Giant squid's dissection reveals toothfish diet

Washington, May 6 : The dissection of a colossal squid by scientists has revealed that a large part of the diet of the huge marine animal includes Antarctic toothfish.

According to a report in Discovery News, the huge, jelly-like animal from Antarctica was hooked in a New Zealand long-line fishing operation in the Ross Sea.

The fishermen netted the squid and placed it in their vessel's freezer. Last week, scientists at the Museum of New Zealand Te Papa thawed and analyzed the squid. Part of that investigation involved the insertion of an endoscope into the specimen's stomach.

"The endoscope revealed nothing. Its stomach was empty," museum spokesperson Jane Keig told Discovery News.

Carol Diebel, the squid project's director, and her team, then focused their dissection efforts on yet another colossal squid housed in the museum.

The stomach of that second squid yielded the remains of toothfish.

Prior studies of colossal squid remains found in the stomachs of whales also revealed evidence of toothfish consumption, so scientists believe this fish could comprise a large portion of the colossal squid's diet.

The word "toothfish" generally refers to two closely related species: the Patagonian toothfish, popularly known as Chilean sea bass, and Antarctic cod, which is sometimes referred to as Antarctic toothfish.

Both species possess a rather toothy, gaped mouth, hence the name, and can grow to around 7 feet or more in length.

Both the toothfish and the colossal squid favor deep water, 3,000 or more feet below the surface, and each has developed special adaptations to live and hunt in the darkness of that environment.

During the week's colossal squid investigation, the researchers were able to get an up-close look at the squid's tentacles. The tentacle tips - appropriately called "clubs" - are armed with two rows of sharp hooks that can swivel in all directions.

While no one has closely observed a colossal squid in hunting action, it's believed the animal moves quickly, grabbing toothfish and other prey with these spiked tentacles, which ironically somewhat resemble long-line fishing lines.

The scientists also discovered the squid has basketball-sized eyes, "the largest known in the animal kingdom," according to Diebel, along with a light organ right near the eye sockets. The researchers believe that this organ may function like a searchlight.

Toothfish also possess special eyes, with retinas that are well adapted to low light levels.

While the mostly clear squid is nearly invisible in deep water, it's probable that colossal squid and toothfish play a continual hide and seek game of survival, where who spots whom first determines which one could live another day.

ANI