. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. BIVALVE NERVES STRUCTURE-FUNCTION 63 c o a 3 •o c o u 30 n 25 0 o !? 20 15 10-. 10 15 20 Temperature. °C S. soUdtsslma T. altemata T plebeiiis G. demtssa 25 »10 Figure 7. Conduction velocities of bivalve cerebro-visceral connec- tives as a function of temperature. Qm values were computed over en- tire temperature range for each species. Data points represent the mean of 20-40 measurements (± standard error). of unspecialized axons (Horridge and Bullock, 1965). The garfish olfactory nerve participates main


. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. BIVALVE NERVES STRUCTURE-FUNCTION 63 c o a 3 •o c o u 30 n 25 0 o !? 20 15 10-. 10 15 20 Temperature. °C S. soUdtsslma T. altemata T plebeiiis G. demtssa 25 »10 Figure 7. Conduction velocities of bivalve cerebro-visceral connec- tives as a function of temperature. Qm values were computed over en- tire temperature range for each species. Data points represent the mean of 20-40 measurements (± standard error). of unspecialized axons (Horridge and Bullock, 1965). The garfish olfactory nerve participates mainly in relay- ing information from the olfactory receptors to the olfac- tory bulb and therefore is also composed of small unspe- cialized axons. In contrast, the rabbit cervical vagus (Keynes and Ritchie, 1965) and the walking leg nerves from the spider crab (Abbott et al,, 1958) are both multi- functional nerves and possess a broad distribution of axon sizes. The electrophysiological characteristics of bivalve ce- rebro-visceral connectives are governed mainly by the axon size distribution and mean axon diameter, not by the presence or absence of neurohemoglobin. Com- pound action potentials are relatively simple (Fig. 6), re- flecting the homogeneity of fiber size. The homogeneous fiber spectra of the pike and garfish olfactory nerves re- sult in action potentials of similar quality (Gasser, 1956; tested, there were no consistent differences between con- nectives with and without neurohemoglobin. The Q,0s for the absolute refractory period of vertebrate myelin- ated A-fibers average , between 5 and 30°C (Gasser, 1931). Examples of threshold curves at near-habitat tempera- tures for the four species are presented in Figure 9. The lower stimulus strengths at each duration represent the threshold voltages required for initiating the first axons to fire and the upper values represent the maximum volt- ages required for recruitment of all axons. Again, consis- tent diffe


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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology