Zoology Notes 008: the shark that eats its siblings, in utero
“At about 100mm TL [total length], the embryo begins to hunt and consume other intrauterine embryos in a process of intrauterine cannibalism or embryophagy ”
At the early stages of pregnancy, a female sand tiger shark may have a litter of as many as ten embryos, five in each of two discrete uterine horns. By the end of gestation, only two survive, one on each side.
“Although only two young are produced at the end of a lengthy gestation period, they have several selective advantages as top predators in marine food webs,” they wrote. The newborn sand tiger sharks are so large they maybe better able to see off predators. It is also possible, they suggest, that the experience of hunting in utero may give them an edge.
Embryonic sand tiger sharks will attack and eat each other inside their mother Photograph: Rafa Rivas/AFP/Getty Images