REPRODUCTIVE-BIOLOGY OF LAMNOID SHARKS

The capture of recently inseminated or pregnant specimens of Carcharias taurus, Isurus paucus, I. oxyrinchus, Alopias superciliosus and A. vulpinus has allowed new information to be obtained on the reproductive biology of these species. Oophagy and embryonic cannibalism (adelphophagy) have been documented in C. taurus, but only oophagy in other lamnoid species. The occurrence of up to nine embryos of similar size per uterus in Isurus and no indication of functional erect teeth in embryos leaves considerable doubt that embryophagy occurs in this genus. Considerable data has been collected on Carcharias taurus which allows a lamnoid reproductive model to be developed and tested, in spite of the obvious differences between the reproductive biology of this species and other lamnoids. Gonad structure, ovarian development, fertilization, early embryonic differentiation, embryonic nutrition and parturition, in C. taurus and other lamnoids differs significantly from other elasmobranchs.