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Journal Article

Partial Characterization and Biological Activity of a Metamorphic Inducer of the Dorid Nudibranch Adalaria proxima (Gastropoda: Nudibranchia)

Walter J. Lambert, Christopher D. Todd and Jörg D. Hardege
Invertebrate Biology
Vol. 116, No. 2 (Spring, 1997), pp. 71-81
Published by: Wiley on behalf of American Microscopical Society
DOI: 10.2307/3226971
Stable URL: http://www.jstor.org/stable/3226971
Page Count: 11
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Partial Characterization and Biological Activity of a Metamorphic Inducer of the Dorid Nudibranch Adalaria proxima (Gastropoda: Nudibranchia)
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Abstract

Larval metamorphosis of the dorid nudibranch Adalaria proxima is induced by a water-borne cue present in seawater that has been conditioned with live Electra pilosa, its preferred bryozoan prey. Extracts and fractions of Electra-conditioned seawater (CSW) were assessed in bioassays of competent larvae to further elucidate the nature of the inductive chemical cue. Extracts of volatile compounds and lipids present in CSW did not induce metamorphosis; the fractions of CSW remaining after extraction still retained the inducer. Heating CSW to 80° C for 5 min did not eliminate the inductive cue, but metamorphic activity was decreased after boiling CSW for 5 min. No larvae metamorphosed in treatments in which CSW was incubated with trypsin or protease before bioassay. Larvae metamorphosed in CSW after centrifugation, filtration (0.22 µm), and treatment with a bactericide. Metamorphosis was induced by ultrafiltrates (10 kDa, 1 kDa, and 500 Da) of CSW, albeit in a variable manner. Up to 45% of larvae metamorphosed in the 500 Da and 1 kDa fractions. There was little response by larvae to the 10 kDa fraction. These procedures eliminated volatile organic molecules, lipids, and large proteins as potential molecules inducing metamorphosis of larvae of A. proxima. Furthermore, that treatment of CSW with trypsin eliminated the inductive cue and that metamorphosis occurred in ultrafiltrates of CSW strongly suggests that larvae of A. proxima respond to a small (<500 Da) arginine- or lysine-containing peptide.

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