Settlement induction of Acropora palmata planulae by a GLW-amide neuropeptide |
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Authors: | P M Erwin A M Szmant |
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Institution: | 1. Center for Marine Science, University of North Carolina Wilmington, 5600 Marvin K. Moss Lane, Wilmington, NC, 28409, USA 2. Centre d’Estudis Avan?ats de Blanes (CEAB, CSIC), Accés Cala S. Francesc 14, 17300, Blanes (Girona), Spain
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Abstract: | Complex environmental cues dictate the settlement of coral planulae in situ; however, simple artificial cues may be all that
is required to induce settlement of ex situ larval cultures for reef re-seeding and restoration projects. Neuropeptides that
transmit settlement signals and initiate the metamorphic cascade have been isolated from hydrozoan taxa and shown to induce
metamorphosis of reef-building Acropora spp. in the Indo-Pacific, providing a reliable and efficient settlement cue. Here, the metamorphic activity of six GLW-amide
cnidarian neuropeptides was tested on larvae of the Caribbean corals Acropora palmata, Montastraea faveolata and Favia fragum. A. palmata planulae were induced to settle by the exogenous application of the neuropeptide Hym-248 (concentrations ≥1 × 10−6 M), achieving 40–80% attachment and 100% metamorphosis of competent planulae (≥6 days post-fertilization) during two spawning
seasons; the remaining neuropeptides exhibited no activity. Hym-248 exposure rapidly altered larval swimming behavior (<1 h)
and resulted in >96% metamorphosis after 6 h. In contrast, M. faveolata and F. fragum planulae did not respond to any GLW-amides tested, suggesting a high specificity of neuropeptide activators on lower taxonomic
scales in corals. Subsequent experiments for A. palmata revealed that (1) the presence of a biofilm did not enhance attachment efficiency when coupled with Hym-248 treatment, (2)
neuropeptide-induced settlement had no negative effects on early life-history developmental processes: zooxanthellae acquisition
and skeletal secretion occurred within 12 days, colonial growth occurred within 36 days, and (3) Hym-248 solutions maintained
metamorphic activity following storage at room temperature (10 days), indicating its utility in remote field settings. These
results corroborate previous studies on Indo-Pacific Acropora spp. and extend the known metamorphic activity of Hym-248 to Caribbean acroporids. Hym-248 allows for directed and reliable
settlement of larval cultures and has broad applications to the study and rehabilitation of threatened Acropora populations in the Caribbean. |
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