A team of marine biologists with the Nautilus Expedition succeeded in filming Asperoteuthis mangoldae, a recently discovered deep-sea squid species, at a depth of 3,151 feet (930 m) near Jarvis Seamount in the Pacific Remote Islands Marine National Monument.

“On July 5, 2019, diving at 3,151 feet depth on Jarvis Seamount, E/V Nautilus and ROV Hercules encountered a very unusual squid swimming just above the bottom,” said team member Dr. Michael Vecchione, a researcher from NOAA’s National Systematics Lab and the Smithsonian National Museum of Natural History.

“At first, it looked like a long, narrow squid with something stuck on it. The ‘something’ was actually part of the squid, a tail extending beyond the fins and effectively doubling the length of the animal.”

“This was an Asperoteuthis mangoldae, a recently discovered species of squid that had never been seen alive until now.”

This elusive squid belongs to Asperoteuthis, a genus of deep-ocean dwelling squid comprising only three species: A. acanthoderma, A. mangoldae and A. lui.

“Members of this genus are characterized by the strange tail that is retained throughout the life of the squid, as well as unusual tentacles,” Dr. Vecchione and colleagues said.

“The tail, which is stiffened by a rod-like structure throughout it length, has sheets of tissue on both sides.”

“These flaps are sometimes called ‘secondary fins’ but, as can be seen clearly on this video, they do not function as fins.”

“Squid fins, like the normal ‘primary’ fins on this squid, flap or undulate to propel the animal and can be used to steer. The tail tissue does neither.”

“Unlike the fins, the tail tissue has very little muscle.”

“We don’t really know its function but it seems to change the appearance of the squid, in this case doubling its size. In related squids, the tail has been interpreted as making the squid look like another kind of animal, such as a siphonophore that has powerful stinging cells.”

“The tail on Asperoteuthis mangoldae is particularly large. This raises a question about how they can swim while pushing or pulling this huge structure around.”

The new video with Asperoteuthis mangoldae answered this question somewhat surprisingly.

“When first seen by the ROV, the tissue of the tail is fully deployed. After a short while, the squid first swims rapidly forward (arms first), collapsing the tail tissue around the rod-like structure,” the scientists said.

“Then it reverses course and swims rapidly backward (tail first, which is typical for high-speed swimming by a squid).”

“While it swims backward the tissue stays tightly held close to the rod, similar to a sail furled on the boom of a schooner.”

“As the squid swims erratically to escape, even changing color and inking once, the tail stays furled, greatly reducing its drag.”

“Therefore, jetting forward to furl the tail seems to be the first step in the squid’s complex escape maneuvers.”