Cell division during the development ofArtemia salina

Cell division during embryonic development of the brine shrimp,Artemia salina has been studied by counting nuclei and mitotic figures. No cell division was observed during development of the encysted gastrula until about an hour before emergence of the embryo (a pre-nauplius) from the cyst, and even then only a few mitotic figures were observed. Following emergence, and during further development up to the stage II nauplius larva an increase of about 25% in the number of cells occurs. However, when the newly hatched larva is exposed to FUdR (10 μg/ml) cell division is largely inhibited, but observable development nevertheless proceeds normally. Evidently all processes involved with the development of the gastrula into a stage II nauplius larva can occur with far fewer cells than normally are present.