Pincer-like claws in centipedes (Chilopoda): multiple evolutionary origin of similar form and serial pattern |
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Authors: | Lucio Bonato Leandro Drago Alessandro Minelli |
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Institution: | 1.Dipartimento di Biologia,Università di Padova,Padova,Italy |
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Abstract: | In most Chilopoda, the walking legs end in a single-tip claw usually accompanied by short accessory spines. Instead, in all
species of three small and only distantly related geophilomorph taxa (Diphyonyx, Neogeophilidae, Eucratonyx), the claws of an anterior set of leg pairs are unusually pincer-like. By integrating different microscopic techniques, including
confocal laser scanning microscopy, we found that these modified claws are very similar in form, internal structure, and pattern
of variation in shape along the trunk in all three taxa: the claws are distinctly swollen and bent, provided with peculiar
bulges, and flanked by a conspicuous additional branch, either cylindrical or flattened, which overreaches the tip of the
claw; instead, the internal cuticular features are not modified with respect to the condition in the other centipedes, claiming
against the possibility of controlled abduction/adduction between claw and branch. Irrespective of the total number of leg
pairs (63–129), the claws change gradually from pincer-like to usual shape invariantly in the range spanning between the 34
and the 45% of the total number of leg pairs. Despite these similarities, pincer-like claws originated independently in the
three taxa, and by way of fundamentally different changes, either by the dramatic modification of the already existent anterior
accessory spine (Diphyonyx, Neogeophilidae) or by the production of a novel cuticular projection (Eucratonyx). Moreover, their shared pattern of variation along the body was most probably constrained by already operating developmental
processes controlling the longitudinal patterning of the trunk. |
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