Environmental Biology of Fishes

Dentition facilitates the release of encapsulated Ragged-tooth Shark ( Carcharias taurus) embryos

The capture of four female Ragged-tooth Sharks, Carcharias taurus, in the early stages of pregnancy in the bather protective nets along the KwaZulu-Natal coastline provided an opportunity to investigate embryonic development. A total of 31 embryos, 8–225 mm total length, were found. Of these, 15 were encapsulated and 16 were found free-floating in the uterus. Six embryos, three of which were encapsulated (35–50 mm) and three free-floating (36–52 mm), were examined under both light and scanning electron microscopy. The embryos possessed tooth-like structures. Spectral analysis of these structures revealed the presence of calcium, phosphorus, fluoride and oxygen, which supports the hypothesis that they are teeth. These teeth would enable embryos to escape encapsulation. These free-floating embryos are the smallest on record, with the previous smallest being a 40 mm embryo. These findings would now amend the current literature of C. taurus embryology. These results could affect the current understanding of C. taurus reproduction and biology and may impact any current breeding programs that are attempting to increase the fecundity of these species.

Glossaire technique

Un jeune organisme dans les stages le plus précoces de son développement.
Fonction par laquelle les êtres vivants perpétuent leur espèce. Mécanisme...
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