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Gecko — Grokipedia Fact-checked by Grok 3 months ago Gecko Ara Eve Leo Sal 1x Geckos are small to medium-sized lizards belonging to the family Gekkonidae , distinguished by their cylindrical or depressed bodies covered in granular or velvety scales, large protruding eyes with vertical slit pupils protected by a fixed transparent spectacle (brille) rather than movable eyelids, and specialized adhesive pads on their toes consisting of microscopic setae that enable them to climb smooth vertical surfaces and even ceilings with ease. [1] The family Gekkonidae represents the largest and most diverse group within the suborder Gekkota, encompassing approximately 1,700 species across about 64 genera, with a global distribution spanning tropical, subtropical, and some temperate regions on all continents except Antarctica . [2] Highest species richness occurs in countries such as Australia , India , Madagascar , and Malaysia , reflecting ancient evolutionary radiations dating back over 200 million years to the Mesozoic era, with ongoing discoveries continuing to increase known diversity. [3] These lizards inhabit a wide array of environments, from arid deserts and rocky outcrops to humid rainforests, woodlands, and urban areas, often favoring crevices, bark, or foliage for shelter. [1] Ecologically, geckos are predominantly nocturnal or crepuscular predators with a generalist diet focused on arthropods such as insects and spiders, though larger species may consume small vertebrates, nectar , or fruit . [4] They exhibit notable behavioral adaptations, including autotomy of the tail for escape (with regeneration possible), prehensile tails in some species for grasping, and unique vocalizations—such as chirps, barks, or screams—that serve for territorial defense, mating, or alarm, setting them apart from most other lizards . [4] Reproduction is typically oviparous, with females laying one to two hard-shelled or parchment-like eggs per clutch in concealed sites, incubated for several weeks before hatching into miniature versions of adults. [4] While many species thrive in natural habitats, some, like house geckos, have become widespread through human-mediated dispersal, highlighting their adaptability and role in controlling pest insects in human settlements. [3] Introduction Etymology The word "gecko" derives from the Malay "gēkoq" or "ge'koq," an onomatopoeic term imitating the animal's distinctive vocalization, such as the chirping or barking calls made by many species during mating or territorial displays. [5] This Malay word itself is borrowed from the Javanese "tokek," which similarly mimics the sound produced by geckos like the tokay species . [6] The term entered scientific nomenclature in 1768 when Ignaz von Laurenti established the genus Gekko in his work Synopsis Naturae , designating Gekko gecko (the tokay gecko ) as the type species ; this built on Carl Linnaeus's earlier 1758 description of the same animal as Lacerta gecko in Systema Naturae . In English, "gecko" first appeared in print in 1774, reflecting European colonial encounters with Southeast Asian fauna , though earlier variant spellings like "chacco" (1711) and "jackoa" (1727) had been used. [5] In binomial nomenclature , the repetition in Gekko gecko exemplifies tautonymy, directly echoing the onomatopoeic root to honor the animal's vocal traits, a convention permitted under the International Code of Zoological Nomenclature for such cases. [6] Across Southeast Asia , geckos bear diverse cultural names rooted in their sounds or habitats, including "tokek" in Indonesian and Javanese, "tuko" or "butiki" in Filipino languages for larger species , "chee chak" or "chi chak" in Malay, and "jing-joke" in Thai; smaller species are often simply called "house lizards " (e.g., "rumah tokek" in Malay or equivalents in regional dialects) due to their prevalence around human homes. [7] General characteristics Geckos are small to medium-sized lizards belonging to the infraorder Gekkota of the order Squamata , encompassing more than 2,300 described species across six families. [8] This diverse clade is characterized by adaptations suited to nocturnal, scansorial ( climbing ), and primarily insectivorous lifestyles, distinguishing them from many other lizard groups through unique cranial modifications such as fused frontals and an edentulous palate in crown-group members. [9] A suite of unifying traits defines geckos, including the lack of movable eyelids in most species (replaced by a transparent spectacle that they clean with their tongue ), nocturnal activity in the majority, the capacity for vocalization through chirping or clicking sounds, and specialized adhesive toe pads composed of lamellae that enable vertical climbing and adhesion to smooth surfaces. [10] These features, present in over 60% of species for the toe pads alone, underscore their evolutionary success in diverse habitats ranging from forests to deserts. [10] Geckos