The thermal dependence and molecular basis of physiological color change in Takydromus septentrionalis (Lacertidae)

Abstract

One 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 3,389 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.

TRPM8 thermosensation in poikilotherms mediates both skin colour and locomotor performance responses to cold temperature

“…In poikilotherms, rapid skin colour changes are produced by the movement of coloured or reflective pigment organelles within the dermal chromatophore cells 15 , 16 . The physiological mechanisms that underlie how temperature change triggers the aggregation/dispersion of pigment-containing organelles to alter skin color are unknown.…”

“…The capacity for absorbed visible light to be converted into heat led to the suggestion that lightening or darkening the skin relates to cooling or warming of body temperature, respectively 3 , 17 . Support for this idea, known as the “thermal melanism hypothesis”, comes from observations in certain poikilotherms that dark-colored individuals warm up faster than their light-colored counterparts 6 , 15 , 16 , 18 , 19 . Changes in skin colour/reflectance, however, underlie ultraviolet (UV) protection and cryptic coloration (i.e.…”

Adaptability of melanocytes post ultraviolet stimulation in patients with melasma

“…Animals change their appearance for signaling/communication, kin recognition, and background matching (camouflage). [1][2][3] The change occurs over multiple timescales, from seconds (cuttlefish and octopus), minutes (some fish), days, and weeks (caterpillars) to months (certain Arctic mammals). 3 In lizards, rapid coloration mediated by the G protein-coupling system helps in thermoregulation 1 ; in human skin, the dynamic pigmentation process is potentially related to genetic factors and ultraviolet (UV) irradiation.…”

“…[1][2][3] The change occurs over multiple timescales, from seconds (cuttlefish and octopus), minutes (some fish), days, and weeks (caterpillars) to months (certain Arctic mammals). 3 In lizards, rapid coloration mediated by the G protein-coupling system helps in thermoregulation 1 ; in human skin, the dynamic pigmentation process is potentially related to genetic factors and ultraviolet (UV) irradiation. Immediate tanning is more prominent in darker individuals and is thought to result from the relocation of melanosomes from the perikaryon to the melanocyte dendrites.…”

“…Color on appearance is mediated by synchronous intracellular transport of pigmented organelles in chromatophores. Animals change their appearance for signaling/communication, kin recognition, and background matching (camouflage) 1–3 . The change occurs over multiple timescales, from seconds (cuttlefish and octopus), minutes (some fish), days, and weeks (caterpillars) to months (certain Arctic mammals) 3 .…”