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Turtles are diapsids of the order Testudines (or Chelonii) seen as a a special bony or cartilaginous shell created from their ribs plus acting as a protect. "Turtle" may refer to the order as the whole (American English) or even to fresh-water and sea-dwelling testudines (British English). The order Testudines includes both extant (living) and extinct species. The earliest known members of this group date from 220 million years ago, making turtles one of the oldest reptile groups and a more ancient group than snakes or crocodilians. Of the 356 known species alive today, some are usually highly endangered.

Turtles are ectotherms—animals commonly called cold-blooded—meaning that their internal temp varies according to the particular ambient environment. However, because of their high metabolic rate, leatherback sea turtles have a body heat that is noticeably increased than that of the surrounding water. Turtles are classified as amniotes, along with other reptiles, birds, and mammals. Like some other amniotes, turtles breathe air flow and do not lay down eggs underwater, although numerous species live in or around water. The study of turtles is known as cheloniology, following the Greek word for turtle. It is usually also sometimes called testudinology, after the Latin name for turtles.

Differences exist in usage of the particular common terms turtle, tortoise, and terrapin, according to the variety of English being used. These terms are typical names and do not reflect exact biological or taxonomic distinctions.

Turtle may either relate to the order since a whole, or to particular turtles that create up a form taxon which is not monophyletic, or might be limited to only marine species. Tortoise usually refers to any land-dwelling, non-swimming chelonian. Terrapin is utilized to describe several species associated with small, edible, hard-shell turtles, typically those found within brackish waters.

In Northern America, all chelonians are usually commonly called turtles. Tortoise is used only within mention of the fully terrestrial turtles or, more narrowly, just those members of Testudinidae, your family of modern property tortoises. Terrapin may refer to small semi-aquatic turtles that live in new and brackish water, particularly the diamondback terrapin (Malaclemys terrapin). Although the users from the genus Terrapene live mostly on land, they will are known as box turtles rather than tortoises. The American Society of Ichthyologists and Herpetologists uses "turtle" to describe all types of the order Testudines, regardless of whether they are land-dwelling or even sea-dwelling, and uses "tortoise" like a more specific term for slow-moving terrestrial varieties.

In the United Kingdom, the word turtle is used for water-dwelling species, which includes ones known in the particular US as terrapins, however, not for terrestrial species, that are known only as tortoises.

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Turtles Survive Frigid Hibernations By Breathing Through Their Butts Dbrief

The word chelonian will be well-liked by veterinarians, scientists, and conservationists working with these types of animals as a catch-all title for any member of the superorder Chelonia, including all turtles living and wiped out, as well as their immediate ancestors. Chelonia will be based on the Ancient greek word for turtles, χελώνη chelone; Greek χέλυς chelys "tortoise" is also utilized in the formation of medical names of chelonians. Testudines, on the other hand, is based on the particular Latin word for tortoise, testudo. Terrapin comes from an Algonquian word regarding turtle.

Some languages do not have this variation, as all of these are known by the particular same name. For instance , in Spanish, the word tortuga is used for turtles, tortoises, and terrapins. A sea-dwelling turtle is tortuga marina, a freshwater types tortuga de río, plus a tortoise tortuga terrestre.

The largest living chelonian is the leatherback ocean turtle (Dermochelys coriacea), which usually reaches a shell duration of 200 cm (6. six ft) and can achieve a weight of over 900 kg (2, 500 lb). Freshwater turtles are usually generally smaller, but along with the largest species, the particular Asian softshell turtle Pelochelys cantorii, a few individuals have been reported upward to 200 cm (6. 6 ft). This dwarfs even the better-known alligator snapping turtle, the largest chelonian in North The united states, which attains a cover length of up to 80 cm (2. six ft) and weighs because much as 113. four kg (250 lb).

Huge tortoises of the overal Geochelone, Meiolania, and other people were relatively widely distributed all over the world into prehistoric periods, and therefore are known to possess existed in North and South America, Australia, and Africa. They became wiped out at the same time as the appearance of man, and it is assumed humans hunted them for food. The only surviving giant tortoises are usually on the Seychelles and Galápagos Islands and can develop to over 130 cm (51 in) in size, and weigh about 300 kg (660 lb).

The largest ever chelonian had been Archelon ischyros, a Past due Cretaceous sea turtle recognized to have been up to 4. 6 m (15 ft) long.

