REACTIONS OF AN ELASMOBRANCH (SQUALUS SUCKLII) TO VARIATIONS IN THE SALINITY OF THE SURROUNDING MEDIUM

¹ From the Pacific Biological Station, Nanaimo, B. C., and the Department of Physiology and Pharmacology, University of Alberta, Edmonton. Alberta

1. An investigation has been made of the effect on Squalus sucklii of transference to the following media: (a) distilled water, (b) tap water, (c) tap water pH 8.4, (d) NaCl solution, (e) NaCl, CaCl₂ solution, (f) NaCl, CaCl₂, KCl solution, (g) NaCl, CaCl₂, KCl, MgSO₄ solution, (h) sea water to which NaCl, CaCl₂, KCl, MgSO₄ had been added.

2. The most toxic solution was sea water with added salts, the solution of NaCl, CaCl₂ and KCl was the least toxic.

3. Tap water had a relatively low toxicity, but tap water which had been given the same pH as sea water by the addition of NaOH was more toxic.

4. Cessation of respiration invariably occurred more readily than did failure of the heart.

5. It appears likely that respiratory failure is the cause of death of fish in abnormal media. This is believed to result from a depression of the respiratory center.

6. No variation which could be ascribed to pregnancy, size or sex was observed in the duration of respiration or heart beat, the change in amount of hemoglobin, weight of fish or of organs while in the experimental solutions.

7. Changes in the amount of hemoglobin closely paralleled the changes in the osmotic pressure of the external media.

8. An increase in weight usually but not invariably resulted from introduction of fish into hypotonic media.

9. It could not be shown that a change in the comparative weight of the liver, spleen or pancreas followed the introduction of the fish into an abnormal medium.