Morphological analysis of the flippers in the franciscana dolphin, Pontoporia blainvillei, applying X-ray technique.

DEL CASTILLO, D.; PANEBIANCO, M. V.; NEGRI, M. F.; CAPPOZZO, H. L.

The Anatomical Record

John Wiley & Sons Inc

Lugar: Malden; Año: 2014

1932-8494

Our goal was to contribute with new anatomical and morphometric data of Pontoporia blainvillei, studying directional asymmetry, allometry, physical maturity and sexual dimorphism of the flipper skeleton, using X-ray technique. Franciscana dolphins were by-caught or stranded on the southern coast of Buenos Aires, Argentina. We recorded the number of carpals, metacarpals and phalanges, and morphometric characters from the humerus, radius, ulna, and digit two. We also determined the number of visible epiphyses and their degree of fusion at the proximal and distal ends of the humerus, radius and ulna. The flipper skeleton was symmetrical, showing a negative allometric trend, with similar growth patterns in both sexes with the exception of the width of the radius (p ≤ 0.01). Sexual dimorphism was also found on the number phalanges of digit two (p ≤ 0.01), ulna and digit two lengths. Females showed a higher relative ulna length and shorter relative digit two length, and the opposite occurred in males (p ≤ 0.01). We suggest that this sexual dimorphism could be related to differential use of the flippers. Epiphyseal fusion pattern proved to be a tool to determine dolphin?s age; franciscana dolphins with a mature flipper were, at least, four years old. This study indicates that the flippers of franciscana dolphins are symmetrical; both sexes show a negative allometric trend; sexual dimorphism is observed in radius, ulna, and digit two; and flipper skeleton allows determine the age class of the dolphins.