A few years ago, a bonnethead shark made the news because one had given birth. Giving birth is not unusual for sharks... except that the female in question had grown up in isolation. Good evidence for parthenogenesis.
Shortly after that, another shark species (blacktip) was autopsied and found to have an embryo that was genetically identical to the mother. Clearly, parthenogenesis in sharks was not happenstance. But in both cases, the parthenogenetic offspring didn’t live long. Are the offspring able to make it to adulthood?
A new paper examined this in white spotted bamboo shark (Chiloscyllium plagiosum). It came to an aquarium as a juvenile, and kept laying eggs that were discarded as nonviable... until word got out about the bonnethead shark, and one of the savvy keepers decided to start keeping the cases. Out of seven eggs, four hatched. One died young, one “committed suicide” (jumped out of the tank), and the other two grew up to be find, upstanding bamboo shark ladies.
DNA testing confirmed that the offspring had the same genetic make-up as the mother. Definitely parthenogenesis going on here.
Feldheim and colleagues also note that the bamboo sharks they tested in aquaria seemed to be quite inbred. They seem to be hinting that this inbreeding may be facilitating parthenogenetic reproduction. With so few individuals to work with at this point, it’s too early to tell.
What is particularly cool and exciting about this finding is not just the evidence that these shark clones are perfectly viable and can live to adulthood, but this particular species is in a completely different order of sharks compared to the previous two species. That means the capability is either very widespread, or has evolved multiple times. Either way, the ecological and evolutionary importance of parthenogenesis in this group is larger than expected.
Feldheim K, Chapman D, Sweet D, Fitzpatrick S, Prodohl P, Shivji M, Snowden B. 2010. Shark virgin birth produces multiple, viable offspring. Journal of Heredity 101(3): 374-377. doi: 10.1093/jhered/esp129
Adult white-spotted bamboo shark picture by Danielguip on Flickr; eggs picture by Questionhead on Flickr. Both are used under a Creative Commons license.