Natural breeding of freshwater apple snail Pila globosa (Swainson) in pond and aquarium

Abstract

The freshwater apple snail, Pila globosa is one of the most abundant and commercially valued molluscs. Over exploitation of P. globosa for prawn farming is an alarming condition. The present study is aimed at elucidating the breeding behavior and reproduction process of P. globosa. The natural breeding experiment was conducted in two ponds- a 52 decimal pond in Gopalgonj sadar and a 40 decimal pond in Kotalipara. The ponds were prepared by applying lime at the rate of 3 kg/decimal and then filled up with water up to 30cm. Wild snails were stocked at the rate of 600 no./decimal. Organic compost (cow-dung, mustard oilcake and urea at the ratio of 1:1:0.5at the rate of 2.5 kg/decimal respectively) spread throughout the pond. Several male and female specimens were collected from experimental gher and brought to the laboratory aquarium to observe their breeding behavior. At the bottom of aquarium substrate like plastic bottle, marbel, artificial tree etc. were provided for egg laying. Breeding involves three processes: copulation, fertilization and laying. Copulation occurs in water on moist land and it takes about 3-4 hrs, then both separated. Fertilization is internal in P. globosa. Egg laying started 2 or 3 days after copulation. They lay eggs in sheltered places or moist land near water in the dyke. A single female lays eggs average 387.89±167.65 no. per clot at a time. The time elapsed between the first and the last hatchings ranged from 6 to 25 days and for 80% of the 5 egg masses were studied. Considering all the eggs in the egg masses (n=1856) more than 60% of the eggs hatched within 13 days of the first hatching. It needs about 25 days for full clot to be hatched. In the laboratory condition hatching success was observed about 80%.