Craspedacusta Sowerbii: An Analysis of an Introduced Species

Abstract

The ecology of Craspedacusta sowerbii Lankester, a fresh-water cnidarian, is a source of interest and confusion for many biologists. The medusoid stage draws special attention because in common parlance at least, “jellyfish do not belong in fresh-water.” For the investigator, on the other hand, this same stage causes puzzlement since the medusae occur only infrequently. Both factors have led to an expanded literature. Russell (1953) in his first volume of The Medusae of the British Isles, compiled a separate but not exhaustive bibliography containing 150 entries on this species. In the light of this rather large and at times conflicting literature, Acker and Muscat (1976) reviewed the information with the purpose of defining more clearly the questions that need to be asked of its ecology. This paper continues that approach by considering the implications of C. sowerbii’s original habitat, suggesting the factors that control medusoid formation, and explaining the probable reasons for the sporadic appearance of medusa populations.