6 Oct 2015

OCD barnacles and gregarious settlement.

I can imagine three or four barnacles lining up by chance, but ten? (I think these are acorn barnacles, Semibalanus balanoides)
I've just done a very quick look over the available online literature to see if juvenile free-swimming barnacles, looking for a suitable spot to settle, have any cues from already settled adult barnacles. Barnacles must have other barnacles settled nearby to reproduce with. I had guessed it would be a chemical signal released into the water. I was wrong.

The free-swimming larval stage (cyprids) have rudimentary eyes which can pick up red flourescent light which, it turns out, is reflected by the shells of settled adults. So possibly the big chap on the right was the pioneer and the rest, looking for a site and potential mate, saw his flourescent beacon, swam on down, cemented their heads to the rock and set up home. I still think it's charming that they've done it in a straight line.

Reference:
Matsumura, Kiyotaka, and Pei-Yuan Qian. "Larval vision contributes to gregarious settlement in barnacles: adult red fluorescence as a possible visual signal." The Journal of experimental biology 217.5 (2014): 743-750.

The link to the academic paper is here and thanks to the Journal of Experimental Biology for making it available free.

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