Department of Biology, Texas A&M University, College Station, TX, 77840, USA.
Organismic and Evolutionary Biology Graduate Program, University of Massachusetts, Amherst, MA, 01003, USA.
J Comp Physiol B. 2024 Jun;194(3):299-313. doi: 10.1007/s00360-023-01523-3. Epub 2023 Nov 1.
Activity patterns tend to be highly stereotyped and critical for executing many different behaviors including foraging, social interactions, and predator avoidance. Differences in the circadian timing of locomotor activity and rest periods can facilitate habitat partitioning and the exploitation of novel niches. As a consequence, closely related species often display highly divergent activity patterns, suggesting that shifts from diurnal to nocturnal behavior, or vice versa, are critical for survival. In Africa's Lake Malawi alone, there are over 500 species of cichlids, which inhabit diverse environments and exhibit extensive phenotypic variation. We have previously identified a substantial range in activity patterns across adult Lake Malawi cichlid species, from strongly diurnal to strongly nocturnal. In many species, including fishes, ecological pressures differ dramatically across life-history stages, raising the possibility that activity patterns may change over ontogeny. To determine if rest-activity patterns change across life stages, we compared the locomotor patterns of six Lake Malawi cichlid species. While total rest and activity did not change between early juvenile and adult stages, rest-activity patterns did, with juveniles displaying distinct activity rhythms that are more robust than adults. One distinct difference between juveniles and adults is the emergence of complex social behavior. To determine whether social context is required for activity rhythms, we next measured locomotor behavior in group-housed adult fish. We found that when normal social interactions were allowed, locomotor activity patterns were restored, supporting the notion that social interactions promote circadian regulation of activity in adult fish. These findings reveal a previously unidentified link between developmental stage and social interactions in the circadian timing of cichlid activity.
活动模式往往具有高度的刻板性，对于执行许多不同的行为（包括觅食、社交互动和避免捕食者）至关重要。运动活动和休息时间的昼夜节律时间差异可以促进栖息地分区和新生态位的利用。因此，密切相关的物种通常表现出高度不同的活动模式，这表明从白天到夜间的行为转变，或者相反，对于生存至关重要。仅在非洲马拉维湖，就有超过 500 种慈鲷，它们栖息在不同的环境中，表现出广泛的表型变异。我们之前已经确定了马拉维湖慈鲷物种的活动模式存在很大的差异，从强烈的白天到强烈的夜间。在许多物种中，包括鱼类，生态压力在生命史阶段有很大的差异，这增加了活动模式可能随个体发育而变化的可能性。为了确定休息-活动模式是否在生命阶段发生变化，我们比较了六种马拉维湖慈鲷物种的运动模式。虽然早期幼鱼和成鱼阶段的总休息和活动没有变化，但休息-活动模式发生了变化，幼鱼表现出明显的活动节律，比成鱼更稳健。幼鱼和成鱼之间的一个明显区别是复杂社会行为的出现。为了确定社会环境是否是活动节律所必需的，我们接下来测量了群体饲养的成年鱼类的运动行为。我们发现，当允许正常的社会互动时，运动活动模式得到恢复，这支持了社会互动促进成年鱼类活动昼夜节律调节的观点。这些发现揭示了慈鲷活动的昼夜节律在发育阶段和社会互动之间以前未被识别的联系。
