. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. AERIAL RESPIRATION IN MUDSUCKER 271 onset of surface gulping by several minutes. Moreover, the rate of opercular movement did not appreciably change as the oxygen concentration was gradually lowered to critical levels: at , opercular beats among 5 aquatic breathers averaged (range, 48-78) ; at , (40-64) among the same fish; at , (38-84) ; at , (40-80) among these fish, one of which was now abortively gulping; at , (36-76) among the three fish tha
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. AERIAL RESPIRATION IN MUDSUCKER 271 onset of surface gulping by several minutes. Moreover, the rate of opercular movement did not appreciably change as the oxygen concentration was gradually lowered to critical levels: at , opercular beats among 5 aquatic breathers averaged (range, 48-78) ; at , (40-64) among the same fish; at , (38-84) ; at , (40-80) among these fish, one of which was now abortively gulping; at , (36-76) among the three fish that were still breathing aquatically ; and at , (36-76) among these three, two of which were now gulping sporadically. It is emphasized that even when adults began gulping in oxygen concentrations greater than about. opercular movements? resting on bottom yes contemplat- ing surface gulping, expelling yes, no gulping, expel- ling orretaining no gulping, retaining I. 8 . 6 I. 4 2 v/A FIGURE 2. Progressive reactions of 13 mudsuckers to successively lowered dissolved oxygen concentrations. The hatched areas represent proportions of fish exhibiting designated reaction; the numbers in the blocks are the actual counts. , opercular movements often continued at the normal rate. Preliminary to the functional gulping, about half of the fish performed abortive intention movements, obviously related to gulping behavior (Fig. 2). Before oxygen had fallen to the critical level, they breathed normally and often rested quietly on the bottom, supported and anchored by their fused pelvic fins, which function as suction cups. As the oxygen was decreased below , however, they would either begin to glance upward, then swim toward but not to the surface, or they would simply approach the surface without the preliminary glancing. Then, as the concentration was further decreased, some fish would break the surface and gulp air, which, however, was almost imm
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
