Procedures are described for mass cultivation of Schistosoma mansoni. Cercariae were pooled, concentrated, and axenized through a series of washes in base medium containing antibiotics. Cercariae were sheared through a double-Luer-ended needle connected to two syringes, and tails separated and discarded. Young schistosomules were grown in a medium based upon BME augmented with lactalbumin hydrolysate, glucose, hormones, and other amendments and supplemented with human serum. Human blood cells (Type O) were added to cultures. Intestinal pigment was seen on the 5th day and gut cecal fusion began on day 11. Schistosomules developed steadily to pairing, which was seen first during the 7th wk of culture. Pairing occurred somewhat later in relation to development in vivo.

Maturation and maintenance of normal reproductive function in female Schistosoma mansoni require a permanent association with the male, but the nature of this relationship is not well understood. The regional localization of a stimulatory factor in the male and its target in the female were investigated. Unisexual female and mature male worms were transected into segments of various lengths. Various combinations of transected male and female segments and intact worms were transferred to the mesenteric veins of recipient hamsters and were also maintained in vitro. In hamsters and in vitro, pairing took place between intact worms of each sex and segments of the other, and between segments of both sexes. The majority of female worms and segments so paired showed some reproductive development, as assessed by vitelline gland differentiation. In intact unisexual females paired with small male segments, vitelline gland development was limited to that portion of the worm that had been held by the male. Worm segments continued to display normal body contractions throughout 24 days of in vitro maintenance and morphological integrity was retained. It is concluded that 1) in the absence of a functioning gut, worm segments can survive for prolonged periods on nutrients absorbed through the tegument; 2) worm pairing, male stimulation, and the female developmental response are independent of central nervous control by the cerebral ganglia; 3) males have no centralized localization for the female-stimulating factor; 4) vitelline gland differentiation in the female requires local stimulation through male contact, and this is not propagated throughout the worm.

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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. The American Society of Parasitologists is collaborating with JSTOR to digitize, preserve and extend access to The Journal of Parasitology. ABSTRACT: The life history of Echinostoma paraensei, a new Brazilian species with 37 collar spines, has been completed experimentally. The planorbid snail Biomphalaria glabrata serves as first intermediate host, and intramolluscan stages also develop in Physa rivalis. Sporocysts usually develop in the heart. Rediae are of two types, distinguishable by large or small pharynges. Cercariae released 25 or more days postexposure develop into metacercariae in the pericardial sac and kidney of snails, sometimes in various tissues of snails infected with rediae. Adults develop in hamsters, mice, or rats after they are fed metacercariae, but not in pigeons, chicks, or ducklings. The natural final host is not known. In recent papers (Basch and Lie, 1966; Lie, 1966a, 1967; Lie et al., 1965) we described the destructive antagonism of larval echinostomes to trematode sporocysts developing in the same snail. Various echinostome species naturally transmitted by Biomphalaria glabrata (Say) in Brazil are being sought and evaluated to determine their efficiency in destroying Schistosoma mansoni Sambon. This paper describes the life history of a new species of echinostome encountered during our studies. MATERIALS AND METHODSCercariae of this species appeared in collections of B. glabrata snails made in Belo Horizonte (Bairro Sao Domingos), Caratinga, and Bambui, all in the State of Minas Gerais, Brazil. Snails were shipped by air to San Francisco, California, where we studied the life histories of their trematodes. Cercariae were permitted to encyst in laboratory-bred B. glabrata, and metacercariae were fed to hamsters and albino rats and mice. Eggs from washed hamster stools produced miracidia, which were used principally to infect laboratory-raised albino B. glabrata of a strain obtained from the National Institutes of Health, Bethesda, Maryland. Infected snails were kept in clear plastic, 1-gal aquaria at 24 to 27 C and fed on red leaf lettuce (Lactuca sativa). Techniques for the study of the parasite were the same as in previous studies (Lie, 1963a; 1965; 1966b, c). All measurements are in microns.

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