Chemical and Physiological Changes During the Embryonic Development of the Spider Crab, Hyas araneus L. (Decapoda: Majidae)

During embryogenesis of the spider crab, Hyas araneus, four developmental phases were distinguished microscopically: cleavage, gastrula, embryo differentiation, prehatching phase. Changes in fresh weight (FW), dry weight (DW), ash-free dry weight (AFDW), water, carbon (C), nitrogen (N), total lipids, proteins, carbohydrates, and respiration rates were measured in developing eggs. The percentage of water increased from 52% to 87% of FW, most rapidly after the beginning of organ differentiation and during hatching. The accumulation of minerals followed a similar pattern, with ash increasing from 3% to 7% of DW in the eggs, and to 26% at hatching. Inverse (decreasing) patterns were observed in organic matter (AFDW, C, N, lipids, proteins). During development from the undivided egg to the freshly hatched zoea larva, 69% of the initial lipid and 35% of protein were depleted. Carbohydrates represented a minor constituent of yolk (1% to 2% of DW). In spite of a decreasing protein content, N remained almost constant. This suggests a final increase in low-molecular nitrogenous substances, which are not quantitatively detected by the Lowry method (probably free amino acids); we suspect that these may play a role in the hatching process. In the gastrula, and from about 3 months after the onset of organ differentiation until 1 or 2 months before hatching, low embryonic respiration rates as well as microscopical observations indicated the existence of developmental resting periods. Such diapause-like intervals may coordinate the time of hatching with a short season of planktonic food production in high latitudes. The relative importance of lipids and proteins as fuel for embryogenesis is compared with that in other crustacean taxa. comp biochem physiol 117B;2:299–306, 1997.  1997 Elsevier Science Inc.