. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. LIMVLUS GILLS AS CIRCULATORY PUMPS 387 Cannula 1st Bronchiocardiac Canal /. Figure 1. Dorsal cutaway illustration of Linntliis/vlypliciniix, illus- trating the position of catheters and electrodes. Redenbaugh, 1899; Lockhead, 1950), little physiological evidence is available to support these interpretations. The present contribution provides evidence that the gill plates help circulate the blood in Limn/us, and docu- ments the hemodynamic relationships between the car- diac and ventilatory systems of intact horseshoe crabs d
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. LIMVLUS GILLS AS CIRCULATORY PUMPS 387 Cannula 1st Bronchiocardiac Canal /. Figure 1. Dorsal cutaway illustration of Linntliis/vlypliciniix, illus- trating the position of catheters and electrodes. Redenbaugh, 1899; Lockhead, 1950), little physiological evidence is available to support these interpretations. The present contribution provides evidence that the gill plates help circulate the blood in Limn/us, and docu- ments the hemodynamic relationships between the car- diac and ventilatory systems of intact horseshoe crabs during all of their known respiratory behaviors. In addi- tion, we present evidence suggesting that, in some cases, phase coupling between the heart and gill rhythms en- hances cardiac output. In crustaceans, there is good evidence that frequency covariation between the gills and heart is mediated by the cardioregulatory nerves (Field and Larimer, 1975a, b; Young, 1978). In a few instances investigators re- corded phasic activity in the cardioregulatory nerves that appeared to be coupled to the ventilatory rhythm; they suggested that this type of activity would help phase-lock the heart rhythm to scaphognathite movements. In Lim- ulus the cardioregulatory nerves also appear to be impor- tant in the tonic regulation of heart rate and in the coor- dination between the cardiac and ventilatory rhythms (Watson, 1979). However, phase coupling between the heart and gills could also be mediated by direct pressure cues. In this study we found that phase coupling between heart and gill rhythms was associated with rhythmic bursts in the cardioregulatory nerves. These data suggest that in Limulus both tonic and phasic coordination between the heart and gills is regulated by the nervous system. BCC Pressure Gill EMG ECG 20 10 •0 B D cmH20 -20 -10 -0 155 Figure 2. The relationship between pressure (cm H2O) in a branchiocardiac canal (BCC, 2nd canal), the electromyogram (EMG) of the gill clo
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
