Rostanga pulchra

Photo couresty of Mary Ellen Hill & Caroline Schooley

We have several red to orangish colored dorid nudibranchs along the Pacific coast of North America, Thordisa rubescens , Rostanga pulchra , Aldisa sanguinea , Acanthodoris lutea and Aldisa cooperi . When we first saw Caroline and Mary Ellen's photo we thought the specimen was a Aldisa cooperi which was originally described as a subspecies, of Aldisa sanguinea . After careful re-examination we changed our minds however, calling this specimen Rostanga pulchra . Specimens of Rostanga are characteristically bright red or scarlet. Light colored specimens are not rare however. We often miss this species as it usually so perfectly matches the color and texture of the sponges it feeds upon. The dorsum of some specimens have a sprinkling of dark specks, which are more obvious in lighter colored specimens like Caroline and Mary Ellen's shown here.

The dorsum of Rostanga is covered with numerous fine caryophylletic tubercles. These tubercles with spicules protruding from their tips give the dorsum a velvety texture appearance. The key to identifying Rostanga are the unique rhinophores. Rostanga's rhinophores have vertical perfoliations.

A. cooperi differs having normal perfoliate rhinophores and is yellow or orange with a series of black specks in a line down the dorsum.

R. pulchra is chemically attracted to and feeds on the red spongesAcarnus, Ophlitaspongia pennata, Esperiopsis originalis and Plocamia karykina. You will often find a small, thin tightly coiled egg ribbon on the sponge.

This species has a very wide range, occurring from Alaska south to Argentina and Chile.

The "Mendocino Nudibranchs " exhibit that Mary Ellen Hill & Caroline Schooley assembled a few years ago has been shown several times in Mendocino and Fort Bragg. It will be on display all summer (weekends only) as part of the marine science exhibit at Point Cabrillo lighthouse, between Mendocino and Fort Bragg. Photos of about 3 dozen species, plus a bit of text about biology & ecology For more information contact Caroline at schooley@mcn.org

David W. Behrens Author: Pacific Coast Nudibranchs Co-Author Coral Reef Animals of the Indo Pacific Proprietor of Sea Challengers Natural History Books ! Send Dave mail at dave@seachallengers.com

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