The aquarium staff of the Alaska SeaLife Center are getting their third opportunity to pull off a feat accomplished only once before: raising a giant pacific octopus from a pea-sized floating hatchling to an adult that might weigh 50 pounds and have an arm-span of 14 feet.
About two weeks ago, SeaLife Center staff noticed tiny hatchlings floating around the tank of Gilligan, the eldest female of the SeaLife Center’s 10 giant pacific octopuses, who had spent nearly a year guarding the clusters of white, tear-shaped eggs she laid in May 2017. The SeaLife Center’s aquarist are now collecting the hatchlings and moving them to a rearing tank, where they’ll try to guide a few of the thousands of newborn octopuses to adulthood.
“That would be the ultimate goal,” said SeaLife Center aquarist Chuck Dimarzio. “The realistic goal is to learn more than we knew from our previous attempt at this — just to refine further our culture techniques for these animals, from tank design, tank shape, playing with different flow systems, and experimenting with different feeding regimens as well.”
Giant pacific octopuses usually lay a clutch of between 20,000 to 80,000 eggs, from which about one percent of the young survive in the wild, according to an Alaska SeaLife Center press release. In captivity the rates are much lower. The only known captive-born giant pacific octopus to reach adulthood was at the Seattle Aquarium in the 1980s — a labor intensive rearing that took one staff member’s full-time work, Dimarzio said, for which the Seattle Aquarium won an award from the American Zoo and Aquarium Association in 1982.
The SeaLife Center has dealt with giant pacific octopus hatchlings twice before — in 2005 they unsuccessfully attempted to raise the young of an octopus named Aurora, and in 2013 the young of an octopus named Lulu.
As for Gilligan’s eggs, about 100 have hatched so far. For about a year, the hatchlings will remain afloat, translucent except for their large eyes and the colored spots of their chromatophores — cells that octopuses can open and close to change color. Their fragility is one reason they’re so difficult to keep alive.
“In the ocean, it’s vast — there’s a bottom and a shore, but realistically they’re not going to bump into anything,” Dimarzio said. “You put them in a tank, regardless of its size, and they inevitably end up against the walls of that tank, and the way they move is by sucking water in and pushing it out — so they’re constantly bobbing up down. If they end up against the tank wall, their mantles are fragile, and they’ll abrade them.”
Dimarzio said the staff might try to avoid this danger by using a cylindrical tank with circular flow around the walls.
The floating hatchlings will jet around their tanks after food, eating “other planktonic creatures such as crab larvae, copepods, amphipods, even larval fish — basically whatever they can get their suckers on,” Dimarzio said. There’s been little research on what octopus hatchlings eat in the wild, he added, but they “only seem to respond to live food.”
“That’s definitely a challenge,” he said. “We’re ramping up some cultures of brine shrimp. We’re going to bring in some copepods and grow those as well. … We’re kind of going with the shotgun approach.”
In the SeaLife Center’s last attempt at raising octopus young — hatched by the female octopus Lulu in 2013 — some hatchlings survived 8 months, close to the age the staff expected the young to settle on the tank bottom and begin growing toward maturity. As it grew, caretakers began feeding it shrimp-like amphipods collected from beneath rocks on Seward’s beach, which they threaded on fishing line to drop into its tank.
Whatever her childrens’ odds of survival are, Gilligan is definitely ending her life, at an estimated age of five and a half years. Octopuses only reproduce at the end of their lives, and after sitting on her eggs for nearly a year, blowing water over them to keep them clean, Gilligan is expected to die in a few months.
“We do feed her regularly, but she kind of loses interest in food,” Dimarzio said. Weighing about 50 pounds when she laid her eggs, Gilligan is around 30 pounds now.
Male octopuses are able to mate dozens of times within the few end-of-life months they become fertile. The father, Leo, died a few months after impregnating Gilligan in December 2017.
Gilligan came to the SeaLife Center in May 2015, along with another pacific giant octopus, the male Ginger. The two were mistakenly named after opposite-sexed characters from the sitcom “Gilligan’s Island” because octopuses are too small to determine sex until they’re about two years old. Gilligan, her eggs, and the hatchlings are on public display in the SeaLife Center’s “Octopus Grotto” exhibit.
Reach Ben Boettger at email@example.com.