Most soft-bodied cephalopods produce and release their eggs once before they die, but the deep-water vampire squid is different—it goes through several egg-making cycles in its lifetime.
Now, researchers say that this unique behavior provides evidence that the vampire squid may live longer compared with its cousins, the coastal squid and octopus, which live in shallower waters.
In a new study published in the journal Current Biology on April 20, researchers reported that the vampire squid alternates between a reproductive and resting phase, as its sluggish lifestyle appears inadequate to support one big reproductive event.
"Perhaps it is therefore that vampire squid return to a gonadal resting phase after spawning, and presumably start accumulating energy for a new reproductive cycle," said study researcher Henk-Jan Hoving from the GEOMAR Helmholtz Centre for Ocean Research Kiel in Germany.
Hoving and colleagues dissected 43 vampire squid specimens and found that almost half of the animals had already released hundreds of eggs while still having about a hundred more immature eggs, an evidence that suggests the marine animal has multiple reproductive cycles. A female specimen, for instance, was found to have released 3,800 eggs but still had a remaining reserve of 6,500.
"This reproductive strategy gives advantages to the vampire squid to save energy in the very poor feeding conditions of the deep sea environment," said Bahadir Onsoy from Mugla Sitki Kocman University in Turkey. "In deep sea habitats, the temperature is low, so the metabolism of an animal that lives there is expected to be slow."
Scientists said that the lengthy and staggered reproduction of the squid provides evidence of a slower pace of life necessary for surviving in deep water. The vampire squid is able to thrive in these parts of the sea with low oxygen levels. They live in dark and chilly waters up to 9,800 feet below the surface.
Unlike their counterparts that live and hunt in shallower waters, the vampire squid drifts, allowing its food, which includes plankton and sinking clumps of particles, to come to them. The vampire squid has a slow metabolism and eats low-calorie food.
Hoving said that this shows diversity and indicates that the vampire squid has a slower pace of life compared with shallow-water cephalopods that are known to grow very fast. He added that age and longevity offer important parameters for scientists to understand how animals live and how their ecosystem works.
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