Studies on Tapeworm Physiology. V. Further Observations on the Maturation of Schistocephalus solidus (Diphyllobothriidae) under Sterile Conditions In vitro

Abstract

Plerocercoid larvae of Schistocephalus from the body-cavity of the stickle-back were cultured to maturity at 40[degree]C under aseptic conditions in vitro, and the histological development and egg embryonation compared with worms matured naturally in birds (the natural host). As acidic byproducts are produced during maturation, the pH of the medium must be carefully controlled or death or abnormal development results; horse serum, being heavilly buffered, was the most successful medium used. Evidence was also obtained to indicate that oxygen tension of the medium was also an important controlling factor and that normal development requires semi-anaerobic conditions. Under suitable cultural conditions, eggs are produced by worms in vitro within 40 hrs." cultivation. Such eggs were mainly irregular in their embryonation, for although up to 86% embryonation was obtained in one expt., only 5% of such embryos hatched as normal coracidia; the remainder developed either miniature or abnormal coracidia. Since the receptaculum seminis of worms matured in vitro never contained spermatozoa, it was concluded that the majority of eggs produced in vitro undergo parthenogenetic development. Eggs from worms matured in birds showed 95-100% egg embryonation and hatched out coracidia easily; the receptaculum of such worms was always filled with masses of spermatozoa. A total of 156 larvae were used in these expts.