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1. The aim of this study was to analyse seasonal fluctuations in the respiration rate of pre-adults of Penaeus aztecus, P. setiferus, Scycionia brevirostris and Callinectes similis, and juveniles of Portunus spinicarpus, Hepatus ephelyticus and Calappa sulcata. 2. A flow respirometer was used to determine the oxygen consumption of these decapods, which was measured every 2 hr during a 24 hr cycle in September (27 +/- 1-degree-C) and in April (22 +/- 1-degree-C). 3. The respiration rates of seven species revealed uni-, bi- and trimodal patterns during the 24 hr cycle during both seasons. Metabolic amplitude of the shrimp species was reduced by 42% during the coldest months of the year. In winter, when H. ephelyticus was absent, the metabolic amplitude of C. sulcata in that community was two-fold the value recorded in the summer. The metabolic amplitude of portunids and calappid species in summer proved to be significantly reduced (P < 0.05) by 0.72 and 0.91% in relation to values recorded for P. aztecus and S. brevirostris, respectively. 4. These results suggest a coupling of the respiration rate of seven species with their nictimeral activity rhythms and the seasonal temperature variations that enhance their chances of resource exploitation in avoiding predation and reducing the competitive interactions with co-occurring shelf-faunal components. |
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