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Schistocephalus solidus; breeding designs; cut halves; selfing rate;
fitness; repeatability
Abstract:
Schistocephalus solidus is one of the few cestodes that can be bred in vitro. Worms have typically been
bred in pairs, so the parents of each offspring can clearly be assigned. From a genetic perspective, it would
be useful to be able to mate an individual worm to multiple partners while still being able to distinguish
among different parents. As each adult S. solidus possesses numerous reproductive complexes, cutting
worms and breeding the pieces separately would facilitate such breeding designs. We halved worms
before in vitro breeding and evaluated whether this affected outcrossing rates and reproductive output.
Cutting did not influence clutch mass, i.e. egg number and size, or outcrossing rates, but eggs from cut
worms had a lower hatching rate than eggs from uncut worms. We found that when two anterior worm
halves were bred together, they produced fewer, smaller eggs with higher hatching rates, compared to
two posterior halves. Moreover, once we controlled for this effect of ‘worm half’, the two halves of an
individual worm tended to reproduce similarly under comparable circumstances. We conclude that cutting
plerocercoids increases the flexibility with which this tapeworm can be experimentally bred without
dramatically affecting the production of viable, outcrossed eggs.
