Vertical distribution of young pond snails (Basommatophora: Pulmonata): implications for survival

Abstract

The vertical distribution of juvenile pond snails (Lymnaea stagnalis and Stagnicola elodes), hatched from egg masses containing known numbers of viable embryos, was recorded daily in artificial containers under outdoor conditions for up to 25 days after hatching. Both species showed an initial vertical movement to the surface of the water with a subsequent return to the bottom sediments after 10–15 days. This pattern was consistent despite differences in the depth of the water column (13 versus 18.5 cm). At 25 days after hatching more than 85% of the population was in the lower half of the container at any one time, almost all being associated with the bottom sediments. The presence of an adult snail of either species in the same container significantly reduced the survival of young snails (from between 85 and 94% to between 1 and 18%). Consumption of the young snails during their first 10 days out of the egg mass, when they were moving to the surface, accounted for the observed differences in survival. Young snails appeared to be ingested incidently by the foraging adults, most often when the former were concentrated at the air–water–glass interface.

Dispersal in pond snails: potential role of waterfowl

“…That the actual number adhering to the feather was between 9-and 22-fold greater than the expected value suggests that when snails contacted the feather they remained adherent to it longer than they otherwise might remain within an area of equal size on the surface tension of the water. This argument is strengthened when one considers that the actual pattern of dispersion of young snails tends not to be random but clumped on the lower walls and bottom of the container (Boag et al 1984). Thus, these observations suggest that the snails were attracted either to the feather itself as to the air-water-plumage interface, a phenomenon similar to the concentration of young snails recorded at the air-water-container wall interface by Boag et al (1984).…”

“….". Boag et al (1984) suggested that, among gastropods, the propensity for newly hatched snails to rise to the surface of the water column, and in some cases to crawl above it onto objects either floating or fixed, may be a mechanism to aid passive dispersal. This could be particularly important when such Can.…”

`Different strokes for different folks': geographically isolated strains ofLymnaea stagnalisonly respond to sympatric predators and have different memory forming capabilities

“…We used three geographically distinct populations of freshly collected snails from (1) (Clarke, 1981;Clifford, 1991) as well as descriptions from other published studies in a similar localities in both The Netherlands and Alberta (Mooijvog et al, 1973;Boag and Pearlstone, 1979;Jager et al, 1979;Boag et al, 1984). In order to further ensure that both the Albertan and Dutch snails were in fact the same species, cross breeding experiments were conducted to ensure that the progeny of the initial crosses (F1s) produced viable offspring (F2s).…”

Differences in LTM-forming capability between geographically different strains of AlbertaLymnaea stagnalisare maintained whether they are trained in the lab or in the wild

“…All collected snails were L. stagnalis. They were identified using the keys of Clarke (Clarke, 1981) and Clifford (Clifford, 1991), as well as descriptions from published works in similar localities in Alberta (Boag and Pearlstone, 1979;Boag et al, 1984). We do not know when or how L. stagnalis was introduced to the 20+ year old Jackson pond.…”