The location of the brooding squid largely explains why their parental skills were never seen before, said Seibel. "Researchers tend to skip this zone as well," he said.
That's because surface waters and the ocean floor are considered the two most productive depths for marine life. The squids are probably brooding between these zones to hide from predatory whales and seals, which also tend to ignore the middle depths when hunting for a calamari snack.
The Gonatus onyx filmed by Seibel and his colleagues carried around an estimated two or three thousand eggs in an open-ended sac, held by hooks in the squid's arms. The mother squid keeps oxygen flowing to the eggs by circulating water through the sac. After the eggs are ready to hatch, the mother probably dies, said Seibel.
"It's very difficult to eat with it," he said, regarding how the egg sac blocks the squid's mouth.
And there's no evidence she can drop it, grab a bite and pick it up again. The terminal nature of squid motherhood is backed up by comparing squids with freshly laid eggs to those with eggs that are ready to hatch.
squids with mature eggs are physically wasted and ready to die, whereas those with younger eggs look much healthier.
"Most squids lay eggs and die in one season," said Seibel. "They live very short lives — one to two years typically."
The female squids accumulate fat stores while they grow and then expend it during the brooding period, he said.
The video evidence of squid brooding puts to rest a long controversy, said squid expert Eric Hochberg of the Santa Barbara Museum of Natural History in California. Hochberg was part of a team of researchers that proposed brooding squids five years ago.
Their evidence was the relatively small number of extraordinarily large eggs brought up in a trawl bucket with an adult Gonatus onyx squid in 1996.
Most squids lay 10,000 to 100,000 small eggs and leave them on the ocean floor. A few survive to adulthood. By watching over their eggs for six to nine months, until they hatch, Gonatus onyx mothers enhance the survival odds of each egg, thereby allowing them to lay fewer and larger eggs.
"We just always had assumed that octopuses carry eggs and squids lay them on the bottom," said Hochberg. Gonatus onyx changes all that, he said, and "there may be other deep-sea squids that are carrying their eggs."
The discovery is important in another way as well, said Seibel. It's one more example of how something that's an important food source to shallow-water species and birds also requires deep waters for its survival.
For this reason, he said, it's important for folks to think twice before signing on to any disposal projects or other plans that can pollute deep ocean waters.
