Polycera alabe Collier and Farmer, 1964
Pacific Coast Nudibranchs (1991 – 2nd edition) included a single photograph of what most of us consider the typical color variation of Polycera alabe, as described by Collier and Farmer. While preparing the NEW Eastern Pacific Nudibranchs book with Ali Hermosillo, I learned that as you proceed south into Mexico, this species displays quite a bit of variation. In this new book we were fortunate to be able to show the variation in this species, as well as others by including multiple color photos.
In the typical variation (Variation A) specimens are black with oval yellow-orange spots as shown above. The gill and rhinophores are black, with yellow spots. This variation is found in the Channel Islands, Isla Cedros and through-out the Gulf of California.
In the variation we refer to as Variation B , specimens have thick orange lines running lengthwise, and the body processes are green. The gill is pink with black tips. Ali and I have observed this variation along the Mexican Pacific. Camacho-Garcia (2005) refers to this variation as Polycera sp. and note its range to be from the Revillagigedos islands to Costa Rica, Panama and the Galapagos.
Further south we find Variation C . This color form is similar but more dramatic than the typical form in having larger bold orange spots, green papillae and gills and rhinophores with orange lines. This variation is found along the Mexican Pacific, and also Costa Rica and Panama.
Variation D is found the farthest south and is the color variation shown in Camacho-Garcia et al. as typical for the area covered in their guide. In this variation the body is brownish, not black, and has orange lines and spots. The papillations are translucent. The gill and rhinophores are the same color as the body and tipped with black.
Examination of the internal anatomy of the four color forms does not provide differences great enough to call these four variants separate species.
Ali Hermosillo and Dave Behrens
Pacific Coast Nudibranchs and Nudibranch Behavior
Send Dave mail at email@example.com