A laboratory study on the thermal tolerance of four southeastern stream insect species (Trichoptera, Ephemeroptera)

The acute, thermal tolerance was determined for four southeastern stream insect species, Ephemerella invaria (Walker), Stenenoma ithaca (Clemens and Leonard), Symphitopsyche morosa (Hagan), and Brachycentrus lateralis (Say), using an artificial stream enclosure. All test species were collected from the Little River and acclimated at 10°C for 72 hours. Animals were then instantaneously immersed into heated water for 96 hours, after which percent mortality was recorded and the temperature at which 50% mortality occurred determined (LT50). Data was subjected to standard statistical analysis.

LT50 values and regression coefficients were found to be significantly different for most of the species tested. Regression coefficients were shown to be related to the temperature range over which individuals of a given species died. This range was considered dependent upon the difference between maximum river water temperature to which a species was exposed during it's life history and the critical thermal maximum of most aquatic life (35°C). N Nonsignificance of LT50 values and regression coefficients were attributed to the small degrees of freedom associated with these experiments and exposure to similar thermal regimes.