VULNERABILITY OF CENTROPAGES HAMATUS (LILLJEBORG) DIAPAUSE EGGS (COPEPODA: CALANOIDA) TO ANOXIA: THE INFLUENCE OF TIME OF INITIAL EXPOSURE
N.H. Marcus
Abstract:
Eggs were obtained from Centropages hamatus that were collected from the northern Gulf of Mexico in late March when normally >90% of the eggs produced are of the diapause type. Within 3.5 hours of being spawned the eggs were transferred to vials of seawater which were made anoxic by bubbling with helium. They were subsequently incubated at ambient field temperatures for as long as 255 days. During this time period replicate vials of eggs were periodically transferred to normoxia and 15 C to determine hatching success. The total hatching success of these eggs ranged from 0.0 to 3.4 +/- 3.0%. When compared to the results of previous studies these data suggest that a sensitive pre-diapause phase precedes the onset of diapause in eggs of C. hamatus. This means that it should be advantageous for C. hamatus to spawn eggs destined for diapause in the upper level of water column to delay their deposition onto the sea bed where conditions for hatching are less suitable.
(Department of Oceanography, Florida State University, Florida, USA, 32306)