Many of these lineages exhibit an array of diurnal-specialized adaptations, most notably eye morphologies, with oil droplets which aid in light filtering and spectral tuning, concaviclivate temporal fovea to aid in binocular vision, and ovoid retinal pigmented epithelia (RPE) to aid in light filtering and absorption. The crown group of geckos (Infraorder Gekkota) are hypothesized to be ancestrally nocturnal, with reversals to diurnality occurring in at least 10 lineages. Despite its conservation in tetrapod evolutionary history, several squamate clades do exhibit temporal niche turnover. Temporal niche appears to be phylogenetically conserved across major tetrapod clades and thus many adaptations to specific temporal niches (diurnal, nocturnal, crepuscular, or cathemeral) are shared among closely related species. heliothermy), whereas nocturnal ectotherms thermoregulate through contact with surfaces of different temperatures (i.e. For example, many diurnal ectotherms thermoregulate through basking behavior (i.e. Temporal niche, also known as diel activity niche, is an important aspect of the biology of an organism, necessitating the evolution of specialized morphology, physiology, ecology, and behavior (e.g. Gekko kuhli achieves its hyperpigmented phenotype through a derived developmental pattern, not seen in any other lizard species investigated to date, suggesting novel temporal differences in the migration and/or differentiation of reptilian neural crest derivatives. kuhli is likely an adaptation to limit damage from occasional daytime UV exposure caused by crypsis-associated basking behavior. kuhli accumulates pigment extremely early in embryonic development, unlike a diurnal/heliothermic gecko species, despite having a similar adult phenotype. We found that temporal niche and thermoregulatory behavior predicted the degree of subcutaneous pigment in the eight gecko species examined. kuhli would resemble that of diurnal/heliothermic as opposed to nocturnal/thigmothermic geckos. We further predicted that embryonic pigment accumulation of G. kuhli would exhibit hyperpigmentation of internal structures like that of diurnal/heliothermic geckos. We predicted that nocturnal/potentially-heliothermic G. To investigate this hypothesized association between temporal niche, behavior, and morphology, we characterized adult subcutaneous pigment for eight gecko species and embryonic pigment accumulation for a subset of four of these species, exhibiting diverse temporal niche and thermoregulatory behaviors. kuhli will have independently evolved a hyperpigmented phenotype. Hiding motionless on tree trunks leaves geckos exposed to sunlight during the day. One such species is Gekko ( Ptychozoon) kuhli, a nocturnal, arboreal gecko that uses extreme crypsis to blend in with tree bark. However, some nocturnal species that exhibit extreme crypsis may be exposed to sunlight and UV and require some means of mediating that damage. Typically, nocturnal species do not require these protections from ultraviolet light. Many smaller squamates have accomplished this protection by hyperpigmentation of the peritoneum and subcutaneous dorsum. Diurnal, heliothermic squamates (lizards and snakes) that bask require protection from ultraviolet radiation (UV) that can damage internal organs such as the brain, viscera, and gonads. Evolutionary transitions in temporal niche necessitates specialized morphology, physiology, and behaviors.
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