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 sm all for insects to eat. In laboratory experiments, we offered the rotifers Hexarthra mira, Plationus patulus and small and large Synchaeta pectinata t o four common insect predators: the notonectids Notonecta lunata and Buenoa macrotibialis, the smaller hemipteran Neoplea striola and small (1.5 mm) a eschnid dragonfly larvae. Excepting Plationus offered to dragonflies, all r otifer preys were consumed to some degree. No size selectivity was apparent for predators that ate few rotifers, but small instar Buenoa ate significa ntly more large (420 mum) than small (300 mum) Synchaeta. Predator size app eared to be less important than predatory style and prey morphology in dete rmining ingestion rates. Neoplea and dragonflies ate more Hexarthra than Pl ationus, while the pattern was reversed for Buenoa, possibly because Buenoa is able to manipulate the hard lorica of Plationus better. Insect predator s are capable of direct suppression of rotifer populations, an interaction which may be particularly important in littoral zones and fishless ponds wh ere macroinvertebrates are numerous.