Life spans of two species of tropical mayfly nymph (Ephemeroptera) from Magela Creek, Northern Territory

Abstract

The nymphs of Cloeon fuviatile and a species of Tasmanocoenis were common in the shallows (< 1 m) of two billabongs in Magela Creek, Northern Territory. Monthly estimates of abundance and length frequency showed that growth and reproduction occurred continuously. Estimates of the ratio of annual production to mean biomass (PIB) were calculated with the size-frequency method, using different values for nymphal life span; these estimates, when compared with P/B values predicted from the literature, suggested that the nymphs had a life span of about 1 month. Such a rapid life cycle is at least in part the result of the high mean temperature (30°C) in the shallows.