دانلود رایگان مقاله کالبد شکافی مجازی خرچنگ پلی چلیدان ماده 165 میلیون ساله

Abstract

Polychelidan lobsters are fascinating crustaceans that were known as fossils before being discovered in the deep-sea. They differ from other crustaceans by having four to five pairs of claws. Although recent palaeontological studies have clarified the systematics and phylogeny of the group, the biology of extant polychelidans and - first of all - their anatomy are poorly documented. Numerous aspects of the evolutionary history of the group remain obscure, in particular, how and when polychelidans colonized the deep-sea and became restricted to it. Surprisingly, the biology of extant polychelidans and the anatomy of all species, fossil and recent, are poorly documented. Here, X-ray microtomography (XTM), applied to an exceptionally well-preserved specimen from the La Voulte Lagerst€ atte, reveals for the first time vital aspects of the external and internal morphology of Voulteryon parvulus (Eryonidae), a 165- million-year-old polychelidan: 1) its mouthparts (maxillae and maxillipeds), 2) its digestive tract and 3) its reproductive organs. Comparisons with dissected specimens clearly identify this specimen as a female with mature ovaries. This set of new information offers new insights into the feeding and reproductive habits of Mesozoic polychelidans. Contrasting with other Jurassic polychelidans that lived in shallowwater environments, V. parvulus spawned in, and probably inhabited, relatively deep-water environments, as do the survivors of the group.

5. Conclusion

Paradoxically, we are experiencing the same problems that pioneer scientists faced, when they first discovered fossil polychelidans in the middle of the nineteenth century: we lack information on extant Polychelida to compare with the data from fossil specimens. By using XTM, we obtained new information on the internal anatomy of Mesozoic polychelidan lobsters that, in some way, goes beyond the current knowledge on the biology of the living representatives of the group. It is therefore crucial to reexplore the anatomy of extant polychelidans with modern techniques such as XTM and also to collect more in-situ observations of deep-sea species.