Morphological, functional and evolutionary aspects of tail autotomy and regeneration in the 'living fossil'Sphenodon (Reptilia: Rhynchocephalia) |
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Authors: | HERVÉ SELIGMANN JIÍ MORAVEC YEHUDAH L WERNER |
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Institution: | Department of Evolution, Systematics and Ecology, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel; Department of Zoology, National Museum, 11579 Praha 1, Czech Republic |
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Abstract: | Tail autotomy and regeneration are less known in Sphenodon ('Reptilia': Rhynchocephalia) than in Squamata. We examined museum specimens, Sphenodon guntheri ( N = 8) and Sphenodon punctatus ( N = 172), wild Sphenodon punctatus ( N = 19) and Sphenodon sp. skeletons ( N = 8). In S. punctatus , unlike in typical Squamata, sexes had similar relative (intact) tail lengths, and regeneration frequencies; tail and body growth was isometric. Tail breakage was usually intravertebral, usually followed by ablation of a variably sized terminal vertebral piece, partly deviating from lizards. Hypothetically, imperfect autotomy results from sphenodon's primitiveness. As in squamates, tail-losers were morphologically more left-side dominant than tail-retainers. Individual directional asymmetries in digit morphology and in digit injury were correlated (in lizards observed only at population level); tail-losers had more fluctuating asymmetry but their exclusion did not facilitate morphological taxonomic distinctions (no 'Seligmann effect'). In S. punctatus , extents and directions of sexual dimorphism paralleled differences between tail-retainers and tail-losers, females resembling tail-losers, also accounting for character interdependence (developmental constraints; employing a method similar to phylogenetic contrasts). The variation in the location of tail injury was correlated with the continuum of variation between injured and intact (pholidotic) morphotypes. These last two phenomena remain to be explored in Squamates. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 93 , 721–743. |
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Keywords: | ablation age effects brain lateralization developmental contrasts directional asymmetry fluctuating asymmetry injury rate intraspecific fighting sexual differences tail length |
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