June 17, 2024

Biometric Measures Indicating Sexual Dimorphism in Stenella coeruleoalba (Meyen, 1833) (Delphinidae) in the North-Central Tyrrhenian Sea


Rossella Carlini, Maria Carla de Francesco, and Simonetta Della Libera


Abstract: Since 1985, the Centro Studi Cetacei (Cetacean Study Centre) in Italy has been committed to the recovery of cetaceans stranded along the Italian coastlines to estimate the abundance of species present and to identify causes of death, disease, and other information useful to the study of cetaceans. The current study analyzed some external morphometric parameters of striped dolphin (Stenella coeruleoalba), the most abundant small cetacean in the Mediterranean Sea, to identify features indicating sexual dimorphism. Identification and measurement of external dimorphic characteristics allowed for determination of the sex of those specimens for which gender was not immediately evident due to decomposition of their external genital organs. Specifically, a total of 37 specimens (19 males, 15 females, and 3 unsexed) of S. coeruleoalba that stranded along the north-central Tyrrhenian Sea coasts (Italy) from 1983 to 1991 were measured; 28 parameters of external morphology were examined; and values were analyzed using the parametric Student t-test and were subsequently validated by stepwise discriminant analysis. According to the data, the total length reached by individuals, which is greater in female specimens, was not a statistically significant parameter leading to gender confirmation—that is, the length reached by individuals was independent of sex. However, the distance between the genital slit and anus (greater in males as in other small odontocetes) and the distance between the umbilicus and anus (greater in females) were found to be statistically significant dimorphic characters. The distance between the genital slit and the median notch of the flukes, which is longer in males, was identified as significant by discriminant analysis only. Thus, it may be considered as a feature indicating sexual dimorphism, but further investigation is required.
Key Words: dimorphic characteristics, Italian coasts, external measurements, striped dolphin, Stenella coeruleoalba, Progetto Spiaggiamento Cetacei
Document Type: Research article
DOI: 10.1578/AM.40.1.2014.59
Page Numbers: 59-68

Info SKU: Vol__40__Iss__1__Carlini Category: