. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 518 J. KEVIN FOSKETT. FIGURE 7. Osmotic concentration of the blood of adult Scsanna reticulatum as a func- tion of osmotic concentration of the medium; each point represents the mean of five individuals; bars indicate ± Spaargaren, 1971). Tidal rhythms and sudden heavy rainfalls cause rapid salin- ity fluctuations to which estuarine organisms are often exposed. Rapid attainment of blood osmotic equilibrium is clearly advantageous to estuarine organisms. How- ever, osmotic adjustments which are too fast will cause bloo
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 518 J. KEVIN FOSKETT. FIGURE 7. Osmotic concentration of the blood of adult Scsanna reticulatum as a func- tion of osmotic concentration of the medium; each point represents the mean of five individuals; bars indicate ± Spaargaren, 1971). Tidal rhythms and sudden heavy rainfalls cause rapid salin- ity fluctuations to which estuarine organisms are often exposed. Rapid attainment of blood osmotic equilibrium is clearly advantageous to estuarine organisms. How- ever, osmotic adjustments which are too fast will cause blood concentrations to fluctuate back and forth in synchrony to external salinity fluctuations with possible detrimental effects (Kinne, 1967). Results obtained in the present study demon- strate that stages I and II larvae of S. reticulatum adjust to salinity changes within 1 hr of exposure. Since the blood concentrations in S. reticulatum larvae follow closely changes in the external salinity, the fact that such adjustments are attained rather rapidly suggests that the body fluids are in a constant state of osmotic flux in variable-salinity estuaries. At the tissue level, therefore, not only must the cells exhibit tolerances to wide ranges in concentration, but adjustment of intracelltilar concentration must be rapid to limit large fluxes of water between blood and cells. No consistent degree of variation between individuals from the same hatch and same test salinities whose body fluids were sampled at the same time were noted for 3\ reticulatum larvae. Variation in the osmotic responses of individual larvae se body fluids are sampled at the same time can be caused by differences in ize, metabolic rates, or general healthiness. It might also be expected that some degree of variation can exist among individuals as a result of their differing genetic pabilities for osmoregulation (Barnes, 1968). Such differences could exist be- M individuals hatched from the same female and betwe
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