Researchers said they have uncovered evidence that some mother squids nurse their eggs for months after laying them, helping to disprove a long-held theory that all female squids simply abandoned new offspring on the ocean floor.

Mother squids of the Gonatus onyx species were found to lug around pouches of new eggs in their tentacles for up to six to nine months at a time, even though the load can weigh a quarter of their own weight and makes the mother slower and more vulnerable to predators, according to a study published in the Dec. 15 issue of the journal Nature.

Physiologist Brad A. Seibel, of the University of Rhode Island, and two researchers from the Monterey Bay Aquarium Research Institute made the discovery while patrolling the deep waters of a submerged canyon off Monterey Bay with a robotic submarine.

"Our finding is unexpected because this behavior differs from the reproductive habits of all other known squid species," Seibel said.

The findings suggest that similar maternal behavior might exist in other squid-like creatures, said Steven H.D. Haddock, one of the Monterey Bay researchers.

There are between 700 and 1,000 known types of squids and octopi.