Tuatara
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The tuatara (Sphenodon punctatus) is a species of reptile endemic to New Zealand. Despite its close resemblance to lizards, it is actually the only extant member of a distinct lineage, the previously highly diverse order Rhynchocephalia.<ref name="TerraNature">Template:Cite web</ref> The name Template:Lang is derived from the Māori language and means "peaks on the back".<ref name="KCC">Template:Cite web</ref>
The single extant species of tuataraTemplate:Efn is the only surviving member of its order, which was highly diverse during the Mesozoic era.<ref name="Herrera-Flores 2017" /> Rhynchocephalians first appeared in the fossil record during the Triassic, around 240 million years ago,<ref name="Jones et al 2013">Template:Cite journal</ref> and reached worldwide distribution and peak diversity during the Jurassic, when they represented the world's dominant group of small reptiles. Rhynchocephalians declined during the Cretaceous, with their youngest records outside New Zealand dating to the Paleocene. Their closest living relatives are squamates (lizards and snakes). Tuatara are of interest for studying the evolution of reptiles.
Tuatara are greenish brown and grey, and measure up to Template:Convert from head to tail-tip and weigh up to Template:Convert<ref name="san diego">Template:Cite web</ref> with a spiny crest along the back, especially pronounced in males. They have two rows of teeth in the upper jaw overlapping one row on the lower jaw, which is unique among living species. They are able to hear, although no external ear is present, and have unique features in their skeleton.
Tuatara are sometimes referred to as "living fossils".<ref name="TerraNature"/> This term is currently deprecated among paleontologists and evolutionary biologists. Although tuatara have preserved the morphological characteristics of their Mesozoic ancestors (240–230 million years ago), there is no evidence of a continuous fossil record to support the idea that the species has survived unchanged since that time.<ref name="MeloroJones2012">Template:Cite journal</ref><ref name="Herrera-Flores 2017">Template:Cite journal</ref>
The species has between five and six billion base pairs of DNA sequence, nearly twice that of humans.<ref>Template:Cite web</ref>
The tuatara has been protected by law since 1895.<ref>Template:Harvnb</ref><ref>Template:Cite book</ref> Tuatara, like many of New Zealand's native animals, are threatened by habitat loss and introduced predators, such as the Polynesian rat (Rattus exulans). Tuatara were extinct on the mainland, with the remaining populations confined to 32 offshore islands,<ref name="DoC">Template:Cite web</ref> until the first North Island release into the heavily fenced and monitored Karori Wildlife Sanctuary (now named "Zealandia") in 2005.<ref name="karori">Template:Cite web</ref> During routine maintenance work at Zealandia in late 2008, a tuatara nest was uncovered,<ref name=":0">Template:Cite press release</ref> with a hatchling found the following autumn.<ref>Template:Cite press release</ref> This is thought to be the first case of tuatara successfully breeding in the wild on New Zealand's North Island in over 200 years.<ref name=":0" />
Taxonomy and evolution
[edit]Relationships of the tuatara to other living reptiles and birds, after Simões et al. 2022<ref>Template:Cite journal</ref> Template:Clade
Tuatara, along with other now-extinct members of the order Rhynchocephalia, belong to the superorder Lepidosauria, as do the order Squamata, which includes lizards and snakes. Squamates and tuatara both show caudal autotomy (loss of the tail-tip when threatened), and have transverse cloacal slits.<ref name="encyclo">Template:Cite book</ref>
Tuatara were originally classified as lizards in 1831 when the British Museum received a skull. John Edward Gray used the name Sphenodon to describe the skull; this remains the current scientific name for the genus.<ref name="Original">Template:CiteQ</ref><ref>Template:Harvnb</ref> Sphenodon is derived from the Greek for "wedge" (σφήν, σφηνός/sphenos) and "tooth" (ὀδούς, ὀδόντος/odontos).<ref>Template:Cite encyclopedia</ref> In 1842, Gray described a member of the species as Hatteria punctata, not realising that it and the skull he received in 1831 were both tuatara.<ref>Template:CiteQ</ref><ref Name="Gray1869">Template:CiteQ</ref>
The genus remained misclassified as a lizard until 1867, when Albert C. L. G. Günther of the British Museum noted features similar to birds, turtles, and crocodiles. He proposed the order Rhynchocephalia (meaning "beak head") for the tuatara and its fossil relatives.<ref name="Günther1867">Template:Cite journal</ref> Since 1869, Sphenodon punctatus (or the variation Sphenodon punctatum in some earlier sources) has been used as the scientific name for the species.<ref name="Gray1869" />
