title: The combined effects of temperature and food consumption on body weight, egg production and developmental time in Chaoborus crystallinus De Geer (Diptera: Chaoboridae) : Some new evidence for the adaptive value of vertical migration.
abstract: Chaoborus crystallinus fourth-instar larvae were reared individually at 14°, 17° and 20° C under different food conditions. Daphnia magna of 1.25 mm average length served as prey. The following were measured: amount of prey ingested, larval weight gain, duration of fourth instar, body weight of the adults, and egg number per female. At a given temperature, the body weight, egg-number and developmental rate increased with food consumption. At a given food consumption, higher temperatures caused a decrease in body weight and egg number, and an increase in developmental rate. Gross production efficiencies for fourth-instar larvae were highest at temperatures around 17° C. The results clearly indicate that from an energetic point of view higher temperatures are disadvantageous. In C. crystallinus vertical migration is evidently a way of lowering the temperature to which the animals are exposed and hence optimizing food conversion into biomass and offspring production, especially if prey densities are below the saturation level.
authors.affiliation: ICH 3, Forschungszentrum Jülich, Postfach 1913, W-5170, Jülich, Federal Republic of Germany.
authors.forename: M
authors.initials: M
authors.lastname: Büns
authors.affiliation: Lehrstuhl für Biologie V (Ökologie), RWTH Aachen, Worringerweg 1, W-5100, Aachen, Federal Republic of Germany.
authors.forename: H T
authors.initials: HT
authors.lastname: Ratte
keywords: Development; Relative food saturation; Reproduction; Temperature; Vertical migration