Flabellina trilineata from California

July 6, 2006
From: Aidan Hampson


Can anyone help me ID this species I saw this weekend. I wish I'd shot more so I could be more help. I think it is Facelina stearnsi. The bryozoans on which it was feeding are clear. The size is about 1", at least 1 central white line was present, maybe three but I can't be certain. It was on a vertical pinnacle at ~40ft. Four individuals were seen within 6 ft radius, but no others seen on 2 other dives on that reef structure. Two of the four individuals were 1", 2 only 0.5" In the same area, several orange bulls-eye ring egg masses were observed (2" diameter) with the same orange pigment as the cerrata on the individual. The pinnacle was unusual in that it was much steeper (a wall) than other rock structures in the reef

Locality: Eagle Reef, deep water (east) side Santa Catalina Island, 40-50ft, CA USA, Pacific, 24 June 2006, Wall of pinnacle 15 ft tall, at edge of reef, kelp forest. Length: 1". Photographer: Aidan Hampson.

Aidan Hampson


Hampson A.J., 2006 (Jul 6) Flabellina trilineata from California. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/17024

Dear Aidan,

After some hard thought I believe your critter is Flabellina trilineata.  I base this identification on the color of the ceratal cores and the fact that it has perfoliate rhinophores ( and your mention of possibly three white lines).  The coloration of Facelina stearnsi is quite different.

Additionally, it is feeding on tubulariid hydroids, not bryozoans.  While hydroid polyps might be confused with the zooids of bryozoans, the ones in your photo have long stalks.  I am unaware of any aeolid that feeds on bryozoans.  Bryozoans are eaten only by a few dorids and arminaceans.

Best wishes,
Dave Behrens

Behrens, D.W., 2006 (Jul 6). Comment on Flabellina trilineata from California by Aidan Hampson. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/17024

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