Roboastra tigris? from Galapagos

January 23, 2004
From: Patty Dilworth

Note added 21 July 2005: This is now named Roboastra leonis

Dear Dr. Rudman,
Sometimes, the more I look, the more confusing things get for slug identification! Thank you for your help with this one. I have sent a second similar looking species in a separate message. Both are from a dive at North Seymour Island in the Galapagos during the first week of July, 2003. Both types were quite numerous between 30-40 feet.

This one was approximately 30 mm long.

Patty Dilworth

Dilworth, P., 2004 (Jan 23) Roboastra tigris? from Galapagos. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Patty,
This is an interesting find. From the long tubular oral tentacles [see dark blue structure in lower right photo] this is a species of Roboastra which are voracious carnivores, well-known for feeding on relatives, such as species of Tambja. The only species I know of from the eastern Pacific is Robosastra tigris which has an ochre background colour and a few longitudinal blue bands outlined with thin pale yellowish lines. It is possible that your animal is a colour form with extra blue bands, but I think we would need to see some animals with an intermediate colour pattern for me to feel comfortable with that suggestion. However considering how little we know of these animals and their distribution in the eastern Pacific, the suggestion is definitely not out of the question. It wiuld be interesting to see if you could observe this animal feeding on other nudibranchs, in particular the Tambja in your other message.

I am certainly interested in seeing photos of any sea slugs you find in the Galapagos Ids. The marine fauna of the East Pacific is not well known so any records from the region, even of apparently common animals is valuable information.

Best wishes
Bill Rudman

Rudman, W.B., 2004 (Jan 23). Comment on Roboastra tigris? from Galapagos by Patty Dilworth. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


Roboastra leonis

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  1. Roboastra leonis - Feeding behaviour
    From: Alicia Hermosillo, July 26, 2007
  2. Roboastra leonis from the eastern Pacific
    From: Bill Rudman, July 22, 2005
  3. Re: Roboastra tigris? from Galapagos
    From: Ray Simpson, January 25, 2004

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