Scientists reveal the strange sex lives of ghost sharks

With sunken dead-looking eyes, winged fins, and long whip-like tail, ghost sharks are already known to be rather strange creatures. Photo / Getty Images

With sunken dead-looking eyes, winged fins, and long whip-like tail, ghost sharks are already known to be rather strange creatures.

And, their sexual habits are, predictably, just as bizarre.

Scientists who are studying the elusive deep-sea fish, that can be found off the coast of New Zealand, have revealed some insight on their reproductive features, including a retractable hook-like apparatus on the heads of males and tubes that allow females to store sperm long after sex - possibly even for years, according to the Daily Mail.

The hooked sex organ found on male chimaera's foreheads allows them to hold onto the fins of the female while they mate, according to National Geographic.

They're also equipped with another set of claspers around the pelvis.

By little surprise, mating "does not seem to be a very pleasant experience for the females," lead author Brit Finucci, a PhD student at Victoria University of Wellington, told National Geographic.

While much about these deep-sea creatures remains a mystery, recent efforts have shed some light on their history and anatomy.

In a new study, researchers examined two types of ghost sharks, also known as chimaera, at different stages of sexual maturity.

The brown chimaera (Chimaera carophila) and the black ghost shark (Hydrolagus homonycteris) are both rarely-caught species.

Examining hundreds of chimaera collected from research trawl catches and commercial fishery catches from 400-1300 meters below the surface, as well as preserved museum specimens, the researchers discovered that females in the family Chimaeridae are capable of storing sperm.

These fish contain a set of small tubes that allows them to pack in sperm and hold onto it for long periods of time.

It's thought that they may even be able to store sperm for years, according to National Geographic.

While they've suspected this may be the case, it's first time the phenomenon has been confirmed in this family, meaning it is now known to be present in all families in the order Chimaeriformes, the researchers explain in the study.

The behaviour may sound strange, but in the solitary conditions of the deep ocean, it may be crucial to their survival.

"Sperm storage could be particularly advantageous for deep-sea species, increasing reproductive efficiency by allowing fertilisation to take place at the optimal time in an environment where food resources may be limited, or where mating may be difficult due to infrequent encounters or sexual spatial segregation," the authors wrote in the study.

"Hydrolagus homonycteris may also store sperm, but further sampling of female individuals will ve required to confirm this hypothesis."