Triopha maculata is one of the most variably colored and large nudibranchs on the Pacific coast of North America. I the first edition of Pacific Coast Nudibranch (the blue cover edition) I was able to show the wide range in body color, from yellow with white or very light blue spots to dark brown with blue spots.
The original name for the yellow color variant of this species was Triopha grandis MacFarland, 1905. Triopha maculata was intended for the dark specimens , as shown in color plate 19 in MacFarland's memiors, published posthumously in 1966. Tony Ferreira's review in 1977 cleaned up the taxonomy for this genus. Surprisingly in this day of taxonomic revision maelstrom, nobody has touched it since.
This species can be found in all sorts of habitats and substrates, in both the subtidal and intertidal. It is most commonly seen on the giant kelp, Macrocystsis , as it feeds on the encrusting bryozoan, Membranipora . The Sea Slug Forum has a good shot of a specimen feeding. When food is plentiful the specimens reach up to 180 mm in length, huge of a California dorid. I have always surmised that smaller lighter colored specimens found in the intertidal were feeding on some other bryozoan species. Why some would be yellow and other red is not known.
Other nudibranchs that feed on Membranipora include Corambe pacifica and Hopkinsia plana . These species are very cryptically colored, matching the bryozoan closely. Because Triopha are so brightly colored suggests that they use repulsive chemicals to defend themselves and may be demonstrate aposomatic, or warning coloration.
As seen here is Tracy's photo, this species lays a large creamy white egg ribbon which is attached to the substrate, a kelp frond in this instance, by one edge. These coils can be as large as 70 mm in diameter.
Ferreira, A.J. 1977. A review of the genus Triopha (Mollusca:
Nudibranchia). Veliger 19(4):387-402.
Picture was taken with a Nikon N90, Subal housing, two YS-90 strobes.
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David W. Behrens
Pacific Coast Nudibranchs
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