Osmoregulation Essay

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The Osmoregulatory Abilities of Two Intertidal Worms, Nereis virens and Phascolopsis gouldii Author’s Name: ___________________________________________________ Biology Department, Hendrix College, Conway, AR 72032 Nereis virens, clam worms, are common marine annelids, which are widespread in the intertidal zone of many beaches in New England. They are particularly abundant in the upper intertidal zone (Fig. 1), where specimens may be found under rocks and in beds of mussels and algae. Phascolopsis gouldii, peanut worms, are another common worm native to the New England coast. They can often be found buried in silty or muddy areas in the lower parts of the intertidal zone (Fig. 1). Most marine worms are in osmotic equilibrium with the sea in which they live; i.e., their body fluids are approximately isoosmotic to seawater. However, the water of the intertidal zone is not always identical in salinity to that of the open sea. Both runoff of fresh water from the land and rainfall may dilute water along the seashore. Alternatively, tide pools may become saltier than the sea because of evaporation during exposure at low tide. Both perturbations tend to increase in magnitude as height above the mean low tide line increases (Laboratory Manual for Principles of Biology, 1992). [pic] Figure 1. The marine intertidal zone. The runoff of freshwater from the terrestrial environment lowers the salinity in this zone while evaporation raises it, resulting in a very variable salinity. Based on their positions within the intertidal zone, I hypothesize that ________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ___________________________________________________ Therefore, if I place

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