Glyphyalinia species are often found in forest leaf-litter in the eastern part of North America. They have a low, translucent shell that is often about half a centimetre in diameter. Whorls of the shell increase regularly in size and are marked by a series of strongly impressed radiating lines in addition to finer growth lines. The umbilicus of the shell varies between species from completely absent to quite wide (Burch & Pearce 1990). The soft body of the animal varies in coloration, again depending on species. That of G. roemeri is all white except for the eyes; that of G. wheatleyi is almost uniformly black. The reproductive system of Glyphyalinia (which are hermaphroditic) includes a well-developed epiphallus and a distinct, ovoid spermathecal sac (Baker 1930).
Multiple species of Glyphyalinia may be found living in a single patch of forest though, at present, we know little about how (and whether) micro-habitats are partitioned between species. Some species seem to tolerate a wide variety of soil types and are correspondingly widely distributed. Others are more selective and localised; some may be considered endangered by habitat degradation. Even supposedly widespread species may be more vulnerable than appreciated: at least some may represent clusters of closely related species rather than truly uniform populations. These tiny snails can be notoriously difficult to study, making for a risk that they might just slip away barely noticed.
REFERENCES
Baker, H. B. 1930. The North American Retinellae. Proceedings of the Academy of Natural Sciences of Philadelphia 82: 193–219.
Burch, J. B., & T. A. Pearce. 1990. Terrestrial Gastropoda. In: Dindal, D. L. (ed.) Soil Biology Guide pp. 201–309. John Wiley & Sones: New York.
Such animals presumably have a pretty high background species extinction rate.
ReplyDeletePresumably, yes, at least in the modern environment. It does raise the question, nevertheless, of whether 'twas always thus, or whether modern habitat fragmentation has increased the rate by making it harder for dispersal to occur between semi-isolated populations.
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