Facts about turtles!

The tiniest turtle is the speckled padloper tortoise of South Africa. It measures simply no more than 8 centimeter (3. 1 in) in length and weighs about 140 g (4. 9 oz). Two other species of small turtles are the American mud turtles plus musk turtles that reside in an area that ranges from Canada in order to South America. The cover duration of many species within this group is less than 13 cm (5. 1 in) long.

Turtles are divided into two groups, according to how they retract their necks to their shells (something the ancestral Proganochelys could not do). The mechanism of neck retraction differs phylogenetically: the particular suborder Pleurodira retracts laterally aside, anterior to shoulder girdles, while the suborder Cryptodira retracts straight back, between shoulder girdles. These motions are largely because of to the morphology and arrangement of cervical backbone. Of all recent turtles, the cervical column is made up of nine joints and eight vertebrae, which are individually independent. Since these types of vertebrae are not fused and are rounded, the particular neck is more versatile, being able to flex in the backwards plus sideways directions. The primary function and evolutionary implication of neck retraction is usually thought to be regarding feeding rather than safety. Neck retraction and testing extension allows the turtle to achieve out further to capture prey while going swimming. Neck expansion creates suction once the head is thrust forward and the oropharynx is expanded, and this particular morphology suggests the retraction function is for feeding purposes as the suction helps catch prey. The protection the shell provides the head when this is retracted is as a result not the main functionality of retraction, thus is usually an exaptation. As for the difference between the particular two methods of retraction, both Pleurodirans and Cryptodirans use the quick expansion of the neck as a method of predation, therefore the difference in retraction mechanism is just not due to a difference in ecological niche.

Head

Most turtles that spend most associated with their lives on land have their eyes looking down at objects in front side of them. Some marine turtles, such as snapping turtles and soft-shelled turtles, have eyes closer in order to the very best of the mind. These species of turtle may hide from predators within shallow water, where they will lie entirely submerged except for their eyes plus nostrils. Near their eyes, sea turtles possess glands that produce salty holes that rid themselves of excess salt consumed from the water they drink.

Turtles have rigid beaks and use their jaws to cut and munch food. Instead of having teeth, which they appear in order to have lost about 150-200 million years ago, the particular upper and lower teeth of the turtle are covered by horny ridges. Carnivorous turtles usually possess knife-sharp ridges for cutting through their prey. Herbivorous turtles have serrated-edged ridges that help them cut through tough plants. They use their tongues in order to swallow food, but unlike most reptiles, they cannot stick out their tongues in order to catch food.

ShellMajor article: Turtle shellTop of the shell of the turtle is called the carapace. The particular lower shell that encases the belly is known as the plastron. The carapace and plastron are became a member of together on the turtle's sides by bony structures called bridges. The internal layer of a turtle's shell is made upward of about 60 bone fragments that include portions associated with the backbone and the ribs, meaning the turtle cannot crawl out of its shell. In most turtles, the outer layer from the shell is covered simply by horny scales called scutes which are part of the outer skin, or skin. Scutes comprise of the particular fibrous protein keratin that also makes up the scales of other lizards. These scutes overlap the particular seams between the cover bones and add power towards the shell. Some turtles don’t have horny scutes; regarding example, the leatherback sea turtle as well as the soft-shelled turtles have shells covered along with leathery skin instead.

The shape of the covering gives helpful clues about how a turtle lives. Most tortoises have a large, dome-shaped shell that can make it difficult for potential predators to crush the cover between their jaws. One of the few exceptions is the African hot cake tortoise, which has a flat, flexible shell that will allows it to conceal in rock crevices. Most aquatic turtles have toned, streamlined shells, which help in swimming and diving. American snapping turtles and musk turtles have small, cross-shaped plastrons that give them more efficient leg motion for walking along the particular bottom of ponds plus streams. Another exception is the Belawan Turtle (Cirebon, West Java), which has sunken-back soft-shell.

The color of a turtle's shell may differ. Shells are commonly coloured brown, black, or olive green. In certain species, covers may have red, fruit, yellow, or grey markings, often spots, lines, or irregular blotches. Probably the most vibrant turtles is the far eastern painted turtle, which includes a yellow plastron and a black or olive shell with red marks around the rim.

