Classification of Aquatic Reptiles, anatomy, Nervous system, digestive system, Reproductive biology, food and feeding Biology, Human uses in traditional, as pets and present conservation status

1. Major Aquatic Reptiles with special focus on
Anatomy and Biology and conservation status of
Turtles
By:
Bhukya Bhaskar
Fisheries
Marine Turtles
Major Fresh water Terrapins

2. Characteristics of aquatic reptiles
• Aquatic reptiles are vertebrates that do not correspond to a single group, but there
are several types which live in different habits.
• Some of them are exclusively aquatic, while others are considered semi-aquatic
because they spend a large part of their time on land.
• They may do so to lay eggs, sunbathe or even breathe.
• While there are many differences, there are certain characteristics all aquatic
reptiles have in common
• Depending on the type, they can inhabit fresh or salt water.
• The greatest diversity of reptiles does not have exclusively aquatic habits.
• Some species manage to dive to great depths, so they can withstand the pressure
of deep sea environments.
• In certain cases, the limbs have been modified to facilitate locomotion in the water
through swimming.
• Species of marine reptiles have mechanisms to expel excess salt through the use of
specialized glands that may be in the mouth, eyes or nose, depending on the
species.
• They have a common feature of valve nostrils which allow them to stop water
entering when submerged.
• The diet varies according to the type of aquatic reptile, some being strictly
carnivorous predators, others omnivores and some herbivores.
• In certain cases, they have quite marked migratory habits, while others remain in
the same habitat throughout their lives.

3. Aquatic reptiles breathe thing
• Each group of these animals has a specific
adaptation to carry out the respiratory process.
• All aquatic reptiles breathe through lungs, which
indicate they may have needed to take air directly
from above the surface of the water.
• Despite the presence of lungs, the amount of time
they can remain underwater varies greatly
according to species.
• Some marine reptiles, such as certain sea turtles or
sea snakes, can stay underwater for hours.
• This is partly carried out by the ability of their skin
or cloaca to carry out gas exchange.

4. Types of aquatic reptiles
• Reptilia class is made up of the following orders:
• Testudines (turtles and tortoises)
• Squamata (snakes, blind shingles, and lizards)
• Crocodilia (crocodiles, alligators and caimans)
• Sphenodontia (tuataras)
• Within the first three we find different types of marine and freshwater reptiles.
• There is only one extant species belonging to the last order which are tuataras and
they are exclusively terrestrial.
• Let's get to know some specific examples of aquatic reptiles:
Testudines
• Turtles are a common example of aquatic reptiles, although there are species with
exclusively terrestrial habits.
• These animals are unmistakable due to their shell or carapace. Rather than a
separate part of the body, they are a modified extension of the spine and ribs.
• Turtles lay their eggs on land, for this reason, they do not live exclusively in water.
• They also need to break the surface water to breathe.
• Turtles are are usually omnivorous animals, although some tend to be more
herbivorous in the adult phase.
• In terms of habitat, there are both freshwater and marine turtles. Some examples
are found in the following species:

5. Squamata
• The animals within the Squamata order are also sometimes referred to as scaly reptiles.
• They include certain species of snakes with aquatic habits, as well as one iguana species.
• The rest have terrestrial habits.
• Some species of aquatic snake are highly poisonous.
• These animals have adapted to life in a marine environment without any problem. In fact,
they are often not well adapted to life on land.
• In general, the entire reproductive cycle occurs in the water with certain exceptions, such as
the genus Laticauda.
• These are types of oviparous animals and lays their eggs on land, They tend to be predators
of other animals that live in the sea.
• Some examples of these aquatic reptiles are:
• Beaked sea snake (Enhydrina schistosa)
• Olive sea snake (Aipysurus laevis)
• Yellow-bellied sea snake (Hydrophis platurus)
• We can also find some species of snake that have semi-aquatic habits. These snakes live in
freshwater ecosystems. Examples include:
• Green anaconda (Eunectes murinus)
• Arafura snake (Acrochordus arafurae)
• Tentacle snake (Erpeton tentaculatum)
• As we have mentioned, there is also an iguana considered a semi-aquatic reptile.
• This is the only one within the group apart from the snakes. It is the marine
iguana (Amblyrhynchus cristatus).
• This aquatic lizard species is endemic to Ecuador, specifically to the Galapagos Islands. It
enters the sea to feed on algae. They spend the rest of the time on land.

6. Crocodilia
• This group is made up of three families that include
commonly known animals such
as crocodiles (Crocodylidae), alligators and
caimans (Alligatoridae), and gharials (Gavialidae).
• They all have semi-aquatic habits.
• Most live in tropical areas, although some exceptions
can be found in North America and China.
• They are carnivorous animals that stalk their prey
using speed and strength.
• They all have a similar body shape, although they vary
in size, ranging from 1.5 to about 7 m (5-23') in length,
so in this group we find giant aquatic reptiles.
• Although most live in freshwater ecosystems, there
are species that tolerate marine or brackish
environments.
• Their habitats are generally associated with lowlands.
• Some species of marine and freshwater reptiles
belonging to this group include:
• Gharial (Gavialis gangeticus)
• Chinese crocodile (Alligator sinensis)
• Cuvier's dwarf caiman (Paleosuchus palpebrosus)
• Orinoco Crocodile (Crocodylus intermedius)
• American alligator (Alligator mississippiensis)
• Marine or saltwater crocodile (Crocodylus
• Scientific classification
• Domain:Eukaryota
• Kingdom:Animalia
• Phylum:Chordata
• Class:Reptilia
• Order:Crocodilia
• Superfamily:Crocodyloidea
• Family:Crocodylidae
Cuvier, 1807
• Type genus Crocodylus
Laurenti, 1768
• Subfamilies: Crocodylinae, Osteolaeminae
(Crocodylus porosus)

