A familiar nudibranch, Berthella californica, has been fooling Phil and me for years. What we thought were simply adult and juvenile forms is actually part of a species complex comprising two different species, Berthella californica and Berthella chacei. Although B. chacei is a more abundant northern species, their ranges happen to overlap in Southern California.

Short version of the morphological differences:
Considerably larger of the two, B. californica has uniform white spots found ONLY on the mantle, which can range in color from white to brown. Most B. californica have a longitudinal, white dorsal stripe on each rhinophore. The considerably smaller B. chacei has variably-sized white tubercles on a smooth white mantle, with scattered white flecks on the rhinophores and foot.

All subjects were found at Golf Ball Reef, Palos Verdes, CA.
Thanks to Phil Garner for his photos of B. chacei.

• Ghanimi, H. et al. 2020. Journal of Molluscan Studies 00: 1-15.

• Cool. Now I'll always know what I'm looking at when I see them :) (-) seahunt 01:32:17 05/18/20 (0)