Tortoises, being land-based, have instead heavy shells. In comparison, aquatic and soft-shelled turtles have lighter shells that will help them avoid settling in water and swim faster with more speed. These lighter shells have got large spaces called fontanelles between the shell bone fragments. The shells of leatherback sea turtles are incredibly lighting because they lack scutes and contain many fontanelles.

It has been suggested by Jackson (2002) that the turtle shell can function as pH buffer. To endure through anoxic conditions, such as wintertime periods trapped beneath snow or within anoxic dirt at the end of ponds, turtles utilize two general physiological mechanisms. In the situation of prolonged periods associated with anoxia, it has already been shown that this turtle shell both releases carbonate buffers and uptakes lactic acid.

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Respiration Turtles

Respiration, for many amniotes, is achieved by the particular contraction and relaxation of specific muscles (i. e. intercostals, abs, and/or the diaphragm) attached with an inner rib-cage that can increase or contract the body wall thus assisting airflow in and out of the lung area. The ribs of Chelonians, however, are fused with their carapace and external to their pelvic and pectoral girdles, a function unique among turtles. This particular rigid shell is not really capable of expansion, plus by rendering their rib-cage immobile, Testudines have had to evolve special modifications for respiration.

Turtle pulmonary ventilation occurs by using specific categories of abdominal muscles attached to their viscera and shell that draw the lungs ventrally throughout inspiration, where air will be drawn in via a negative pressure gradient (Boyle's Law). In expiration, the contraction from the transversus abdominis is the driving force by propelling the viscera into the lungs and expelling air under good pressure. Conversely, the comforting and flattening of the oblique abdominis muscle drags the transversus back lower which, once again, draws air flow back into the lungs. Important auxiliary muscles used for ventilatory processes are the pectoralis, which is used in conjunction with the particular transverse abdominis during motivation, and the serratus, which techniques with all the abdominal oblique accompanying expiration.

The lungs associated with Testudines are multi-chambered plus attached their entire length throughout the carapace. The quantity of chambers can vary in between taxa, though most often they will have three lateral chambers, three medial chambers, and something terminal chamber. As previously mentioned, the act of particular abdominal muscles pulling down the viscera (or pressing back up) is exactly what allows for respiration within turtles. Specifically, it will be the turtles large liver organ that pulls or pushes on the lungs. Ventral to the lungs, within the coelomic cavity, the liver of turtles is connected directly to the right lung, and their abdomen is directly attached to the left lung by the ventral mesopneumonium, which is attached to their liver with the ventral mesentery. When the liver is drawn down, inspiration begins. Assisting the lungs is the post-pulmonary septum, which is discovered in all Testudines, and is thought to prevent the lungs from collapsing.

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Turtles Epidermis and molting

As pointed out above, the outer layer of the shell will be part of the epidermis; each scute (or plate) on the shell corresponds to a single modified scale. The remainder associated with the skin has much smaller scales, just like the epidermis of other reptiles. Turtles do not molt their skins all at once as snakes do, yet continuously in small pieces. When turtles are kept in aquaria, small bedding of dead skin may be seen in the particular water (often appearing in order to be a thin item of plastic) having been sloughed off when the particular animals deliberately rub on their own against a piece of wood or even stone. Tortoises also lose skin, but dead epidermis is allowed to accumulate in to thick knobs and plates that provide protection to parts of the entire body outside the shell.

Simply by counting the rings created by the stack associated with smaller, older scutes on top of the larger, newer types, you are able to estimate the age of a turtle, if one knows how many scutes are produced in per year. This method is not really very accurate, partly since growth rate is not constant, but also due to the fact some of the scutes eventually fall away from the shell.

Turtles Braches

Terrestrial tortoises have short, durable feet. Tortoises are popular for moving slowly, in part because of their weighty, cumbersome shells, which restrict stride length.

Skeleton associated with snapping turtle (Chelydra serpentina)

Amphibious turtles normally have limbs similar to the ones from tortoises, except that the feet are webbed plus often have long paws. These turtles swim using all four feet within a way similar in order to the dog paddle, with the feet on the particular right and left side of the particular body alternately providing thrust. Large turtles tend to swim less than smaller ones, and the very big species, such since alligator snapping turtles, hardly swim in any way, preferring to walk along the bottom associated with the river or river. As well as webbed feet, turtles have very long claws, used to help them clamber onto riverbanks and floating records upon which they bask. Male turtles tend in order to have particularly long claws, and these appear to be used to stimulate the female while mating. While many turtles have webbed foot, some, like the pig-nosed turtle, have true flippers, along with the digits being fused into paddles and the paws being relatively small. These types of species swim in the same way as sea turtles do (see below).

