Echinostoma caproni: mating behavior and the timing of development and movement of reproductive cells.

The development and movement of reproductive cells were determined in Echinsostoma caproni on autoradiograms by labeling nuclei of stem cells during exposure to [3H]thymidine and then transplanting the worms to mice for various times. The development and movement of sperm, primary oocytes, and vitelline cells were much more rapid in E. caproni than other digenetic trematodes investigated previously. Mating behavior was determined by labeling the sperm of 1 adult by in vitro exposure to [3H]tyrosine and transplanting alone or with unlabeled worms to mice for 4 and 6 days. Echinostoma caproni adults self-inseminated when isolated and self- and cross-inseminated when in groups. This behavior is similar to that found for the frog rectal fluke Megalodiscus temperatus but unlike that determined for eyeflukes in the genus Philophthalmus. Worm size was not a barrier to insemination in E. caproni. Cross-insemination could not be detected in 6-day transplants probably because of dilution or elimination of radioactive sperm due to rapid turnover or frequent sperm transfer. An increased number of structural anomalies was noted in the transplanted worms. The most common anomaly was an accumulation of vitelline cells in the vitelline reservoir and ducts.