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 PO2 at oxygen tensions above 8.88 kPa. However, Pc 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 PO2 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 (PO2 = 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

Published in MEPS Vol. 194 (2000) on March 17
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 2000