Sea turtles are usually almost entirely aquatic plus have flippers instead associated with feet. Sea turtles take flight through the water, using the up-and-down motion of the front flippers to generate thrust; the back feet are not used for propulsion yet may be used as rudders regarding steering. Compared with fresh water turtles, sea turtles have very limited mobility upon land, and in addition to the dash from the nest to the sea as hatchlings, male sea turtles normally in no way leave the sea. Women must come back on to land to lay ovum. They move very gradually and laboriously, dragging on their own forwards using their flippers.

Behavior of Turtles

Senses of Turtles are believed to get exceptional night eyesight due to the unusually large number of rod cells within their retinas. Turtles have color vision with the wealth of cone subtypes with sensitivities ranging from the near ultraviolet (UVA) to red. Some land turtles have very bad pursuit movement abilities, which are normally found just in predators that quest quick-moving prey, but carnivorous turtles are able to move their heads rapidly to snap.

Turtles Communication

The particular Arrau turtle has the sizable vocal repertoire.

While typically thought of since mute, turtles make various sounds when communicating. Tortoises may be vocal when courting and mating. Various species of both freshwater and sea turtles emit numerous types of calls, frequently short and low rate of recurrence, from the time these are in the egg to if they are adults. These vocalizations may serve in order to create group cohesion when migrating.

Turtle Intelligence

See furthermore: Animal cognition

It offers been reported that wooden turtles are better compared to white rats at learning to navigate mazes. Situation studies exist of turtles playing. They are doing, however, have got a very low encephalization quotient (relative brain in order to body mass), and their hard shells enable them to live without fast reflexes or elaborate predator prevention strategies. In the lab, turtles (Pseudemys nelsoni) may learn novel operant tasks and have demonstrated a long-term memory of at minimum 7. 5 months.

Turtle Mating Methods

An example of mounting behavior within turtles

Turtles are recognized for displaying a broad variety of mating actions, however , they are not known for forming pair-bonds or for being part of a social team. Once fertilization has occurred and an offspring provides been produced, neither mother or father will provide care regarding the offspring once it can hatched. Females generally outnumber males in various turtle species (such as Eco-friendly turtles), and thus, most males will participate in multiple copulation with multiple partners throughout their lifespan. However, because of to the sexual dimorphism present in most turtle species, males must develop different courting strategies or use alternate methods to gain access to any mate. Most terrestrial species have males that are usually larger than females, and combating between males often decides a hierarchical order in which the higher upward the order an individual is, the better the particular chance is of the individual getting access to a potential mate. For most semi-aquatic species and bottom-walking aquatic species, combat takes place less often. Males belonging to semi-aquatic and bottom-walking species instead often make use of their larger size advantage to forcibly mate with a female. In fully marine species, males are often smaller than females and therefore they can not use the same strategy as their semi-aquatic relatives, which depends on overpowering the females with power. Males in this category resort to using courtship displays in an attempt to gain mating entry to a female.

Combating Between Males Turtles

Saddle back Galapagos tortoise

Wood turtles invariably is an example of the terrestrial species where the males have a hierarchical ranking system based upon dominance through fighting, plus it's shown that the particular males with the maximum rank and thus the most wins in battles have the most offspring.

Galapagos tortoises are an additional example of a varieties which has a hierarchical rank which is determined by dominance displays, and accessibility to food and friends is regulated by this particular dominance hierarchy. Two male saddle backs most usually compete for access in order to cactus trees, which is their own source of food. The winner is the person who stretches their neck of the guitar the highest, and that individual gets access to the cactus tree, which can attract potential mates.

Force Mating Turtles

Male (left) plus female (right) radiated tortoise

The male scorpion mud turtle is an illustration of a bottom-walking aquatic species that depends on overwhelming females with its larger size as a mating strategy. The male techniques the female from the rear, and often resorts in order to aggressive methods such as biting the female's tail or even hind limbs, then a mounting behavior in which the male clasps the edges of her carapace with his forelimbs and hind limbs to hold the girl in position. The male follows this action by laterally waving his mind and sometimes biting the particular female's head in an attempt to get her to withdraw her go to her shell. This unearths her cloaca, and along with it exposed, the man can attempt copulation by seeking to insert his grasping tail.