8. Major Marine and Fresh water Turtles
Lifespan
• Turtles can live long lives. The oldest living
turtle and land animal is said to be
a Seychelles giant tortoise named Jonathan,
who turned 187 in 2019.
• A Galápagos tortoise named Harriet was
collected by Charles Darwin in 1835; it died
in 2006, having lived for at least 176 years.
Most wild turtles do not reach that age.
Turtles keep growing new scutes under the
previous scutes every year, allowing
researchers to estimate how long they have
lived. They also age slowly. The survival rate
for adult turtles can reach 99% per year
• Scientific classification Domain:
Eukaryota
• Kingdom: Animalia
• Phylum: Chordata
• Class: Reptilia
• Clade: Pantestudines
• Clade: Testudinata
• Clade: Perichelydia
• Order: Testudines
Batsch, 1788
• Subgroups:
Cryptodira,Pleurodira,Paracryptodira
• Diversity: 14 living families
 Major Saltwater Turtles :
• Loggerhead sea turtle (Caretta caretta)
• Green sea turtle (Chelonia mydas)
• Hawksbill sea turtle (Eretmochelys
imbricate)
 Major Freshwater turtles :
• Spotted turtle (Clemmys guttata)
• Razor-backed musk turtle (Sternotherus
carinatus)
• Pig-nosed turtle (Carettochelys insculpta)

9. Taxonomic Groups, Distribution and habitats of Turtles
• Turtles are widely distributed across the world's
continents, oceans, and islands with terrestrial,
fully aquatic, and semi-aquatic species. Sea turtles
are mainly tropical and subtropical, but
leatherbacks can be found in colder areas of the
Atlantic and Pacific. Living Pleurodira all live in
freshwater and are found only in the Southern
Hemisphere. The Cryptodira include terrestrial,
freshwater, and marine species, and these range
more widely. The world regions richest in non-
marine turtle species are the Amazon basin,
the Gulf of Mexico drainages of the United States,
and parts of South and Southeast Asia.
• For turtles in colder climates, their distribution is
limited by constraints on reproduction, which is
reduced by long hibernations. North American
species barely range above the southern Canadian
border. Some turtles are found at high altitudes,
for example, the species Terrapene ornata occurs
up to 2,000 m (6,600 ft) in New Mexico.
Conversely, the leatherback sea turtle can dive
over 1,200 m (3,900 ft).
• Species of the genus Gopherus can tolerate both
below freezing and over 40 °C (104 °F) in body
temperature, though they are most active at 26–
34 °C (79–93 °F).

10. Tortoise Morphology
• All turtles show
morphological specialization
associated with terrestrial,
freshwater and marine
habitats. • They are easily
identified with armored shell
– Carapace Plastron • The
limbs are heavy – required
for carrying about the
unusually heavy body. •
When the animal is
threatened with danger – the
head, neck limbs and tail are
withdrawn into the shell. •
Teeth are absent in all turtle
and being replaced by a
horny-beak like structure.

11. Marine turtles
 Dermochelyidae:
• Dermochelys
coriacea (leatherback sea
turtle)
 Cheloniidae
• Caretta caretta (Loggerhead
sea turtle)
• Lepidochelys kempii (Kemp's
ridley)
• Lepidochelys olivacea (Olive
ridley)
• Chelonia mydas (Green sea
turtle)
• Eretmochelys
imbricata (Hawksbill sea
turtle)
• Natator depressus (Flatback
sea turtle)
Dermochelys coriacea
Caretta caretta
Lepidochelys kempii
Chelonia mydas Eretmochelys imbricata
Natator depressus

12. Turtles
• The word turtle is borrowed from the French word tortue or tortre 'turtle, tortoise‘
• The name of the order, Testudines, is based on the Latin word testudo 'tortoise';[ and was coined by German
naturalist August Batsch in 1788.[1] The order has also been historically known as Chelonii (Latreille 1800)
and Chelonia (Ross and Macartney 1802),[2] which are based on the Ancient Greek word χελώνη (chelone)
'tortoise.
• Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from
their ribs.
• Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden
necked turtles), which differ in the way the head retracts.
• There are 360 living and recently extinct species of turtles, including land-dwelling tortoises and
freshwater terrapins.
• They are found on most continents, some islands and, in the case of sea turtles, much of the ocean. Like
other amniotes (reptiles, birds, and mammals) they breathe air and do not lay eggs underwater, although many
species live in or around water.
• Turtle shells are made mostly of bone; the upper part is the domed carapace, while the underside is the
flatter plastron or belly-plate. Its outer surface is covered in scales made of keratin, the material of hair, horns,
and claws.
• The carapace bones develop from ribs that grow sideways and develop into broad flat plates that join up to
cover the body.
• Turtles are ectotherms or "cold-blooded", meaning that their internal temperature varies with their direct
environment. They are generally opportunistic omnivores and mainly feed on plants and animals with limited
movements.
• Many turtles migrate short distances seasonally.
• Sea turtles are the only reptiles that migrate long distances to lay their eggs on a favored beach.
• Turtles have appeared in myths and folktales around the world. Some terrestrial and freshwater species are
widely kept as pets. Turtles have been hunted for their meat, for use in traditional medicine, and for their
shells. Sea turtles are often killed accidentally as bycatch in fishing nets.
• Turtle habitats around the world are being destroyed.

