Re: Aggregation of Stylocheilus striatus [2]

January 23, 2006
From: Paul Whitehead

Concerning message #15378 on aggregation of Stylocheilus:

Dear Bill,
As promised attached are some photos of the other two aggregation species, which all aggregated with the same week and on the same site (Retal Larry, Lembeh Straits) following the spetember full moon.

Locality: Retak larry. Lembeh Straits, Indonesia. Depth: 3 meters. 15 September 2005. black sand beach with sparse cover. Photographer: Paul Whitehead

Immediately after the Stylocheilus aggregation this "white" species aggregated over the site are covering an area of about 20 meters by 20 meters and avaeraging about 10 animals per square meter. Whilst this aggregation was occurring the third species [see message #15629] aggregated covering the same area with about 10 animals per square meter again.

The whole cycle of the three aggregations lasted 1 week.

Paul

pw@whiteheadimages.com

Whitehead, Paul, 2006 (Jan 23) Re: Aggregation of Stylocheilus striatus [2]. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/15630

Dear Paul,
Thanks for following up with these photos. It is certainly an interesting st of observations. I guess the sequence is a response to the same physical conditions - water temperature, currents etc - as these animal are not really equipped to quickly gang up on their prey when a prey species is in large numbers. This 'white' one is Gymnodoris ceylonica. It certainly is known to occur in large aggregations. See Scott Johnson's message [#1289] where he suggests they move from deeper water to spawn. Interestingly, species of Gymnodoris, eat other opisthobranchs, but I don't recall if Stylocheilus has been recorded as part of their diet.
Best wishes,
Bill Rudman

Rudman, W.B., 2006 (Jan 23). Comment on Re: Aggregation of Stylocheilus striatus [2] by Paul Whitehead. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/15630

Factsheet

Gymnodoris ceylonica

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