Environment, adaptation and evolution: Scallop ecology across the latitudinal gradient

Marine biota show latitudinal gradients in distribution, composition and diversity. Most studies of latitudinal gradients in organism biology and ecology are based on between-species comparisons and hence are hampered by taxon-related variability in the parameters under investigation. To reduce taxonomic noise and to minimize the risk of otherwise misleading generalisations I used species from one single bivalve family (Pectinidae, scallops.Ecological (e.g. age, growth, productivity) and physiological (standard metabolic rate, enzyme kinetics) parameters of three scallop species (Adamussium colbecki, Aequipecten opercularis and Zygochlamys patagonica) were measured and combined with data extracted from literature. The resulting database comprised 226 studies of 26 species living over a temperature range of 28°C. The overall growth performance of scallops increases with decreasing latitude, i.e. it is strongly coupled to annual solar energy input but weakly coupled to average annual water temperature. Mean annual water temperatures and annual solar energy input by themselves can explain only a small part of the variability observed in growth performance. An analysis of 82 published studies on standard metabolism provided no evidence for metabolic cold adaptation at the organism level. In contrast, mitochondrial proliferation caused a rise in oxygen demand in the Antarctic scallop indicating that metabolic cold adaptation does occur on the cellular level. It must be assumed that energy savings occur to counterbalance the cost of cellular MCA. At which organisational level such savings may occur remains unanswered so far.The present study indicates that many scallop species have developed strong life-history adaptations to the particular conditions of both alimentation and temperature they experience. In addition, the established pectinid database (ScallopBASE) provides a good basis for the evaluation of evolutionary adaptations and constraints.