A Bizarre New Shark

Live goblin shark Mitsukurina owstoni, from here.

It's a bit unusual for me to be posting anything on a Sunday, but I've just received notice of something so incredibly cool that I couldn't wait to tell you all about it. A new paper has just come out describing a truly remarkable new species of shark:

Takahashi, N., & N. Yuasa. 2012. First recorded use of weaponised light by an elasmobranch. National Daiei Journal 7: 17-87.

The new species, Neomitsukurina nodai, is most closely related to the unusual goblin shark Mitsukurina owstoni, and the resemblance between the two is clearly visible in the head region:

Photo of the new shark species from Takahashi & Yuasa.

Nevertheless, it possesses several remarkable differences. First there is the distinctive fin array, somewhat more extensive than that found in most shark species. The denticles in the skin are much reduced, giving the body an almost rubbery appearance. Furthermore, in a remarkable case of life imitating art, Neomitsukurina differs in its jaw morphology. The vast majority of depictions of goblin sharks show it with protruding jaws but, as can be seen in the photo at the top of the post, this is not the usual appearance of this species: the jaws are generally only protruded when the shark is picking up food. In Neomitsukurina, however, the jaws are seemingly permanently protruded, and the upper jaw has been modified into a sharpened beak. The most interesting distinction of all, however, is the presence of a massively enlarged photophore on the underside of the rostrum, above the jaws:

Close-up of the head of Neomitsukurina nodai, from Takahashi & Yuasa.

The photophore contains a unique lens structure that focuses the light it produces. So strongly focused is the light, in fact, that it can be used in prey capture by the shark. Through a mechanism not yet fully understood, but possibly a shock reaction to its brightness, the light causes potential prey animals to become stunned, after which they can be easily picked off. Preliminary observations of Neomitsukurina suggest that it may be willing to take on quite large prey: even turtles have not proven immune to stunning, though the shark did not always immediately ingest stunned prey animals. Neomitsukurina has also been observed gliding above the surface of the water through the use of its enlarged pectoral fins.

It might be wondered how such a distinctive and mobile predator eluded discovery until the present, but Neomitsukurina's strict nocturnality might have something to do with it. It is also worth noting that sightings of what may, in hindsight, have been Neomitsukurina have been described in the past (a particularly famous sighting occurred in 1971, near the island of Niemonjima), but attempts to follow up such records have so far only collected other animals such as sea bass.