Feeding and fecundity of planorbidae bred in the laboratory: IV - Helisoma duryi (Wetherby, 1879). (Putmonata, Planorbidae)

Abstract

After experiments with two types of food, lettuce and "aquariol" (i.e., animal protein flour for ornamental fish) both isolated and in association, in the breeding of Helisoma (Seminolina) duryi (Wetherby, 1879), the following results: were obtained: 1. Snails fed on fresh lettuce yielded, at the end of 17 weeks, 826 egglavings or, better, 17,707 eggs. 2. Specimens fed on "aquariol" produced 534 egg clutches or 11,361 eggs. 3. Snails fed on both fresh lettuce and "aquariol" happened to provide 1,355 egglayings or 34,645 eggs. 4. On the average, each batch of 15 snails or three group of 5 ones (each specimen displyaing 10-14 mm diameter) liberated 95.5, 148.8 and 291.1 eggs/day, in accordance with their type of meal - lettuce, "aquariol" or both foods in association - the number of daily egglayings being, respectively, 4.5, 6.9 and 8.4. 5. The studied specimens were descendent from a strain suposed to be recently introduced in Formosa county, State of Goiás (Brasil) from elsewhere in the Nearctic region (North America). Some remarks on eventual measures for the biological control of Biomphalaria species through the Helisoma duryi, are put forward, since for some time now biological and ecological investigations have been going on.