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MEPS prepress abstract   -  DOI:

Lipid allocation in late-stage barnacle larvae from subtropical and temperate waters

Inês Leal*, Katrin Bohn, Stephen J. Hawkins, Stuart R. Jenkins, Augusto A. V. Flores, Réjean Tremblay

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ABSTRACT: The transition of planktonic late-stage barnacle larvae to a benthic life requires enough energy to power settlement and metamorphosis, and may be compromised by food limitation during early ontogeny. We carried out a comparative study to better understand the larval physiology of space-monopolizing barnacles exposed to contrasting regimes of primary productivity: Chthamalus bisinuatus under a meso-oligotrophic regime on the southeastern coast of Brazil, and Chthamalus montagui under a highly-productive regime on the south coast of the British Isles. We used an index based on lipid composition, the triacylglycerol (TAG) to phospholipid (PL) ratio, to characterize lipid allocation (energy/structure) in the tissues of cyprid larvae and anticipated depleted TAG reserves in cyprids from less productive waters. Despite the considerably different levels of primary productivity between subtropical (1.31 ± 0.4 mg Chl-a/m3) and temperate waters (3.09 ± 1.2 mg Chl-a/m3), TAG/PL and settlement success were comparable for C. bisinuatus and C. montagui. Lipid allocation of daily cohorts was also comparable for both chthamalids, with cyprids equally storing TAG reserves (3 50% of total lipid content). This points to an energetic threshold below which nauplii cannot develop to a cyprid and/or selection for lipid accumulation under poor trophic conditions. We highlight the challenges of directly relating estimates of primary productivity with food supply and larval physiological status, as lower Chl-a concentrations do not necessarily indicate food limitation for barnacle nauplii. We propose a conceptual model to clarify the process of lipid allocation (energetic to structural lipids) in the tissues of cyprid larvae.