13. Anatomy of Turtles

14. Size and Shell of Turtles
• The largest living species of turtle (and fourth-
largest reptile) is the leatherback turtle, which can reach
over 2.7 m (8 ft 10 in) in length and weigh over 500 kg
(1,100 lb).
• The largest known turtle was Archelon ischyros, a Late
Cretaceous sea turtle up to 4.5 m (15 ft) long, 5.25 m
(17 ft) wide between the tips of the front flippers, and
estimated to have weighed over 2,200 kg (4,900 lb).
• The smallest living turtle is Chersobius signatus of South
Africa, measuring no more than 10 cm (3.9 in) in length
and weighing 172 g (6.1 oz).
• The shell of a turtle is unique among vertebrates and
serves to protect the animal and provide shelter from the
elements.
• It is primarily made of 50–60 bones and consists of two
parts: the domed, dorsal (back) carapace and the flatter,
ventral (belly) plastron. They are connected by lateral
(side) extensions of the plastron.
• The carapace is fused with the vertebrae and ribs while
the plastron is formed from bones of the shoulder
girdle, sternum, and gastralia (abdominal ribs).
• During development, the ribs grow sideways into a
carapacial ridge, unique to turtles, entering
the dermis (inner skin) of the back to support the
carapace.
• The development is signaled locally by proteins known
as fibroblast growth factors that include, the shoulder
girdle in turtles is made up of two bones, the scapula
and the coracoid.
• Both the shoulder and pelvic girdles of turtles are
located within the shell and hence are effectively within
the rib cage. The trunk ribs grow over the shoulder
girdle during development.[
• Development of the shell. The ribs are growing sideways
into the carapacial ridge, seen here as a bud, to support
the carapace.
• The shell is covered in epidermal (outer skin) scales
known as scutes that are made of keratin, the same
substance that makes up hair and fingernails.
• Typically, a turtle has 38 scutes on the carapace and 16
on the plastron, giving them 54 in total. Carapace scutes
are divided into "marginals" around the margin and
"vertebrals" over the vertebral column, though the scute
that overlays the neck is called the "cervical". "Pleurals"
are present between the marginals and vertebrals.
• Plastron scutes include gulars (throat), humerals,
pectorals, abdominals, and anals. Side-necked
turtles additionally have "intergular" scutes between the
gulars.
• Turtle scutes are usually structured like mosaic tiles, but
some species, like the hawksbill sea turtle, have
overlapping scutes on the carapace

15. Head and Neck of Turtles
• he turtle's skull is unique among living amniotes (which
includes reptiles, birds and mammals), it is solid and rigid
with no openings for muscle attachment (temporal
fenestrae).
• Muscles instead attach to recesses in the back of the skull.
Turtle skulls vary in shape, from the long and narrow skulls
of softshells to the broad and flattened skull of the mata
mata.
• Some turtle species have developed large and thick heads,
allowing for greater muscle mass and stronger bites.[
• Turtles that are carnivorous or durophagous (eating hard-
shelled animals) have the most powerful bites. For example,
the durophagous Mesoclemmys nasuta has a bite force of
432 lbf (1,920 N).
• Species that are insectivorous, piscivorous (fish-eating),
or omnivorous have lower bite forces.
• Living turtles lack teeth but have beaks made of keratin
sheaths along the edges of the jaws.
• These sheaths may have sharp edges for cutting meat,
serrations for clipping plants, or broad plates for
breaking mollusks.
• The necks of turtles are highly flexible, possibly to
compensate for their rigid shells. Some species, like sea
turtles, have short necks while others, such as snake-necked
turtles, have long ones.
• Despite this, all turtle species have eight neck vertebrae, a
consistency not found in other reptiles but similar to
mammals.
• Some snake-necked turtles have both long necks and large
heads, limiting their ability to lift them when not in water.
• Some turtles have folded structures in
the larynx or glottis that vibrate to produce sound. Other
species have elastin-rich vocal cords.

