Fan Marie, Stuart-Fox Devi, Cadena Viviana
Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Penryn, United Kingdom; Zoology Department, University of Melbourne, Parkville, Victoria, Australia.
Zoology Department, University of Melbourne, Parkville, Victoria, Australia.
PLoS One. 2014 Oct 29;9(10):e111504. doi: 10.1371/journal.pone.0111504. eCollection 2014.
The ability to change colour rapidly is widespread among ectotherms and has various functions including camouflage, communication and thermoregulation. The process of colour change can occur as an aperiodic event or be rhythmic, induced by cyclic environmental factors or regulated by internal oscillators. Despite the importance of colour change in reptile ecology, few studies have investigated the occurrence of a circadian rhythm in lizard pigmentation. Additionally, although colour change also entails changes in near-infrared reflectance, which may affect thermoregulation, little research has examined this part of the spectrum. We tested whether the bearded dragon lizard, Pogona vitticeps, displays an endogenous circadian rhythm in pigmentation changes that could be entrained by light/dark (LD) cycles and how light affected the relative change in reflectance in both ultraviolet-visible and near-infrared spectra. We subjected 11 lizards to four photoperiodic regimens: LD 12:12; LD 6:18; LD 18:6 and DD; and measured their dorsal skin reflectance at 3-hour intervals for 72 hours after a habituation period. A proportion of lizards displayed a significant rhythm under constant darkness, with maximum reflectance occurring in the subjective night. This endogenous rhythm synchronised to the different artificial LD cycles, with maximum reflectance occurring during dark phases, but did not vary in amplitude. In addition, the total ultraviolet-visible reflectance in relation to the total near-infrared reflectance was significantly higher during dark phases than during light phases. We conclude that P. vitticeps exhibits a circadian pigmentation rhythm of constant amplitude, regulated by internal oscillators and that can be entrained by light/dark cycles.
快速变色的能力在变温动物中广泛存在，具有多种功能，包括伪装、通讯和体温调节。颜色变化过程可以是无规律的事件，也可以是有节律的，由周期性环境因素诱导或由内部振荡器调节。尽管变色在爬行动物生态学中很重要，但很少有研究调查蜥蜴色素沉着中的昼夜节律的发生情况。此外，虽然颜色变化也会导致近红外反射率的变化，这可能会影响体温调节，但很少有研究考察这部分光谱。我们测试了鬃狮蜥（Pogona vitticeps）是否在色素沉着变化中表现出内源性昼夜节律，这种节律是否可以被光/暗（LD）周期所调节，以及光如何影响紫外-可见光和近红外光谱中反射率的相对变化。我们将11只蜥蜴置于四种光周期方案下：LD 12:12；LD 6:18；LD 18:6和DD；在适应期后的72小时内，每隔3小时测量它们背部皮肤的反射率。一部分蜥蜴在持续黑暗条件下表现出显著的节律，最大反射率出现在主观夜间。这种内源性节律与不同的人工LD周期同步，最大反射率出现在黑暗阶段，但幅度没有变化。此外，黑暗阶段的总紫外-可见光反射率与总近红外反射率的比值显著高于光照阶段。我们得出结论，鬃狮蜥表现出振幅恒定的昼夜色素沉着节律，由内部振荡器调节，并且可以被光/暗周期所调节。
