Translocation of fixed carbon from symbiotic bacteria to host tissues in the gutless bivalve Solemya reidi |
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Authors: | C. R. Fisher J. J. Childress |
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Affiliation: | (1) Scripps Institution of Oceanography, A-008, 92093 La Jolla, California, USA |
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Abstract: | Naturally-occurring lipophilic inducers of larval settlement and metamorphosis wer isolated and identified for Phragmatopoma californica, a gregarious tube worm from southern California. Organic solvent extraction of the sand/organic cement matrix of tubes diminished the inducing capacity of the tube matrix. The inducing capacity was restricted to a single, highly active, HPLC-purified fraction of the organic solvent extract. Chemical analysis of this fraction revealed a mixture of free fatty acids (FFAs), dominated by eicosapentaenoic acid (20:5, 20%), palmitic acid (16:0, 14%) and palmitoleic acid (16:1, 12%). In assays of the nine FFAs that each contributed 3% or more to the active fraction, only 16:1, 18:2, 20:4 and 20:5 induced larval settlement and metamorphosis, while the others were ineffective. The larval response was contact-dependent, highly specific, and concentration-dependent, with a significant response to 16:1 and 20:4 at as low as 10 g FFA spread onto 1 g of sand (surface area 36 cm2). Active FFAs were extracted at approximately 14 g g-1 sand from the tube matrix, although the levels encountered by larvae in nature are believed to be higher. |
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