16. Limbs and Locomotion in Turtles
• Due to their heavy shells, turtles are slow-moving on land. A desert
tortoise moves at only 0.22–0.48 km/h (0.14–0.30 mph). By contrast,
sea turtles can swim at 30 km/h (19 mph).
• The limbs of turtles are adapted for various means of locomotion and
habits and most have five toes. Tortoises are specialized for terrestrial
environments and have column-like legs with elephant-like feet and
short toes. The gopher tortoise has flattened front limbs for digging in
the substrate.
• Freshwater turtles have more flexible legs and longer toes
with webbing, giving them thrust in the water. Some of these species,
such as snapping turtles and mud turtles, mainly walk along the water
bottom, as they would on land. Others, such as terrapins, swim by
paddling with all four limbs, switching between the opposing front and
hind limbs, which keeps their direction stable.
• Sea turtles have streamlined shells and limbs adapted for fast and
efficient swimming.
• Sea turtles and the pig-nosed turtle are the most specialized for
swimming. Their front limbs have evolved into flippers while the
shorter hind limbs are shaped more like rudders. The front limbs
provide most of the thrust for swimming, while the hind limbs serve as
stabilizers.
• Sea turtles such as the green sea turtle rotate the front limb flippers
like a bird's wings to generate a propulsive force on both the upstroke
and on the downstroke.
• This is in contrast to similar-sized freshwater turtles (measurements
having been made on young animals in each case) such as the Caspian
turtle, which uses the front limbs like the oars of a rowing boat,
creating substantial negative thrust on the recovery stroke in each
cycle.
• In addition, the streamlining of the marine turtles reduces drag. As a
result, marine turtles produce a propulsive force twice as large, and
swim six times as fast, as freshwater turtles. The swimming efficiency
of young marine turtles is similar to that of fast-swimming fish of open
water, like mackerel.
• Compared to other reptiles, turtles tend to have reduced tails, but
these vary in both length and thickness among species and between
sexes. Snapping turtles and the big-headed turtle have longer tails;
the latter uses it for balance while climbing.
• The cloaca is found underneath and at the base, and the tail itself
houses the reproductive organs.
• Hence, males have longer tails to contain the penis. In sea turtles, the
tail is longer and more prehensile in males, who use it to grasp mates.
Several turtle species have spines on their tails.[

17. Senses in Turtles
• Turtles make use of vision to find food and mates,
avoid predators, and orient themselves. The retina
light-sensitive cells include both rods for vision in low
light, and cones with three
different photopigments for bright light, where they
have full-color vision.
• There is possibly a fourth type of cone that
detects ultraviolet, as hatchling sea turtles respond
experimentally to ultraviolet light, but it is unknown
if they can distinguish this from longer wavelengths.
A freshwater turtle, the red-eared slider, has an
exceptional seven types of cone cell.
• Sea turtles orient themselves on land by night, using
visual features detected in dim light. They can use
their eyes in clear surface water, muddy coasts, the
darkness of the deep ocean, and also above water.
Unlike in terrestrial turtles, the cornea, the curved
surface that lets light into the eye, does not help to
focus light on the retina, so focusing underwater is
handled entirely by the lens, behind the cornea. The
cone cells contain oil droplets placed to shift
perception toward the red part of the spectrum,
improving color discrimination. Visual acuity, studied
in hatchlings, is highest in a horizontal band with
retinal cells packed about twice as densely as
elsewhere. This gives the best vision along the visual
horizon. Sea turtles do not appear to use polarized
light for orientation as many other animals do. The
deep-diving leatherback turtle lacks specific
adaptations to low light, such as large eyes, large
lenses, or a reflective tapetum. It may rely on seeing
the bioluminescence of prey when hunting in deep
water.
• Turtles have no ear openings; the eardrum is
covered with scales and encircled by a bony otic
capsule, which is absent in other reptiles
• Their hearing thresholds are high in comparison to
other reptiles, reaching up to 500 Hz in air, but
underwater they are more attuned to lower
frequencies.
• The loggerhead sea turtle has been shown
experimentally to respond to low sounds, with
maximal sensitivity between 100 and 400 Hz.
• Turtles have olfactory (smell)
and vomeronasal receptors along the nasal cavity,
the latter of which are used to detect chemical
signals.
• Experiments on green sea turtles showed they
could learn to respond to a selection of different
odorant chemicals such
as triethylamine and cinnamaldehyde, which were
detected by olfaction in the nose. Such signals
could be used in navigation.

18. Breathing in Turtles
• The rigid shell of turtles is not capable of expanding
and making room for the lungs, as in other
amniotes, so they have had to evolve special
adaptations for respiration.[
• The lungs of turtles are attached directly to the
carapace above while below, connective tissue
attaches them to the organs.
• They have multiple lateral (side) and medial
(middle) chambers (the numbers of which vary
between species) and one terminal (end) chamber.[
• The lungs are ventilated using specific groups of
abdominal muscles attached to the organs that pull
and push on them.
• Specifically, it is the turtle's large liver that
compresses the lungs. Underneath the lungs, in
the coelomic cavity, the liver is connected to the
right lung by the root, and the stomach is directly
attached to the left lung, and to the liver by
a mesentery. When the liver is pulled down,
inhalation begins.Supporting the lungs is a wall
or septum, which is thought to prevent them from
collapsing.
• During exhalation, the contraction of
the transversus abdominis muscle propels the
organs into the lungs and expels air. Conversely,
during inhalation, the relaxing and flattening of
the oblique abdominis muscle pulls the transversus
back down, allowing air back into the lungs.[
• Although many turtles spend large amounts of their
lives underwater, all turtles breathe air and must
surface at regular intervals to refill their lungs.
Depending on the species, immersion periods vary
between a minute and an hour.
• Some species can respire through the cloaca, which
contains large sacs that are lined with many finger-
like projections that take up dissolved oxygen from
the water

