The word "iguana" is derived from the originalTaino name for the species,iwana.[9]In addition to the two species in the genusIguana, several other related genera in the same family have common names of the species including the word "iguana".[10]
Iguanas are largelizards that can range from 1.2 to 2.0 m (4 to 6.5 ft) in length, including their tails. They possess adewlap and a row of elongated scales running from the midline of theirnecks down to theirtails. Iguanas have varying types of scales covering different areas of their body; for example, some large, roundtuberculate scales are scattered around the lateral region of the neck among smaller, overlapping scales.[12] The scales on thedorsal trunk of their bodies are also thicker and more tightly packed than those on theventral sides.[12] These scales may be a variety of colors and are not always visible from close distances. They have a large, round scale on their cheeks known as a subtympanic shield.[13]
Iguana eating flower.
Iguanas have keen vision and can see shapes, shadows, colors, and movement at long distances. Their visual acuity enables them to navigate through crowded forests and to locate food. They employ visual signals to communicate with other members of the same species.[13]
Thetympanum, the iguana'seardrum, is located above the subtympanic shield (or "ear shield") behind each eye.
Iguanas are often hard to spot, as they tend to blend into their surroundings, and their coloration enables them to hide from larger predators.[13]
Like mostreptiles, an iguana has a three-chamberedheart with two atria, one ventricle, and two aortae with asystemic circulation.[14]The muscles of an iguana are very light in color due to the high proportion offast-twitch, glycolytic muscle fibers (type A). TheseA fibers are not very vascularized and are low inmyoglobin, giving them their pale look. This high density ofA fibers allows iguanas to move very quickly for a short period of time, which facilitates short bursts of movement, but is inefficient for long duration movement, since cellular respiration inA fibers isanaerobic.
Several species of lizards, including the iguanas, have a pale scale towards the back of their heads marking theparietal eye. This organ is sensitive to changes in illumination and sends signals to thepineal gland noting the change between day and night. A photopigment commonly found in thelamprey, known as parapinopsin, is also found in the iguana, and is sensitive toultraviolet light and aids in the signaling between day and night.[15]
Iguanas have developed anherbivorous lifestyle, foraging exclusively on vegetation and foliage.[16] To acquire, process, and digest plant matter, herbivorous lizards must have a higher bite force relative to their size in comparison tocarnivorous oromnivorous reptiles. The skull of the iguana has undergone modifications resulting in a strong bite force and efficient processing ofvegetation, according to one study.[17] To accomplish thisbiomechanically, herbivorous lizards have taller and wider skulls, shorter snouts, and larger bodies relative to carnivorous and omnivorous reptiles.[17] Increasing the strength of the skull allows for increased muscle presence and increases the ability of the skull to withstand stronger forces.[18]
Albino Iguana - Bred to be kept as a petGreen iguana skull and teeth: The teeth of thegreen iguana sit on the surface of the jawbone, known asacrodontal placement.[19]Simple phylogeny withReptilia highlighted in green: Iguanians are withinLepidosauria.
Furthermore, the teeth of the iguana areacrodontal, meaning that their teeth sit on top of the surface of the jaw bone[19] and project upwards. The teeth themselves are small and serrated - designed to grasp and shear food.[20]
Male iguanas, like other male examples ofSquamata, have twohemipenes. During copulation, one hemipenis is inserted into the female'scloacal vent.[21] A female canstore sperm from previous mates for several years to continue to fertilize her eggs in case she finds no male within her territory when she is ready to lay again.[22][23][24]
Iguanas tend to follow a promiscuous orpolygynandrous mating style during the dry season. Mating during the dry season ensures that their offspring will hatch during the wet or rainy season when food will be more plentiful. Females control large territories, where they make several nests. Males compete for the females in an area and mark their won territory with apheromone secreted from thefemoral pores on the dorsal side of their hind limbs. Male behavior during sexual competition involves head bobbing, extending and retracting theirdewlap, nuzzling and biting the necks of females, and on occasion, changing color. Once a female chooses a male, he straddles the female and holds her in place by biting onto her shoulder, which sometimes leaves scars on females. After copulation, eggs are laid within several nests and allowed to incubate. This low level of parental intervention with their offspring makes iguanas an example ofr-strategy reproduction.[citation needed]
Aphylogeny based on nuclear protein-coding genes, reviewed by Vidal and Hedges (2009), suggested that thesubcladeIguania is in a group withsnakes andanguimorphs (lizards). These groups share an oral gland capable of secreting toxins (a derived trait).[25] The phylogeny based on wholemitochondrial genomes, though, as proposed by Rest et al. (2003), places thegreen iguana as the closest relative of themole skink (Plestiodon egregius).[26]Lepidosaurs are reptiles with overlapping scales, and within this group both iguanians andtuataras (Sphenodon) project their tongues to seize prey items instead of using their jaws, which is called tongueprehension. Iguanians are the only lineage within theSquamata that display this trait, meaning that it was gained independently in both iguanians and tuataras.[25] Iguanians are also the only squamates that primarily use their sight to identify and track prey rather than chemoreception or scent, and employ anambush technique of catching prey instead of active searching.[25]
A study by Breuilet al. (2020) found the taxonomy of the genusIguana as follows, withI. delicatissima being the mostbasal member of the group.[7] The species are classified as subspecies based on the ReptileDatabase definitions.
