Hatching, chemokinesis, and transformation of miracidia of Schistosoma mansoni

Abstract

Hatching, chemokinesis, and transformation of miracidia of Schistosoma mansoni were examined with a light microscope equipped with a video recording system. Saline, linearly and reversibly, inhibited miracidial hatching and swimming. Both hatching and swimming were inhibited at 4 C and 12 C and accelerated at 34 C relative to rates at 22 C. Hatching was an explosive event that began with ciliary beating when the egg was placed in artificial pond water (APW) and culminated in the parasite's escape from the shell in 100 to 300 msec. Broken egg shells had sharp, complementary edges. Neither miracidia nor eggs swelled prior to hatching. Accumulation of miracidia in a spot of snail conditioned water (SCW) occurred rapidly due to a 60-75% decrease in the exit rate from the spot, rather than by an increase in the entry rate. The turning rate in SCW increased tenfold and the time spent in the spot was 6 times that of controls. Eserine sulfate inhibited miracidial turning and accumulation in SCW. Parasites accumulated in a spot of serotonin by increasing their rate of turning. Miracidia transformed to sporocysts in either complex media containing serum, RPMI-1640, Hanks' salts or phosphate buffered saline, but not in amino acids or vitamins. Transformation was inhibited when miracidia were incubated with serotonin or when miracidia had not been exposed previously to APW.