We had a H.S. group from Parker School out for an overnight last night. This morning they did an invasive seaweed lab and found a very cool sea slug/ nudibranch (naked gilled sea slug).
|Image M. Heckman|
I asked the students to look it up and at first glance they keyed it out to Dendrodoris rubra from John Hoover's invertebrate book. But, there was some question about the ID. It seemed to be missing the light edge band. Good call on their part. I just had a look at it more closely and I am going with Dendrodoris fumata, the "smoky nudibranch" (name via Keoki and Yuko Stender's site).
The issues with identifying marine life show up well here - this species has a range of colors and is very close to a couple of other types in description. Our specimen, however, fits the D. fumata physical characteristics the best as far as I can tell. Add to this the fact that it came from a habitat similar to one described for others of this species that have been found in Hawaii - shallow protected waters (S. Johnson, 1982) and our id seems at least probable. In our case, this animal came from clumps of Gracilaria salicornia (gorilla ogo seaweed) in 1 - 3 feet of water along the edges of our salt water pool below the beach pavilion, Moku o Lo'e (Coconut Island) Kane'ohe Bay.
|Dendrodoris fumata - image M. Heckman|
Like many nudibranchs of this type, it most likely eats sponge. If that is the case, it was in the right location. The most common animals found in the invasive seaweed mats are various clumps of sponges!
|Upside down crawling across the water surface - image M. Heckman|
For more information on this nudibranch, see:
Smoky Nudibranch, from Keoki and Yuko Stenders MarineLifePhotograpy site http://www.marinelifephotography.com/marine/mollusks/slugs/dendrodoris-fumata.htm
The Sea Slugs of Hawaii site by Cory Pittman and Pauline Fiene
The Sea Slug Forum site