Eubranchus rustyus

Photo courtesy of Terry Strait
La Jolla Shores, San Diego, Calif
Sept., 2008

Eubranchus rustyus, (Marcus 1961)

One of the most puzzling nudibranch observations is the disappearance and reappearance, over a period of years, of many species. Webmaster Mike first noted this in his BOW on Hypselodoris californiensis (revisited 03/24/03)
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Surprisingly, all the slug-nuts (aka - Branchers) in the San Diego area have recently come across zillions of specimens of Eubranchus rustyus, after years of total absence. The only hypothesis I can offer is that the species planktotrophic larvae stay in the plankton, floating around and around the North Pacific Gyre (current) for years before sensing that chemical cue causing them to settle out. The problem with this hypothesis is that the chemical cue is always present, as this species feeds on the very abundant hydroids Obelia and Plumularia.

This species is highly variable in color as you will note quite a difference here is Terry’s photo above and the photo in Eastern Pacific Nudibranchs (page 112). Key characteristics to look for are inflated, irregular cerata; green to brown spots on the white body and cerata; and rhinophores and cerata tipped in white with a sup-apical green/brown band.

Terry and Kim first suspected the abundance of some tiny nudibranch when they found hundreds of arc shaped egg ribbons on the hydroids. Due to rough water conditions they couldn’t find any slugs however. After repeated return trips, Kim’s sharp eyes spotted a couple of the tiny (4-5 mm) aeolids munching away on hydroid polyps.

These very cryptic little critters are hard to spot, let alone get a photo of in-situ. Good work guys.

I was certified in 2002 as a Christmas present for my girlfriend and I. After my first open water dive I was hooked. Now 4 years later I have over 600 dives and no plans on slowing down. Most of my diving is right here off the San Diego coast where I have ample opportunity to pursue my passion of searching for and photographing nudibranchs. I didn't even know what a 'branch was until Sean Kearney opened my eyes to the amazing world of the sea slug. Thanks to Sean I have spent way more money than was prudent on dive boats, dive gear and cameras.....all so I can say...."look what I found". I am presently shooting a Nikon D40x with a Nikkor 60mm macro lens in an Ikelite housing. Two DS125 strobes. Send Terry email at divinman@sbcglobal.net

From left to right, Terry Gosliner, Angle Valdes, Dave Behrens La Jolla, Calif.

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