Triopha maculata
Orange-tubercled nudibranch logged across California's kelp reefs in 12-17C water, year-round and usually easy to spot once you know the shape.
Grows to around 12 cm, with a pale cream to greenish-white body covered in raised orange-tipped bumps (tubercles) running down its back. The rhinophores (the paired sensory stalks on the head) and the frilly gill cluster near the tail are both tipped in the same orange-red, which is the fastest way to pick it out against rock or algae. It moves slowly across the substrate and holds its body slightly arched, giving it a bumpy, almost spiny silhouette rather than a smooth slug outline.
Divers typically find it parked on rock and algae-covered reef, moving at the unhurried pace typical of nudibranchs while grazing rather than reacting to a torch or camera. It shows up most often as a solitary animal rather than in groups, so most sightings are logged as uncommon or rare even at sites where it's known to occur. It pays no attention to divers and won't move off if you get close for a photo.
Like other dorid nudibranchs, it feeds on specific sponges and can store or repurpose chemical compounds from that diet as a defence against predators, which is part of why it can sit exposed on open rock without much cover.
Logged year-round with no clear seasonal spike, which fits its cool-water comfort zone of roughly 11.6 to 16.9C, the kind of temperature California's rocky reefs and kelp forests hold for most of the year.
Reef neighbours a diver could mistake it for. Use the identification notes above to tell them apart.
Overwhelmingly a California species: it turns up most consistently on dive sites through California, with smaller but reliable numbers logged in British Columbia, Canada, and Baja California, Mexico. A few sightings extend the range into the Pacific Northwest, Alaska and the Mountain West of the United States, but California is where divers actually find it with any regularity.
Mapping where Spotted Triopha is logged…
California is by far the most reliable place, with sites throughout the state producing the bulk of sightings. Smaller numbers are also logged in British Columbia, Canada and Baja California, Mexico, with occasional records further north into the Pacific Northwest and Alaska.
There's no strong seasonal pattern in the sightings, so it's considered a year-round find. Its comfort range of roughly 12 to 17C matches the cool water California's coast holds most months.
Look for a pale cream to greenish body dotted with orange-tipped bumps, with matching orange on the head stalks and tail gills. It moves slowly over rock and algae and rarely reaches more than about 12 cm.
They typically reach around 12 cm in length, making them one of the larger nudibranchs a diver is likely to spot on a California reef.
No. It poses no threat to divers and has no means of stinging or biting that would affect a person; it simply grazes on sponges and ignores anything nearby.
It likely takes on defensive chemicals from the sponges it eats, which may explain why it can sit exposed on open rock without needing to hide from predators.
Site and sighting data is aggregated from diver logs, iNaturalist and GBIF. For taxonomy and conservation status:
Chromodoris joshi
Blue Dragon
3,163 sites
