Pleurobranchaea californica and Navanax inermis

Image courtesy of Brenda Bridgett
South Wall, La Jolla Shores, Calif
Cannon Powershot A570 IS, 7.1 megapixel, using internal flash at LJS in March.
Copyright 2011, Brenda Bridgett

Brenda Bridgett
Pleurobranchaea californica versus Navanax inermis

Wow, Brenda has caught some pretty exciting shots here. Both of these species are slugivores. Yes thats right - they both feed on other sea slugs. Pleurobranchaea will even cannibalize its own young. I first noted this many years ago when I examined the guts of several large specimens dredged up in the Los Angeles sludge fields. The specimens measured nearly 10 inches in length. I was surprised to find a variety of sand and mud bottom invertebrates in the gut, as well as a couple of unsuspecting fish, a small sole and a couple of sanddabs. The most surprising however was, one of the individuals contained 7 - one inch long specimens of its younger brethren.

Brenda has lived in San Diego and has been diving for more than 20 years, a good part of it at the "shores, so she is certainly familiar with the "turf" and it's inhabitants." On this particular encounter she cruising the south wall of Vallecitos Point and noticed a Navanax on an interdiction path with a Pleurobranchaea californica . Brenda quickly got her camera gear in order sensing there would be an encounter detrimental to one of the two known predators.

To Quote Brenda

"... The Navanax realized its mistake only when it actually touched the side of the larger branch and even though it reared up and tried to turn away, the P. californica knew there was food to be had..."

I am not aware of any documented instances where Navanax has fed on small Pleurobranchaea, but with not? It feeds on most other opisthobranch species.

The head to head attach suggests that both the critters may have had the same idea in mind - Dinner. Recall, these guys can't see so don't know the size of their soon to be meal. It is not uncommon to see a slugivore like Gymnodoris (Bill Rudman's Sea Slug Forum) take on a culinary challenge much too large to swallow. But when you have two slugivores - this complicates matters - one is going to win out. I am guessing that this unfortunate match up allowed the larger specimen of the two slugivores to overpower the smaller.

A short flash video of the encounter from start to "finish" is available of this seldom seen event!

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Dave Behrens
Gig Harbor, Washington
July, 2011

The 12 Annual San Diego UnderSea Film Exhibition is set for Friday and Saturday evenings, September 9 and 10, 2011 7:00 pm at Irwin M Jacobs' Qualcomm Hall.

Thirty-two short underwater films, produced by leading professional and amateur videographers from around the world, will be highlighted at the 12 Annual San Diego UnderSea Film Exhibition in Irwin M Jacobs' Qualcomm Hall big screen auditorium!

Starting at 7:00 pm, each evening will feature 16 different films, most in high definition, limited to 5 minutes each of fast-paced action. A state-of-the-art digital projection system will bring the world beneath the surface to the eyes of the audience.

This exhibition is unique because there are no entry fees and no prizes, except for the prestige of having a film chosen. An independent panel of three distinguished judges will select the best films among many international entries.

Each year the bar is raised in terms of quality and excitement. From the kelp forests of California to the coral islands of Indonesia, from the sperm whales of the Caribbean to the mantas of the Maldives, there will be something for everybody.

Also shown for the first time will be the winner of Capture the World, an international video competition. Tickets are available for $15 per evening online at SDUFEX . SDUFEX is a 501c3 nonprofit organization.

A portion of the proceeds will go to Birch Aquarium , San Diego Coastkeeper, and the Chula Vista Nature Center. Previous shows have been sellouts, so get your tickets early. A limited number of tickets may be available at the gate.

Seating is open, and doors open 30 minutes prior to the show. Parking is free on the Qualcomm campus. Further information is available online at Contact information: Pete Fowler, Mary Lynn Price , or Eric Hanauer .

A Film Trailer of the forthcoming event is now up on YOU Tube !

Send Pete email at
Send Mary Lynn email at
Send Eric email at

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

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© The Slug Site, Michael D. Miller 2011. All Rights Reserved.