Experimental evidence of the fundamental feeding niche in Cenocorixa (Hemiptera: Corixidae)

Abstract

The fundamental feeding niche of Cenocorixa bifida hungerfordi Lansbury and Cenocorixa expleta (Uhler) from saline lakes (500–20 000 μS cm−1 at 25 °C) was determined in laboratory experiments. Each species was offered a variety of potential foods, to determine potential dietary overlap. No significant differences in food acceptance were seen between corixids collected from different lakes or at different seasons. The species were both carnivorous and predaceous, showing little propensity to feed on plant material. Adults of both species attacked and fed on chironomid larvae most frequently; larval instars were less specific. Cenocorixa expleta adults and larval instars of both C. expleta and C. bifida fed more on dead than living food organisms. When offered mixed live Zooplankton, C. bifida chose more Ceriodaphnia than Diaptomus, whereas C. expleta showed no such selection; these differences were not seen with dead Zooplankton. Cenocorixa bifida and C. expleta coexist at moderate salinities, and appear physiologically capable of inhabiting the entire salinity range encountered. Their fundamental feeding niches, although not identical, overlap considerably and could result in competition for food. This could lead to the exclusion of C. expleta from low salinity lakes.