PREDATION BY Apocyclops royi (CYCLOPOID: COPEPOD) ON CILIATES AND ROTIFERS

We studied the prey consumption rates in Apocyclops royi on neonate and adult rotifers, Brachionus rotundiformis and ciliate, Euplotes sp. in the presence and absence of algae, the smaller Isochrysis galbana and the larger Tetraselmis chui. Both males and females of A. royi were able to successfully ingest neonate and adult rotifers and ciliate. The prey consumption rates were significantly lower in males than in females of A. royi. Regardless of sex and reproductive state of the copepod, prey consumption rates were higher on neonates rotifer than on adults. However, the prey consumption rates were significantly lower on ciliate than rotifer in the female copepods. Further, the prey ingestion rates did not differ statistically between ovigerous and non-ovigerous adults of A. royi females. The ovigerous rotifer was ingested at lower rates than either non-ovigerous or neonates rotifer by both males and females of A. royi. The presence of algae (no matter I. galbana or T chui) negatively influenced the rotifer and ciliate consumption rates. The present study provides first information on predatory efficiency of A. royi, and attests its omnivory feeding habit. Our results suggest that A. royi can utilize heterotrophic food efficiently and can derive nutrients during periods of low primary production. The present study points to the role of A. royi in forming a link between the microbial loop and classical food chain, which expedites the flow of bacterial carbon to higher trophic levels in estuarine ecosystems.