MEPS 198:303-310 (2000)  -  doi:10.3354/meps198303

Physiological condition and barnacle larval behavior: a preliminary look at the relationship between TAG/DNA ratio and larval substratum exploration in Balanus amphitrite

Gilles Miron*, Linda J. Walters**, Réjean Tremblay***, Edwin Bourget

GIROQ, Département de biologie, Université Laval, Québec, Québec G1K 7P4, Canada
Present addresses: *Département de biologie, Université de Moncton, Moncton, Nouveau-Brunswick E1A 3E9, Canada. E-mail: **Department of Biology, University of Central Florida, Orlando, Florida 32816, USA ***Centre aquicole marin, Ministère de l¹Agriculture, des Pêcheries et de l¹Alimentation, Direction générale des Pêches et de l¹Aquiculture commerciales, Grande-Rivière, Québec G0C 1V0, Canada

ABSTRACT: Behavior of laboratory-reared larvae of the barnacle Balanus amphitrite was examined in Beaufort, North Carolina (USA), in relation to their physiological condition. Cyprid substratum exploration was monitored by means of video endoscopy using various experimental surface types (clean, biofilm, 1 and 2 wk fouled) and 2 water flow regimes (still water and ca 5 cm s-1) at room temperature (21°C). We used the triacylglycerol/DNA (TAG/DNA) ratio of small batches of larvae as a measure of physiological condition in 0 to 12 d old cyprids. The physiological condition of cyprids decreased significantly with age (p < 0.001), ratios severely dropping between 5 and 8 d. Although exploration behavior did not show much variation with age, the overall number of active exploring cyprids appeared to be age dependent. Additionally, the relationship between surface exploration behavior and age also appeared to vary with substratum type as well as flow rate. For example, fewer young cyprids (0 to 5 d old) explored unfavorable substrata (clean and biofilm treatments) than older ones in still water. Exploration responses, however, appeared to differ in relation to flow regimes (still vs moving water trials). Time spent by cyprids on surfaces before returning to the water column (non-exploratory behavior) appeared to vary in relation to age and substratum type in still water trials. Duration of exploration and distance explored by cyprids in flow generally peaked with cyprids from the 3 d cohort. Overall, our results showed that habitat selection in barnacle cyprids results from a complex relationship involving substratum type, hydrodynamics and larval age (i.e. physiological condition and competency).

KEY WORDS: Balanus amphitrite · Barnacle · Cyprid · Larval behavior · Larval ecology · Lipid condition · TAG/DNA ratio

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