Trembley Annie M, Rowsey Lauren E, Speers-Roesch Ben
Department of Biological Sciences, University of New Brunswick, Saint John, New Brunswick, Canada.
J Fish Biol. 2024 Dec;105(6):1843-1849. doi: 10.1111/jfb.15930. Epub 2024 Sep 15.
The metabolic rate of a freely moving fish (routine metabolic rate) is tightly coupled with volitional movement (spontaneous activity), both of which commonly show strong daily cycles linked to the species-specific diel activity pattern. Mummichog (Fundulus heteroclitus), an important estuarine fish in the north western Atlantic Ocean, are historically reported as diurnal (i.e., more active during daylight). Our recent laboratory studies on a Bay of Fundy population, however, showed a free-running (i.e., similarly active daytime and night-time) or even nocturnal (i.e., more active at night-time) diel activity pattern. In the laboratory, near-infrared (NIR) illumination is commonly used with a NIR-sensitive camera to visualize fish activity across the light-dark periods of the day. Because NIR light is close to the visible light spectrum and certain fishes show sensitivity to NIR, the use of NIR with mummichog possibly could disturb the animals and obscure the identification of their true diel activity pattern. We aimed to determine if NIR illumination (940 nm wavelength) influences the diel activity pattern of mummichog. We used measurements of routine metabolic rate (oxygen consumption rate, MO) as a proxy for activity, as evaluating the effect of NIR requires treatments where NIR lights are off, which precludes visualization and direct assessment of fish activity at night-time. We measured routine MO of mummichogs over 6 days, exposed to either NIR off-on-off (2 days for each off or on period) or the opposite sequence of NIR on-off-on (to control for time-dependent effects). NIR lights did not influence the diel cycle of routine MO, and activity by proxy, in mummichog. Thus, NIR illumination is a suitable method to visualize mummichog during light-dark diel cycles. Routine MO, and presumably activity, was similar or higher during night-time periods compared to daytime periods, confirming a free-running or nocturnal activity pattern for at least certain populations of mummichog.
自由游动的鱼类的代谢率（常规代谢率）与自主运动（自发活动）紧密相关，这两者通常都呈现出与物种特定的昼夜活动模式相关的强烈日周期。米氏弹涂鱼（Fundulus heteroclitus）是大西洋西北部一种重要的河口鱼类，历史记载其为昼行性（即白天更活跃）。然而，我们最近对芬迪湾种群的实验室研究表明，其呈现出自由运行的（即白天和夜间活动相似）甚至夜行性（即夜间更活跃）的昼夜活动模式。在实验室中，近红外（NIR）照明通常与近红外敏感相机一起使用，以观察鱼类在一天的明暗周期中的活动。由于近红外光接近可见光谱，且某些鱼类对近红外光敏感，因此对米氏弹涂鱼使用近红外光可能会干扰动物，并模糊其真实昼夜活动模式的识别。我们旨在确定近红外照明（940纳米波长）是否会影响米氏弹涂鱼的昼夜活动模式。我们使用常规代谢率（耗氧率，MO）的测量值作为活动的指标，因为评估近红外光的影响需要进行近红外光关闭 - 打开 - 关闭（每个关闭或打开周期为2天）或相反顺序的近红外光打开 - 关闭 - 打开（以控制时间依赖性影响）的处理。近红外光不会影响米氏弹涂鱼常规MO的昼夜周期以及由此推断的活动。因此，近红外照明是在明暗昼夜周期中观察米氏弹涂鱼的合适方法。与白天相比，夜间的常规MO以及推测的活动相似或更高，这证实了至少某些米氏弹涂鱼种群的自由运行或夜行性活动模式。
