Notes on the Pelagic Squaloid Shark Isistius brasiliensis

AbstractOne hundred thirty specimens of Isistius brasiliensis (Quoy and Gaimard, 1824), including Dana material and the holotype of I. plutodus (Garrick and Springer, 1964), were measured and their stomach contents and reproductive systems examined. No differences were found between Atlantic and Indo-Pacific populations of I. brasiliensis. I. plutodus differs from I. brasiliensis in 8 of 15 morphometric and meristic characters used. Teeth of the fossils I. trituratus (Winkler, 1878) and I. triangulus (Probst, 1879) have shorter bases, but caps similar to those of modern Isistius.Isistius brasiliensis is distributed circumtropically, ranging from the surface to a depth of probably 1500 meters or more. Males mature at about 360 mm total length and attain a maximum length of about 400 mm. Females mature at about 390 mm total length and reach a maximum of about 500 mm. The I. plutodus holotype is a 423 mm mature female. The uteri of Isistius are thickly lined with villi, suggesting these sharks are ovovivipar...