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Journal of Experimental Biology 19,176-185 (1942)
Published by Company of Biologists 1942

Studies on the Physiology of Arenicola Marina L. : III. The Potassium Relations of the Isolated Extrovert (with Remarks on the Effects of varying the Lever Weight

G. P. WELLS ¹ and I. C. LEDINGHAM ¹

¹ Department of Zoology, University College, London

1. The effects on the isolated extrovert of Arenicola marina L. of varying the potassium concentration of the bathing medium are described. Data are also presented on K : Mg antagonism. Potassium and magnesium concentrations are given as multiples of their concentrations in artificial sea water, which was taken as the ‘normal’ starting fluid.

2. The extrovert normally shows a distinctive pattern of alternating periods of activity and rest, superposed on the more general properties of rhythm and tone. This pattern is very sensitive to changes in potassium concentration. Moderate changes produce modifications of the pattern. Severe changes abolish the pattern and produce effects on rhythm and tone resembling those shown by most rhythmic muscles under like conditions.

3. Moderate K excess (K 1.5-3.5) excites tone and rhythm. Accommodation occurs during long exposure. The effects resemble those of Mg deficit, and can be completely abolished by increasing the Mg concentration.

4. An increase of lever weight has effects on the rhythm resembling those of a moderate K excess or a moderate Mg deficit, but in this case there is no accommodation. It is suggested that the extrovert contains a steady state system such as k₀ k SA B where S is a source and the performance of the extrovert depends, through B, on the rate of the process AB. If change in the K : Mg balance acts on k, its result will be following automatically by accommodation. Change in tension can produce the same end-result, without accommodation, by acting on B.

5. Severe K excess (K 5-10) causes contracture and inhibition of the rhythm. The contracture is partly antagonized by simultaneous increase in Mg, but the inhibition is not antagonized.

6. Moderate K deficit (K 0.75-0.33) causes initial excitement, then a characteristically modified pattern, with widely spaced activity outbursts, and an occasional abnormally long outburst. These effects are not antagonized by simultaneous decrease in Mg. As, however, they are not seen in preparations exposed to sea water diluted to four times its volume, they are due to disturbance of a balance between K and some other constituent of the medium.

7. Severe K deficit (K 0.05 or 0.00) causes partial contracture with chaotic activity, which lasts for many hours. Neither effect can be antagonized by simultaneous decrease in Mg. With borderline deficits (K 0.25 or 0.20) the preparation reacts at first as if to severe deficit, then accommodates itself and gives the pattern characteristic of moderate deficit.

8. The potassium paradox occurs on returning to artificial sea water after severe deficit. With borderline deficits (K 0.25 or 0.20) it is seen after short exposure, but not after long.