Female squid carrying ‘giant’ eggs is determined to be an as yet undescribed species
Proving once again how little we know about the world’s oceans, scientists from the Monterey Bay Aquarium Research Institute (MBARI) have reported the discovery of a new species of deep-sea squid – almost ten years after it was first sighted.
The squid was first observed in March 2015, when MBARI scientists were conducting deep-sea using the research institute’s ROV Doc Ricketts to investigate the distribution of life in the ocean’s low-oxygen zones.
At a depth of 2566m, a female squid with a mantle length of just over 20cm was observed carrying a clutch of eggs fewer in number but larger in size than those carried by previously observed brooding mothers.
The cephalopod was thought to be a member of the Gonatidae family, also known as the ‘armhook squid’, which are widely distributed in deeper, colder waters of the world’s oceans, but little is known about their life cycles and reproductive behaviour. The authors of the new paper had previously observed brooding squid of the species Gonatus onyx at a similar depth and location, but the females were carrying an estimated 2,000-3,000 tiny eggs in a ‘blanket’ that extended beyond the limits of their arms.
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The size of the eggs the squid was carrying was brought to the scientist’s attention during a recent review of past ROV footage examining similar species. The eggs, at an estimated 11.6mm in length, are at least twice the size of those being carried by any previously observed specimen.
Most species of squid that have been observed reproducing either deposit their eggs on the sea floor or set them adrift in a neutrally buoyant mucous balloon. It is thought that carrying the eggs is a survival strategy that has evolved to cope with the deep, cold, oxygen-depleted water – but it is a strategy that comes with a heavy price.
‘Brooding takes a lot out of a mother squid,’ said Henk-Jan Hoving, lead author of the study. ‘She won’t eat while carrying her eggs and ultimately dies after her eggs hatch, but her sacrifice improves the chances that her offspring will survive. It’s just one of the many remarkable adaptations that may help cephalopods to survive in the deep sea.’
Producing thousands of small eggs is a strategy common to many species that inhabit environments with limited resources and high rates of predation, as it gives at least a handful of offspring a chance of survival. Larger eggs that are fewer in number may be a strategy more beneficial in the more predictable conditions of the deep sea, but the investment involved in ensuring the offspring survive is much greater – the scientists speculate that it may take 1.4 years – and, perhaps, more than 4 – for the eggs to mature, far longer than the entire life cycle of most shallow-water cephalopods, which rarely live longer than 1 year.
The new species offers insights into life in an environment which is extremely difficult to study, but one which the scientists hope will become easier to explore with advances in technology.
‘Squid play an important role in the ocean—they’re fierce predators and a vital food source for lots of animals, even humans—but we still have a lot to learn about the squid that live in the deep sea.
‘Advanced underwater robots are helping us better understand the lives of deep-water squids, revealing fascinating new information about their biology and behaviour,’ added Hoving; ‘each new observation is another piece of the puzzle.’
The complete paper, ‘Giant eggs in deep-sea-squid’ by Henk-Jan T Hoving, Steven H D Haddock, Bruce H Robison and Brad A Seibel is published under an Open Access license in the online journal Ecology.
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