ON A LOGISTIC MODEL FOR MORPHOLOGICAL COVARIATION PATTERNS BETWEEN Colossoma macropomum AND THE HYBRID Colossoma macropomum (♀) x Piaractus orinoquensis (♂)

Currently, great importance has been given to the study of external morphology, especially in fish, when it is used as a means of identifying hybrids. This paper considers a multiple logistic regression model based on the truss protocol to compare morphological covariation patterns between specimens of C. macropomum and the hybrid C. macropomum (♀) x P. orinoquensis (♂). In this study, 25 specimens of C. macropomum and 20 specimens of the hybrid C. macropomum (♀) x P. orinoquensis (♂), respectively, were analyzed. The method "Truss protocol" or "trusses" was used. Multiple logistic regression model based on the morphological covariation patterns between the two species showed a good fit and allowed to correctly classify most of the specimens. Only two covariates were significant; eye diameter and fat fin base. Differences between the hybrid and its parent were observed in the head area and in the anterior part of the fish, which were associated with hydrodynamic abilities and with foraging.