| Summary: | Little is known of respiratory physiology in Dallia pectoralis , an arctic air‐breathing fish. We used electromyography and electromyostimulation to identify muscles involved in air breathing. We attempted to determine the hindbrain innervation of the respiratory muscles using retrograde fluorescent labeling. We identified and validated function of respiratory muscles and motoneuron activities associated with aquatic respiration but were unable to fully characterize aerial respiration. Current attempts to investigate aerial respiration employ a partial preparation with intact respiratory structures. Identification of respiratory muscles and nerves enables us to assess central CO 2 chemosensitivity (cCO 2 ‐CS) in D. pectoralis . cCO 2 ‐CS has been identified in other air‐breathing fish of divergent phylogeny, such as gar (Holostei) and betta (Teleostei), but not in a primitive air‐breathing fish such as amia (Holostei). Preliminary data suggest that D. pectoralis is unlike its fellow teleost; they lack cCO 2 ‐CS. With a complete data set, we will be able to assess the phylogenetic origins of cCO 2 ‐CS. If cCO 2 ‐CS exists in gar and both teleost species, this characteristic likely arose in a common actinopterygian ancestor of Teleostei and Holostei. In contrast, if cCO 2 ‐CS is absent from D. pectoralis , then it likely arose independently multiple times among the air‐breathing teleosts.
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