19. Circulation
• urtles share the linked circulatory and pulmonary
(lung) systems of vertebrates, where the three-
chambered heart pumps deoxygenated blood
through the lungs and then pumps the
returned oxygenated blood through the body's
tissues. The cardiopulmonary system has both
structural and physiological adaptations that
distinguish it from other vertebrates. Turtles have a
large lung volume and can move blood through non-
pulmonary blood vessels, including some within the
heart, to avoid the lungs while they are not
breathing.
• They can hold their breath for much longer periods
than other reptiles and they can tolerate the
resulting low oxygen levels. They can moderate the
increase in acidity during anaerobic (non-oxygen-
based) respiration by chemical buffering and they
can lie dormant for months,
in aestivation or brumation.[
• The heart has two atria but only one ventricle. The
ventricle is subdivided into three chambers. A
muscular ridge enables a complex pattern of blood
flow so that the blood can be directed either to the
lungs via the pulmonary artery, or to the body via
the aorta.
• The ability to separate the two outflows varies
between species. The leatherback has a powerful
muscular ridge enabling almost complete
separation of the outflows, supporting its actively
swimming lifestyle. The ridge is less well developed
in freshwater turtles like the sliders (Trachemys).
• Turtles are capable of enduring periods of
anaerobic respiration longer than many other
vertebrates. This process breaks down sugars
incompletely to lactic acid, rather than all the way
to carbon dioxide and water as in aerobic (oxygen-
based) respiration.
• They make use of the shell as a source of
additional buffering agents for combating
increased acidity, and as a sink for lactic acid

20. Digestive System in Turtle
• Most vertebrates have similar
digestive systems and the turtle
is no exception.
• Turtles are not strictly
herbivores.
• All species are found to eat at
least some meat which causes
them to have powerful digestive
enzymes.
• In addition turtles swallow their
food with very little chewing.
• Food particles are often whole
or in fairly large chunks.
• The salivary glands of the turtle
help to soften and break down
the food to make swallowing
possible.

21. Diet and feeding Behaviour of Turtles
• A green sea turtle grazing on seagrassMost turtle
species are opportunistic omnivores; land-dwelling
species are more herbivorous and aquatic ones
more carnivorous
• Generally lacking speed and agility, most turtles feed
either on plant material or on animals with limited
movements like mollusks, worms, and insect larvae.
• Some species, such as the African helmeted
turtle and snapping turtles, eat fish, amphibians,
reptiles (including other turtles), birds, and
mammals. They may take them by ambush but also
scavenge.
• The alligator snapping turtle has a worm-like
appendage on its tongue that it uses to lure fish into
its mouth. Tortoises are the most herbivorous group,
consuming grasses, leaves, and fruits.
• Many turtle species, including tortoises, supplement
their diet with eggshells, animal bones, hair, and
droppings for extra nutrients.
• Turtles generally eat their food in a straightforward
way, though some species have special feeding
techniques.
• The yellow-spotted river turtle and the painted
turtle may filter feed by skimming the water surface
with their mouth and throat open to collect particles
of food. When the mouth closes, the throat
constricts and water is pushed out through the
nostrils and the gap in between the jaws.
• Some species employ a "gape-and-suck method"
where the turtle opens its jaws and expands its
throat widely, sucking the prey in.
• The diet of an individual within a species may
change with age, sex, and season, and may also
differ between populations. In many species,
juveniles are generally carnivorous but become
more herbivorous as adults.[13][65] With Barbour's
map turtle, the larger female mainly eats mollusks
while the male usually eats arthropods. Blanding's
turtle may feed mainly on snails or crayfish
depending on the population. The European pond
turtle has been recorded as being mostly
carnivorous much of the year but switching
to water lilies during the summer.[66] Some species
have developed specialized diets such as the
hawksbill, which eats sponges, the leatherback,
which feeds on jellyfish, and the Mekong snail-
eating turtle

