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 developmen tal phases were distinguished microscopically: cleavage, gastrula,;emb ryo differentiation, prehatching phase. Changes in fresh weight (FW), dry weight (DW), ash-free dry weight (AFDW), water, carbon (C), nitrog en (N), total lipids, proteins, carbohydrates, and respiration rates w ere measured in developing eggs. The percentage of water increased fro m 52% to 87% of FW, most rapidly after the beginning of organ differen tiation and during hatching. The accumulation of minerals followed a s imilar pattern, with ash increasing from 3% to 7% of DW in the eggs, a nd 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 initi al 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 inc rease in low-molecular nitrogenous substances, which are not quantitat ively detected by the Lowry method (probably free amino acids); we sus pect that these may play a role in the hatching process. In the gastru la, and from about 3 months after the onset of organ differentiation u ntil 1 or 2 months before hatching, low embryonic respiration rates as well as microscopical observations indicated the existence of develop mental resting periods. Such diapause-like intervals may coordinate th e time of hatching with a short season of planktonic food production i n high latitudes. The relative importance of lipids and proteins as fu el for embryogenesis is compared with that in other crustacean taxa. ( C) 1997 Elsevier Science Inc.