Sclerite
A sclerite (
Sclerites in combination
Sclerites may occur practically isolated in an organism, such as the sting of a cone shell. Also, they can be more or less scattered, such as tufts of defensive sharp, mineralised bristles as in many marine polychaetes. Or, they can occur as structured, but unconnected or loosely connected arrays, such as the mineral "teeth" in the radula of many Mollusca, the valves of chitons, the beak of a cephalopod, or the articulated exoskeletons of Arthropoda.
When sclerites are organised into an unarticulated structure, that structure may be referred to as a scleritome, a term largely used in paleontology.
Arthropods
In
Dorsal sclerites of a body segment, often plate-like, are known as tergites. Similarly the ventral sclerites of a body segment are referred to as sternites. Separate sclerites on the lateral aspects of body segments, the pleura, are called pleurites.[1]
Invertebrates other than arthropods
Wide ranges of sclerites of various kinds occur in various invertebrate
Many other invertebrates grow a few hard parts, largely mineralised, as statoliths and similar structures, but those are not generally referred to as sclerites.
Clamps, the main attachment structure of the parasitic polyopisthocotylean monogenean flatworms,[2][3] are composed of various sclerites and associated musculature, located on a posterior organ called the haptor. Clamps are specialized structures attached to the host fish, generally to its gill.
Prehistory
A scleritome is a skeleton made of isolated elements, like the scales of organisms such as the
Although sclerites are of considerable importance in the study of extant animals, in palaeontology they are of far greater relative importance because they often are the only parts of an animal that fossilize at all, let alone well or clearly. Many extinct groups are known only from sclerites, leaving moot the question of what their gross anatomy might have looked like.
An example of the use of the term in paleontology is to describe hollow calcium carbonate,
It has been suggested that the sclerites of the Cambrian Wiwaxia are homologous with the bristles of
References
- ISBN 0-412-61390-5.
- Bychowsky, B. E.(1961). Monogenetic Trematodes their systematics and phylogeny. English translation edited by W. J. Hargis Jr. Washington: American Institute of Biological Sciences.
- ^ Kearn, G. C. (2004). Leeches, Lice and Lampreys. A natural history of skin and gill parasites of fishes. Dordrecht: Springer.
- S2CID 86083492.
- ^ JSTOR 1304949.
- S2CID 88100863.
- S2CID 38386600.)
{{cite journal}}
: CS1 maint: multiple names: authors list (link