Predation on dorids

September 6, 2001
From: Brian K. Penney

Hi Bill-
Good idea on the predation page. In five years at Bamfield (west coast of Vancouver Island in British Columbia, Canada) I have only seen one instance of predation on local dorids in the field. About three years ago I saw a crow pick up an Archidoris montereyensis from the shore in front of the marine station. The bird soon dropped the slug, but I am not sure if it was truly rejecting the slug, or annoyed at me frantically following behind. When I recovered the slug, its viscera had been pecked around a fair bit, but were all still there. The slug died the next day.

I have tried some lab predation experiments with live Cadlina luteomarginata against various generalist molluscivores: crabs (Cancer sp.), anemones (Anthopleura sp.), sea stars (Pycnopodia helianthoides) and fish (Hexagrammos decagrammus). Crabs and fish would taste the slugs with their mouthparts, and then throw them away; when tested a second time, they wouldn't even pick up the slug! Anemones and sea stars would consume the slug, then spit it out by the following day. Most of these slugs (>50%) lived at least one more week in the lab.

If anyone is interested in more detail on the latter results, I should be submitting them for publication within the next year or so. But it seems:
• dorid defenses work well against numerous predator types,
• some predators learn to avoid dorids after one sample and
• predator sampling does not invariably lead to the slug's death.

Hope this is helpful.

Penney, B.K., 2001 (Sep 6) Predation on dorids. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Thanks Brian,
Building up feeding observations is a slow business, so any reports are of great value and will hopefully encourage more. Please let me know when your paper is published.
best wishes,
Bill Rudman

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