At one point, many disparate species were incorrectly referred to the Rhynchocephalia, resulting in what taxonomists call a "wastebasket taxon".<ref name="fraser">Template:Cite book</ref> Williston in 1925 proposed the Sphenodontia to include only tuatara and their closest fossil relatives.<ref name="fraser" /> However, Rhynchocephalia is the older name<ref name="Günther1867" /> and in widespread use today. Many scholars use Sphenodontia as a subset of Rhynchocephalia, including almost all members of Rhynchocephalia, apart from the most primitive representatives of the group.<ref name=":9" />
The earliest rhynchocephalian, Wirtembergia, is known from the Middle Triassic of Germany, around 240 million years ago.<ref name=":9">Template:Cite journal</ref> During the Late Triassic, rhynchocephalians greatly diversified,<ref name="Herrera-Flores 2017" /> going on to become the world's dominant group of small reptiles during the Jurassic period,<ref name=":20">Template:Cite journal</ref> when the group was represented by a diversity of forms, including the aquatic pleurosaurs and the herbivorous eilenodontines.<ref name=":20" /> The earliest members of Sphenodontinae, the clade which includes the tuatara, are known from the Early Jurassic of North America. The earliest representatives of this group are already very similar to the modern tuatara.<ref name=":14">Template:Cite journal</ref> Rhynchocephalians declined during the Cretaceous period,<ref>Template:Cite journal</ref> possibly due to competition with mammals and lizards,<ref name="Jonesetal2009a" /> with their youngest record outside of New Zealand being of Kawasphenodon, known from the Paleocene of Patagonia in South America.<ref name=":15">Template:Cite journal</ref>
A species of sphenodontine is known from the Miocene Saint Bathans fauna from Otago in the South Island of New Zealand. Whether it is referable to Sphenodon proper is not entirely clear, but it is likely to be closely related to tuatara. The ancestors of the tuatara were likely already present in New Zealand prior to its separation from Antarctica around 82–60 million years ago.<ref name="Jonesetal2009a">Template:Cite journal</ref>
Cladogram of the position of the tuatara within Sphenodontia, after Simoes et al., 2022:<ref name=":12">Template:Cite journal</ref>Template:Clade
Species
[edit]While there is currently considered to be only one living species of tuatara, two species were previously identified: Sphenodon punctatus, or northern tuatara, and the much rarer Sphenodon guntheri, or Brothers Island tuatara, which is confined to North Brother Island in the Cook Strait.<ref name="BBC">Template:Cite web</ref> The specific name punctatus is Latin for "spotted",<ref>Template:Cite book</ref> and guntheri refers to German-born British herpetologist Albert Günther.<ref>Template:Cite book xiii + 296 pp. (Sphenodon guntheri, p. 110).</ref> A 2009 paper re-examined the genetic bases used to distinguish the two supposed species of tuatara, and concluded they represent only geographic variants, and only one species should be recognised.<ref name="Hay">Template:Cite journal</ref> Consequently, the northern tuatara was re-classified as Sphenodon punctatus punctatus and the Brothers Island tuatara as Sphenodon punctatus guntheri. The Brothers Island tuatara has olive brown skin with yellowish patches, while the colour of the northern tuatara ranges from olive green through grey to dark pink or brick red, often mottled, and always with white spots.<ref name="karori" /><ref name="encyclo" /><ref name="lutz16">Template:Harvnb</ref> In addition, the Brothers Island tuatara is considerably smaller.<ref name="NZRG">Template:Cite book</ref> However, individuals from Brothers Island could not be distinguished from other modern and fossil samples on the basis of jaw morphology.<ref name="Vaux 2019">Template:Cite journal</ref>
An extinct species of Sphenodon was identified in November 1885 by William Colenso, who was sent an incomplete subfossil specimen from a local coal mine. Colenso named the new species S. diversum.<ref name="colenso1885">Template:Cite journal</ref> Fawcett and Smith (1970) consider it a synonym to the subspecies, based on a lack of distinction.<ref>Template:Cite journal</ref>
Description
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Tuatara are the largest reptiles in New Zealand.<ref>Template:Cite web</ref> Adult S. punctatus males measure Template:Convert in length and females Template:Convert.<ref name="encyclo" /> Tuatara are sexually dimorphic, males being larger.<ref name="encyclo" /> The San Diego Zoo even cites a length of up to Template:Convert.<ref>Template:Cite web</ref> Males weigh up to Template:Convert, and females up to Template:Convert.<ref name="encyclo" /> Brothers Island tuatara are slightly smaller, weighing up to 660 g (1.3 lb).<ref name="NZRG" />
Their lungs have a single chamber with no bronchi.<ref>Template:Cite book</ref>
The tuatara's greenish brown colour matches its environment, and can change over its lifetime. Tuatara shed their skin at least once per year as adults,<ref name="lutz16" /> and three or four times a year as juveniles. Tuatara sexes differ in more than size. The spiny crest on a tuatara's back, made of triangular, soft folds of skin, is larger in males, and can be stiffened for display. The male abdomen is narrower than the female's.<ref>Template:Cite web</ref>
