Correspondence: Naoko NIHEI
Naoko NIHEI
Tamotsu KANAZAWA
Department of Parasitology, National Institute of Health, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162, Japan.
Hiroshi ITAGAKI
Tasuhide SAITO
Masami KANEKO
Department of Parasitology, Azabu University School of Veterinary Medicine, Fuchinobe, Sagamihara, Kanazawa 229, Japan.
Abstract
Mass breeding of Oncomelania quadorasi, the vector snail of schistosemiasis in the Philippines, was attempted in the laboratory and the conditions for snails to propagate or grow well, such as optinum population density , composition of bed substratum and temperature, were examined. In order to breed juvenile snails, water-circulating aquaria provided with the bed com:posed of crushed oyster-shell were used. 337 to 1000 juveniles per aquarium with a size of 18.5 cmx32.5 cm and 23.5cm deep, were raised to adults during a period of 8 to 12 weeks, showing no crowding effect. The aerated closed-aquaria as well as the circulating were favorable for young snails to grow although a crowding effect appeared when more than 200 snails were kept in one aquarium. Shallow unglazed clay pots with a soil bed were suitable for the snails to reproduce as well as in the case of O. nosophora. The optimum temperature for young snails to grow was 25 or 30'C. At 20'C snails natured although the growth was retarded. At 15'C, however, only half of the snails grew to adults at a slow pace. Parent snails could reproduce at 20, parent snails to reproduce . The bed composed of crushed oystershell mixed with Rofu soil was suitable for the reproduction of parent snails. However. Kofu soil or gray paddy soil inhabited by O. nosophora in Japan was the best for O. quadorasi.
Key words: mass breeding; Oncomelania quadorasi; oystershell; reproduction; Schictosomiasis.