The summer months bring low morning tides along the California coast, providing an opportunity to see one of the state’s most unusual inhabitants, sea slugs.
Also called nudibranchs, many of these relatives of snails are brightly colored and stand out among the seaweed and anemones living next to them in tidepools.
“Some of them are bright red, blue, yellow — you name it,” said Terry Gosliner, senior curator of invertebrate zoology and geology at the California Academy of Sciences in San Francisco. “They’re kind of designer slugs.”
But without a protective shell, big jaws or sharp claws, how do these squishy little creatures get away with such flamboyant colors in a habitat full of predators?
As it turns out, the nudibranchs’ colors serve as a warning to predators: These sea slugs are packing some very sophisticated defenses. And some aren’t above stealing weapons from their prey.
Gosliner and Brenna Green and Emily Otstott, graduate students at San Francisco State University, were out at dawn earlier this summer searching tidepools and floating docks around the Bay Area. They want to learn more about how these delicate little sea slugs survive and how changing ocean temperatures might threaten their futures.
Nudibranchs come in a staggering variety of shapes and sizes. Many accumulate toxic or bad-tasting chemicals from their prey, causing predators like fish and crabs to learn that the flashy colors mean the nudibranch wouldn’t make a good meal.