At a depth of 4,560 feet below the sea surface, a remotely operated vehicle (ROV) captured video of a bright red deep-sea squid carrying gelatinous strings of hundreds of pearl-like eggs off the coast of California. The footage of the unknown species represents the second time scientists have seen this genus of squid (Bathyteuthis) exhibiting brooding behavior, reports Science Alert's Michelle Star. The first time was in 2005 when they spotted a Bathyteuthis berryi holding a sheet of 360 eggs, per a statement.
While the squid appears colossal alongside her eggs, the species' main part of the body, called a mantle, has a length of three inches, reports Live Science's Harry Baker. Bathyteuthis squid can be found worldwide and typically feed on krill.
Most female squids will reproduce by depositing egg cases on the ocean floor or by releasing eggs in a gelatinous mass that flows and drifts in open water, a statement explains. Squids don't usually brood their eggs and generally die soon after laying them, Chau Tu reported for Science Friday in 2016. So, capturing footage of a squid holding its eggs is extremely rare.
Currently, only three squid species are known to brood their eggs, and while experts may not know why, they suspect it's to keep the eggs from becoming a predator's lunch and improve the hatchlings' chances of survival. Based on these observations, biologists suspect other deep-dwelling squids may also be brooders. Octopuses have been more commonly observed showing brooding behaviors, a statement explains.
The first type of squid observed brooding eggs was Gonatus onyx, or the clawed arm hook squid. The species was spotted in Monterey Bay in 2002 using MBARI's ROV, Tiburon. Footage of G. onyx revealed that the squid uses the hooks on its arms to carry large clusters of up to 3,000 eggs, a MBARI statement from 2006 explains. Scientists published details on the egg cradling behavior in G. onyx in Nature in 2005. Both Bathyteuthis and Gonatus belong to separate families of squids, which suggests that brooding evolved independently and may be a common strategy among squids in the deep ocean, per a statement.
Researchers at the Monterey Bay Aquarium Research Institute (MBARI) captured the stunning 4K high-definition footage of Bathyteuthis using the ROV Doc Ricketts. The deep-sea is challenging to study, and teams of researchers only capture glimpses of sea life while using ROVs. Documenting videos such as the one of the squid and her eggs show the importance of exploring deeper waters and learning about elusive species. "The deep ocean is challenging to study, and we only get brief glimpses into the behaviors of deep-sea animals," MBARI researchers say in a statement. "Each observation logged by our ROVs provides another piece of the puzzle and helps improve our understanding of life in the deep."