Advanced underwater robots discover deep-sea squids hatching giant eggs

The deep sea is the largest living space on Earth, but many of the animals and habitats far below the ocean’s surface remain shrouded in mystery. MBARI’s advanced underwater robots, including remotely operated vehicles (ROVs), help explore life in the depths of the ocean.

During a 2015 expedition to Mexico’s Gulf of California, MBARI’s ROV Doc Ricketts came across a mother squid cradling a cluster of eggs. MBARI researchers had previously observed deep-sea squids hatching their eggs, but this observation was striking because the eggs were twice the size of those of other breeding deep-sea squids.

A team of researchers from MBARI, GEOMAR’s Helmholtz Center for Ocean Research Kiel and the University of South Florida conducted a painstaking review of the ROV images and examined specimens of similar-looking squid collected during previous expeditions to the Gulf of California .

The team determined that this individual likely represents an unknown species of the family Gonatidae and a species that broods giant eggs. Researchers classified their findings Ecology.

‘Squids play an important role in the ocean – they are fierce predators and an essential food source for many animals, even humans – but we still have a lot to learn about the squids that live in the deep sea. These are advanced underwater robots. it helps us better understand the lives of deepwater squids and reveals fascinating new information about their biology and behavior. Every new observation is a new piece of the puzzle,” says Henk-Jan Hoving, a former postdoctoral researcher at MBARI who now leads the Depth. marine biology working group at GEOMAR and was the lead author of this new study.

Scientists still have many unanswered questions about the lives of deep-sea squids. In most deep-sea squids, researchers have never observed adult females or their spawned eggs.

Although maternal care is common in octopuses, breeding has only been observed in a handful of squids. Most species of squid leave clumps of eggs on the seabed or release neutrally buoyant egg masses containing thousands of eggs that float in the water column. These reproductive strategies require relatively little effort compared to caring for eggs after spawning.

“Breeding takes a lot out of a mother squid. She doesn’t eat while she’s carrying her eggs and eventually dies after her eggs hatch. But her sacrifice increases the chances that her offspring will survive. It’s just one of many remarkable adaptations that may be possible. are.” help cephalopods to survive in the deep sea,” Hoving explains.

MBARI researchers were the first to observe the breeding behavior of a deep-sea squid. During 37 years of deep-sea research, MBARI’s ROVs have recorded 17 sightings of breeding squid. These include multiple sightings of breeding black-eyed squid (Gonatus onyx) and other arm hook squid (Gonatus sp.) that are difficult to identify from video alone, as well as the deep-sea squid Bathyteuthis. But the squid spotted in the Gulf of California stood out to researchers.

“The deep sea is the largest living space on earth and there is still much to discover. Our unexpected encounter with a squid hatching giant eggs caught the attention of everyone in the ship’s control room. This remarkable observation underlines the diversity of ways in which animals adapt to the unique challenges of life in the deep,” said MBARI Senior Scientist Steven Haddock, lead scientist on the expedition that encountered this breeding squid.

By analyzing the video footage and studying specimens of similar-looking squid collected during previous expeditions to the Gulf of California, the research team determined that this was likely an undescribed species in the family Gonatidae.

It was the large size of this squid’s eggs (about 11.6 millimeters in diameter) that caught the research team’s attention. Previous observations of breeding Gonatus squid reported eggs half that size, with a maximum diameter of only six millimeters (about a quarter of an inch).

The squid observed in the Gulf of California also hatched far fewer eggs than other Gonatus squid. Researchers estimate that she was carrying 30 to 40 eggs, while the Gonatus squid seen in the past were known to hatch as many as 3,000 eggs at a time.

Producing numerous small eggs is beneficial in environments with limited food and/or high predation. In these environments, a greater number of offspring offers a greater chance that at least some will survive.

Giant eggs may be more favorable in the more stable and predictable conditions of the deep sea, allowing higher investment in fewer offspring that have a better chance of survival. This has been observed in other deep-sea cephalopods, including the warty deep-sea octopus (Graneledone sp.) and the pearl octopus (Muusoctopus robustus).

Extrapolating from egg development data reported by other scientists, the research team estimated that the eggs of this new deep-sea squid require one to four years to develop, which is longer than the entire life cycle of most shallow-water squids. water.

Deep-sea squid play a crucial role in the ocean’s food network. They are predators that feast on fish and aquatic invertebrates, and in turn they are eaten by large fish, sharks, whales, dolphins, seals and seabirds. Deep-sea squid make up a large portion of the diets of commercially important fish such as tuna, swordfish and sailfish.

Despite their ecological and economic importance, we still know very little about the reproductive biology and natural history of deep-sea squids. MBARI scientists and their collaborators answer fundamental questions about the biology of deep-sea cephalopods.