Skull
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Unlike the vast majority of lizards, the tuatara has a complete lower temporal bar closing the lower temporal fenestra (an opening of the skull behind the eye socket), caused by the fusion of the quadrate/quadratojugal (which are fused into a single element in adult tuatara) and the jugal bones of the skull. This is similar to the condition found in primitive diapsid reptiles. However, because more primitive rhynchocephalians have an open lower temporal fenestra with an incomplete temporal bar, this is thought to be derived characteristic of the tuatara and other members of the clade Sphenodontinae, rather than a primitive trait retained from early diapsids. The complete bar is thought to stabilise the skull during biting.<ref name=":02">Template:Cite journal</ref>
The tip of the upper jaw is chisel- or beak-like and separated from the remainder of the jaw by a notch,<ref name="Günther1867" /> this structure is formed from fused premaxillary teeth, and is also found in many other advanced rhynchocephalians.<ref>Template:Cite journal</ref> The teeth of the tuatara, and almost all other rhynchocephalians, are described as acrodont, as they are attached to the apex of the jaw bone. This contrast with the pleurodont condition found in the vast majority of lizards, where the teeth are attached to the inward-facing surface of the jaw. The teeth of the tuatara are extensively fused to the jawbone, making the boundary between the tooth and jaw difficult to discern, and the teeth lack roots and are not replaced during the lifetime of the animal, unlike those of pleurodont lizards.<ref>Template:Cite journal</ref> It is a common misconception that tuatara lack teeth and instead have sharp projections on the jaw bone;<ref name="lutzp27">Template:Harvnb</ref> histology shows that they have true teeth with enamel and dentine with pulp cavities.<ref name="Kieser2009">Template:Cite journal</ref> As their teeth wear down, older tuatara have to switch to softer prey, such as earthworms, larvae, and slugs, and eventually have to chew their food between smooth jaw bones.<ref>Template:Cite news</ref>
The tuatara possesses palatal dentition (teeth growing from the bones of the roof of the mouth), which is ancestrally present in reptiles (and tetrapods generally).<ref name=":13">Template:Cite journal</ref> While many of the original palatal teeth present in reptiles have been lost,<ref name=":13" /> as in all other known rhynchocephalians, the row of teeth growing from the palatine bones in the tuatara have been enlarged, and as in other members of Sphenodontinae the palatine teeth are orientated parallel to the teeth in the maxilla; during biting the teeth of the lower jaw slot between the two upper tooth rows.<ref name="Jones2008">Template:Cite journal</ref> The structure of the jaw joint allows the lower jaw to slide forwards after it has closed between the two upper rows of teeth.<ref name="Jones et al. 2012">Template:Cite journal</ref> This mechanism allows the jaws to shear through chitin and bone.<ref name="encyclo" />
The brain of Sphenodon fills only half of the volume of its endocranium.<ref name="larsson2001">Template:Cite book</ref> This proportion has been used by paleontologists trying to estimate the volume of dinosaur brains based on fossils.<ref name="larsson2001" /> However, the proportion of the tuatara endocranium occupied by its brain may not be a very good guide to the same proportion in Mesozoic dinosaurs since modern birds are surviving dinosaurs but have brains which occupy a much greater relative volume in the endocranium.<ref name="larsson2001" />
Sensory organs
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Eyes
[edit]The eyes can focus independently, and are specialised with three types of photoreceptive cells, all with fine structural characteristics of retinal cone cells<ref>Template:Cite journal</ref> used for both day and night vision, and a tapetum lucidum which reflects onto the retina to enhance vision in the dark. There is also a third eyelid on each eye, the nictitating membrane. Five visual opsin genes are present, suggesting good colour vision, possibly even at low light levels.<ref name="Gemmell2020">Template:Cite journal</ref>
Parietal eye (third eye)
[edit]Like some other living vertebrates, including some lizards, the tuatara has a third eye on the top of its head called the parietal eye (also called a pineal or third eye) formed by the parapineal organ, with an accompanying opening in the skull roof called the pineal or parietal foramen, enclosed by the parietal bones.<ref name=":1">Template:Cite journal</ref> It has its own lens, a parietal plug which resembles a cornea,<ref>Template:Cite journal</ref> retina with rod-like structures, and degenerated nerve connection to the brain. The parietal eye is visible only in hatchlings, which have a translucent patch at the top centre of the skull. After four to six months, it becomes covered with opaque scales and pigment.<ref name="encyclo" /> While capable of detecting light, it is probably not capable of detecting movement or forming an image.<ref>Template:Cite journal</ref> It likely serves to regulate the circadian rhythm and possibly detect seasonal changes, and help with thermoregulation.<ref name="encyclo" /><ref name=":1" />