22. Reproduction and life cycle of Turtles
• Turtles have a wide variety of mating behaviors but do not
form pair-bonds or social groups. In green sea turtles,
females generally outnumber males. In terrestrial species,
males are often larger than females and fighting between
males establishes a dominance hierarchy for access to
mates. For most semi-aquatic and bottom-walking aquatic
species, combat occurs less often. Males of these species
instead may use their size advantage to mate forcibly.
• In fully aquatic species, males are often smaller than
females and rely on courtship displays to gain mating access
to females:
Temperature Dependent Sex Determination in Turtle
• For most turtles and tortoises, the temperature of the nest
controls whether the eggs hatch into males or females.
• A very warm nest usually produces females, and a cooler nest
produces males.
• In some species, an extremely cold nest temperature produces
females.
• In a few species, the nests have about equal numbers of males
and females, no matter what the temperature of the nest.
Courtship and mounting
• Courtship varies between species, and with habitat. It is
often complex in aquatic species, both marine and
freshwater, but simpler in the semi-aquatic mud turtles
and snapping turtles. A male tortoise bobs his head, then
subdues the female by biting and butting her before
mounting. The male scorpion mud turtle approaches the
female from the rear, and often resorts to aggressive
methods such as biting the female's tail or hind limbs,
followed by a mounting.
• Female choice is important in some species, and female
green sea turtles are not always receptive. As such, they
have evolved behaviors to avoid the male's attempts at
copulation, such as swimming away, confronting the male
followed by biting or taking up a refusal position with her
body vertical, her limbs widely outspread, and her plastron
facing the male. If the water is too shallow for the refusal
position, the females resort to beaching themselves, as
the males do not follow them ashore.[83]
• Mounting behavior in the three-toed box turtleAll turtles
fertilize internally; mounting and copulation can be
difficult. In many species, males have a concave plastron
that interlocks with the female's carapace. In species like
the Russian tortoise, the male has a lighter shell and
longer legs.
• The high, rounded shape of box turtles are particular
obstacles for mounting. The male eastern box turtle leans
backward and hooks onto the back of the female's
plastron. Aquatic turtles mount in water,[87][88] and female
sea turtles support the mounting male while swimming
and diving.[89] During copulation, the male turtle aligns his
tail with the female's so he can insert his penis into her
cloaca.[90] Some female turtles can store sperm from
multiple males and their egg clutches can have multiple
sires.

23. Eggs and hatchlings
• Turtles, including sea turtles, lay their eggs on land, although some lay
eggs near water that rises and falls in level, submerging the eggs. While
most species build nests and lay eggs where they forage, some travel
miles. The common snapping turtle walks 5 km (3 mi) on land, while
sea turtles travel even further; the leatherback swims some 12,000 km
(7,500 mi) to its nesting beaches
• Most turtles create a nest for their eggs. Females usually dig a flask-like
chamber in the substrate. Other species lay their eggs in vegetation or
crevices. Females choose nesting locations based on environmental
factors such as temperature and humidity, which are important for
developing embryos. Depending on the species, the number of eggs
laid varies from one to over 100. Larger females can lay eggs that are
greater in number or bigger in size. Compared to freshwater turtles,
tortoises deposit fewer but larger eggs. Females can lay multiple
clutches throughout a season, particularly in species that experience
unpredictable monsoons
• Marginated tortoise emerges from its eggMost mother turtles do no
more in the way of parental care than covering their eggs and
immediately leaving, though some species guard their nests for days or
weeks.[94] Eggs vary between rounded, oval, elongated, and between
hard- and soft-shelled.[95] Most species have their sex determined by
temperature. In some species, higher temperatures produce females
and lower ones produce males, while in others, milder temperatures
produce males and both hot and cold extremes produce
females.[13] There is experimental evidence that the embryos
of Mauremys reevesii can move around inside their eggs to select the
best temperature for development, thus influencing their sexual
destiny. In other species, sex is determined genetically. The length of
incubation for turtle eggs varies from two to three months for
temperate species, and four months to over a year for tropical
species.[13] Species that live in warm temperate climates can delay their
development.
• Hatching young turtles break out of the shell using an egg tooth, a
sharp projection that exists temporarily on their upper beak.
• Hatchlings dig themselves out of the nest and find safety in
vegetation or water. Some species stay in the nest for longer, be it for
overwintering or to wait for the rain to loosen the soil for them to dig
out., Young turtles are highly vulnerable to predators, both in the egg
and as hatchlings. Mortality is high during this period but significantly
decreases when they reach adulthood. Most species grow quickly
during their early years and slow down when they are mature

24. Osmoregulation &Thermoregulation in Turtles
Osmoregulation:
• In sea turtles, the bladder is one unit and in most freshwater
turtles, it is double-lobed.
• Sea turtle bladders are connected to two small accessory
bladders, located at the sides to the neck of the urinary
bladder and above the pubis.
• Arid-living tortoises have bladders that serve as reserves of
water, storing up to 20% of their body weight in fluids. The
fluids are normally low in solutes, but higher during droughts
when the reptile gains potassium salts from its plant diet.
• The bladder stores these salts until the tortoise finds fresh
drinking water.
• To regulate the amount of salt in their bodies, sea turtles and
the brackish-living diamondback terrapin secrete excess salt in
a thick sticky substance from their tear glands.
• Because of this, sea turtles may appear to be "crying" when
on land
• Smaller pond turtles, like these northern red-bellied cooters,
regulate their temperature by basking in the sun.
Thermoregulation:
• Smaller pond turtles, like these northern red-bellied
cooters, regulate their temperature by basking in the
sun.Turtles, like other reptiles, have a limited ability
to regulate their body temperature. This ability varies
between species, and with body size.
• Small pond turtles regulate their temperature by crawling
out of the water and basking in the sun, while small
terrestrial turtles move between sunny and shady places
to adjust their temperature.
• Large species, both terrestrial and marine, have
sufficient mass to give them substantial thermal inertia,
meaning that they heat up or cool down over many
hours.
• The Aldabra giant tortoise weighs up to some 60
kilograms (130 lb) and is able to allow its temperature to
rise to some 33 °C (91 °F) on a hot day, and to fall
naturally to around 29 °C (84 °F) by night. Some giant
tortoises seek out shade to avoid overheating on sunny
days. On Grand Terre Island, food is scarce inland, shade
is scarce near the coast, and the tortoises compete for
space under the few trees on hot days. Large males may
push smaller females out of the shade, and some then
overheat and die.
• Adult sea turtles, too, have large enough bodies that they
can to some extent control their temperature. The largest
turtle, the leatherback, can swim in the waters off Nova
Scotia, which may be as cold as 8 °C (46 °F), while their
body temperature has been measured at up to 12 °C
(22 °F) warmer than the surrounding water. To help keep
their temperature up, they have a system
of countercurrent heat exchange in the blood vessels
between their body core and the skin of their flippers.
The vessels supplying the head are insulated by fat
around the neck.

