Oophagous sharks

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Oophagy, or egg eating, is a means of nutrition by which the developing embryos of some sharks eat their 'potential siblings' while still in the mother's uterus.

Shortfin Mako embryo
A Shortfin Mako embryo of approximately 50 cm total length. It has a distended stomach that is full of egg yolk from eggs it has been eating while still inside the body of the female shark. (CSIRO H.3213-01) Image: T. Carter
© CSIRO

The images on this page show embryos of Shortfin Mako Shark, Isurus oxyrinchus and Porbeagle, Lamna nasus.  Embryos of these species are 'intra-uterine cannibals'. Individuals that have hatched inside the female shark eat successive batches of unfertilised eggs that are continuously ovlulated by the female.

Porbeagle embryo
A 35 cm long Porbeagle embryo that was collected off Hobart in November 1995. The distended stomach of this specimen is full of egg yolk from ingested eggs. Image: T. Carter
© CSIRO

Another species that practises intra-uterine cannibalism is the Greynurse Shark, Carcharias taurus.  The first embryo to hatch eats the other ova within the egg-case.  Greynurse Shark embryos take the process a step further by being adelphophagous.  This means that the embryo actually feeds on other embryos within the uterus of the female.  Two pups are born from each litter, one from each uterus.

The images were kindly supplied by Mr A. Graham, Collection Manager, ISR Munro Ichthyological Collection, CSIRO Division of Marine Research, Hobart.

Porbeagle, Lamna nasus
A 55 cm long Porbeagle. The stomach is swollen due to consumption of eggs while still in the body of the adult female. Image: T. Carter
© CSIRO

References

  1. Last, P.R. & J.D. Stevens. 2009. Sharks and Rays of Australia. Edition 2. CSIRO. Pp. 644, Pl. 1-91.
  2. Stevens J.D. 1987 Sharks. Golden Press. Pp. 240.
  3. Stevens, J.D. in Gomon, M.F., Glover, J.C.M. & R.H. Kuiter (Eds). 1994. The Fishes of Australia's South Coast.  State Print, Adelaide. Pp. 992.