Of all extant tetrapods, the parietal eye is most pronounced in the tuatara. It is part of the pineal complex, another part of which is the pineal gland, which in tuatara secretes melatonin at night.<ref name="encyclo" /> Some salamanders have been shown to use their pineal bodies to perceive polarised light, and thus determine the position of the sun, even under cloud cover, aiding navigation.<ref>Template:Cite book</ref>
Hearing
[edit]Together with turtles, the tuatara has the most primitive hearing organs among the amniotes. There is no tympanum (eardrum) and no earhole,<ref name="lutzp27" /> and the middle ear cavity is filled with loose tissue, mostly adipose (fatty) tissue. The stapes comes into contact with the quadrate (which is immovable), as well as the hyoid and squamosal. The hair cells are unspecialised, innervated by both afferent and efferent nerve fibres, and respond only to low frequencies. Though the hearing organs are poorly developed and primitive with no visible external ears, they can still show a frequency response from 100 to 800 Hz, with peak sensitivity of 40 dB at 200 Hz.<ref>Template:Cite web</ref>
Odorant receptors
[edit]Animals that depend on the sense of smell to capture prey, escape from predators or simply interact with the environment they inhabit, usually have many odorant receptors. These receptors are expressed in the dendritic membranes of the neurons for the detection of odours. The tuatara has around 472 receptors, a number more similar to what birds have than to the large number of receptors that turtles and crocodiles may have.<ref name="Gemmell2020" />
Spine and ribs
[edit]The tuatara spine is made up of hourglass-shaped amphicoelous vertebrae, concave both before and behind.<ref name="lutzp27" /> This is the usual condition of fish vertebrae and some amphibians, but is unique to tuatara within the amniotes. The vertebral bodies have a tiny hole through which a constricted remnant of the notochord passes; this was typical in early fossil reptiles, but lost in most other amniotes.<ref>Template:Cite book</ref>
The tuatara has gastralia, rib-like bones also called gastric or abdominal ribs,<ref>Template:Cite web</ref> the presumed ancestral trait of diapsids. They are found in some lizards, where they are mostly made of cartilage, as well as crocodiles and the tuatara, and are not attached to the spine or thoracic ribs. The true ribs are small projections, with small, hooked bones, called uncinate processes, found on the rear of each rib.<ref name="lutzp27" /> This feature is also present in birds. The tuatara is the only living tetrapod with well-developed gastralia and uncinate processes.
In the early tetrapods, the gastralia and ribs with uncinate processes, together with bony elements such as bony plates in the skin (osteoderms) and clavicles (collar bone), would have formed a sort of exoskeleton around the body, protecting the belly and helping to hold in the guts and inner organs. These anatomical details most likely evolved from structures involved in locomotion even before the vertebrates ventured onto land. The gastralia may have been involved in the breathing process in early amphibians and reptiles. The pelvis and shoulder girdles are arranged differently from those of lizards, as is the case with other parts of the internal anatomy and its scales.<ref>Template:Cite web</ref>
Tail and back
[edit]The spiny plates on the back and tail of the tuatara resemble those of a crocodile more than a lizard, but the tuatara shares with lizards the ability to break off its tail when caught by a predator, and then regenerate it. The regrowth takes a long time and differs from that of lizards. Well illustrated reports on tail regeneration in tuatara have been published by Alibardi and Meyer-Rochow.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> The cloacal glands of tuatara have a unique organic compound named tuataric acid.
Age determination
[edit]Currently, there are two means of determining the age of tuatara. Using microscopic inspection, hematoxylinophilic rings can be identified and counted in both the phalanges and the femur. Phalangeal hematoxylinophilic rings can be used for tuatara up to ages 12–14 years, as they cease to form around this age. Femoral rings follow a similar trend, however they are useful for tuatara up to ages 25–35 years. Around that age, femoral rings cease to form.<ref>Template:Cite journal</ref> Further research on age determination methods for tuatara is required, as tuatara have lifespans much longer than 35 years (ages up to 60<ref name="KCC" /> are common, and captive tuatara have lived to over 100 years).<ref name="Disc-Mag-2009-01-26" /><ref name="NZHer-2009-01-26" /><ref name="BBCNews-2009-01-26" /> One possibility could be via examination of tooth wear, as tuatara have fused sets of teeth.
