Egg Production of Pseudosuccinea columella and Fossaria cubensis (Lymnaeidae) in Laboratory Culture

Abstract

The lymnaeid snails Pseudosuccinea columella (=Lymnaea columella) and Fossaria cubensis (=Lymnaea cubensis) serve as intermediate hosts for Fasciola hepatica in Florida and Puerto Rico (Batte et al., 1951, Journal of the American Veterinary Medical Association 68: 139-141; De Leon et al., 1972, Journal of Agriculture of University of Puerto Rico 56: 88-92). Isseroff and Smith (1978, Journal of Parasitology 64: 11341135) described a culture technique for F. cubensis in which conditioned water was maintained at a pH of 7.6 and snails were fed a commercial diet. De Leon (1970, Journal of Agriculture of University of Puerto Rico 54: 297305) presented an elaborate system for rearing P. columella in tanks with a soil substrate in which snails fed on algae and boiled leaves of Hibiscus sp. The present report describes production of eggs in mature snails of F. cubensis and P. columella using a modified culture technique which provided a simple, economical method for rearing large numbers of snails. Up to 20 snails may be reared in each container, although only 1 snail per container was used in the egg production study described below. Snails 4-6 mm long were collected from a stream adjacent to the Animal Research Facility (University of Florida) in Gainesville, Alachua County, Florida. Individual F. cubensis usually were found on sparsely vegetated mud banks in shallow water (less than 5 cm) whereas individual P. columella frequently were found in deeper water (up to 10 cm) attached to aquatic vegetation. For egg production studies, individual snails were placed in covered plastic containers (31 x 26 x 10 cm) containing 3 L of water obtained from the same stream and filtered through a #200 U.S. Standard Testing Sieve. Water depth was approximately 3.5 cm. The water was changed every 2 wk, and no attempt was made to adjust the pH, which ranged from 6.5 to 8.0 depending on the time of collection. The containers were kept at ambient room temperature (22-30 C). Each snail was fed fresh lettuce every 3 days after unconsumed lettuce was removed. Three styrofoam blocks (5 cm square) were placed in each container, since the snails preferentially laid eggs on the bottoms of these blocks rather than on the sides of the tank. During a 6-wk period, egg production was monitored on a daily basis for individuals of both species. Styrofoam blocks were removed and the undersurface examined at 10 x for eggs with a stereoscopic microscope. A total of 152 and 173 egg masses was examined from snails of F. cubensis (n = 12 snails) and P. columella (n = 8 snails), respectively. Mean weekly egg mass production per snail in P. columella (6.02) was twice that seen in F. cubensis (3.01), and total weekly egg production per snail was almost 7 times higher in P. columella (123.4) than F. cubensis (18.2). The mean number of eggs per mass was 20.5 for P. columella and 6.1 for F. cubensis. The former value agreed closely with De Leon (1970, loc. cit.) who reported a mean of 19 eggs per mass for P. columella. Isseroff and Smith (1978, loc. cit.) did not report egg production in F. cubensis. Individual P. columella produced many more eggs than F. cubensis, possibly because culture conditions more closely resembled their natural environment (deeper water) than that of F. cubensis (shallow mudbanks). Eggs of both species hatched in 5-7 days and snails began producing egg masses within 3-5 wk. Laboratory reared individuals of both F. cubensis and P. columella proved to be suitable intermediate hosts of F. hepatica with cercarial shedding beginning less than 7 wk after exposure to miracidia. We have maintained colonies of snails for over 1 yr under these conditions and have reared large numbers of snails with a minimum expenditure of time and effort. Published as Florida Agricultural Experiment Station Journal Series No. 6464.