Lipid dynamics during the embryonic development of Plesionika martia martia (Decapoda; Pandalidae), Palaemon serratus and P. elegans (Decapoda; Palaemonidae): relation to metabolic consumption

Abstract

The present study examines the changes in volume and lipid biochemistry during the embryonic development of 3 temperate caridean species —Plesionika martia martia, Palaemon serra- tus and P. elegans —with similar reproductive strategies but occupying different ecological niches. Egg volume, water content and lipid embryonic metabolism are analysed and discussed in relation to early life history and environmental conditions. An increase in egg volume and water content during embryogenesis was noted in all species, although it was larger in P. serratus. P. serratus also had the largest eggs, followed by P. elegans and P. martia martia. The quantitatively most important fatty acids (FA) in the eggs are the saturates (SFA) 14:0, 16:0 and 18:0, the monounsaturates (MUFA) 16:1(n-7), 18:1(n-9) and 18:1(n-7), and the polyunsaturates (PUFA) 18:2(n-6), 18:3(n-3), 20:4(n-6), 20:5(n-3) (eicosapentaenoic acid, EPA) and 22:6(n-3) (docosahexaenoic acid, DHA). Looking at the predominant FA, there appears to be a higher similarity between P. martia martia and P. serratus. The eggs of these species present similar levels of SFA, highly unsaturated (HUFA) and (n-3) FA but P. martia martia eggs have an extremely elevated MUFA and a low PUFA content. P. elegans has high levels of SFA, PUFA, HUFA and (n-3) FA. P. serratus and particularly P. martia martia eggs are characterised by a higher DHA:EPA ratio than P. elegans. The similarity between the FA profile of P. martia martia and P. serratus eggs may suggest that these 2 species are exposed to more comparable environmental condi- tions than P. elegans. As for the utilisation of FA classes during embryonic development, all species showed the same trend—MUFA were found to be the major energetic fuel during embryonic devel- opment while SFA and HUFA seemed to be conserved. A steady decrease in total lipids, particularly tri- (TAG) and diacylglycerol (DAG), and FA contents was noted in the 3 species. The utilisation of these lipid classes during the incubation period was comparatively low in P. martia martia and P. ele- gans in relation to P. serratus eggs. This may suggest a higher dependence of the newly hatched larvae of P. martia martia and P. elegans on their lipid reserves and has been interpreted as an adaptation to the early life history of these species, during which there might be a reduced availability of food.