Physiology
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Adult tuatara are terrestrial and nocturnal reptiles, though they will often bask in the sun to warm their bodies. Hatchlings hide under logs and stones, and are diurnal, likely because adults are cannibalistic. Juveniles are typically active at night, but can be found active during the day. The juveniles' movement pattern is attributed to genetic hardwire of conspecifics for predator avoidance and thermal restrictions.<ref>Template:Cite journal</ref> Tuatara thrive in temperatures much lower than those tolerated by most reptiles, and hibernate during winter.<ref>Template:Cite web</ref> They remain active at temperatures as low as Template:Convert,<ref>Template:Cite news</ref> while temperatures over Template:Convert are generally fatal. The optimal body temperature for the tuatara is from Template:Convert, the lowest of any reptile.<ref name="UofM">Template:Cite web</ref> The body temperature of tuatara is lower than that of other reptiles, ranging from Template:Convert over a day, whereas most reptiles have body temperatures around Template:Convert.<ref>Template:Cite journal</ref> The low body temperature results in a slower metabolism.Template:Clear
Ecology
[edit]Burrowing seabirds such as petrels, prions, and shearwaters share the tuatara's island habitat during the birds' nesting seasons. The tuatara use the birds' burrows for shelter when available, or dig their own. The seabirds' guano helps to maintain invertebrate populations on which tuatara predominantly prey, including beetles, crickets, spiders, wētās, earthworms, and snails.<ref name="Sphenodon punctatus Tuatara">Template:Cite web</ref> Their diets also consist of frogs, lizards, and bird's eggs and chicks.<ref name="Vaux 2019" /> Young tuatara are also occasionally cannibalised.<ref name="Sphenodon punctatus Tuatara" /> The diet of the tuatara varies seasonally, and they consume mainly fairy prions and their eggs in the summer.<ref>Template:Cite thesis</ref> In total darkness no feeding attempt was observed,<ref>Template:Cite journal</ref> and the lowest light intensity at which an attempt to snatch a beetle was observed occurred under 0.0125 lux.<ref>Template:Cite journal</ref> The eggs and young of seabirds that are seasonally available as food for tuatara may provide beneficial fatty acids.<ref name="encyclo" /> Tuatara of both sexes defend territories, and will threaten and eventually bite intruders. The bite can cause serious injury.<ref>Template:Cite encyclopedia</ref> Tuatara will bite when approached, and will not let go easily.<ref name="lutz24">Template:Harvnb</ref> Female tuatara rarely exhibit parental behaviour by guarding nests on islands with high rodent populations.<ref>Template:Cite journal</ref>
Tuataras are parasitised by the tuatara tick (Archaeocroton sphenodonti), a tick that directly depends on tuataras.<ref name="godf">Template:Cite journal</ref> These ticks tend to be more prevalent on larger males, as they have larger home ranges than smaller and female tuatara and interact with other tuatara more in territorial displays.<ref>Template:Cite journal</ref>
Reproduction
[edit]Tuatara reproduce very slowly, taking 10 to 20 years to reach sexual maturity.<ref>Template:Cite news</ref> Though their reproduction rate is slow, tuatara have the fastest swimming sperm by two to four times compared to all reptiles studied earlier.<ref>Template:Cite web</ref> Mating occurs in midsummer; females mate and lay eggs once every four years.<ref>Template:Cite journal</ref> During courtship, a male makes his skin darker, raises his crests, and parades toward the female. He slowly walks in circles around the female with stiffened legs. The female will either allow the male to mount her, or retreat to her burrow.<ref>Template:Cite journal</ref> Males do not have a penis; they have rudimentary hemipenes; meaning that intromittent organs are used to deliver sperm to the female during copulation. They reproduce by the male lifting the tail of the female and placing his vent over hers. This process is sometimes referred to as a "cloacal kiss". The sperm is then transferred into the female, much like the mating process in birds.<ref>Template:Harvnb</ref> Along with birds, the tuatara is one of the few members of Amniota to have lost the ancestral penis.<ref>Template:Cite journal</ref>
Tuatara eggs have a soft, parchment-like 0.2 mm thick shell that consists of calcite crystals embedded in a matrix of fibrous layers.<ref>Template:Cite journal</ref> It takes the females between one and three years to provide eggs with yolk, and up to seven months to form the shell. It then takes between 12 and 15 months from copulation to hatching. This means reproduction occurs at two- to five-year intervals, the slowest in any reptile.<ref name="encyclo" /> Survival of embryos has also been linked to having more success in moist conditions.<ref>Template:Cite journal</ref> Wild tuatara are known to be still reproducing at about 60 years of age; "Henry", a male tuatara at Southland Museum in Invercargill, New Zealand, became a father (possibly for the first time) on 23 January 2009, at age 111, with an 80 year-old female.<ref name="NZHer-2009-01-26">Template:Cite news</ref><ref name="BBCNews-2009-01-26">Template:Cite news</ref><ref name="Disc-Mag-2009-01-26" />
