellular organisms on morphological grounds, and doing so is often dependent on features of cell ultrastructure that are unlikely to be preserved in fossils.

Mention should also be made of the nannofossil Stomiosphaera minutissima which was described as having a calcareous cell wall of two layers - a thin inner layer and an outer layer composed of radiating fibres. 'Stomiosphaera' was shown by Aubry et al. (1988) to be the same as Schizosphaerella, but diagenetically altered (diagenesis is the process by which the nature of a fossil can be altered by geological processes after it gets deposited). The inner layer represented the two plates of the original fossil fused together while the outer layer resulted from crystal formation around the fossil.


Mean Schizosphaerella size over time compared to levels of carbonate production, from Mattioli et al. (2009).

Schizosphaerella seems to have preferred oligotrophic conditions with a deep nutricline (i.e. nutrients in the sea were spread out rather than being concentrated near the surface). An inverse relationship existed between Schizosphaerella and coccolith abundance (Cobianchi & Picotti, 2001) that was also related to the concentration of organic carbon in the water - high organic carbon (i.e. eutrophic conditions) meant more coccoliths and fewer schizospheres, low organic carbon the reverse. Periods of schizosphere abundance also relate to higher sea levels as reduced land level meant reduced organic run-off into the oceans. Both calcareous groups, however, showed reductions during periods of elevated CO₂ levels that punctuated the Mesozoic. The Toarcian anoxic event in the early Jurassic seems to have resulted from extensive vulcanism in southern Africa; the mean size of schizospheres becomes much smaller during this period as calcification became reduced by higher ocean acidity (Mattioli et al., 2009). This reduction in calcification is correlated with the extinction of a number of other organisms. Study of such past events is the best means available to us of understanding the effects that elevated carbon dioxide levels could potentially have in our own time (see, palaeontology can be practical too!).

REFERENCES

Aubry, M.-P., F. Depêche & T. Dufour. 1988. Stomiosphaera minutissima (Colom, 1935) from the Lias of Mallorca (Balearic Islands) and Umbria (Italy), and Schizosphaerella punctulata Deflandre & Dangeard, 1938: taxonomic revision. Geobios 21 (6): 709-727.

Cobianchi, M., & V. Picotti. 2001. Sedimentary and biological response to sea-level and palaeoceanographic changes of a Lower–Middle Jurassic Tethyan platform margin (Southern Alps, Italy). Palaeogeography, Palaeoclimatology, Palaeoecology 169 (3-4): 219-244.

Erba, E. 2004. Calcareous nannofossils and Mesozoic oceanic anoxic events. Marine Micropaleontology 52: 85-106.

Mailliot, S., S. Elmi, E. Mattioli & B. Pittet. 2007. Calcareous nannofossil assemblages across the Pliensbachian/Toarcian boundary at the Peniche section (Ponta do Trovão, Lusitanian Basin). Ciencias da Terra (UNL) 16: 1-13.

Mattioli, E., B. Pittet, L. Petitpierre & S. Mailliot. 2009. Dramatic decrease of pelagic carbonate production by nannoplankton across the Early Toarcian anoxic event (T-OAE). Global and Planetary Change 65 (3-4): 134-145.

Perch-Nielsen, K. 1989. Mesozoic calcareous nannofossils. In Plankton Stratigraphy vol. 1. Planktic foraminifera, calcareous nannofossils and calpionellids (H. M. Bolli, J. B. Saunders & K. Perch-Nielsen, eds) pp. 329-426. Cambridge University Press.

Streng, M., T. Hildebrand-Habel & H. Willems. 2004. A proposed classification of archeopyle types in calcareous dinoflagellate cysts. Journal of Paleontology 78 (3): 456-483.