Armina californica

Armina californica (Cooper, 1863)

This sand dweller has been reported from Vancouver Island, Canada, to Panama. It pushes its way through sand or mud-sand bottoms from the low intertidal to 250 feet (80 m) deep.

Ranging in length from 2-4 inches (50-100 mm), this creature has a pale gray, brown, black or red-brown dorsum, on which are numerous white longitudinal wavy ridges.

I have found Armina fairly regularly while diving near the La Jolla Canyon. Crawling over shallower sandy bottoms above the canyon's edge, it is searching for a mate or its preferred alcyonarian prey, Renilla koellikeri and Stylatula elongata. The bioluminescent responses of Renilla while being eaten do not faze Armina's ardor for its meal; that chemical defense may be protective against other predators. If Renilla could see, this would be its last glimpse before being scraped by Armina's radula. I have found Armina actually positioned on the upright stalk of Stylatula, as well as approaching it. Once I watched Armina move closer and closer to a sea pen; it reached about 1-2 mm distance from its prey, paused, pulled its anterior region back slightly, and then lunged forward, grabbing a mouthful of Stylatula's polyps. The sea pen nearly instantly retracted back down into the protection of the sand; Armina had to crawl away with only an appetizing morsel.

Photos and text by Dr. Hans Bertsch

Dr. Hans Bertsch

192 Imperial Beach Blvd. #A
Imperial Beach, CA 91932
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