Re: Dendronotus nanus rediscovered in California

May 18, 2006
From: Phil Garner

Concerning message #14507:

There has been a population explosion of Dendronotus iris at Marineland in Rancho Palos Verdes, California the past month. I have witnessed dozens of them laying eggs and have spotted two that resemble the 'Dendronotus nanus colour form' in the same area. There have also been reports of both 'species' together in La Jolla. I have always wondered if they are the same species with widely variable colorations, but D. iris seems to have appendages compared to the cerata of  D. nanus.

Locality: Rancho Palos Verdes, 45-70 feet, California, USA, Eastern Pacific, 02 April 2006, Edge of a rocky reef on or near Pachycerianthus fimbriatus. Length: 1 inch to 10 inches. Photographer: Phil Garner.

I found a great picture from Stephanie Truhler on the DiveBums site. It shows both 'species', or variations of the same species, laying identical eggs side by side.

Phil Garner

Garner, Philip, 2006 (May 18) Re: Dendronotus nanus rediscovered in California. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Phil,
Thanks for the photos. As you will see from other messages, the Californian experts all agree that D. nanus is just a colour form of D. iris. Is it usual for them to lay their egg ribbons on the tubes of their food, as seen in your photos? It would seem a bit dangerous for the larvae when they hatched out, but I guess it is a handy 'hard' surface for the slug to attach its eggs to.

I notice in your photo alongside that there is a small? animal in the Pachycerianthus tube. I presume Dendronotus can get stung by their food, so venturing into the 'lion's den' like this would seem a fairly risky activity.

Thanks for alerting me to Stephanie's photo. I have been in touch with her and am posting her photo separately [message #16634 ]

Best wishes,
Bill Rudman

Rudman, W.B., 2006 (May 18). Comment on Re: Dendronotus nanus rediscovered in California by Phil Garner. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


Dendronotus iris

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