Studies onSchistocephalus solidus

Abstract

The growth rate ofSchistocephalus soliduswas measured in culture at 4°, 7°, 12°, 17°, 23°, 27°, 30°, 33°, 35° and 40 °C. Between 7° and 23 °C the rate of growth increased nearly exponentially, with aQ₁₀of 3·6. Between 23° and 27 °C growth rate was maximal; above 27 °C, after 8 days in culture, weight increase was shown only by worms which were too small to mature. Even in these worms the weight increase was very small and was probably due to partial maturation which occurs from 30 °C upwards. The larger the plerocercoid and the higher the temperature up to 40 °C the bigger the percentage weight loss, due to earlier maturation.Incubation of plerocercoids for 4 days at 35 °C, although inducing maturation and suppressing somatic growth, did not destroy the ability of the worm to grow when returned to 23 °C.Two hypotheses to explain the pattern of morphogenesis inSchistocephalusplerocercoids and adults are propounded; the evidence favours the existence of two enzyme systems, one controlling somatic growth with peak efficiency near 23 °C and the other controlling maturation with peak efficiency near 40 °C.The authors gratefully acknowledge financial support for this work from Shell International Petroleum Company Limited. It is also a pleasure to thank Miss Patricia Grant for technical help.