Ontogenetic changes in dry weight, elemental composition (CHN) and activities of digestive enzymes (total protease, amylase) were studied through the moulting cycles of all larval stages (zoea I-II, megalopa; ZI, ZII, M) of the spider crab Maja brachydactyla Balss 1922 reared in the laboratory. All analyses were performed in single larvae to evaluate individual variability. Digestive enzyme activities were analysed by fluorometry. Changes in dry weight were only in premoult M statistically significant, whereas no differences were observed among Z and postmoult M (Fig. 1). No clear pattern was observed in the elemental composition (CHN in % of DW). An increase in enzyme activities throughout development was observed, although no statistically significant differences were found. Amylase (Fig. 2) and total protease activities were different among M moulting stages, being highest at premoult and lowest at intermoult. It seems that high individual variability (high standard errors) masked ontogenical changes in digestive enzyme activities, since previous data obtained from larval pools using spectophotometry analyses indicated that total protease and amylase activities were significantly higher between ZI and M. Despite lacking significance, the present study shows that different moulting stages presented different physiological conditions, and therefore, nutritional requirements may undergo marked changes during larval moult cycles. Hence, moulting stages must be taken into account in future studies to evaluate the nutritional condition of crustacean larvae.
Helmholtz Research Programs > PACES I (2009-2013) > TOPIC 2: Coastal Change > WP 2.2: Integrating evolutionary Ecology into Coastal and Shelf Processes