Effects of microalgae as diets on the survival, development and fecundity of a pelagic cyclopoid copepod Apocyclops borneoensis

It has been proposed that the feeding habit of cyclopoids is different from that of calanoid copepods in that they feed mainly on microalgae during early development but become carnivorous later. However, a different view also exists, believing that microalgae are the prime food for some cyclopoid copepods. In the present study, microalgae from various taxonomic groups, including a dinoflagellate (Prorocentrum micans), three diatoms (Chaetoceros muelleri, Skeletonema costatum and Nitzschia closterium f. minutissima), and a prymnesiod (Isochrysis galbana), were offered at different concentrations to the cyclopoid copepod, Apocyclops borneoensis, with survival, development and reproduction of the copepod closely monitored. The results showed that A. borneoensis is capable of utilizing any of the microalgae species tested for development and reproduction, but significant differences in survival, development rates of both nauplii and copepodites, and fecundity were detected among species. The results also showed that within a same algal species, food concentration also significantly affected various biological parameters measured. Overall, C. muelleri and I. galbana were the better diets for A. borneoensis and their optimal food concentration ranged from 8.50 to 17.00 mg C ml21. The optimal food concentration of P. micans was also found to be 8.50–17.00 mg C ml21, however for the other two algae, S. costatum and N. closterium f. minutissima, it was lower at 1.70–8.50 mg Cml21. The present study provides novel information on the feeding habit of A. borneoensis and the effects of both quality and quantity of microalgae diets on a range of biological parameters are described.