Goniobranchus kuniei was unknown in the Marshalls for many years. For a few months in 1989 and 1990, nearly 20 specimens were found crawling in the open on the steep leeward seaward slope of Kwajalein Atoll at depths of 20 to 40 meters. A single specimen was spotted several years later, then no more were seen until two more were observed in 2005. It would seem that this species only occasionally reaches Kwajalein, and then does not last all that long when it does. The species does occur at Pohnpei, in the Caroline Islands to the west of Kwajalein, and perhaps only during El Niño years when the Pacific Ocean currents change does an occasional group of planktonic nudibranch larvae from further west make it all the way to Kwaj. Unfortunately, they seem to have never managed to grab a firm foothold. Possibly their always exposed habits leave them vulnerable to predation. Not much eats nudibranchs since they are usually distasteful or downright toxic, but predatory fish unfamiliar with them might be willing to try a bite. Even if the fish spit the nudibranch back out, perhaps this tasting is enough to kill off every new wave of migrants that reach the Marshalls.
This has to be one of the most photogenic species around.
The one below is crawling across a clump of algae, possibly Martensia fragilis.
This species is one of several that waves its mantle margins up and down as it crawls along. It's not all that discernable in a still photo, but there is video of its movement in the Underwater Kwajalein video. Someday maybe I'll try to get a short mpeg on this site.
Young individuals can be recognized by their reduced number of spots. This one was found in the latter stages of the 2015-2016 El Niño.
Created 14 December 2005
Updated 8 April 2016