The sex of a hatchling depends on the temperature of the egg, with warmer eggs tending to produce male tuatara, and cooler eggs producing females. Eggs incubated at Template:Convert have an equal chance of being male or female. However, at Template:Convert, 80% are likely to be males, and at Template:Convert, 80% are likely to be females; at Template:Convert all hatchlings will be females.<ref name="KCC" /> Some evidence indicates sex determination in tuatara is determined by both genetic and environmental factors.<ref>Template:Cite journal</ref>
Tuatara probably have the slowest growth rates of any reptile,<ref name="encyclo" /> continuing to grow larger for the first 35 years of their lives.<ref name="KCC" /> The average lifespan is about 60 years, but they can live to be well over 100 years old;<ref name="KCC" /> tuatara could be the reptile with the second longest lifespan after tortoises.Template:Citation needed Some experts believe that captive tuatara could live as long as 200 years.<ref name="CNNDad">Template:Cite news</ref> This may be related to genes that offer protection against reactive oxygen species.Template:Explain The tuatara genome has 26 genes that encode selenoproteins and 4 selenocysteine-specific tRNA genes. In humans, selenoproteins have a function of antioxidation, redox regulation and synthesis of thyroid hormones. It is not fully demonstrated, but these genes may be related to the longevity of this animal or may have emerged as a result of the low levels of selenium and other trace elements in the New Zealand terrestrial systems.<ref name="Gemmell2020" />
Genomic characteristics
[edit]The most abundant LINE element in the tuatara is L2 (10%). Most of them are interspersed and can remain active. The longest L2 element found is 4 kb long and 83% of the sequences had ORF2p completely intact. The CR1 element is the second most repeated (4%). Phylogenetic analysis shows that these sequences are very different from those found in other nearby species such as lizards. Finally, less than 1% are elements belonging to L1, a low percentage since these elements tend to predominate in placental mammals.<ref name="Gemmell2020" /> Usually, the predominant LINE elements are the CR1, contrary to what has been seen in the tuatara. This suggests that perhaps the genome repeats of sauropsids were very different compared to mammals, birds and lizards.<ref name="Gemmell2020" />
The genes of the major histocompatibility complex (MHC) are known to play roles in disease resistance, mate choice, and kin recognition in various vertebrate species. Among known vertebrate genomes, MHCs are considered one of the most polymorphic.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> In the tuatara, 56 MHC genes have been identified; some of which are similar to MHCs of amphibians and mammals. Most MHCs that were annotated in the tuatara genome are highly conserved, however there is large genomic rearrangement observed in distant lepidosaur lineages.<ref name="Gemmell2020" />
Many of the elements that have been analyzed are present in all amniotes, most are mammalian interspersed repeats or MIR, specifically the diversity of MIR subfamilies is the highest that has been studied so far in an amniote. 16 families of SINEs that were recently active have also been identified.<ref name="Gemmell2020" />
The tuatara has 24 unique families of DNA transposons, and at least 30 subfamilies were recently active. This diversity is greater than what has been found in other amniotes and in addition, thousands of identical copies of these transposons have been analyzed, suggesting to researchers that there is recent activity.<ref name="Gemmell2020" />
The genome is the second largest known to reptiles. Only the Greek tortoise genome is larger.<ref>Did Lizards Follow Unique Pathways in Sex Chromosome Evolution?</ref> Around 7,500 LTRs have been identified, including 450 endogenous retroviruses (ERVs). Studies in other Sauropsida have recognised a similar number but nevertheless, in the genome of the tuatara it has been found a very old clade of retrovirus known as Spumavirus.<ref name="Gemmell2020" />
More than 8,000 non-coding RNA-related elements have been identified in the tuatara genome, of which the vast majority, about 6,900, are derived from recently active transposable elements. The rest are related to ribosomal, spliceosomal and signal recognition particle RNA.<ref name="Gemmell2020" />
The mitochondrial genome of the genus Sphenodon is approximately 18,000 bp in size and consists of 13 protein-coding genes, 2 ribosomal RNA and 22 transfer RNA genes.<ref name="Gemmell2020" />
DNA methylation is a very common modification in animals and the distribution of CpG sites within genomes affects this methylation. Specifically, 81% of these CpG sites have been found to be methylated in the tuatara genome. Recent publications propose that this high level of methylation may be due to the amount of repeating elements that exist in the genome of this animal. This pattern is closer to what occurs in organisms such as zebrafish, about 78%, while in humans it is only 70%.<ref name="Gemmell2020" />
Conservation
