MEPS 194:179-191 (2000)  -  doi:10.3354/meps194179

ABSTRACT: The influence of hypoxia and anoxia on the oxygen consumption, survivorship and rate of metamorphosis of field-caught postlarvae (megalopae) and first-instar juveniles of the blue crab Callinectes sapidus was observed under laboratory conditions. Rates of oxygen uptake by megalopae were independent of P_O2 at oxygen tensions above 8.88 kPa. However, P_c for juvenile crabs was significantly higher than for megalopae (89.6 vs 43.2% saturation). Tolerance of blue crab megalopae of hypoxic conditions below 20% saturation (~4.12 kPa) was greater than for newly metamorphosed juveniles. Juvenile crabs also succumbed to the effects of anoxia more rapidly than megalopae, but neither group survived exposure of >5 h. Megalopae and crabs that became immobile in anoxic water quickly recovered when returned to normoxic conditions. Metamorphosis of megalopae to the first-juvenile stage was delayed when they were exposed to P_O2 values of 8.21 and 12.32 kPa (40 and 60% saturation). Similarly, time to metamorphosis increased significantly when megalopae were temporarily exposed to hypoxic conditions (P_O2 = 4.12 kPa) for 4 h each day. However, there was no significant difference between the time to metamorphosis for megalopae exposed to hypoxic conditions for 2 h each day and those maintained in oxygen-saturated water. These results suggest that the presence of hypoxic and anoxic water in deep water layers and shallow near-shore habitats of estuaries during the summer months may influence the onshore migration, settlement and survival of blue crab megalopae and newly metamorphosed juvenile crabs.

KEY WORDS: Callinectes sapidus · Blue crab · Respiration · Hypoxia · Anoxia · Megalopae · Juveniles · Metamorphosis · Survivorship