Male radiated tortoises are also known to use the force mating strategy wherein they use around vegetation to trap or even prevent females from getting away, then pin them down for copulation.

Turtles Courtship Shows

Red-eared sliders are a good example of a fully aquatic species where the male works a courtship behavior. In this case the man extends his forelegs with the palms facing out and flutters his forelegs in the female's face. Female options are important in this technique, and the females of several species, such as eco-friendly sea turtles, aren't always receptive. As such, they've progressed certain behaviors to avoid the male's attempts in copulation, such as swimming away, confronting the man followed by biting, or even a refusal position within which the female assumes a vertical position along with her limbs widely outspread and her plastron dealing with the male. If the water is too superficial to perform the refusal position, the females will certainly resort to beaching themselves, which is a verified deterrent method, as the particular males will never follow them ashore.

Ecology and life history of turtles

Ocean turtle swimming

Although numerous turtles spend large amounts of their lives underwater, all turtles and tortoises breathe air and should surface at regular intervals to refill their lungs. They can also spend much or all of their lives on dry land. Aquatic respiration within Australian freshwater turtles is currently being studied. Several species have large cloacal cavities that are lined with many finger-like projections. These types of projections, called papillae, have a rich blood provide and boost the surface region of the cloaca. The turtles can take up dissolved oxygen from the water providing a few papillae, within much the same way that fish use gills to respire.

Like other reptiles, turtles lay ovum that are slightly soft and leathery. The ovum from the largest species are usually spherical while the ovum of the rest are usually elongated. Their albumen is white and contains an alternative protein from bird eggs, such that it will certainly not coagulate when prepared. Turtle eggs ready to consume consist mainly of yolk. In some species, temp determines whether an egg develops into a man or a female: a increased temperature the female, a lower temperature the male. Large numbers of ovum are deposited in holes dug into mud or sand. They are after that covered and left to incubate by themselves. Depending upon the species, the ovum will typically take 70–120 days to hatch. When the turtles hatch, they squirm their way to the surface and head toward the water. There are simply no known species in which the mom cares for her youthful.

Sea turtles lay their eggs on dry, sandy beaches. Immature sea turtles are not cared with regard to by the adults. Turtles can take many years to achieve breeding age, plus in many cases, breed of dog every few years rather than annually.

Researchers have recently learned a turtle's internal organs do not gradually break lower or become less efficient over time, unlike most other animals. It has been found that the liver, lungs, and kidneys associated with a centenarian turtle are usually almost indistinguishable from all those of its immature version. This has inspired genetic researchers to commence evaluating the turtle genome regarding longevity genes.

A group of turtles is actually a bale.

Turtles Diet

A green ocean turtle grazing on

A turtle's diet varies greatly determined by the atmosphere by which it lives. Adult turtles typically eat marine plants; (citation needed) invertebrates for example insects, snails, and worms; and have already been reported to occasionally eat dead marine animals. Several small freshwater species are usually carnivorous, eating small seafood and an array of aquatic existence. However, protein is important to turtle growth and juvenile turtles are solely carnivorous.

Sea turtles typically feed on jellyfish, sponges, and other soft-bodied microorganisms. Some species with better jaws have been noticed to eat shellfish, while others, like the green sea turtle, do not eat meat at all and, instead, possess a diet largely made up of algae.

Systematics and evolution of Turtles

Main article: Turtle classification

See|Observe|Notice} also: List of Testudines households

Life restoration associated with Odontochelys semitestacea, the oldest known turtle relative along with a partial shell

"Chelonia" from Ernst Haeckel's Kunstformen der Natur, 1904

Based on body fossils, the particular first proto-turtles are thought to have existed in the particular late Triassic Period associated with the Mesozoic era, about 220 million years back, and their shell, which has remained a remarkably stable body plan, is considered to have evolved from bony extensions of their own backbones and broad steak that expanded and increased together to form a complete shell that provided protection at every phase of its evolution, actually when the bony component of the shell was not really complete. This is backed by fossils of the particular freshwater Odontochelys semitestacea or even "half-shelled turtle with teeth", from the late Triassic, which have been found near Guangling in south west China. Odontochelys displays the complete bony plastron and an incomplete carapace, comparable to an early phase of turtle embryonic advancement. Prior to this discovery, the particular earliest-known fossil turtle ancestors, like Proganochelys, were terrestrial and had a complete covering, offering no clue to the evolution of the exceptional anatomical feature. With the late Jurassic, turtles had extended widely, and their fossil history becomes better to read.

