Observations of insect predation on rotifers

Interactions between rotifers and their insect predators have not received adequate attention, possibly due to the assumption that rotifers are too small for insects to eat. In laboratory experiments, we offered the rotifers Hexarthra mira, Plationus patulus and small and large Synchaeta pectinata to four common insect predators: the notonectids Notonecta lunata and Buenoa macrotibialis, the smaller hemipteranNeoplea striola and small (1.5 mm) aeschnid dragonfly larvae. Excepting Plationus offered to dragonflies, all rotifer preys were consumedto some degree. No size selectivity was apparent for predators that ate few rotifers, but small instar Buenoa ate significantly more large (420 Mum) than small (300 Mum) Synchaeta. Predator size appeared tobe less important than predatory style and prey morphology in determining ingestion rates. Neoplea and dragonflies ate more Hexarthra than Plationus, while the pattern was reversed for Buenoa, possibly because Buenoa is able to manipulate the hard lorica of Plationus better.Insect predators are capable of direct suppression of rotifer populations, an interaction which may be particularly important in littoralzones and fishless ponds where macroinvertebrates are numerous. [ABSTRACT FROM AUTHOR]