Biological data on two Hector's beaked whales, <i>Mesoplodon hectori</i>, stranded in Buenos Aires province, Argentina

Abstract

Beaked whales or ziphiids are the least known cetaceans, and are among the least studied of all mammalian groups. In August and September of 2002, a male and a female beaked whale stranded alive on the Argentine coast, 110km away from each other. The specimens died shortly after the stranding and their bodies were collected for dissection and analysis. The specimens were identified as belonging to the genus Mesoplodon. Further measurements of the skulls, shape and location of teeth as well as molecular analyses of the mtDNA control region and cytochrome b, allowed unambiguous identification of both specimens as Hector's beaked whale, Mesoplodon hectori. The color pattern was different between male and female. Standard length was 3.94 meters for the male and 3.84 meters for the female. The female's vertebral formula was C7 + T10 + L11 + Ca21 = 49. Histo-pathological analysis of the female revealed the presence of Sarcocystis sp. in the skeletal muscle, and lung lesions related to parasitic damage and pneumonia or chronic infection. The stomach of both individuals was empty. The digestive tract of both specimens was infected by larval stages L4 of Anisakis sp. The female was also infected by Tetrabothrius sp. and Bolbosoma sp. while Braunina cordiformis was only found in the male. Different composition of parasitic fauna suggests possible sex-related differences in the diet or individual variability. Total length, teeth eruption (in the male) and the degree of vertebral epiphyses fusion suggest that both individuals were mature.