The Reptile Database synonymizesI. rhinolopha withI. iguana, only considering it a distinctive population, and recognizesI. insularis andI. melanoderma assubspecies ofI. iguana. Four subspecies of green iguana are recognized under this treatment:I. i. insularis (Saint Vincent & the Grenadines andGrenada),I. i. sanctaluciae (Saint Lucia),I. i. melanoderma (parts of the northern Lesser Antilles, and potentially coastalVenezuela, theVirgin Islands, andPuerto Rico), andI. i. iguana (mainland South America).
Saba,Montserrat, and formerlyRedonda, but also possibly coastal Venezuela, the Virgin Islands, and Puerto Rico (at least parts of this range may derive from (pre)historic introductions).
The Central American iguana (I. rhinolopha orI. i. rhinolopha), sometimes considered a distinct species, is largely considered synonymous withI. iguana, as the presence of horns does not necessarily indicate a new species or subspecies. The two described subspecies ofI. insularis (the Saint Lucia horned iguana,I. i. sanctaluciae, and the Grenadines horned iguana,I. i. insularis) were originally described as subspecies ofI. iguana, although they are genetically very similar and may not be separate subspecies from one another.[28] Recent studies have recoveredI. rhinolopha andI. insularis as distinct species based on genetics, but the Reptile Database disagrees with these conclusions, and classifiesI. rhinolopha as synonymous withI. iguana, andI. insularis as a subspecies ofI. iguana.[29] TheCuraçao population of green iguanas shows major genetic divergence and may also represent an as-of-yetundescribed species or subspecies.[7][30]
Iguanas have historically featured in the culinary traditions of Mexico and Central America. Iguana meat is also consumed in parts of the United States, Dominican Republic, and Puerto Rico.[31]Also, the eggs of iguana are consumed in some parts of Latin America, such as Nicaragua and Colombia.[32]
^Laurenti, J.N. (1768).Specimen Medicum, Exhibens Synopsin Reptilium Emendatam cum Experimentis circa Venena [Medical specimen, presenting a revised synopsis of reptiles with experiments on venom] (in Latin).
^Coles, William (2002).Green iguana(PDF) (Report). U.S.V.I. Animal Fact Sheet. Vol. 08. Department of Planning and Natural Resources, US Virgin Islands Division of Fish and Wildlife. Archived fromthe original(PDF) on 11 December 2007.
^Herrel, Anthony (2009). "Jaw and hyolingual muscle activity patterns and bite forces in the herbivorous lizardUromastyx acanthinurus".Archives of Oral Biology.54 (8):772–782.doi:10.1016/j.archoralbio.2009.05.002.PMID19481732.
^Rest, Joshua S.; Ast, Jennifer C.; Austin, Christopher C.; Waddell, Peter J.; Tibbetts, Elizabeth A.; Hay, Jennifer M.; Mindell, David P. (2003). "Molecular systematics of primary reptilian lineages and the tuatara mitochondrial genome".Molecular Phylogenetics and Evolution.29 (2):289–297.Bibcode:2003MolPE..29..289R.doi:10.1016/S1055-7903(03)00108-8.PMID13678684.
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