The mating behaviour of Zygocotyle lunata adults grown in mice

Zygocotyle lunata adults grown in mice were treated in vitro with 3-H-adenosine to label sperm and then transplanted to the caecum of mice singly or with 6 to 8 unlabelled adults. After 6 to 10 days, worms were recovered, processed for autoradiography, and observed for radioactive sperm in their seminal receptacles. Adults would not incorporate radioactive thymidine into dividing cells. Tyrosine was utilized only by juvenile worms and then not enough to label germinal cells for mating studies. Four of 13 (31%) worms transplanted singly self-inseminated, whereas 9 of 10 (90%) labelled worms in multiple infections self-inseminated. When in groups, the labelled worms cross-inseminated with 14 of 43 (33%) unlabelled worms. This mating pattern was unrestricted in that both self- and cross-insemination took place in multiple infections, much like the mating pattern in another paramphistomatid, Megalodiscus temperatus, but unlike the restrictive pattern shown by three species of eyeflukes.