Vampyroteuthis infernalis, which translates to “vampire squid of hell,” is a true deep-sea relic.

It may look like a true squid at first glance, but the vampire squid is actually the last surviving member of a separate order, called vampyromorphida. These luminescent creatures live in otherwise inhospitable deep-ocean environments, and rarely survive long in captivity, so researchers struggle to record their behaviors reliably. But a new study in Current Biology offers fresh insight into the reproductive strategies of these strange creatures – and in doing so, shows just how much we have left to learn about deep-sea life.

Henk-Jan Hoving, of the Helmholtz Centre for Ocean Research Kiel, was observing decades-old vampire squid collections at the Santa Barbara Museum of Natural History when he noticed something unusual. True squids spawn only once in their lifetime, but many vampire squid females still had viable oocytes for producing more eggs. What’s more, some weren't actively developing eggs at all. Dr. Hoving and his colleagues determined that vampire squids, unlike true squids, experience alternating reproducing and resting phases.

Scientist suggest that the vampire squids, unlike true squids, lack the energy to put all their eggs into a single mating event.

“The pace of life in vampire squid is likely slower due to their low metabolic rates, low calorie food intake and inactive mode of life,” Hoving says. “It could be that vampire squid cannot mobilize enough energy for one reproductive cycle – as other semelparous coleoid cephalopods can – to provide enough eggs to ensure lifetime reproductive success.”

According to the study, a single vampire squid might spawn over 100 times in its lifetime. And longer reproductive cycles usually mean longer life – in other words, vampire squids could have longer lifespans than their shallow-water counterparts.

But while new discoveries improve our understanding of this and other deep-sea species, biodiversity in the pelagic zone is still shrouded in mystery.

“There are many aspects of the biology of vampire squid that are still not known,” Hoving says. “One of them is that we do not know how old they become, or at what age they reach sexual maturity.”

Vampire squids are not alone in being poorly understood. Indeed, most species on Earth remain unknown to science.

Get the Monitor Stories you care about delivered to your inbox. By signing up, you agree to our Privacy Policy

Since 2006, researchers have identified roughly 18,000 new species per year. That number may seem high, but there could be upwards of 10 million species still undiscovered, according to some scientific estimates. Fewer than 2 million species have been cataloged to date – in other words, it is possible that only a fifth of Earth’s creatures have been identified.

Researchers are in a race against time to record new species. Environmental factors like global warming and habitat loss, many of which are thought to be caused by humans, threaten biodiversity on the global scale – some scientists worry species are dying out faster than we can record them. In the meantime, new understanding of already-identified species can remind us of an important fact: in a time when we are planning for a manned mission to Mars, there still remain unexplored places on own planet.