[edit]Tuatara are absolutely protected under New Zealand's Wildlife Act 1953.<ref>Template:Cite web</ref> The species is also listed under Appendix I of the Convention on International Trade in Endangered Species (CITES) meaning commercial international trade in wild sourced specimens is prohibited and all other international trade (including in parts and derivatives) is regulated by the CITES permit system.<ref>Template:Cite web</ref>
Distribution and threats
[edit]Tuatara were once widespread on New Zealand's main North and South Islands, where subfossil remains have been found in sand dunes, caves, and Māori middens.<ref>Template:Cite journal</ref> Wiped out from the main islands before European settlement, they were long confined to 32 offshore islands free of mammals.<ref name="DoC"/> The islands are difficult to get to,<ref>Template:Harvnb</ref> and are colonised by few animal species, indicating that some animals absent from these islands may have caused tuatara to disappear from the mainland. However, kiore (Polynesian rats) had recently become established on several of the islands, and tuatara were persisting, but not breeding, on these islands.<ref>Template:Cite journal</ref><ref name=cree_etal1995>Template:Cite journal</ref> Additionally, tuatara were much rarer on the rat-inhabited islands.<ref name=cree_etal1995/> Prior to conservation work, 25% of the distinct tuatara populations had become extinct in the past century.<ref name = "Daugherty_1990">Template:Cite journal</ref>
The recent discovery of a tuatara hatchling on the mainland indicates that attempts to re-establish a breeding population on the New Zealand mainland have had some success.<ref name=bergner>Template:Cite news</ref> The total population of tuatara is estimated to be between 60,000<ref name=encyclo /> and 100,000.<ref>Template:Cite encyclopedia</ref>
Climate change
[edit]Tuatara have temperature-dependent sex determination meaning that the temperature of the egg determines the sex of the animal. For tuatara, lower egg incubation temperatures lead to females while higher temperatures lead to males. Since global temperatures are increasing, climate change may be skewing the male to female ratio of tuatara. Current solutions to this potential future threat are the selective removal of adults and the incubation of eggs.<ref>Template:Cite web</ref><ref>Template:Cite journal</ref>
Eradication of rats
[edit]Tuatara were removed from Stanley, Red Mercury and Cuvier Islands in 1990 and 1991, and maintained in captivity to allow Polynesian rats to be eradicated on those islands. All three populations bred in captivity, and after successful eradication of the rats, all individuals, including the new juveniles, were returned to their islands of origin. In the 1991–92 season, Little Barrier Island was found to hold only eight tuatara, which were taken into in situ captivity, where females produced 42 eggs, which were incubated at Victoria University. The resulting offspring were subsequently held in an enclosure on the island, then released into the wild in 2006 after rats were eradicated there.<ref>Template:Cite report</ref>
In the Hen and Chicken Islands, Polynesian rats were eradicated on Whatupuke in 1993, Lady Alice Island in 1994, and Coppermine Island in 1997. Following this program, juveniles have once again been seen on the latter three islands. In contrast, rats persist on Hen Island of the same group, and no juvenile tuatara have been seen there as of 2001. In the Alderman Islands, Middle Chain Island holds no tuatara, but it is considered possible for rats to swim between Middle Chain and other islands that do hold tuatara, and the rats were eradicated in 1992 to prevent this.<ref name=recovery/> Another rodent eradication was carried out on the Rangitoto Islands east of D'Urville Island, to prepare for the release of 432 Cook Strait tuatara juveniles in 2004, which were being raised at Victoria University as of 2001.<ref name=recovery />
Brothers Island tuatara
[edit]Sphenodon punctatus guntheri is present naturally on one small island with a population of approximately 400. In 1995, 50 juvenile and 18 adult Brothers Island tuatara were moved to Titi Island in Cook Strait, and their establishment monitored. Two years later, more than half of the animals had been seen again and of those all but one had gained weight. In 1998, 34 juveniles from captive breeding and 20 wild-caught adults were similarly transferred to Matiu/Somes Island, a more publicly accessible location in Wellington Harbour. The captive juveniles were from induced layings from wild females.<ref name=recovery />
In late October 2007, 50 tuatara collected as eggs from North Brother Island and hatched at Victoria University were being released onto Long Island in the outer Marlborough Sounds. The animals had been cared for at Wellington Zoo for the previous five years and had been kept in secret in a specially built enclosure at the zoo, off display.<ref>Template:Cite press release</ref>
There is another out of country population of Brothers Island tuatara that was given to the San Diego Zoological Society and is housed off-display at the San Diego Zoo facility in Balboa.<ref>Template:Cite news</ref> No successful reproductive efforts have been reported yet.
