Squids make devoted mothers
http://www.sfgate.com/cgi-bin/article.cgi?file=/c/a/2005/12/...
Scary though they look, some squids make devoted mothers, researchers have discovered.
Scientists used to assume that female squids simply laid their eggs on the sea bottom and then abandoned them to survive on their own.
But now, researchers patrolling the deep, dark waters of the submerged canyon off Monterey Bay say they have confirmed a controversial, decade-old
hypothesis that one type of mama squid is maternal indeed. In her tentacle arms, she lugs a bulging, tubular pouch of eggs around for months, even
though the load slows her down and makes her vulnerable to predators.
From time to time, the squid -- technically known as Gonatus onyx -- flaps her tentacles to stir the water. This generates air bubbles that increase
the flow of life-giving oxygen to the eggs, the scientists report in today's issue of the journal Nature. She also guards the eggs by skittering away
with them when predators approach.
"Our finding is unexpected because this behavior differs from the reproductive habits of all other known squid species," of which there are hundreds,
says the article by physiologist Brad A. Seibel of the University of Rhode Island and two colleagues from Monterey Bay Aquarium Research Institute at
Moss Landing. They made the discovery by guiding a robotic sub up to 7,000 feet below the waves of Monterey Bay.
Based on the discovery, one of the three scientists, Steven H.D. Haddock, speculates that maternal behavior might also exist in some other squid-like
creatures. There are 700 to 1,000 known types of squids and octopi, which dominate the class of animals known as cephalopods.
In the mid-1990s, Seibel, then employed at the Monterey institute, first suspected that the squid species Gonatus onyx cares for its eggs rather than
abandoning them to the dangers of ocean life. He got the idea when the nets of research boats simultaneously dragged to the surface squids, squid eggs
and baby squids that possibly had just hatched. Previously, scientists had believed that female squids abandoned the big pouches of baby eggs -- up to
a few thousand per pouch -- shortly after generating them. But the proximity of the squids, eggs and babies in the same net encouraged Seibel's
suspicion that female squids hang on to the pouches of eggs to tend and protect them.
Seibel published his hypothesis in the journal Marine Biology in 2000. The hypothesis was quickly criticized by other experts, and "some (critics)
went as far as to publish papers saying it was wrong," Seibel recalled in a phone interview Wednesday. Among his critics was Kir N. Nesis, a
distinguished Russian expert on squids who has since died.
In the Nature article, Seibel describes how he, Haddock and Bruce H. Robison verified the squid-mom hypothesis.
They lowered a 6-foot-high robotic vehicle named Tiburon from a 117-foot-long research ship, Western Flyer, into the deep waters of the canyon just
offshore in Monterey Bay. A fiber-optic line connected Tiburon to the boat. While remotely piloting Tiburon through the water, they watched TV-like
images of objects that passed before the robot's camera.
They observed female squids hauling around the dark-color, gelatinous pouches, some of which contained mature eggs while others contained young eggs.
In a few instances, they observed baby squids -- just a few millimeters wide -- hatching from the eggs.
Normally, the squids swim at depths several hundred feet below the ocean surface. However, the mother squids had retreated to much deeper, darker
water, evidently because at such depths they and their eggs were safer from predators such as sharks and sea lions, Seibel said.
When the Tiburon robot with its bright lights approached, the squid fled along with their pouches of eggs, although they could have fled faster by
dropping the load. Haddock estimates the pouch weighs roughly one-fourth as much as the mother squid herself.
Mother squids appear to haul around the pouches for six to nine months at a time, although the exact length of time isn't yet clear, Seibel said.
"Each time we find something (new) like this," Haddock said, "it's just another example of the cliche of how little we know about the deep sea."
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