Placida brookae

Image courtesy of Brook Peterson
Catalina Island, Southern California

Placida brookae ,McCarthy, Krug & Valdes 2017

Well here is the second in the series of new species of Placida. This is another Placida cremoniana (Courtesy of Bill Rudman's Sea Slug Forum) look-alike that has been named to honor friend and super UW photographer, Brook Peterson.

Externally the species in this color complex look very similar, but internals and protein sequencing tell the tale. Externally the coloration of the head and rhinophores is the key. The cerata are very similar between the geography distant 4 species. Like P. kevinleei the anterior stripe on the rhinophores of P. brookae extends only about half their length. Like P. cremoniana, the head and oral tentacles are black. P. brookae also has a yellow stripe extending posteriorly from the eye spot.

Geographically this species ranges from Anacapa and Catalina Islands to La Paz, Mexico and the Galapagos.

For an in depth overview on how Brook was able to find and have the this rare sea slug identified, the reader is invited to visit an excellent article Brook wrote for California Diving Magazine .


McCarthy, J.B., P.J. Krug & A. Valdes, 2017. Integrative systematics of Placida cremoniana (Trinchese, 1892) (Gastropoda, Heterobranchia, Sacoglossa) reveals multiple pseudocryptic species. Mar Biodiv. 2526-017-0812-2. Senckenberg Gesellschaft fur Naturforschung and Springer-Verlag GmbH Germany.

Dave Behrens
Sammamish, WA 98074
Mar., 2018
Send Dave email at

WEBMASTER'S NOTES: Congratulations are certainly in order to Brook for having brought Placida brookae to our (Angel Valdes and students) attention and the consequent introduction of yet another new slug to Southern California waters. So for all you SoCal divers, Keep your eyes on the ready, you may be the next to find a "diamond in the ruff". I was fortunate to be on the same boat as Brook during the Jan. 2017 CritterFest at Crystal Blue in the Philippines! It was certainly evident to me that Brook left no stone unturned in her quest to photograph the strange and unusual in the waters of Anilao, Philippines! Her dedication to sea slugs was exemplified by her "custom" hood! What more can be said!

Brook on location at Anilao, Philippines for the Jan. 2017 CritterFest at Crystal Blue Resort

Brook Peterson is an avid scuba diver and underwater photographer who enjoys capturing the beauty of the underwater environment throughout the world. She is an ambassador for Sea&Sea Underwater Imaging as an original member of the SEA&SEA Alpha program. Her work has been featured in both print and online magazines. She is the owner of and authors a blog on underwater photography and techniques.

Brook has a Nikon D810 in a Sea&Sea Housing with YS-D2 strobes. Favorite lenses are Nikon 105mm, and Nikon 8-15mm fisheye. The SMC and the SMS-2 are also in her kit bag for the tiny stuff.

Join Brook for an underwater photography workshop and critter hunt May 20th-30th at Crystal Blue in Anilao, Philippines!

Send Brook email at

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