. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 350 D. W. KRAUS AND J. E. DOELLER Table II Time in minutes required for compound action potential amplitude of bivalve cerebro-visceral connectives to reach 50% of starling value after change in condition Tellina Spisula Tagelus Geukensia Conditions alternata solidissima p/ebeius" demissa' AirtoN," ± ± ± ± (7)c (6) (4) (4) Air + COtoN;b ± ± ± ± (5) (4) (3) (3) Airtoair+1 ± ± ± ± mAfouabain" (3) (3) (3) (3) a Species withou
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 350 D. W. KRAUS AND J. E. DOELLER Table II Time in minutes required for compound action potential amplitude of bivalve cerebro-visceral connectives to reach 50% of starling value after change in condition Tellina Spisula Tagelus Geukensia Conditions alternata solidissima p/ebeius" demissa' AirtoN," ± ± ± ± (7)c (6) (4) (4) Air + COtoN;b ± ± ± ± (5) (4) (3) (3) Airtoair+1 ± ± ± ± mAfouabain" (3) (3) (3) (3) a Species without neurohemoglobin. b Stimulus frequency 2 pulses per second. c Numbers are given as average ± standard deviation (number of rep- etitions). d After 30 min equilibration; stimulus frequency 1 pulse per second. tives both with and without neurohemoglobin ap- proached baseline in 5 minutes or less and electrical ex- citability was eliminated in the region of application of the drug (Table II). Discussion The basal oxygen consumption rate of any tissue rep- resents the metabolic cost of cellular maintenance, and is characteristic of that tissue. In accordance, the mass specific resting oxygen consumption rates of nonmyelin- ated nerves do not vary greatly from one nerve type to another (Fig. 4; Ritchie, 1973). On the other hand, action potential conduction is a membrane phenomenon and the commensurate increase in oxygen consumption rate is a function of total axonal surface area (Ritchie, 1973). Compound nerves with small diameter axons contain more membrane surface area and possibly more energy- consuming Na-K pumps per gram than nerves with large diameter axons (Ritchie, 1973). Moreover, small diame- ter axons have a large surface area to volume ratio, and the dependency on active membrane-bound ionic pumps to maintain ion gradients may be high to com- pensate for the large fraction of ion content exchanged per action potential. Nonmyelinated bivalve cerebro-vis- cer
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