Abstract
The freshwater gastropod Clea helena has recently been targeted by the freshwater ornamental industry due to its predation abilities on other snail species. This work describes for the first time some life history traits of this species, including reproduction, growth and development under laboratory conditions. Additionally, appropriate stocking densities were studied in order to assess the production viability of healthy snails in close-circuits systems. The species is dioecious and breeds under laboratory conditions but fertility rates presented were low. Hatching occur 52 ± 6 days after oviposition, at 25.0°C. Development is direct and juveniles hatch at shell length SL=3.1 ± 0.3mm (n=20) and resemble the adults in shell shape and color. Growth rates during a maximum period of 60 days were compared between snails fed on three different diets and results showed they were influenced by the different diets treatments (P<0.05). Growth performance experiments at three stocking densities (5, 10, 20 snails/L) with three replicates per treatment were also performed. During the first month, individuals stocked at 5 snails/L had significantly faster growth rates than those stocked at 20 snails/L. No significant growth responses were found during the second month among all densities and overall growth rates for this experiment also revealed no density dependent growth responses.
Highlights
The family Buccinidae (Gastropoda: Neogastropoda), commonly known as true whelks, presents a worldwide distribution, with the larger species occurring at the subtidal zones of both northern and southern temperate and cold seas
Twelve days after broodstock accommodation started, mating behaviors were recorded, with males climbing over females shell
Afterwards, male slightly slides towards female right side and starts grasping with his penial sheath searching for genital aperture
Summary
The family Buccinidae (Gastropoda: Neogastropoda), commonly known as true whelks, presents a worldwide distribution, with the larger species occurring at the subtidal zones of both northern and southern temperate and cold seas. Clea helena (Philippi, 1847) is one of very few whelks that lives its entire life in freshwater habitats and can be natively found in Tropical Indo-West Pacific regions like China, Thailand and Indonesia [1]. The shell presents five to six whorls spiral with lateral ridges and an operculum. Nothing is known about this species’ natural life traits This poorly studied freshwater snail has recently been targeted by the freshwater ornamental industry, due to its predation abilities on other snail species that frequently became aquarium pests. For this reason it is commonly called “Assassin Snail” in the trade
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