Taxonomy

Rarity

Abundance rates how many are in suitable habitat. Find difficulty rates how hard it is to locate one on a daylight snorkel or freedive through 50 ft. A higher find score means a harder search. The rarity category also reflects the kind of encounter; it is not an average of the 2 scores.

Seasonality

Location

San Diego dorids live on rock, in the rocky intertidal and in surge channels and on subtidal reef down to about 115 feet. They feed on sponges, several kinds of them, so they are found where sponges grow on the rock.

It is a large dorid, up to about 3 inches long, and its mark is a set of dark rings. The body is usually pale gray, sometimes cream, yellow, white, orange or dark brown, and the center of the back carries blackish-brown rings up to about half an inch across. Most animals have about 10 rings, and the count runs from 4 to 41. The rings stay on the middle of the back and never reach the edge of the mantle, the broad skirt of skin around the body.

Deep Dive

That last detail turned out to separate 2 species. For most of its history the San Diego dorid was treated as a single animal ranging across the North Pacific from Japan to Mexico. A 2016 genetic study found 2 species inside it with consistent differences in color pattern that earlier studies had missed. The key is the mantle edge. The northern species, which now has its own name, carries spots right out to the edge of the mantle and usually many more of them, while the San Diego dorid keeps its rings on the center of the back.

The 2 also split by habitat. The northern species is restricted to the intertidal zone and to bays from Fort Bragg, California north. The San Diego dorid is found throughout the region and is more common below the tide line. South of Fort Bragg, a large pale dorid with dark rings and a clean mantle edge is the San Diego dorid.

It lays its eggs as a narrow white ribbon, attached by one edge in an oval spiral under a rock ledge.

Where to Find Them

Researched habitat and range candidates

These locations have suitable habitat within the species range. An assignment is a possible encounter, not a confirmed sighting at every beach. Season, depth, and local conditions still matter. Historical habitat without present-day evidence is excluded.