LONGEVITY OF SUBITANEOUS AND DIAPAUSE EGGS OF CENTROPAGES HAMATUS (COPEPODA, CALANOIDA) FROM THE NORTHERN GULF-OF-MEXICO

Copepod resting eggs are abundant in the seabed of many bays and estua ries where they provide a potential source of recruits for growth of p lanktonic populations. In the northeastern Gulf of Mexico the copepod Centropages hamatus (Lillejeborg) occurs In the water column only duri ng the late fall, winter and early spring. The species produces subita neous and diapause eggs, and both egg types have been found in the sea bed. We determined the longevity of these two egg types to ascertain t heir potential for contributing to the growth of the planktonic popula tion and for sustaining a persistent egg bank. Eggs were collected fro m females and incubated in the laboratory under temperature and oxygen conditions chosen to simulate field conditions. The diapause eggs wer e also exposed to sulfide. The total hatching success of subitaneous e ggs in two experiments declined from highs of 78 and 97% to zero after 60 and 90 d of exposure to anoxia. The total hatching success of diap ause eggs that were exposed to anoxia for 90 d however was typically g reater than 80%. Some diapause eggs hatched after being incubated unde r anoxia for 437 d. Diapause eggs survived longer at ambient field tem peratures when incubated under anoxia (437 d) compared to normoxia (11 8 d). Exposure to sulfide did not result in greater mortality of diapa use eggs compared to anoxia alone. Diapause eggs that were incubated a t ambient field temperatures did not hatch when exposed to normoxia un til the temperature dropped io <20 degrees C. The results of this stud y suggest that C. hamatus sustain a short-term reserve of subitaneous eggs in the seabed that provides recruits for the current year's popul ation. The greater longevity of diapause eggs suggests that they susta in the seasonal reappearance of the species year after year in the nor theastern Gulf of Mexico. However, the contribution of diapause eggs o f C. hamatus from the Gulf of Mexico to a persistent egg bank is quest ionable since hatching ceased after 437 d.