Bizarre egg cases lead to discovery of new deepwater catshark species, demon shark

Scientists discover a new species of deepwater catshark, Apristurus ovicorrugatus, off the coast of northwestern Australia through a museum collection.
Kavita Verma
An adult female Aspiritus ovicorrugatus
Newly discovered species of deep water catshark sheds light on diverse shark populations in Australia

White et al. (2023), Journal of Fish Biology, CC BY-NC-ND 4.0 

After discovering bizarre egg cases in a museum collection that led them to an unknown species of deepwater catshark, researchers have made a ground-breaking discovery. The eggs were determined to be from the Apristurus ovicorrugatus species, which was previously mistaken for Apristurus sinesis due to its milky white eyes.

Uncovering the mysterious deepwater catshark

The Western Australia Museum and the Australian National Fish Collection from the Commonwealth Scientific and Industrial Research Organisation (CSIRO) both have collections of fish samples where the egg cases were discovered. The strange, rigid structure of the egg cases fascinated the scientists. They discovered that the unidentified samples matched those of an in-storage deceased, pregnant female shark specimen with identical eggs. The specimen was taken from water more than 1,800 feet (550 meters) deep off the coast of northwest Australia.

The specimen was initially thought to be an Apristurus sinesis. Still, after further examination of the shark and its embryos, the scientists discovered that it is a new species of deepwater catshark called A. ovicorrugatus. The finding is especially noteworthy because, to date, only two species of Apristurus have been identified off the coast of northwest Australia.

The milky white irises and peculiar egg casings, which have very pronounced longitudinal ridges and are T-shaped in cross-section, are characteristics of the new species. Only one other species in the world has been found to have egg cases with that type of ridging, and that species belongs to a completely different genus. This is because the egg cases are so unusual.

Demon shark with a meager length

The recently discovered Apristurus ovicorrugatus, which measures only 1.5 feet (0.46 meters) long and has milky white eyes, lives up to the epithet "demon shark" given to the genus. The results were released in the Journal of Fish Biology last month.

The discovery of A. ovicorrugatus is a positive development for the field of shark biology, especially since a team of scientists withdrew their paper in March that purported to be the first account of a goblin shark sighting in the Mediterranean Sea. According to experts, the goblin shark specimen that was photographed was apparently only a plastic toy.

A. ovicorrugatus, a new species of deepwater catshark, has been discovered, which is excellent news for the scientific community. The discovery of this novel species highlights the value of researching museum holdings to find novel and undiscovered species.

The results of the study emphasize the necessity of further research into deepwater ecosystems and the significance of accurate specimen identification. The discovery of A. ovicorrugatus highlights the importance of ongoing research into the varied and exciting world of sharks, which continue to be some of the most enigmatic and fascinating marine life.

Study Abstract:

Apristurus ovicorrugatus, a new species of deepwater catshark, is described from northwestern Australia. Unique egg cases belonging to an unknown species of Apristurus prompted a more detailed investigation of Apristurus specimens off northwestern Australia. One specimen previously identified as A. sinensis collected off Dampier Archipelago was found gravid with a single egg case. Removal of this egg case confirmed that this species was responsible for producing the unique egg cases previously recorded. The egg cases of this species have strong T-shaped longitudinal ridges on the dorsal and ventral surfaces which are unique in the genus Apristurus. The ridges most closely resemble those present in Bythaelurus canescens from South America, but are larger and always T-shaped. The holotype is closest morphologically to A. sinensis but differs in having a medium brown buccal cavity (vs. jet black), ridged egg cases (vs. smooth egg cases), fewer intestinal spiral valve turns and larger pectoral fins. The holotype is also similar, and closest on a molecular level, to A. nakayai with which it shares a unique synapomorphic character, the white shiny iris (apomorphic within the genus). A late-term embryo removed from an egg case superficially resembled the holotype except in having two parallel rows of enlarged dermal denticles on the dorsolateral predorsal surface. Recent nomenclatural changes to the genera Apristurus and Pentanchus are discussed and challenged. This study highlights the important contribution that egg case morphology has on oviparous elasmobranch taxonomy.

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