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Skull morphology and diet
Iguanas have developed an herbivorous
A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpar ...
lifestyle, foraging exclusively on vegetation and foliage. To acquire, process, and digest plant matter, herbivorous lizards must have a higher bite force relative to their size in comparison to carnivorous
A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other so ...
or omnivorous
An omnivore () is an animal that has the ability to eat and survive on both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize the nut ...
reptiles. The skull of the iguana has undergone modifications resulting in a strong bite force and efficient processing of vegetation, according to one study. To accomplish this biomechanically, herbivorous lizards have taller and wider skulls, shorter snouts, and larger bodies relative to carnivorous and omnivorous reptiles. Increasing the strength of the skull allows for increased muscle presence and increases the ability of the skull to withstand stronger forces.[
Furthermore, the teeth of the iguana are ]acrodont Acrodonty (from Greek ''akros'' 'highest' + ''dont'' 'tooth') is an anatomical placement of the teeth at the summit of the alveolar ridge of the jaw, without sockets, characteristic of bony fish. Functionally, acrodont tooth implantation may be rela ...
al, meaning that their teeth sit on top of the surface of the jaw bone and project upwards. The teeth themselves are small and serrated - designed to grasp and shear food.[
]
Reproduction
Male iguanas, like other male examples of Squamata, have two hemipenes
A hemipenis (plural hemipenes) is one of a pair of intromittent organs of male squamates ( snakes, lizards and worm lizards). Hemipenes are usually held inverted within the body, and are everted for reproduction via erectile tissue, much like ...
. During copulation, one hemipenis is inserted into the female's cloacal vent. A female can store 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.
Mating/courtship
Iguanas tend to follow a promiscuous or polygynadrous 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 a pheromone secreted from the femoral pore Femoral pores are a part of a holocrine secretory gland found on the inside of the thighs of certain lizards and amphisbaenians which releases pheromones to attract mates or mark territory. In certain species only the male has these pores and in ...
s on the dorsal side of their hind limbs. Male behavior during sexual competition involves head bobbing, extending and retracting their dewlap, 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 of r-strategy
In ecology, ''r''/''K'' selection theory relates to the selection of combinations of traits in an organism that trade off between quantity and quality of offspring. The focus on either an increased quantity of offspring at the expense of individ ...
reproduction.
Phylogeny
A phylogeny based on nuclear protein-coding genes, reviewed by Vidal and Hedges (2009), suggested that the subclade
In genetics, a subclade is a subgroup of a haplogroup.
Naming convention
Although human mitochondrial DNA (mtDNA) and Y chromosome DNA (Y-DNA) haplogroups and subclades are named in a similar manner, their names belong to completely separate sys ...
Iguania is in a group with snakes and anguimorphs (lizards). These groups share an oral gland capable of secreting toxins (a derived trait). The phylogeny based on whole mitochondrial genomes, though, as proposed by Rest et al. (2003), places the green iguana as the closest relative of the mole skink (''Plestiodon egregius'').[ ]Lepidosaurs
The Lepidosauria (, from Greek meaning ''scaled lizards'') is a subclass or superorder of reptiles, containing the orders Squamata and Rhynchocephalia. Squamata includes snakes, lizards, and amphisbaenians. Squamata contains over 9,000 specie ...
are reptiles with overlapping scales, and within this group both iguanians and tuataras (''Sphenodon'') project their tongues to seize prey items instead of using their jaws, which is called tongue prehension. Iguanians are the only lineage within the Squamata that display this trait, meaning that it was gained independently in both iguanians and tuataras. Iguanians are also the only squamates that primarily use their sight to identify and track prey rather than chemoreception or scent, and employ an ambush technique of catching prey instead of active searching.
A study by Breuil ''et al.'' (2020) found the taxonomy of the genus ''Iguana'' as follows, with ''I. delicatissima'' being the most basal member of the group. The species are classified as subspecies based on the ReptileDatabase definitions.
The Reptile Database synonymizes ''I. rhinolopha'' with ''I. iguana'', only considering it a distinctive population, and recognizes ''I. insularis'' and ''I. melanoderma'' as subspecies of ''I. iguana''. Four subspecies of green iguana are recognized under this treatment: ''I. i. insularis'' (Saint Vincent & the Grenadines
Saint Vincent and the Grenadines () is an island country in the Caribbean. It is located in the southeast Windward Islands of the Lesser Antilles, which lie in the West Indies at the southern end of the eastern border of the Caribbean Sea wh ...
and Grenada
Grenada ( ; Grenadian Creole French: ) is an island country in the West Indies in the Caribbean Sea at the southern end of the Grenadines island chain. Grenada consists of the island of Grenada itself, two smaller islands, Carriacou and ...
), ''I. i. sanctaluciae'' ( Saint Lucia), ''I. i. melanoderma'' (parts of the northern Lesser Antilles, and potentially coastal Venezuela, the Virgin Islands, and Puerto Rico), and ''I. i. iguana'' (mainland South America).
Extant species
Two extant species in the genus ''Iguana'' are widely recognized.
Subspecies
Three Caribbean
The Caribbean (, ) ( es, El Caribe; french: la Caraïbe; ht, Karayib; nl, De Caraïben) is a region of the Americas that consists of the Caribbean Sea, its islands (some surrounded by the Caribbean Sea and some bordering both the Caribbean S ...
subspecies of the green iguana are also recognized:
The Central American iguana (''I. rhinolopha'' or ''I. i. rhinolopha''), sometimes considered a distinct species, is largely considered synonymous with ''I. iguana'', as the presence of horns does not necessarily indicate a new species or subspecies. The two described subspecies of ''I. insularis'' (the Saint Lucia horned iguana, ''I. i. sanctaluciae'', and the Grenadines horned iguana, ''I. i. insularis'') were originally described as subspecies of ''I. iguana'', although they are genetically very similar and may not be separate subspecies from one another. Recent studies have recovered ''I. rhinolopha'' and ''I. insularis'' as distinct species based on genetics, but the Reptile Database disagrees with these conclusions, and classifies ''I. rhinolopha'' as synonymous with ''I. iguana'', and ''I. insularis'' as a subspecies of ''I. iguana''. The Curaçao population of green iguanas shows major genetic divergence and may also represent an as-of-yet undescribed species
In taxonomy, an undescribed taxon is a taxon (for example, a species) that has been discovered, but not yet formally described and named. The various Nomenclature Codes specify the requirements for a new taxon to be validly described and named. U ...
or subspecies.
As food
Iguanas have historically featured in the culinary traditions of Mexico and Central America. Iguana meat is also consumed in parts of the United States and Puerto Rico.
Also, the eggs of iguana are consumed in some parts of Latin America, such as Nicaragua and Colombia.
References
Further reading
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External links
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{{Authority control
Lizard genera
Lizards of Central America
Lizards of the Caribbean
Lizards of North America
Lizards of South America
Taxa named by Josephus Nicolaus Laurenti
cs:Leguánovití
de:Leguan