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Iheringia. Série Zoologia

Print version ISSN 0073-4721On-line version ISSN 1678-4766


CABRERA, Mario R.  and  COLANTONIO, Sonia E.. Ontogenetic variation of plastral spotting pattern in Phrynops hilarii (Testudines, Chelidae). Iheringia, Sér. Zool. [online]. 2001, n.91, pp.115-122. ISSN 0073-4721.

The plastral spotting variation in the chelid turtle Phrynops hilarii (Duméril & Bibron, 1835) in relation to sex, size, and geographic procedence of individuals was analyzed. States for qualitative characters were analyzed using non-parametric tests. Quantitative characters (shell and scute measurements) were standardized for body size by linear regression against carapace length, and were subjected to principal components analysis and canonical discriminant function analysis. Results suggest that increased plastral spotting is a polymorphic ontogenetic trait in P. hilarii. Neither hatchlings nor juveniles have plastral pattern moderately or heavily pigmented. The simplest pattern, however, may persist without changes in some adults. There are no differences between sexes. The spatial distribution of the plastral pattern is not ordered latitudinally or longitudinally, showing no relationship with gradients of elevation, temperature, or precipitation. This pattern trait lacks of taxonomic significance. The morphometric analysis failed to reveal any character of diagnostic utility in the plastron to support the possibility that these patterns correspond to different sympatric taxa.

Keywords : Reptilia; Chelidae; Phrynops; pattern variation; South America.

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