Graduate Thesis Or Dissertation
 

Osmotic and ionic regulation in the Dungeness crab, Cancer magister (Dana)

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  • Osmotic and ionic regulation was studied in the Dungeness crab, Cancer magister, after acute exposure to a range of five salinities from 25% to 125% sea water (100% = 32%). Blood, urine and muscle tissue were sampled at 24 and 48 hours after exposure. Analyses were made of blood and urine osmotic concentrations, as well as blood and urine sodium, potassium, calcium, and chloride ion concentrations. Data were also obtained for these ions and the total amino nitrogen (ninhydrin positive substances) in muscle tissue from crabs at the experimental salinities. Measurements of muscle extracellular space (interfiber water) and blood volume were determined with inulin-C¹⁴. In dilute sea water, blood is hyperposmotic to the medium but remains isosmotic at 100% sea water. Urine is slightly blood hypoosmotic over the salinity range. Hyperregulation is also demonstrated for the blood cations: sodium, potassium, and calcium. Blood chloride, however, is weakly regulated and the blood:medium gradient is low. Urine cation concentrations are blood hypoionic in the salinities of 75% and 100% sea water compared to 25% and 50% sea water where they are isoionic, Urine chloride is isoionic in 75% and 100% sea water, but blood hyperionic in 25% and 50% sea water. Increases in tissue water content as well as muscle extracellular (interfiber water) space occur when crabs are placed in dilute sea water. The inulin extracellular space is 7.3% in 100% sea water and this is lower than the chloride spaces (18%). Reductions in muscle ions concentrations and free amino nitrogen compounds occur. The blood:tissue gradient for potassium indicates intracellular regulation of this ion, while no regulation of sodium and chloride is found. Decreases in free amino nitrogen compounds in dilute sea water do not contribute significantly to decreases in cell volume through loss of osmotically active nonelectrolytes in the muscle. In concentrated sea water (125%), there is some indication of blood hypoosmotic regulation while urine is regulated blood hypoosmotic, The pattern of blood sodium, potassium and chloride regulation suggests slight hypoionic regulation. Urine sodium and potassium are significantly blood hypoionic, while urine chloride is isoionic. Muscle tissue in crabs at 125% sea water indicate decreases in tissue water content, muscle sodium and muscle chloride in comparison to controls. Muscle potassium is regulated. Large increases in free amino nitrogen compounds are noted in muscle from crabs at this stress, and appear to indicate intracellular compensation for the cells to tolerate increased osmotic concentration.
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file details AlspachGeorgeSamuelJr1972.pdf 2017-08-19 Pubblico Scaricare