Observations on spermatogenesis and inseminative behavior of Megalodiscus temperatus adults in frogs.

Upon in vitro exposure to 3H-adenosine, spermatogonial cells in adult Megalodiscus temperatus were readily labeled on autoradiograms. At least 20 days were required for these cells to produce labeled sperm, the longest time reported so far for digenetic trematodes. Labelled worms transplanted to hosts for 24--31 days showed both self- and cross-insemination in multiple infections. When alone, half of the transplanted adults self-inseminated.