Deep-sea discovery: Mother squid with massive eggs baffles scientists
During an expedition to the Gulf of California in 2015, a remotely operated underwater vehicle recorded a mother squid holding massive eggs in her arms. Scientists suggest that this may be a species unknown to science.
Researchers believe that squid populations are relatively numerous in the depths of the oceans. However, these animals are somewhat mysterious because they are rarely seen alive. It is even rarer to see a female caring for her eggs, which is exactly what the remotely operated underwater vehicle owned by the Monterey Bay Aquarium Research Institute (MBARI) recorded on video.
The observations' descriptions and results were published in the journal Ecology (DOI: 10.1002/ecy.4319).
Rare specimen
The deep sea is the largest habitat on Earth, but many animals and habitats deep below the ocean's surface remain unexplored. MBARI’s advanced underwater robots help study life in the ocean’s depths. They proved their effectiveness by capturing footage of a rare specimen – a female taking care of her as-yet-unhatched offspring.
Scientists at MBARI had previously observed deep-sea squid caring for their eggs, but the footage from 2015 shows a mother holding eggs that are twice the size of eggs from other deep-sea squid.
Squid are cephalopods belonging to the Decapodiformes. As the name suggests, they have ten arms covered in suckers, and a rounded, torpedo-shaped body. There are hundreds of known species of these creatures, with some inhabiting the deepest parts of the oceans.
Squid are creatures shrouded in mystery. Mainly because the crushing pressure and darkness of the ocean depths are deadly environments for humans, and until recently, there were no tools to observe them. Since the advent of remotely operated underwater vehicles, scientists have been combing the vast ocean depths with their help. But there is still a huge space to explore.
Remarkable footage
“Our unexpected encounter with the squid holding gigantic eggs caught the attention of everyone in the ship's control room,” said Steven Haddock of MBARI, who led the research expedition during which the squid was encountered in the Gulf of California.
The squid's eggs were not only unusually large but also significantly fewer than scientists might have expected. Many ocean species lay many small eggs to maximise their survival chances in this hostile environment. But in the depths, things look different. The relatively predictable environmental conditions at depths of 1,000-4,000 metres, as researchers indicate, allow for laying fewer eggs. The mother could also have chosen larger eggs to care for and abandoned smaller ones.
“Caring for eggs is very costly for the mother. While carrying the eggs, she does not eat and ultimately dies after the eggs hatch,” explained Henk-Jan Hoving, the study’s lead author. “However, her sacrifice increases the chances of the offspring’s survival. This is just one of many extraordinary adaptations that may help cephalopods survive in the deep sea,” he added.
While maternal care is common among octopuses, similar behaviours have been observed in only a handful of squids. Most squid species lay their eggs on the sea floor or leave them drifting in the water column. These reproductive strategies require relatively little effort compared to providing care for the eggs.
Unknown species
“Squid play an important role in the ocean. They are fierce predators and a vital food source for many animals, including humans, but we still have much to learn about squid living in the deep sea. Advanced underwater robots help us better understand the life of deep-sea squids, revealing fascinating new information about their biology and behaviour. Each new observation is another piece of the puzzle,” emphasised Hoving.
Over more than 30 years of deep-sea exploration, remotely operated underwater vehicles have only recorded squid caring for their eggs 17 times. These observations mainly involved the species Gonatus onyx and Bathyteuthis. There were others, but researchers stress that it is challenging to identify a species based solely on video footage.
Analysing the video footage and examining specimens of similarly appearing squids collected during previous expeditions to the Gulf of California, the research team determined that it is likely an as-yet-undescribed species from the Gonatidae family.
