Tenellia adspersa (Nordmann, 1845)
Image courtesy of Robin Agarwal
Quivira Basin, Mission Bay, San Diego Bay Marina, California

This strange little aeolid appears to have a rather cosmopolitan distribution. In the north Atlantic it has been reported from various European sites including the UK and the Mediterranean. It has also been reported from the Atlantic coast of South America and in the North Pacific from Japan and much of the west coast of North America. Introduced or invasive, it appears all over the place.

We have some genetic evidence that T. adspersa maybe a cryptic complex of two or more species. This gets a little technical so hang in here with me. Karin Fletcher has identified what appears to be two groups of Tenellia adspersa from the Western Atlantic - BOLD:ACW9065 and BOLD:ACW9066 which are 4% different from each other. BOLD:ACW9065 (Barcode of Life Database) (: nearest neighbor is the private BIN BOLD:AEB5462 (1.76%) with two specimens from the Western Atlantic (Virginia). BOLD:ACW9066: nearest neighbor is the same private BIN BOLD:AEB5462 from the Western Atlantic. The distance is 4.49%. Here is a tree generate in BOLD of those relationships.

No specimens of Tenellia adspersa have been sequenced from the Eastern Pacific. It will be interesting to see if/how the specimen Robin collected is related to the ones that are already sequenced. Did you get all of that?

Adding to this new information we know that this species has two types of larval development, suggesting again, maybe we are dealing with two species. One produces a few large eggs which hatch out as small crawling young. The other produces more smaller eggs which develop into swimming veliger larvae, which do not feed in the plankton after hatching but quickly settle on the bottom and turn into a crawling slug. This short free-swimming larval stage may be an advantage for some populations, as it allows the young to move further from the parental home.

Not only are Robin's excellent photos of this species welcome, but also some ecological observations she has shared with Mike and I. "The specimen was found on drift kelp in the Quivira Basin, Mission Bay, San Diego, marina. The same kelp had Tenellia phoenix with eggs, Polycera atra, both Corambe species, and one small Triopha maculata." Wow - a Branchers party.

This species has an interesting behavior - when it crawls it flaps its frontal veil. Thanks to Robin and Karin for their great discoveries.

Dave Behrens
Sammamish, WA 98074
Apr., 2022
Send Dave email at davidwbehrens@gmail.com
Send Karin email at karin@milltech.com

Image courtesy of Robin Agarwal

I don't dive. And I don't own an unwieldy,expensive underwater camera rig. What I do is peer into tidepools and hang my head over the side of floating docks, hoping to spot a nudibranch and get a few snaps with the trusty little point-and-shoot, underwater macro camera that fits in my pocket.

I was a tidepool kid who went astray and graduated with a liberal arts degree. In the last decade, I've returned to the tidepools and found a particular passion for photographing nudibranchs and other intertidal marine life. I'm co-editor of the California Sea Slugs Guide on iNaturalist.org, where I have posted about 4,000 geotagged observations of nudibranchs, mostly along the Central California coast. Since I offer all my photos free to non-profit organizations (my way of thanking them for the work they do), you can find them all over the internet as well as Bay Nature magazine and NOAA National Marine Sanctuary informational signage. I've also been an enthusiastic contributor to a few scientific papers on nudibranchs, such as Heterobranch Sea Slug Range Shifts in the Northeast Pacific Ocean Associated with the 2015-16 El Nino by Goddard et al. (2018).


Robin Agarwal

Send Robin email at robingwenagarwal@gmail.com

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

Send Dave email at davidwbehrens@gmail.com

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