TROPISTIC BEHAVIOR IN SCHISTOSOMIASIS: MIRACIDIA AND CERCARIAE PREDATORS.
Rept. no. 4 (Final),
MINAS GERAIS UNIV BELO HORIZONTE (BRAZIL) INSTITUTO DE BIOLOGIA
Pagination or Media Count:
Biomphalaria glabrata and cercariae of Schistosoma mansoni were tagged by exposing infected snails to H275SeO3 or 75Se-methionine. Labeled cercariae were observed to be shed as early as 3 days after exposure-readioactivity per organism increased slowly reaching maximum count after 3 weeks. Separate counts of the shell and the soft tissue indicated radioselenium to be incorporated chiefly in the soft tissue. Immobilization or death of S. mansoni cercariae occur after exposure to emulsions of epoxygeranylgeraniol at concentrations as low as 1 ppm. Cercariae exposed to 4 ppm epoxygeranylgeraniol displayed crawling movements similar to those observed prior to active penetration through mammalian skin. Circadian rhythm of cercarial emergence was observed to be consonant with naturally occurring emergence when a temperature was maintained constant with natural diurnal light variations or b when continuous darkness was maintained with natural diurnal variations of temperature. Rhythm is interrupted under a constant temperature and darkness and b constant temperature and continuous artificial illumination. Inversion of circadian rhythm was observed after two successive periods of light or two successive periods of darkness 24 hours. Author