Calcium as a limiting factor in the biology of Biomphalaria pfeifferi (Krauss), (Gastropoda: Planorbidae)

Life cycles and distribution of the aquatic gastropod molluscs Bithynia tentaculata (L.), Gyraulus albus (Muller), Planorbis planorbis (L.) and Lymnaea peregra (Muller) in relation to water chemistry

“…Lack of time did not permit a multiple regression analysis of chemical and biological data from the larger number of sites, and this probably explains the lack of significance of bicarbonate alkalinity as a factor in the distribution of the species investigated here . Akalinity certainly does seem important when cations are present in low concentrations (Nduku & Harrison, 1976) . Boycott (1936) indicated that P. planorbis had a distribution similar to P. carinatus but the former was more often found in ditches and ponds, an observation confirmed by Macan (1950) and myself.…”

Water relations and osmotic pressure in Biomphalaria pfeifferi (Krauss), Biomphalaria glabrata (Say) and Helisoma trivolvis (Say) (Gastropoda : Planorbidae) in response to cationic alterations of the medium

“…The origins of the snail material are given in Nduku & Harrison (1979) together with the design of the culture series; culture methods are noted in Nduku & Harrison (1976); culture density of larger snails was kept at not more than one snail per 500 ml of medium; all snails were lettuce fed.…”

An improvement of calcium determination technique in the shell of molluscs

“…But the shell is not an inert mineral structure. Calcium is a metal that exerts an essential role on the biology of the snails, once that, this ion is the main component of the snails shell, constituting an important limiting factor that determine the distribution and survival of the adult snails, oviposition rate, survival and development of eggs and the embryos (Thomas et al, 1974;Nduku and Harrison, 1976;Appleton, 1978;Dawies and Erasmus, 1984). The calcium ion still participates in many enzymatic reactions and is required to metabolic processes related to acid-basic equilibrium in the hemolymph (Sminia et al, 1977;De With and Sminia, 1980).…”