Northern tuatara
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S. punctatus punctatus naturally occurs on 29 islands, and its population is estimated to be over 60,000 individuals.<ref name=encyclo/> In 1996, 32 adult northern tuatara were moved from Moutoki Island to Moutohora. The carrying capacity of Moutohora is estimated at 8,500 individuals, and the island could allow public viewing of wild tuatara.<ref name=recovery/> In 2003, 60 northern tuatara were introduced to Tiritiri Matangi Island from Middle Island in the Mercury group. They are occasionally seen sunbathing by visitors to the island.<ref>Template:Cite web</ref><ref>Template:Cite web</ref>
A mainland release of S.p. punctatus occurred in 2005 in the heavily fenced and monitored Karori Sanctuary.<ref name="karori"/> The second mainland release took place in October 2007, when a further 130 were transferred from Stephens Island to the Karori Sanctuary.<ref>Template:Cite news</ref> In early 2009, the first recorded wild-born offspring were observed.<ref>Template:Cite news</ref>
Captive breeding
[edit]Template:More citations needed section The first successful breeding of tuatara in captivity is believed to have achieved by Sir Algernon Thomas at either his University offices or residence in Symonds Street in the late 1880s or his new home, Trewithiel, in Mount Eden in the early 1890s.Template:Citation needed
Several tuatara breeding programmes are active in New Zealand. Southland Museum and Art Gallery in Invercargill was the first institution to have a tuatara breeding programme; starting in 1986 they bred S. punctatus and have focused on S. guntheri more recently.<ref>Template:Cite book</ref>
Hamilton Zoo, Auckland Zoo and Wellington Zoo also breed tuatara for release into the wild. At Auckland Zoo in the 1990s it was discovered that tuatara have temperature-dependent sex determination. The Victoria University of Wellington maintains a research programme into the captive breeding of tuatara, and the Pūkaha / Mount Bruce National Wildlife Centre keeps a pair and a juvenile.Template:Citation needed
The WildNZ Trust has a tuatara breeding enclosure at Ruawai. One notable captive breeding success story took place in January 2009, when all 11 eggs belonging to 110 year-old tuatara Henry and 80 year-old tuatara Mildred hatched. This story is especially remarkable as Henry required surgery to remove a cancerous tumour in order to successfully breed.<ref name="CNNDad"/>
In January 2016, Chester Zoo, England, announced that they succeeded in breeding the tuatara in captivity for the first time outside its homeland.<ref>Template:Cite news</ref>
Cultural significance
[edit]Tuatara feature in a number of indigenous legends, and are held as ariki (God forms). Tuatara are regarded as the messengers of Whiro, the god of death and disaster, and Māori women are forbidden to eat them.<ref>Template:Cite web</ref> Tuatara also indicate tapu (the borders of what is sacred and restricted),<ref name="ramdstad">Template:Cite journal</ref> beyond which there is mana, meaning there could be serious consequences if that boundary is crossed.<ref name=ramdstad /> Māori women would sometimes tattoo images of lizards, some of which may represent tuatara, near their genitals.<ref name=ramdstad /> Today, tuatara are regarded as a taonga (special treasure) along with being viewed as the kaitiaki (guardian) of knowledge.<ref>Template:Harvnb</ref><ref>Template:Cite web</ref>
The tuatara was featured on one side of the New Zealand five-cent coin, which was phased out in October 2006. Tuatara was also the name of the Journal of the Biological Society of Victoria University College and subsequently Victoria University of Wellington, published from 1947 until 1993. It has now been digitised by the New Zealand Electronic Text Centre, also at Victoria.<ref>Template:Cite web</ref>
In popular culture
[edit]- A tuatara named "Tua" is prominently featured in the 2017 novel Turtles All the Way Down by John Green.<ref>Template:Cite news</ref>
- There is a brand of New Zealand craft beer named after the Tuatara which particularly references the third eye in its advertising.<ref>Template:Cite web</ref>
- In the season one finale of Abbott Elementary<ref>Template:Cite newsTemplate:Dead link</ref> an old tuatara named Duster is used to represent themes of ageing and transition.
- In the 2023 animated movie Leo, the main character is a tuatara named Leo.
See also
[edit]Notes
[edit]References
[edit]Further reading
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External links
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