Marine Biology Research Division, Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093, USA.
1] Marine Biology Research Division, Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093, USA [2] Fisheries Resource Division, Southwest Fisheries Science Center, NOAA Fisheries, La Jolla, California 92037, USA.
Nat Commun. 2014;5:3022. doi: 10.1038/ncomms4022.
The polypterids (bichirs and ropefish) are extant basal actinopterygian (ray-finned) fishes that breathe air and share similarities with extant lobe-finned sarcopterygians (lungfishes and tetrapods) in lung structure. They are also similar to some fossil sarcopterygians, including stem tetrapods, in having large paired openings (spiracles) on top of their head. The role of spiracles in polypterid respiration has been unclear, with early reports suggesting that polypterids could inhale air through the spiracles, while later reports have largely dismissed such observations. Here we resolve the 100-year-old mystery by presenting structural, behavioural, video, kinematic and pressure data that show spiracle-mediated aspiration accounts for up to 93% of all air breaths in four species of Polypterus. Similarity in the size and position of polypterid spiracles with those of some stem tetrapods suggests that spiracular air breathing may have been an important respiratory strategy during the fish-tetrapod transition from water to land.
巨口鱼目（弓鳍鱼和象鼻鱼）是现存的基干肉鳍鱼类，它们用肺呼吸，与现存的肉鳍鱼（肺鱼和四足动物）在肺部结构上有相似之处。它们也与一些化石肉鳍鱼，包括早期的四足动物，在头顶上有大的成对开口（鳃孔）相似。鳃孔在巨口鱼呼吸中的作用一直不清楚，早期的报告表明，巨口鱼可以通过鳃孔吸入空气，而后来的报告则在很大程度上否定了这些观察结果。在这里，我们通过呈现结构、行为、视频、运动学和压力数据来解决这个存在了 100 年的谜团，这些数据表明，在 4 种巨口鱼属中，鳃孔介导的抽吸呼吸占所有空气呼吸的 93%。巨口鱼的鳃孔大小和位置与一些早期四足动物的相似，这表明在鱼类到四足动物从水中到陆地的过渡过程中，鳃孔呼吸可能是一种重要的呼吸策略。