25. Communication and intelligence, Defense and Migratory behaviour of turtles
Communication and intelligence:
• While popularly thought of as mute, turtles make various sounds to
communicate
• One study which recorded 53 species found that all of them
vocalized. Tortoises may bellow when courting and mating.
• Various species of both freshwater and sea turtles emit short, low-
frequency calls from the time they are in the egg to when they are
adults. These vocalizations may serve to create group cohesion
when migrating. The oblong turtle has a particularly large vocal range;
producing sounds described as clacks, clicks, squawks, hoots, various
kinds of chirps, wails, hooos, grunts, growls, blow bursts, howls, and
drum rolls.
• Play behavior has been documented in some turtle species.
• In the laboratory, Florida red-bellied cooters can learn novel tasks and
have demonstrated a long-term memory of at least 7.5 months.
• Similarly, giant tortoises can learn and remember tasks, and master
lessons much faster when trained in groups.
• Tortoises appear to be able to retain operant conditioning nine years
after their initial training.
• Studies have shown that turtles can navigate the environment using
landmarks and a map-like system resulting in accurate direct routes
towards a goal.
• Navigation in turtles have been correlated to high cognition function in
the medial cortex region of the brain.
Defense:
• When sensing danger, a turtle may flee, freeze or withdraw into its
shell. Freshwater turtles flee into the water, though the Sonora mud
turtle may take refuge on land as the shallow temporary ponds they
inhabit make them vulnerable.
• When startled, a softshell turtle may dive underwater and bury itself
under the sea floor.[78] If a predator persists, the turtle may bite or
discharge from its cloaca. Several species produce foul-smelling
chemicals from musk glands. Other tactics include threat displays
and Bell's hinge-back tortoise can play dead. When attacked, big-
headed turtle hatchlings squeal, possibly startling the predator.
Migration
• Turtles are the only reptiles that migrate long distances, more
specifically the marine species that can travel up to thousands of
kilometers. Some non-marine turtles, such as the species
of Geochelone (terrestrial), Chelydra (freshwater),
and Malaclemys (estuarine), migrate seasonally over much shorter
distances, up to around 27 km (17 mi), to lay eggs. Such short
migrations are comparable to those of some lizards, snakes, and
crocodilians.
• Sea turtles nest in a specific area, such as a beach, leaving the eggs to
hatch unattended. The young turtles leave that area, migrating long
distances in the years or decades in which they grow to maturity, and
then return seemingly to the same area every few years to mate and
lay eggs, though the precision varies between species and
populations. This "natal homing" has appeared remarkable to
biologists, though there is now plentiful evidence for it, including
from genetics.
• How sea turtles navigate to their breeding beaches remains unknown.
One possibility is imprinting as in salmon, where the young learn the
chemical signature, effectively the scent, of their home waters before
leaving, and remember that when the time comes for them to return
as adults. Another possible cue is the orientation of the earth's
magnetic field at the natal beach.
• There is experimental evidence that turtles have an effective
magnetic sense, and that they use this in navigation. Proof that
homing occurs is derived from genetic analysis of populations of
loggerheads, hawksbills, leatherbacks, and olive ridleys by nesting
place.
• For each of these species, the populations in different places have
their own mitochondrial DNA genetic signatures that persist over the
years. This shows that the populations are distinct and that homing
must be occurring reliably
Nervous System
• The brain consists of the olfactory bulb, cerebral
cortex, thalamus, hypothalamus, pituitary, optic lobes, cerebellum,
and medulla
• Turtles have two meningeal layers – the inner leptomeninx and
outer dura mater. The space between these is used for intrathecal
injections and CSF collection.
– There is no subarachnoid space.
– The epidural space does not contain CSF
• Turtles have the same 12 cranial nerves as in other animals.

