Yolk Sac - in Fish

In Fish

All bony fishes, some sharks and rays have yolk sacs at some stage of development, with all oviparous fished retaining the sac after hatching. Lamniform sharks are ovoviviparous, in that their eggs hatch in utero, in addition to eating unfertilized eggs, unborn sharks participate in intrauterine-cannibalism: stronger pups consume their weaker womb-mates.

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