#oxynotidae

The Prickly Dogfish (Oxynotus bruniensis) is a deep-sea shark, endemic of the deep waters of southern Australia and New Zealand, also is one of five Angular sharks species known to science. Despite they are triangular shaped, with distinctive body characteristics, the sightings of individual in nature seem to be uncommon and their life history is virtually unknown.

But everytime we know more about these rare sharks. In a recent study, Australian and New Zealand researchers, using molecular analysis and looking at stomach content figured out that these sharks are feeding primarily on the eggs and embryos of chimaeras, potentially making it the only known elasmobranch with a diet reliant solely upon other chondrichthyans.

The prickly dogfish’s diet  include the Pacific spookfish (Rhinochimaera pacifica) and the brown chimaera (Chimaera carophila), besides the longnose chimaera (H. raleighana) a chimaera similar to zero from Nightmare Before Christmas movie.

   - Examples of stomach contents from a prickly Dogfish, including (a) egg case fragments and (b) a longnose chimaera embryo.

Apparently, is not a sole example, in 2015, Spanish researchers proved that the Atlantic angular roughshark (Oxynotus centrina) preys on the egg cases of other elasmobranchs, as well  on another small invertebrates.

Photo by  Mark Norman

The angular roughshark (Oxynotus centrina) at 60/70 m depth in Saint Thecla, Italy.

 A specimen of angular roughshark (Oxynotus centrina) has been kept successfully in captivity for the first time. Over a period of 24 months, the specimen preyed exclusively on the contents of elasmobranch egg cases, suggesting a specialized trophic niche.

Angular roughshark  is a deep-water shark occurring in theeastern Atlantic Ocean and Mediterranean Sea. Biological knowledge of this rarely caught species is limited and it is listed as vulnerable (globally) and critically endangered (Mediterranean Sea) by the IUCN.

Photograph by  L'Elasmogrup

Reference Open Access: Guallart et al. 2015.Angular roughshark Oxynotus centrina (Squaliformes: Oxynotidae) in captivity feeding exclusively on elasmobranch eggs: an overlooked feeding niche or a matter of individual taste? Journal of Fish Biology