Reproductive success and growth of two species of Erpobdellidae: the effect of water temperature

Abstract

Cocoon production and hatchling growth of two species of Erpobdellidae (Nephelopsis obscura and Erpobdella punctata) were compared at different water temperatures (5–20 °C). Based on the mean number of cocoons produced per individual, mean numbers of eggs per cocoon, cocoon hatching success, and hatchling growth rates, E. punctata has an ecological advantage over N. obscura at 5 and 10 °C. At 15 and 20 °C, neither species displayed a clear advantage over the other in relation to production or growth of offspring. It is suggested that the observed interspecific differences may at least in part explain the numerical dominance of E. punctata in colder lotic ecosystems.