SUBITANEOUS, DIAPAUSE, AND DELAYED-HATCHING EGGS OF PLANKTONIC COPEPODS FROM THE NORTHERN GULF-OF-MEXICO - MORPHOLOGY AND HATCHING SUCCESS

Experiments were conducted to examine the morphology and hatching succ ess of eggs, either spawned by freshly caught planktonic copepods or r ecovered from bottom sediments in the northern Gulf of Mexico. Collect ions were made between August 1992 and September 1995. Eggs of nine sp ecies were described and these differed in their diameter, color and s urface attributes. Three types of eggs were distinguished: subitaneous , diapause, and delayed-hatching. Three species, Labidocera aestiva Wh eeler, Acartia tonsa Dana, and Centropages velificatus (Oliveira) prod uced only subitaneous eggs. Hatching success varied greatly among thes e species. Two species, Labidocera mirabilis Fleminger and Centropages hamatus (Lilljeborg) produced diapause eggs and subitaneous eggs. The length of the refractory phase of the diapause eggs differed greatly both within and between these two species. A third type of dormant egg , delayed-hatching, was recognized in Labidocera scotti Giesbrecht and Pontella meadi Wheeler. The existence of delayed-hatching eggs may be an adaptive response of subtropical species to less seasonal fluctuat ion. Based upon morphological characteristics of the eggs and rearing of nauplii to an identifiable stage, benthic dormant eggs of eight spe cies of calanoid copepods were also identified.