Their exact ancestry provides been disputed. It has been believed they are the only surviving branch of the ancient evolutionary grade Anapsida, which includes organizations such as procolophonids, millerettids, protorothyrids, and pareiasaurs. All anapsid skulls lack a temporal opening while all other extant amniotes have temporary openings (although in mammals, the hole has turn out to be the zygomatic arch). The millerettids, protorothyrids, and pareiasaurs became extinct in the late Permian period plus the procolophonoids during the particular Triassic.

However , it was later recommended that this anapsid-like turtle head may be due to reversion rather than to anapsid descent. More recent morphological phylogenetic studies with this particular in mind placed turtles firmly within diapsids, slightly closer to Squamata in order to Archosauria.[55][56] All molecular studies possess strongly upheld the positioning of turtles within diapsids; some place turtles within Archosauria, or, more frequently, as a sister group to extant archosaurs,[58][59][60][61] though an analysis performed by Lyson et al. (2012) recovered turtles as the sister group of lepidosaurs instead. Reanalysis of before phylogenies suggests that these people classified turtles as anapsids both because they assumed this classification (most of all of them studying what sort of anapsid turtles are) plus because they did not really sample fossil and extant taxa broadly enough for constructing the cladogram. Testudines were suggested to have diverged from other diapsids among 200 and 279 mil years ago, though the debate is far through settled. Even the traditional placement of turtles outdoors Diapsida cannot be ruled out at this point. A combined analysis associated with morphological and molecular information conducted by Lee (2001) found turtles to become anapsids (though a relationship with archosaurs couldn't end up being statistically rejected).[64] Similarly, a morphological study conducted by Lyson ou al.. (2010) recovered them as anapsids most carefully related to Eunotosaurus. A molecular analysis of 248 nuclear genes from 16 vertebrate taxa shows that turtles are a sister group to birds and crocodiles (the Archosauria).[66] The date of separation of turtles and birds and crocodiles was approximated to be 255 million years back. The most latest common ancestor of living turtles, corresponding towards the divided between Pleurodira and Cryptodira, was estimated to have occurred around 157 million years ago. The oldest conclusive crown-group turtle (member from the modern clade Testudines) may be the species Caribemys oxfordiensis from the late Jurassic period (Oxfordian stage). Through utilizing the first genomic-scale phylogenetic analysis associated with ultraconserved elements (UCEs) to check into the placement of turtles within reptiles, Crawford et al. (2012) also suggest that turtles are a sister group to birds and crocodiles (the Archosauria).

The first genome-wide phylogenetic analysis was completed by Wang et al. (2013). Using the draft genomes of Chelonia mydas and Pelodiscus sinensis, the group used largest turtle data started date in their analysis and concluded that turtles are likely a sister group of crocodilians and birds (Archosauria). This placement within the diapsids suggests that the turtle lineage lost diapsid head characteristics as it now possesses an anapsid-like skull.

The earliest known completely shelled member of the particular turtle lineage is the late Triassic Proganochelys. This genus already possessed several advanced turtle traits, and thus probably indicates numerous millions of years associated with preceding turtle evolution; this is further supported simply by evidence from fossil songs from the Early Triassic of the United States (Wyoming and Utah) plus from the Middle Triassic of Germany, indicating that will proto-turtles already existed since early as the first Triassic. Proganochelys lacked the ability to draw its head into its shell, had a lengthy neck, and had the long, spiked tail closing in a club. While this body form is similar to that of ankylosaurs, this resulted from convergent development.

Turtles are divided directly into two extant suborders: Cryptodira and Pleurodira. The Cryptodira is the larger associated with the two groups and includes all the ocean turtles, the terrestrial tortoises, and several of the fresh water turtles. The Pleurodira are sometimes known as the side-necked turtles, a guide to the way they retract their own heads to their shells. This smaller group consists primarily of various freshwater turtles.