Bressman N R, Love J W, King T W, Horne C G, Ashley-Ross M A
Department of Biology, Wake Forest University, Winston-Salem, NC 27109, USA.
Maryland Department of Natural Resources, Annapolis, MD 21401, USA.
Integr Org Biol. 2019 Oct 25;1(1):obz026. doi: 10.1093/iob/obz026. eCollection 2019.
Most fishes known for terrestrial locomotion are small and/or elongate. Northern snakeheads () are large, air-breathing piscivores anecdotally known for terrestrial behaviors. Our goals were to determine their environmental motivations for emersion, describe their terrestrial kinematics for fish 3.0-70.0 cm and compare kinematics among four substrates. For emersion experiments, was individually placed into aquatic containers with ramps extending through the surface of the water, and exposed to 15 ecologically-relevant environmental conditions. For kinematic experiments, fish were filmed moving on moist bench liner, grass, artificial turf, and a flat or tilted rubber boat deck. Videos were digitized for analysis in MATLAB and electromyography was used to measure muscular activity. Only the low pH (4.8), high salinity (30 ppt), and high dCO (10% seltzer solution) treatments elicited emersion responses. While extreme, these conditions do occur in some of their native Asian swamps. Northern snakeheads >4.5 cm used a unique form of axial-appendage-based terrestrial locomotion involving cyclic oscillations of the axial body, paired with near-simultaneous movements of both pectoral fins. Individuals ≤3.5 cm used tail-flip jumps to travel on land. Northern snakeheads also moved more quickly on complex, three-dimensional substrates (e.g., grass) than on smooth substrates (e.g., bench liner), and when moving downslope. Release of snakeheads onto land by humans or accidentally by predators may be more common than voluntary emersion, but because northern snakeheads can respire air, it may be necessary to factor in the ability to spread overland into the management of this invasive species.
大多数以陆地移动而闻名的鱼类体型较小和/或呈细长状。北方黑鱼体型较大，是能呼吸空气的肉食性鱼类，据传有陆地活动行为。我们的目标是确定它们上岸的环境动机，描述体长3.0至70.0厘米的鱼的陆地运动学特征，并比较在四种基质上的运动学特征。在上岸实验中，将北方黑鱼单独放入带有延伸至水面的斜坡的水族箱中，并使其暴露于15种与生态相关的环境条件下。在运动学实验中，拍摄鱼在潮湿的实验台衬垫、草地、人造草皮以及平坦或倾斜的橡皮艇甲板上移动的情况。视频被数字化以便在MATLAB中进行分析，并使用肌电图来测量肌肉活动。只有低pH值（4.8）、高盐度（30ppt）和高溶解二氧化碳（10%的苏打水）处理引发了上岸反应。虽然这些条件较为极端，但在它们原产的一些亚洲沼泽中确实会出现。体长超过4.5厘米的北方黑鱼采用一种独特的基于轴向附肢的陆地移动形式，包括轴向身体的周期性摆动，并伴有两个胸鳍几乎同时的运动。体长小于等于3.5厘米的个体在陆地上通过尾部翻转跳跃来移动。北方黑鱼在复杂的三维基质（如草地）上比在光滑基质（如实验台衬垫）上移动得更快，且在下坡移动时也是如此。人类放生或捕食者意外将黑鱼放到陆地上的情况可能比它们主动上岸更为常见，但由于北方黑鱼能够呼吸空气，在管理这种入侵物种时，可能有必要考虑其在陆地上扩散的能力。
