Development of salinity tolerance in the marine pulmonate Amphibola crenata (Gmelin)

Growth and survival of veligers of Amphibola crenata (Gmelin) were followed in a range of salinities from 4 to 35%. In salinities of 18%. and below, growth was slowed and a large proportion of veligers died. In 4 to 12%., no larvae survived to metamorphosis, but these low salinities were tolerated for short periods.Newly post-metamorphic snails and juveniles collected from the field survived well even at 4%., showing that greater tolerance of low external salinities developed at metamorphosis. Examination of the physiology of adult snails suggested that this may be due to the development of osmoregulating mechanisms, because the adults maintain the blood hyperosmotic to the medium in 4 and 9%. The kidney, however, does not seem to be involved in this regulation because urine is isosmotic with the blood. An extra-renal mechanism of salt uptake is, therefore, postulated.