26. Conservation Status of Turtles
• Among vertebrate orders, turtles are second only
to primates in the percentage of threatened
species. 360 modern species have existed since
1500 AD. Of these, 51–56% are considered
threatened and 60% considered threatened or
extinct. Turtles face many threats, including habitat
destruction, harvesting for consumption, the pet
trade, light pollution, and climate change. Asian
species have a particularly high extinction risk,
primarily due to their long-term unsustainable
exploitation for food and medicine, and about 83%
of Asia's non-marine turtle species are considered
threatened. As of 2021, turtle extinction is
progressing much faster than during
the Cretaceous-Tertiary extinction. At this rate, all
turtles could be extinct in a few centuries.
• Turtle hatcheries can be set up when protection
against flooding, erosion, predation, or heavy
poaching is required, Chinese markets have sought
to satisfy an increasing demand for turtle meat with
farmed turtles. In 2007 it was estimated that over a
thousand turtle farms operated in China.
• All the same, wild turtles continue to be caught and
sent to market in large numbers, resulting in what
conservationists have called "the Asian turtle crisis".
• In the words of the biologist George Amato, the
hunting of turtles "vacuumed up entire species from
areas in Southeast Asia", even as biologists still did
not know how many species lived in the region. In
2000, all the Asian box turtles were placed on
the CITES list of endangered species.
• Harvesting wild turtles is legal in some American
states,[156] and there has been a growing demand
for American turtles in China.[157][158] The Florida
Fish and Wildlife Conservation
Commission estimated in 2008 that around 3,000
pounds of softshell turtles were exported weekly
via Tampa International Airport.[158] However, the
great majority of turtles exported from the US
between 2002 and 2005 were farmed.[157]
• Large numbers of sea turtles are accidentally killed
in longlines, gillnets, and trawling nets as bycatch.
A 2010 study suggested that over 8 million had
been killed between 1990 and 2008; the Eastern
Pacific and the Mediterranean were identified as
among the areas worst affected.[141] Since the
1980s, the United States has required all shrimp
trawlers to fit their nets with turtle excluder
devices that prevent turtles from being entangled
in the net and drowning.[142] More locally, other
human activities are affecting marine turtles. In
Australia, Queensland's shark culling program,
which uses shark nets and drum lines, has killed
over 5,000 turtles as bycatch between 1962 and
2015; including 719 loggerhead turtles and 33
hawksbill sea turtles, which are listed as critically
endangered.[159]
• Native turtle populations can also be threatened
by invasive ones. The central North American red-
eared slider turtle has been listed among the
"world's worst invasive species", pet turtle having
been released globally. They appear to compete
with native turtle species in eastern and western
North America, Europe, and Japan.

27. Human uses of Turtles
 Uses of titles In Traditional Culture:
• In Hindu mythology, the World Turtle, named Kurma or
Kacchapa, supports four elephants on his back; they, in
turn, carry the weight of the whole world on their backs.
The turtle is one of the ten avatars or incarnations of the
god Vishnu.[163] The yoga pose Kurmasana is named for the
avatar. World Turtles are found in Native American cultures
including the Algonquian, Iroquois, and Lenape. They tell
many versions of the creation story of Turtle Island. One
version has Muskrat pile up earth on Turtle's back, creating
the continent of North America. An Iroquois version has the
pregnant Sky Woman fall through a hole in the sky between
a tree's roots, where she is caught by birds who land her
safely on Turtle's back; the Earth grows around her. The
turtle here is altruistic, but the world is a heavy burden, and
the turtle sometimes shakes itself to relieve the load,
causing earthquakes.
• A turtle was the symbol of the Ancient Mesopotamian
god Enki from the 3rd millennium BCE onward. An ancient
Greek origin myth told that only the tortoise refused the
invitation of the gods Zeus and Hera to their wedding, as it
preferred to stay at home. Zeus then ordered it to carry its
house with it, ever after.[170] Another of their gods, Hermes,
invented a seven-stringed lyre made with the shell of a
tortoise.[171] In the Shang dynasty Chinese practice
of plastromancy, dating back to 1200 BCE, oracles were
obtained by inscribing questions on turtle plastrons using
the oldest known form of Chinese characters, burning the
plastron, and interpreting the resulting cracks. Later, the
turtle was one of the four sacred animals in Confucianism,
while in the Han period, steles were mounted on top of
stone turtles, later linked with Bixi, the turtle-shelled son of
the Dragon King
 As pets
• Some turtles, particularly small terrestrial and freshwater
species, are kept as pets.[184][185] The demand for pet
turtles increased in the 1950s, with the US being the main
supplier, particularly of farm-bred red-eared sliders. The
popularity for exotic pets has led to an increase in
illegal wildlife trafficking. Around 21% of the value of live
animal trade is in reptiles, and turtles are among the more
popularly traded speci
 As food and other uses
• The flesh of captured wild turtles continues to be eaten in
Asian cultures,[188] while turtle soup was once a popular
dish in English cuisine.[189] Gopher tortoise stew has been
popular with some groups in Florida.[190] The supposed
aphrodisiac or medicinal properties of turtle eggs created
a large trade for them in Southeast Asia.[164] Hard-shell
turtle plastrons and soft-shell carapaces are widely used
in traditional Chinese medicine; Taiwan imported nearly
200 metric tons of hard-shells from its neighbors yearly
from 1999 to 2008.[191] A popular medicinal preparation
based on herbs and turtle shells is guilinggao jelly.[192] The
substance tortoiseshell, usually from the hawksbill turtle,
has been used for centuries to make jewelry, tools, and
ornaments around the Western Pacific.[164] Hawksbills have
accordingly been hunted for their shells.[193] The trading of
tortoiseshell was internationally banned in 1977 by
CITES.[194] Some cultures have used turtle shells to make
music: Native American shamans made them into
ceremonial rattles, while Aztecs, Mayas,
and Mixtecs made ayotl drums

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