display considerable variation in size, with the smallest species, Sphaerodactylus ariasae (Jaragua dwarf gecko), reaching a total length of just 1.6 cm as adults, representing one of the minimal sizes for terrestrial amniotes. [11] At the opposite extreme, the New Caledonian giant gecko ( Rhacodactylus leachianus ) can exceed 40 cm in total length and weigh up to 500 grams, making it the largest extant gecko species. [12] Their general body plan features a cylindrical form with soft, delicate skin , short stout limbs adapted for agility, and disproportionately large heads housing vertical pupils and robust dentition . [10] Physical characteristics Body structure and size Geckos exhibit considerable morphological diversity in body shape, adapted to various ecological niches. Robust forms, such as the tokay gecko ( Gekko gecko ), feature a dorso-ventrally flattened body with powerful, well-defined limbs suited for climbing on vertical surfaces. [13] In contrast, slender body shapes are common in terrestrial or sand-dwelling species, exemplified by Stenodactylus petrii , which facilitates burrowing and rapid movement across open substrates. [14] Leaf-like morphologies, seen in genera like Uroplatus (e.g., U. phantasticus ), involve flattened bodies with irregular skin flaps and textured surfaces that enhance camouflage against foliage and bark in forested habitats. [14] [15] Limb adaptations in geckos vary with lifestyle, though most species retain the primitive condition of five toes per foot. Fossorial species, such as Chondrodactylus angulifer , often display reduced digit lengths, particularly in the third toe, which shortens the out-lever arm to improve force generation during digging. [13] Prehensile tails, capable of grasping branches, have evolved independently in arboreal genera including Correlophus (crested geckos) and Rhacodactylus , aiding stability during climbing. [16] Skeletal features contribute to the geckos' functional versatility. The skull is notably flexible due to a kinetic construction , including a streptostylic quadrate bone that pivots freely, enabling a wide jaw gape for prey capture. [17] Unlike many lizards with dermal armor, geckos generally lack osteoderms across the body, resulting in smooth cranial bones without extensive sculpturing, which supports lightweight construction and cranial mobility. [18] [19] Gecko sizes span a broad range, from the diminutive Sphaerodactylus ariasae at 18 mm snout-vent length (SVL) to the giant Rhacodactylus leachianus reaching 360 mm SVL, reflecting adaptations to microhabitats from leaf litter to tree trunks. [20] Growth follows a determinate pattern, with juveniles achieving adult proportions early; neonates closely resemble miniature adults in form due to direct development without larval stages. [20] Sexual dimorphism in size occurs in several lineages, such as the day geckos ( Phelsuma ), where males are typically larger than females, often exceeding them in SVL and mass. [21] [22] Skin and molting Gecko skin consists of a thin, semi-transparent epidermis overlaid with small, granular keratin scales that provide protection while maintaining flexibility essential for climbing and navigating varied terrains. The outer epidermal layer is primarily composed of β- keratin , a protein that forms a durable yet pliable barrier against abrasion and desiccation , distinguishing it from the more rigid α- keratin dominant in other vertebrate skins. This structure allows geckos to thrive in diverse habitats, from arid deserts to humid forests, by balancing toughness with elasticity. [23] [24] [25] The renewal of this skin occurs through ecdysis , a complete shedding process where the entire outer layer is sloughed off in one continuous piece from the snout to the tail tip, in contrast to the fragmented molting observed in many other lizard species. This holistic shedding typically happens every 2–6 weeks in growing juveniles, influenced by factors such as temperature and metabolic rate, while adults may cycle less frequently, around every 4–8 weeks. The process is hormonally regulated, primarily by thyroid hormones like thyroxine, which accelerate epidermal cell proliferation and separation of the old stratum corneum ; disruptions in thyroid function can lead to incomplete or irregular ecdysis . [26] [27] In captivity, improper humidity levels can lead to incomplete shedding (dysecdysis), causing stuck skin that may harm the animal if not addressed. [28] Recommended practices include increasing enclosure humidity through misting or moist hides to facilitate natural shedding. Controversial methods, such as blowing air under the skin to assist removal, have been criticized by reptile experts for potential risks including skin damage, stress, eye irritation, and bacterial transmission; safer alternatives are always preferred. [29] [28] Gecko skin displays intricate cryptic patterns of bands, spots, or mottling that facilitate camouflage against predators and prey by mimicking natural