Evidences of sibling bites in porbeagle shark (Lamna nasus) embryos.

The porbeagle, top predator with amphi-temperate, coastal and oceanic distribution, ranges 26-57°S in the Southwest Atlantic. An injured, pregnant female was found stranded on the coast of Quequén, with two male embryos in each uterus. The embryos in the right uterus differed in size, and the smaller one had injuries. Our hypothesis is that embryos have the ability to perform lateral movements that allow them to bite obliquely along the anteroposterior axis of the uterine sac, so that the lacerations of the smaller embryo would be the result of lateral bites from its sibling, as the latter would not have space to attack it in a more dangerous way.