Growth rates of mayflies (Ephemeroptera) reared in the field differed under contrasting temperatures

HANKEL, GUILLERMO E; MOLINERI, CARLOS

Austral Entomology

Austral Entomology

Año: 2021 vol. 60 p. 578 - 587

2052-174X

Aquatic insect growth is tightly linked to environmental temperature. Growth rate tends to increase with rising temperatures. Growth rate integrates different factors related to population fitness, being partly responsible forspecies distribution. We aim to estimate daily growth rates from mayfly nymphs reared under different thermalregimes in the field, during five different periods from 2016 to 2018. Twelve species of mayflies were reared inmesocosms in six streams (from three altitudinal levels with a mean elevation 725, 1069, and 1509 m.a.s.l.).Additionally, we transplanted nymphs between lowest and highest pairs of streams, thus rearing them under adifferent thermal regime. Temperature and other ambient variables were recorded at regular intervals. Daily growthrate (dgr) of most species resulted lower in the higher pair of streams (colder sites) than in the medium and lowerstreams (warmer sites). Transplant experiment also clearly showed this tendency: (1) nymphs transplanted tocolder thermal regimes grew slower than those reared under their natural (warmer) regime and (2) nymphstransplanted to hotter thermal regimes grew faster than those reared under their original (colder) regime. Nymphsof three species (Americabaetis alphus, Leptohyphes eximius, and Cloeodes penai) did not show differences ingrowth among treatments. Our findings relating sensitiveness of Ephemeroptera nymps to small temperaturechanges suggest that the distribution of some species will modify by increases in temperature derived fromclimatic change.