An analysis of water‐content regulation in osmoconforming limpets (Mollusca: Patellacea)

Abstract

0 s m o c on f o r m i ng L i m pe t s ( M o I I u sc a : ABSTRACTThe capacity to regulate body volume is important in the ability of soft-bodied osmoconforming marine animals to withstand osmotic stress. In the present study two intertidal limpets, Collisella digitalis and Notoacmea scutum, which differ in their tolerance of osmotic stress, are compared in their ability to regulate water content. Two direct measurements and two mathematical approaches developed by Oglesby (' 75) and Machin ('751, respectively, have been used. Both species are osmoconformers over the range 500-1,500 mOs/l but showed a slight tendency to hyporegulate C1-and Na' in the hemolymph. In weight and tissue hydration changes following a change in osmotic pressure of the medium, C. digitalis did not vary as widely as did N. scutum and so appears to have better control of body volume. This correlates well with the previous finding that C. digitalis tolerates a wider range of salinity than does N. scutum.

Osmoregulation and Excretion in Prosobranch Gastropods Part I: Physiology and Biochemistry

“…Tarr (1977), however, recorded both ions as being less concentrated in the blood by approximately 40 mM l -l . Tarr (1977), however, recorded both ions as being less concentrated in the blood by approximately 40 mM l -l .…”

“…In most marine prosobranchs placed in diluted sea water, body weight increases, as in Scutus (Tucker, 1970a), the limpets Colisella and Acmaea (Webber & Dehnel, 1968b;Tarr, 1977), and Littorina saxatilis (Olivi) (Avens & Sleigh, 1965). Many workers have studied permeability by measuring simultaneously changes in blood concentration and in body weight.…”

“…Avens & Sleigh, 1965;Rumsey, 1973;Tarr, 1977), that of many Archaeogastropoda, Neritacea, Mesogastropoda and Neogastropoda is hyperosmotic to normal sea water by 5 to 12 mM I7 1 NaCl (Avens," 1965;Bedford, 1972;Little, 1972;Staaland, 1970;Toddi 1964a. While in some species of prosobranch the blood is isosmotic with external sea water (see, e.g.…”

“…The levels of sodium, magnesium, and chloride in the blood of snails in diluted sea water follow the osmotic pressure, at least in Littorina littorea (Rumsey, 1973) and two limpets, Colisella digitalis (Rathke) and Acmaea (cited as Notacmaea) scutum (Tarr, 1977). Potassium and calcium, however, are maintained at a relatively constant concentration in Littorina even when external levels are half those for normal sea water (Rumsey, 1973).…”

“…Generally it is thought at euryhaline animals show better volume regulation than stenohaline ones, but the evidence is not ally conclusive (Lange, 1972). Colisella digitalis has been investigated by Tarr (1977), and Tegula funebralis (A. aams) by Peterson & Duerr (1969). This is fortunate because different tissues probably have different capacities for volume regulation.…”