Responses of the False Limpet, Siphonaria Pectinata Linnaeus (Gastropoda, Pulmonata) to Osmotic Stress

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Marine Biological Laboratory is collaborating with JSTOR to digitize, preserve and extend access to Biological Bulletin.The presence of an external shell or shells in molluscs lends to this group a unique potential for a rather specialized behavioral response during osmotic stress. This response consists of temporary exclusion of the environment by clamping or closing of the valves; it has been suggested to occur in several different species of molluscs as a mechanical method of osmoregulation. The principle involved here is quite similar to that shown by the eggs of marine and fresh-water fish. In this case, the eggs are protected against osmotic stress by the fact that they are impermeable to both water and salts. Thus a barrier against equilibration during periods of concentration differences is erected.Among the molluscs, Krogh (1939) demonstrated that the bivalves Mytilus, Crassostrea, and Modiolus respond for varying lengths of time to transfer from normal to dilute sea water by closing the valves. With the valves closed, these marine pelecypods could survive and maintain the hemolymph undiluted for several days. However, if the valves are forced open, the animal swells rapidly and little volume regulation is observed. Among these bivalves, Mytilus seems to show some degree of volume regulation, since Krogh (1939) found that the hemolymph and tissue chloride concentrations had become reduced in dilute sea water. Further evidence that Mytilus is able to tolerate dilute sea water was furnished by Milne (1940), who found that, at low tide, the salinity inside the mantle cavity of Mytilus was 24%o, while the salinity of the environment had fallen to 7%0. Freeman and Rigler (1957) demonstrated that the estuarine lamellibranch Scrobicularia plana tolerates wide salinity variations by closure of the valves, seriously decreasing the rate of equilibration of the body fluids with the external milieu after environmental concentration changes.Among the gastropods, Mayes (1962) found a gradual increase in weight in all the species of British Littorina, an operculate snail, upon transfer of the animals to 25% sea water. In this medium, all animals remained retracted until death; Mayes therefore concluded that the survival times of each species in this medium were correlated with the goodness of fit of the operculum. Avens and Sleigh (1965) have verified these findings using Littorina saxatilis. These workers concluded that hyperosmoticity of the body fluids of this animal in dilute solutions is a result of avoidance of deleterious conditions by retraction, rather than active hyperosmotic regulation, since active animals were always isosmotic with the medium. Thus, Avens and Sleigh conclu...

Comparative salinity tolerances of four siphonariid limpets in relation to habitat restriction of the rare and endangeredSiphonaria compressa

“…Typically, molluscs demonstrate little, if any, ability to regulate their blood osmolality (Morritt et al 2007). McAlister and Fisher (1968) found that the presence of an external shell in molluscs gives them the potential for behavioural responses during osmotic stress, involving the temporary exclusion of the environment by clamping down the shell or closing the valves. Arnold (1957) found that limpets show such retraction and clamping responses, and that the cephalic tentacles and mantle fringe contain receptors for the perception of salinity.…”

“…Arnold (1957) found that limpets show such retraction and clamping responses, and that the cephalic tentacles and mantle fringe contain receptors for the perception of salinity. Activity rhythms are characteristic of many limpets, including most species of Siphonaria (Branch 1988), and their movements have been related to avoidance of potentially harmful osmotic stress, desiccation, predation, food shortage and wave action (McAlister and Fisher 1968, Branch and Cherry 1985, Branch 1988.…”

Osmotic Balance in a Marine Pulmonate,Amphibola crenata

“…Bedford (1969) reported that the New Zealand pulmonate limpet Siphonaria zelandica could regulate the concentration of its body fluids below 30% seawater. McAlister and Fisher (1968), however, demonstrated decreased survival and no osmotic regulation at low salinity in the closely related Texan species 5. pectinata. They noted that it was the animals' ability to clamp down on the substrate which enhanced its survival capabilities in low salinities and produced a hyperosmotic haemolymph.…”

“…Several authors have demonstrated that such gastropods avoid dilution of their body fluids by behavioural means such as pulling in the operculum or clamping down on the substrate (Todd, 1964a, b;Vasiljeva et al 1960;McAlister and Fisher, 1968). Those few gastropods known to be totally holoeuryhaline are osmotic regulators in low salinity: Assimea grayana (Little and Andrews, 1977) and Melanopsis trifasciata (Bedford, 1971a, b) amongst the prosobranchs and Amphibola crenata (Shumway, 1981;Shumway and Marsden, 1982) amongst the pulmonates.…”

Influence of salt concentrations on survival, body weight and blood chloride of the freshwater snail, Indoplanorbis exustus (Deshyes)

“…These related problems have been investigated in freshwater snails mainly by Machin (1964), Van Aardt (1968), Fromter & Diamond (1972 and McAlister & Fisher (1968) .…”