DESCRIPTION OF THE DEVELOPMENTAL STAGES IN ACARTIA-BIFILOSA GIESBRECHT (COPEPODA, CALANOIDA)

The developmental stages and increase in length of Acartia bifilosa, a dominant planktonic copepod in Kyeonggi Bay, Yellow Sea, Korea, were investigated in a laboratory. Adults laid eggs at a rate of 2.5 eggs d ay(-1) female(-1) and up to 97% of eggs hatched. The eggs were 92 mu m in diameter and larger than the eggs of other Acartia species. The bo dy segmentation was recognizable at the fifth nauplius stage and sex d istinction was possible at the fourth copepodite stage. The six naupli us stages took similar to 7.5 days and the five copepodite stages simi lar to 8.5 days. Sexually mature males and females appeared at the 16t h day, and by the 20th day the adults laid eggs that hatched and grew successfully into the nauplius stages. The detailed morphological char acteristics of each developmental stage are presented and discussed in relation to A. clausi.