Peter G. Beninger’s research while affiliated with Université de Bretagne Occidentale and other places

The variations in relative organic matter (ROM: organic matter/total dry weight) were studied in larval cultures of Mytilus edulis L. reared at 15°C and at 20°C, using single and mixed algal diets. A characteristic inverted peak is observed prior to metamorphosis, with higher minimum values in cultures reared at 20°C and fed a mixed algal diet. The shape of the ROM curve appears to reflect major physiological events in M. edulis larvae and is thus appropriate as a convenient condition index from the first larval stages to the post-larval phase.

1.1. Seasonal variations in fatty acid composition of the triacylglycerols and phospholipids of an indigenous and an introduced clam species reared in a common habitat were analyzed using gas-liquid capillary column chromatography.2.2. Despite different geographical origins, the fatty acid spectra of the two related species were quite similar.3.3. In both species the fatty acids of the triacylglycerol fraction, but not the phospholipid fraction, showed clear seasonal variation corresponding to the annual temperature cycle and not to reproductive activity.4.4. It is argued that such variations are related to the diet and are not endogenous.

1.1. The levels of four major cations, Na+, K+, Mg2+ and Ca2+ were measured using flame spectrophotometry over a 16-month period in two populations of adult marine clam reared in a common habitat.2.2. The variations in absolute and relative values of Na+ and Mg2+ were virtually identical within each species; the relative values showed a marked increase during the period of negative energy balance previously reported, even when the external salinity decreased.3.3. Calcium levels showed very irregular long-term variations, reflecting its multiple roles as a metabolic, osmotic and structural element.4.4. A close relationship was observed between the levels of K+ and organic constituents, especially glycogen.5.5. An adaptive benefit of this relationship is postulated.

The condition, reproductive activity, and gross biochemical composition of an indigenous and an introduced adult clam population raised in acommon habitat of the French Atlantic coast were examined over a 74-wk period. The indigenous species, Tapes decussatus L. (Jeffreys) and the introduced species, T. philippinarum (Adams & Reeve) were raised together on the south Finistère coast of Brittany. The gross biochemical composition of a standard animal of each population was significantly correlated with the population condition indices. During the winter, no reproductive activity was observed in either population, and the contribution of protein, glycogen, and lipids to the maintenance energy was calculated. Protein formed the main reserve, while lipids contributed as much as glycogen in T. decussatus, and twice as much in T. philippinarum. Although some species differences were noted in the mean levels of biochemical components, the overall seasonal variations were similar in both populations.

The relative and absolute levels of four major lipid classes in an indigenous and an introduced adult clam population raised in a common habitat were determined over a 74-wk period. The standard animal of each population contained a low and stable amount of the fraction containing wax esters, hydrocarbons, and sterol esters. The absolute levels of triacylglycerols and phospholipids closely followed the indices of reproductive activity. Following the summer spawning a severe negative energy balance was observed throughout the winter. During this period, both triacylglycerols and phospholipid contributed to the maintenance energy, although the phospholipids' contribution was greater in both populations.A comparison of the seasonal variations of absolute and relative values underscores the advantages of absolute values in the calculation of lipid class levels. Although some specific differences were found in mean lipid class levels, the overall seasonal variations of the lipid classes were similar in both populations.