Dentition facilitates the release of encapsulated Ragged-tooth Shark (Carcharias taurus) embryos Kristina Naidoo & Anil A. Chuturgoon & Geremy Cliff & Megan T. Ellis & Nicholas M. Otway & Michael A. Gregory & Sanil D. Singh & Subashen L. Naidu Received: 12 December 2016 /Accepted: 20 July 2017 # Springer Science+Business Media B.V. 2017 Abstract The capture of four female Ragged-tooth Sharks, Carcharias taurus, in the early stages of preg- nancy 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 mi- croscopy. The embryos possessed tooth-like structures. Spectral analysis of these structures revealed the pres- ence of calcium, phosphorus, fluoride and oxygen, which supports the hypothesis that they are teeth. These teeth would enable embryos to escape encapsu- lation. These free-floating embryos are the smallest on record, with the previous smallest being a 40 mm em- bryo. These findings would now amend the current literature of C. taurus embryology. These results could affect the current understanding of C. taurus reproduc- tion and biology and may impact any current breeding programs that are attempting to increase the fecundity of these species. Keywords Carcharias taurus . Dentition . Embryos . Encapsulation . Ragged-tooth . South Africa Introduction The reproductive biology of C. taurus, known in South Africa as the Ragged-tooth Shark, has been well docu- mented, mainly in the United States of America, where it is known as the Sand Tiger shark. Embryo nourish- ment of this aplacental species is oophagous, a trait found in all lamnoid sharks. C. taurus, however appears to be the only species that also follows the additional unique nutrient and survival strategy of intrauterine cannibalism that results in a single well-developed em- bryo being conceived from each uterus (Springer 1948; Hamlett 1983; Gilmore et al. 2005). This extremely low Environ Biol Fish DOI 10.1007/s10641-017-0647-5 K. Naidoo : A. A. Chuturgoon (*) Discipline of Medical Biochemistry, University of KwaZulu-Natal, Durban, South Africa e-mail: chutur@ukzn.ac.za G. Cliff KwaZulu-Natal Sharks Board, Umhlanga, South Africa M. T. Ellis Gladstone Ports Corporation, Gladstone, QLD, Australia N. M. Otway New South Wales Department of Primary Industries, Port Stephens Fisheries Institute, Taylors Beach, NSW, Australia M. A. Gregory School of Health Sciences, University of KwaZulu-Natal, Durban, South Africa G. Cliff : S. D. Singh Biomedical Resource Unit, University of KwaZulu-Natal, Durban, South Africa S. L. Naidu Microscopy and Microanalysis Unit (MMU), University of KwaZulu-Natal, Pietermaritzburg, South Africa