Some aspects of the reproductive biology of the telescope snail <i>Telescopium telescopium</i> (Linne) in milkfish ponds

Abstract

<i>Telescopium telescopium,</i> a mudsnail locally known as “bagungon” , is important since at high densities it may become a pest in fish aquaculture ponds. Knowledge of its reproductive biology is necessary in order to properly manage this resource. Thus, this study aimed to 1) describe histologically the different gonadal stages of <i>T. telescopium</i>, 2) determine the reproductive cycle and spawning peaks of the species based on the gonadosomatic index (GSI), and 3) determine the size at sexual maturity of the species in the milkfish ponds. Monthly samples were collected from May 1997 to March 1998 (except for September 1997) from brackishwater milkfish ponds. Shell length and GSI for each snail was measured. The gonads were processed histologically after all sampling activities were concluded. Histological examination showed the following gonadal stages: immature, developing (male and female), ripe (male and female), spawning ( female), and redeveloping ( female). The GSI profile showed no marked fluctuations, indicating partial and continuous spawning. However, the mean monthly GSI values may have been greatly affected by the harvesting of the snails done in the milkfish ponds and the presence of immature gonads with weights that could not be determined using the available balance (weights<0.01 g). The smallest observed mature male had a shell length of 43.32 mm, and the smallest observed mature female had a shell length of 36.42 mm.