Cal Day must-see: Octopus mom with thousands of eggs

A female Octopus rubescens from Monterey Bay with a clutch of thousands of eggs, probably about two and a half weeks old. In another 3-4 weeks, they will hatch and the mother will die. Video by Roxanne Makasdjian and Stephen McNally.

Cal Day visitors who drop by the Valley Life Sciences Building on Saturday are in for a rare treat. On display will be a mother octopus tending her eggs, several thousand of them draped like pearls beside her as she nestles inside an abandoned clam shell.

The octopus mom was one of some 100 sea creatures collected by UC Berkeley divers on April 11 to put on display in the kelp forest exhibit in the inner courtyard of VLSB at Cal Day.

“I was looking for something exciting to show for Cal Day, and when I saw some eggs poking out of a dead clam shell, I knew I had it,” said marine biologist Tim Herrlinger, an academic coordinator and lecturer who has collected sea life for Cal Day displays for the past 14 years.

While Herrlinger returns all the animals to the place he collected them along the Monterey Bay shoreline, he plans to keep the octopus until her eggs hatch. Octopus mothers don’t eat while they tend their eggs, for from six weeks to months, and die once the eggs hatch.

The kelp forest exhibit, sponsored by the Department of Integrative Biology, proves to be one of the most popular hands-on demonstrations of UC Berkeley’s annual open house, with tanks where children can touch the animals and signs with information about the marine ecosystem.

The VLSB courtyard is filled with many other popular displays featuring animals, plants and specimens from the campus’s natural history museums.

Herrlinger, who was accompanied on the dive near the Monterey wharf by colleague Gaby Keeler-May, said he had never before seen an octopus guarding its eggs in more than 2,000 dives. Neither had the campus’s octopus expert, Roy Caldwell, professor of biology, who has been studying marine creatures for 63 years.

The red-hued mother, Octopus rubescens, about 7 to 8 inches from her head to the tip of her eight arms, laid between 1,000 and 2,000 eggs, he estimates. As you’d expect from any doting mother, she periodically cleans and rearranges them to make sure they get enough oxygen. They should start popping out as miniature, millimeter-size versions of their mom in 3-4 weeks, Caldwell estimated.

Other animals he collected for display are colorful nudibranchs, sea stars, crabs, snails, sea anemones, sea urchins, sea cucumbers, hermit crabs, worms and a variety of seaweeds, plus the delicate red-eye hydromedusa (see video below). The kelp forest exhibit is open to the public on Cal Day from 10 a.m. until 3 p.m.

Polyorchis penicillatus, or the red-eye hydromedusa, is a jellyfish the size of a shot glass from Monterey Bay. Video by Roxanne Makasdjian and Stephen McNally.
Cal Day program