An experimental study of the effects of salinity on the mud-dwelling amphipod,Corophium volutator(Pallas), indicates that, if supplied with mud, it will survive the salinity range of 2.50 %0, and without mud the range 7.5-47–5 %0. Moulting occurred in salinities of 2.6–46 %0, but most frequently in the range 5–20 %0. Growth occurred at a maximum rate in 15.4 %0, and only slightly slower at 4.4 and 30.6 %0; but below 4.4 %0the growth rate was progressively reduced. Freezing point studies showC, volutatorto be a hyperosmotic regulator, having a tissue tolerance range of 13–50 %0. The importance of a supply of mud, and the significance of hyperosmotic regulation are briefly discussed.INTRODUCTIONThe amphipodCorophium volutator(Pallas) is an inhabitant of littoral muds, the populations often reaching high densities. It has been most commonly reported from shores of estuaries, although Zenkevitch (1963) has stated that it may also occur in muds submerged to a depth of 10 m. Segerstråle (1959) has summarized the data available on the occurrence and distribution ofC. volutator. Since that date, work has been done on substrate selection (Meadows 1964a–c), on burrowing behaviour (Meadows & Reid, 1966) and on rhythmical swimming activity under tidal control (Morgan, 1965). Many authors (Nicol, 1935; Thamdrup, 1935; Beanland, 1940; Spooner & Moore, 1940; Rees, 1940; Goodhart, 1941; Stopford, 1951; Rullier, 1959; Gee, 1961) have described the substrate in whichC. volutatoroccurs. They have agreed thatC. volutatoris found in mud or muddy sand, containing approximately 37 % silt or clay.
