It was 1984, and Jeff Goddard, who was about to start his PhD studying intertidal critters, was having the time of his life traipsing through tidepool paradise, searching for sea slugs. On the rocky shores of Drakes Estero in Point Reyes, one caught his attention.
The untrained eye might not have spotted it at all: this sea slug, a nudibranch in the genus Doto, was a few millimeters long—it would barely stretch across the barrel of a #2 pencil. Two neat rows of prominent salmon-colored adornments tipped in pearly white covered its translucent, milky body.
Goddard had a sneaking suspicion this could be something new. At the time, most other scientists and field guides would identify the tiny creature as Doto amyra. But Goddard had seen countless D. amyras by then. This one looked brighter, and had smaller eggs. Goddard took a few mystery nudibranchs back to his lab to study their life cycle under a microscope. Within a few days, triggered by the stress of captivity, the adults laid masses of eggs. He discovered this nudibranch’s larvae took longer to metamorphosize than D. amyra’s, and fended for themselves as mini-predators after hatching. Still, Goddard wasn’t certain this was a new species—sometimes, individuals from the same species can develop differently.
Forty years later, Goddard’s suspicion has been proven right, with the help of some new molecular tech. In a paper published last year that unveiled two new-to-science nudibranchs, researchers at the California Academy of Sciences named Goddard’s discovery Doto urak—and began unravelling its near-alien anatomy and mysterious sex life.
Terry Gosliner, senior author on the paper and the man who has discovered roughly one-third of the world’s sea slugs, says that the paper is part of a broader effort by researchers to work through a backlog of hundreds, if not thousands, of nudibranchs suspected to be new species. “The fact of the matter is we find things at a much more rapid rate than we can actually go through the process of naming them,” he says.
Jessica Goodheart, assistant curator of invertebrate zoology at New York’s American Museum of Natural History, agrees. “Every time we go in the field, we pretty much find new ones,” says Goodheart. She says we can’t protect species unless we know they exist. And so, according to Goodheart, D. urak represents one important drop in the bucket towards a more complete understanding of nudibranchs.
Doto urak got its spotlight thanks to a high schooler. In 2022, Sneha Adayapalam, then a senior in Charlotte, North Carolina, came to the California Academy of Sciences on a National Science Foundation grant that gives high schoolers research lab experience. Adayapalam spent two months among jars of sponges and sharks in Cal Academy’s wet specimen collection, cutting the mystery of D. urak wide open. She extracted tissue samples for genetic analysis and cut open Doto specimens to map their reproductive systems.
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Over the long days, Adayapalam’s genetic analysis sealed the deal. And her detailed dissections of D. urak and D. amyra specimens showed how unique D. urak is among its fellow Dotos.
All nudibranchs have weird sex, in human terms. “They are outside of our normal binary thinking about sex and about expression,” says Siobhan O’Neill, a self-described “intertidal admirer” and avid nudibranch iNaturalist-poster. For efficiency’s sake, every Doto has both sperm and eggs: “If you think of a drawer full of socks, where all socks are the same color, when you reach in, any pair of socks is going to make a pair,” says Terry Gosliner, Adayapalam’s mentor on the project and the man who has discovered roughly one-third of the world’s sea slugs.
Our more reserved readers may blush, but Dotos can have extensive courtships, full of sinuous dances around and atop each other. For both individuals to be fertilized, the two Dotos line up—genital pores and penises poised to give and receive—and copulate. It’s rarely a quick encounter: couplings often last 20 minutes or more.
Adayapalam’s initial research on D. urak complicates our scientific understanding of sex among the more than 90 species in the Doto genus. Its reproductive system is organized entirely differently from its peers: “The female reproductive tract is connected to where they’re storing sperm,” says Adayapalam. Every other type of Doto keeps these compartments separate.
How this unique internal plumbing might benefit D. urak’s sex life—or the survival of the species—remains an open question. “Oftentimes, what you find is that closely related species will have different reproductive systems,” says Gosliner. “Which is thought to be a way of making sure that only individuals of the same species can mate with each other.”
You, too, could discover a Doto if you’re willing to get down on your knees and dirty for it. Goddard says the first thing he does is start peering in crannies. “You get a knock for spotting which [rocks] might have a little bit of space underneath, as opposed to ones that are just literally half-buried in sand,” Goddard says. These dark hiding spots protected from wave action are where the prey of nudibranchs—squishy, boneless marine creatures like sponges and hydrozoans—flourish.
Although its name is a year old, and most tidepoolers consider it rare, D. urak already has more than 800 observations logged on iNaturalist, scattered from northern Baja California to Eureka, Calif. It’s tiny, so you’ll need sharp eyes. Even still, Gosliner notes that amateur nature enthusiasts are bringing many new nudibranch species to the attention of researchers. “There are so few scientists going around looking for these things,” he says.
In his early days of tidepooling, O’Neill went out every day to the rocky shore to go nudibranch-hunting. He’s now the top observer of Doto urak on the platform. “You kind of get addicted to it,” says O’Neill.
Update, May 14, 2026: The spelling of Sneha Adayapalam’s was corrected.
