Vampire squid have been observed from old photographs, revealing secrets of sex 10,000 feet beneath the surface of the ocean. Researchers found that the reproductive habits of the squid are unlike those of other cephalopods.

The squid do little powered swimming between 1,600 and 9,800 feet underwater. Instead, they essentially float as they feed on zooplankton and other biological debris drifting nearby. Investigators believe this laid-back lifestyle could play a part in altering their mating habits.

Most cephalopods mate just once, late in life. Investigators discovered that vampire squid employ mating patterns more like those practiced by fish, alternating between periods of mating and relaxation. It is possible that the squid may be building up energy between mating sessions for their next sexual encounter.

"We know very little about deep-sea organisms and their life-cycle patterns, in particular in the water column of the deep sea. The patterns we know from coastal and shallow-water organisms may not apply to deep-sea species," Henk-Jan Hoving of the GEOMAR Helmholtz Centre for Ocean Research Kiel said.

Photographs of vampire squid taken in the 1960s and 1970s were being examined by Hoving and other researchers when they noticed that many of the females had previously released eggs but were no longer carrying or developing new eggs. This led the researchers to conclude that the animals were in a reproductive resting phase, a highly unusual condition for cephalopods. The study involved examination of around 40 female vampire squid.

One of the female cephalopods was found to be carrying around 6,500 reproductive germ cells known as oocytes despite the fact she had already spawned around 3,800 eggs. Each spawning session releases around 100 eggs, suggesting the cephalopod was around one-third of the way through the mating period of her life. This would indicate that females of the species have sex around 100 times during their lives, compared with once for other varieties of squid.

These deep-sea squid appear to live longer than their cousins in shallower waters, according to findings of the new study.

Vampire squid do not drink blood, but the name derives from their webbing that resembles a dark cloak as well as their piercing red eyes that give the animals a look much like that of the undead creatures. These animals, first described in 1903, are found throughout tropical and temperate waters around the globe.

This current study sheds new light on the lifestyles of vampire squid. Researchers hope that this investigation helps conservation groups devise new strategies to help protect the animals.

Analysis of the mating habits of vampire squid was detailed in the journal Current Biology.

Photo: Anne-Lise Heinrichs | Flickr

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