Abstract
ABSTRACTOne of the main functions of physiological color change is thermoregulation. This change occurs much more rapidly than morphological color change, but the underlying mechanism remains poorly understood. Here, we studied the thermal dependence and molecular basis of physiological color change in lizards using Takydromus septentrionalis (Lacertidae) as the model system. Body color was thermally sensitive, becoming increasingly light as body temperatures deviated from the level (∼30°C) preferred by this species. We identified 3389 differentially expressed genes (DEGs) between lizards at 24°C and 30°C, and 1,097 DEGs between lizards at 36°C and 30°C. Temperature affected the cAMP signal pathway, motor proteins, cytoskeleton, and the expression of genes related to melanocyte-stimulating hormone (MSH) and melanocyte-concentrating hormone (MCH). Our data suggest that the role of physiological color change in thermoregulation is achieved in T. septentrionalis by altering the arrangement of pigments and thus the amount of solar radiation absorbed and reflected. G protein-coupling system inhibits adenylate cyclase activity to transform ATP into cAMP and thereby causes rapid pigment aggregation. MCH deactivates the G proteins and thereby initiates pigment dispersion. This mechanism differs from that reported for teleost fish where MCH activates the G proteins and thereby causes pigment aggregation.This article has an associated First Person interview with the first author of the paper.
Highlights
Color change is mediated by synchronous intracellular transport of pigmented organelles in chromatophores and has functional roles in signaling, background matching, and thermoregulation (Baling et al, 2016; Smith et al, 2016a,b)
Our data show that body color is thermally sensitive in T. septentrionalis, and that lizards quickly change body color in response to the thermal environment around them
From the pattern of temperaturedependent color change found in T. septentrionalis we may conclude that pigments are more dispersed at body temperatures around Tp than at other lower or higher levels
Summary
Color change is mediated by synchronous intracellular transport of pigmented organelles in chromatophores and has functional roles in signaling (visual communication), background matching (camouflage), and thermoregulation (Baling et al, 2016; Smith et al, 2016a,b). Thermoregulation is important for animals because body temperature affects numerous physiological and. Animals regulate body temperature by a combination of behavioral and physiological mechanisms. Body temperature is dependent on environmental temperature in ectotherms, and this is especially true for those in thermally uniformed environments where behavioral thermoregulation is constrained (Angilletta, 2001; Muri et al, 2015). Morphological color is determined by the number and quality of chromatophores in the dermis, and physiological color by the relative state of pigment dispersion and aggregation within each chromatophore (Ligon and McCartney, 2016)
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