Onchidoris bilamellata aggregation in Maine, USA

September 9, 2009
From: Drew Villeneuve

Dear Bill,

Here are some pictures of Onchidoris bilamellata from a project studying population density in intertidal areas that I took a year ago. Just thought you might like the nudis on the driftwood and the huge population density in the pools - up to 1023 individuals in a space of 915 square meters. A lot of these pictures are out of focus because I didn't have an underwater camera with me - and it would have been useless anyways, judging from the shallowness of the water.

Locality: Bar Island, Deer Island, Maine, USA, Penobscot Bay, Atlantic Ocean, intertidal, 23 August 2008, Rocky Shore. Length: ~1-2.5 cm. Photographer: Drew Villeneuve

Regards,
Drew Villeneuve,
St. Albans School

kapsberger@gmail.com

Villeneuve, D., 2009 (Sep 9) Onchidoris bilamellata aggregation in Maine, USA. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/22650

Thanks Drew,

When I see photos like these I can understand why ecologists in the northern hemisphere have been attracted to Onchidoris bilamellata. We can see in your middle photos that the animals cluster into depressions and channels in the rock at low tide, which I guess is to keep them moist.

We don't get any shallow water dorids appearing in these densities down here in Australia and New Zealand, but we often find Sea Hares doing so.

Best wishes,
Bill Rudman

Rudman, W.B., 2009 (Sep 9). Comment on Onchidoris bilamellata aggregation in Maine, USA by Drew Villeneuve. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/22650

Factsheet

Onchidoris bilamellata

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