Parthenogenesis in sharks

Parthenogenesis, from the Greek meaning “virgin birth” is an odd quirk of embryonic development that allows female animals of some species to give rise to offspring without a male genetic contribution - usually by a doubling of the egg genome to generate a new embryo with the proper number of chromosomes. Parthenogenesis is common in insects, and among vertebrates it occurs in some species of fish and reptiles, and strangely enough, in turkeys.

Parthenogenesis has also been documented in several species of shark and rays. In the previously studied cases, however, only a single animal was produced by parthenogenesis, and none survived more than a few days. It was unclear then if elasmobranch parthenotes were as healthy as animals produced from normally fertilized eggs. A recent study led by Kevin Feldheim of the Pritzker Laboratory for Molecular Systematics and Evolution at the Field Museum in Chicago, and Demian Chapman of the Institute for Ocean Conservation Science at Stony Brook University in New York, advances this field one step further. They show that a white-spotted bamboo shark female gave rise to parthenogenetic offspring that have survived for several years. Parthenogenetic sharks are therefore not inherently less viable - normal sharks can be produced using only female-contributed chromosomes. It remains unknown whether elasmobranchs actually use parthenogenesis as a method of reproduction in the wild. The studied instances have occurred among animals in the controlled environment of aquaria, where the female was isolated from males for a long period of time. The reference for the published manuscript is: Feldheim, KA, Chapman, DD, Sweet, D, Fitzpatrick, S, Prodohl, PA, Shivji, MS and Snowden, B. Shark Virgin Birth Produces Multiple, Viable Offspring (2010) Journal of Heredity, 101:374-377.

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