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 µg C ml−1. The optimal food concentration of P. micans was also found to be 8.50–17.00 µg C ml−1, however for the other two algae, S. costatum and N. closterium f. minutissima, it was lower at 1.70–8.50 µg C ml−1. 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.

The predatory behavior of adult females of Thermocyclops decipiens in relation to two cladoceran prey, Ceriodaphnia cornutaand Diaphanosoma spinulosum, was analyzed by laboratory observations. The number of attacks, captures, and ingestionswere quantified. Probabilities of capture after attack (C/A) and ingestion after capture (I/C) were calculated as indicators of preypost-encounter vulnerability. T. decipiens attacked, captured and ingested both cladoceran species, but vulnerabilities of preywere relatively low. C/A was higher in C. cornuta than in D. spinulosum. Larger individuals of D. spinulosum showed higherC/A and I/C than smaller individuals but no effects of size were observed in C. cornuta. The ability of escape as well as thestrength and shape of carapace, seem to partially explain differences in vulnerability among these species. Our results suggestthat intensity of mechanical perturbations and other size-dependent factors, but not body size alone, could be important in determiningpost-encounter prey vulnerability among individuals of a same species.