Observations on the Biology of the Snail Lymnaea stagnalis appressa During Twenty Generations in Laboratory Culture

Abstract

A simple inexpensive method is described for culturing L. s. appressa in large numbers in relatively small space through an indefinite number of generations. The method involves rearing snails in 3 to 10 liters of constantly aerated water in deep covered glass jars located in subdued natural light, in alkaline water of high Ca and Mg content. Water is changed weekly or bimonthly. Sand, used in the trituration of food by the snail gizzard, is retained in the aquaria. Loose green-leaf lettuce if fed daily as eaten, and wheat cereal cooked in milk and a mixture of balanced salts is supplied weekly. Pre-hatching mortality by this method is negligible. Sexual maturity is reached in about 3 mo. and the av. final length of shell reached is between 50 and 55 mm. The longest snail ever cultured measured 62.5 mm. The max. life span in the laboratory is about 14 mo. Observations on crawling and feeding movements concerned with respiration, overcrowding copulation, oviposition and egg production, gross embryology hatching, exchange of water for air in the lung, desiccation, etc., are recorded. Egg production was roughly doubled by the addition of the cooked wheat cereal mixture to a diet of lettuce alone. Snails maintained in separate containers apart from all other snails throughout their sexually mature existence laid a greater quantity of eggs than snails kept in groups, but group snails oviposited sooner. In snails isolated as above, egg production per day increased after the onset of egg laying, reached a peak somewhere in the middle of the egg-laying period and then tapered at the end. Laying in such solitary snails occurred in periods of variable duration alternating with rest periods.