Platyschismatinae

Platyschisma helicoides, from Knight et al. (1960).

In an earlier post on this site, I commented on some of the various ways that gastropods deal with the fact that their development tends to put their anus uncomfortably close to their mouth. A common solution is the development of a sinus or slit in the shell that provides spaces for the anus to be moved backwards.

One of the major gastropod groups exhibiting such a feature is known as the Pleurotomarioidea. In the modern fauna, pleurotomarioids are not hugely abundant, with living species restricted to deep waters. However, they were one of the dominant gastropod groups back in the Palaeozoic when they were represented by a number of families. One Palaeozoic pleurotomarioid group is the Platyschismatinae, known from the Lower Ordovician to the Middle Permian (Knight et al. 1960). Platyschismatines went with the sinus option, with a sinus present at or above the midpoint on the outer edge of the shell opening. Knight et al. (1960) included five genera in the Platyschismatinae. The type genus, Platyschisma, has a slightly flattened spiral and a relatively thin shell. Some of the other platyschismatines were also relatively flat.

REFERENCE

Knight, J. B., L. R. Cox, A. M. Keen, R. L. Batten, E. L. Yochelson & R. Robertson. 1960. Gastropoda: systematic descriptions. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt I. Mollusca 1: Mollusca—General Features, Scaphopoda, Amphineura, Monoplacophora, Gastropoda—General Features, Archaeogastropoda and some (mainly Paleozoic) Caenogastropoda and Opisthobranchia pp. I169-I331. Geological Society of America, and University of Kansas Press.

Jewels among Beetles

There are many contenders for the title of most stunning-looking insect but there is no question that the jewel beetles have a place among the line-up. Some of these brilliantly coloured insects look as if they could have been sculpted from gleaming metal:

Buprestis niponica, copyright Kohichiro Yoshida.

Buprestis is a genus of jewel beetles found in the Holarctic region, with the greater diversity around the Mediterranean and North America. Somewhere between forty and eighty species are recognised, depending on whether the closely related genera Cypriacis and Yamina are regarded as distinct or not. Species of Buprestis come in a variety of colours, with green, blue or black backgrounds often patterned with yellow or red.

Female Buprestis octoguttata ovipositing, copyright Christian Fischer.

Despite their attractive appearance, jewel beetles are not always welcome. They spend the larval part of their life cycle burrowing into wood so some are known for damaging timbers. The preferred hosts of most Buprestis species, where known, appear to be conifers such as pine, spruce and larch. They primarily attack dead and dying wood, and females of some species are known for searching the trunks of trees following fires to find where protective bark has cracked open (some jewel beetle species in other genera are commonly known as 'fire beetles' in reference to this habit). Buprestis larvae have been claimed to live for extraordinarily long periods. Mature beetles have been observed emerging from furniture and the like multiple decades after the original tree was felled, leading to claims of larval life spans of up to 51 years! It almost goes without saying that such inferences have attracted their share of scepticism, with detractors suggesting the possibility of eggs being laid after the wood was already worked. It is true that the low nutritious value of dry wood might be expected to lead to slow development, but how slow are you willing to believe?

Hairy-Winged Barklice

Forewing and fore tibia of Siniamphipsocus fusconervosus, from Mockford (2003). Scale bar for the femur = 0.1 mm.

For my next semi-random post, I drew Siniamphipsocus, a genus of more than twenty species of barklice known from eastern Asia. Most of these species were described by China by the almost ludicrously prolific psocopterologist Li Fasheng who over the course of his career has described close to 1000 psocopteran species—nearly a fifth of the world's barklouse fauna. It should be noted, though, that this productivity has not entirely come without criticism: for instance, in the case of the Siniamphipsocus species, most if not all are known from a single sex with some described from males and others from females (Li 2002).

Siniamphipsocus is a genus of the Amphipsocidae, a family of barklice most easily recognised by their wings which have a double row of setae along each of the veins. Amphipsocids can be relatively large as barklice go: the largest Siniamphipsocus species, S. aureus, has a body length of four millimetres, with the forewings being up to 6.75 millimetres long. Features distinguishing Siniamphipsocus from other amphipsocids include the absence of the brush of hairs present at the base of the hind wing in many other species, the absence of a spur vein in the rear of the forewing pterostigma, and the presence of a row of minute spines along the fore femur (Li 2002). Distinguishing the individual species of the genus requires fine attention to details such the patterns of markings on the face, the proportions of the wing veins, and details of the genitalia.

REFERENCES

Li F. 2002. Psocoptera of China (2 vols). Science Press: Beijing.

Mockford, E. L. 2003. New species and records of Psocoptera from the Kuril Islands. Deutsche Entomologische Zeitschrift 50 (2): 191–230.

Sordariomycetidae: Soil Fungi A-Plenty

I'm pretty sure I've commented before that, although most of us tend to associate the word 'fungi' with mushrooms and other eye-catching fruiting bodies, the vast majority of fungal diversity is minute and tends to go unnoticed. Nevertheless, despite their obscurity, many of these microfungi are crucial to our own continued existence. These are the decomposers, the organisms that break down fallen plant matter and animal wastes in their own search for nourishment and so contribute to the release of locked-up nutrients back into the environmental cycle.

Neurospora growing on sugar cane waste, from here.

The group of fungi that I drew for today's post, the Sordariomycetidae, is primarily made up of these minute decomposers. Sordariomycetids have already made an appearance here at Catalogue of Organisms, in a post from ten years ago on black mildews. Depending on how broadly the group is circumscribed, the Diaporthales could also be included. Due to a simple morphology that provides few distinct characters, the Sordariomycetidae are primarily defined on the basis of molecular phylogenies. The difficulty of classifying microfungi by morphology alone is underlined by cases where species previously classified within the same genus have proven to belong to entirely distinct fungal lineages.

In general, the vegetative body of most Sordariomycetidae consists of little more than disassociated hyphae embedded in their substrate, with the only distinct structures being the reproductive fruiting bodies. These are perithecia: that is, globular or flask-shaped fruiting bodies with a single small opening or ostiole at the top through which the mature spores are released. In some cases, the internal structure of the mature perithecium will simply dissolve, freeing the spores to escape through the ostiole in the manner of a miniature puffball. In others, the spores become entangled in a long strand or seta that is then extruded through the ostiole like toothpaste being squeezed out of a tube.

Perithecium of Chaetomium extruding spore-bearing setae, from here.

Sordariomycetids are found in almost every habitat imaginable: as well as soil- and dung-dwelling forms, they may also be found in aquatic and even marine habitats. Perhaps the best-known sordariomycetid is Neurospora crassa, red bread mould, which is widely used in laboratories as a model organism for genetic research. Indeed, it was investigations into N. crassa in the 1950s that first led to the proposal of the 'one gene, one enzyme' model that became a cornerstone of molecular genetics.