Sea slugs: The British Columbian Doto

The Doto is a species of sea slug, also known as a nudibranch. It is a marine gastropod in the family Dotidae. This species was first discovered in British Columbia and has been reported as far south as Santa Barbara, California.

British Columbian Doto
British Columbian Doto

Another Northwest slug?

The Northwest is known for the slugs and snails that thrive in the undergrowth of its damp mossy forests. Critters like this also live under the sea, like Doto columbiana, commonly called the British Columbian Doto.

It’s a nudibranch

The British Columbian Doto belongs to a category of animals called nudibranchs (pronounced NEW-dih-bronks), often referred to as sea slugs. There are over 3,000 species of nudibranchs worldwide, but fewer than 20 species exist in the Puget Sound.


Classification of Doto columbiana

D. columbiana is a tiny critter, only reaching about 8 mm in length. Along the sides of its body are soft lumpy structures called cerata (plural for ceras) that look like clusters of grapes and function as digestive glands. The leopard-like coloration on D. columbiana can vary between individuals but generally consists of brown mottling throughout the body along with darker rings at the base of each grape-like tubercle. You can see the tubercle, ceras and other body parts labeled in the photo of the preserved D. columbiana to the right.

Excuse me? My “antennae” are called rhinophores!

The antenna-like structures on the nudibranchs’ heads are called rhinophores. These are a type of chemo-sensory structure, allowing nudibranchs to sense the world around them. The word “rhinophore” comes from the Greek word “rhino,” meaning nose, which is appropriate since they function as an organ of “smell.”

D. columbiana

D. columbiana - profile of whole 
preserved specimen stained pink

However, while humans smell scents in the air with their noses, nudibranchs “smell” or detect scents that are dissolved in the sea water around them to find food. The rhinophores’ worm-like appearance makes them an easy target for predators, so they can be quickly retracted into a trumpet-shaped rhinophore sheath for protection.

You are what you eat

D. columbiana on a colony

D. columbiana on a colony of the hydroid Aglaophenia

Nudibranchs are carnivorous and get their pigmentation, or colors, from the food they eat. Nudibranchs that eat brightly colored creatures are brighter too. In fact, many have brilliant bodies of intensely contrasting colors.

The British Columbian Doto is quite drab by comparison. D. columbiana eats hydroids from the genus Aglaophenia. Hydroids are colonies of tinier critters called “polyps” that are related to jellyfish. An Aglaophenia colony looks like a brown fern frond or feather plume, and these neutral colors are incorporated into D. columbiana’s body to help camouflage it from predators.

D. columbiana conveniently lives on what it eats as well, laying its eggs on the underside of the hydroid’s branches. When the eggs hatch, the young larvae have shells which disappear as the nudibranchs become adults.

Taxonomy troubles

Doto columbiana

Doto columbiana has a soft body that does not preserve very well.

D. columbiana, like many soft-bodied critters, does not preserve well. The colors can be lost and the shape can become distorted. Benthic taxonomists, the scientists who identify these small marine critters, have to look closely at features like the cerata and rhinophores to determine which critter they have collected.

About the Author: 
Dany Burgess and Angela Eagleston are scientists who work for the Marine Sediment Monitoring program at the Washington State Department of Ecology.