Observations on the development of Rhabdochona phoxini Moravec, 1968 (Nematoda: Rhabdochonidae).

The life-cycle of the nematode Rhabdochona phoxini, an intestinal parasite of the fish Phoxinus phoxinus, has been studied experimentally. The mayfly nymphs, Habrophlebia lauta Eaton and H. fusca (Curtis) were found to serve as experimental intermediate hosts. After the eggs of R. phoxini have been swallowed by the mayfly nymph, the toothed first-stage larvae of this parasite are released and penetrate through the intestinal wall into t-e body cavity of the mayfly. Before reaching the infective third stage, the larvae moult twice in the body of the invertebrate host (2 to 16 and20 to 36 days after infection at water temperatures of 13--15 degrees C). However, the development of the encysted infective larvae does not cease in the intermediate host and the larvae may undergo one more moult. One of two moults then occur in the intestine of the definitive host (Phoxinus phoxinus) (depending on the fact whether it was infected with third- or fourth-stage larvae) before the larvae attain the maturity. The development of R. phoxini in the definitive host lasts about two months.