It's a tough life deep in the ocean, so you can't really blame the vampire squid for taking a break. All other species of soft-bodied cephalopod so far studied produce their offspring in one glorious bout of reproduction, usually just before they die. But not the vampire squid. This sinister-looking creature feeds on zooplankton and decaying organic material in its struggle to survive up to 3000 metres deep.
Henk-Jan Hoving at the Helmholtz Centre for Ocean Research in Kiel, Germany, and his team dissected 43 female vampire squid captured in tow nets off the coast of southern California. They found 20 adults that had released some eggs, but still had immature egg cells available for future spawning. One squid had released at least 3800 eggs, judging by her empty follicles, but still had around 6500 left.
Based on the number of eggs the team observed ripening together in batches, they estimated that the squid release about 100 eggs at a time – suggesting this female had already undergone at least 38 bouts of spawning, and could have gone on for another 65.
This could be an adaptation to their life in the deep ocean. "By reproducing in multiple cycles, it may allow vampire squid to make use of its low-calorie food source," says Hoving.
"This reproductive strategy gives advantages to the vampire squid to save energy in the very poor feeding conditions of the deep sea environment," says Bahadir Önsoy of 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."
Daniel Stephen of Utah Valley University in Orem agrees the strategy is probably an adaptation to the squid's environment, but he isn't surprised. Repeated bouts of spawning are known in their shelled relatives, the nautiluses.
Journal reference: Current Biology, DOI: 10.1016/j.cub.2015.02.018
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