Sea turtles are reptiles that live in the ocean. Sea turtles (superfamily Chelonioidea), sometimes called marine turtles, are reptiles of the order Testudines and of the suborder Cryptodira. They are cold blooded animals

1. Biology of Sea
Turtles
 Submitted by:-
 Vinod kumar
 FRM

2. Introduction
 Sea turtles are reptiles that live in the ocean.
 Sea turtles (superfamily Chelonioidea), sometimes called
marine turtles, are reptiles of the order Testudines and of
the suborder Cryptodira.
 They are cold blooded animals.However,they can
regulate their body temperature by controlling the blood
flow in the skin and fins.
 They often undergo a resting condition called hibernation
during winter season.

3. Taxonomic Classification

4. Habitats
 Sea turtles inhabit tropical
and subtropical waters
around the world.
 The adults stay in shallow
water and near the coasts,
but sometimes they enter
the open sea.
 Estuaries, brackish areas
where water from the ocean
mixes with fresh water from
the rivers, mangroves, and
seagrass with tall
vegetation,coral reefs are
also part of their habitat.

5. Distribution
 Green sea turtle (Chelonia mydas) – the Atlantic Ocean, Gulf of Mexico, Puerto
Rico, Mediterranean Sea, African coasts, Northern Australia, Argentina, Pacific
Ocean.
 Loggerhead sea turtle (Caretta caretta) – coastal bays and streams of all
continents, except Antarctica.
 Kemp’s Ridley sea turtle (Lepidochelys kempii) – the Gulf of Mexico, South of the
United States and some specimens in Morocco and the Mediterranean Sea.
 Olive Ridley sea turtle (Lepidochelys olivacea) – Mexico, Panama, Costa Rica
and India.
 Hawksbill sea turtle (Eretmochelys imbricata) – Indo-Pacific Regions, Africa,
Brazil, Australia.
 Flatback sea turtle (Natator depressus) – Australian coasts as well as southern
Indonesia and Papua New Guinea.( limited distribution).
 Leatherback sea turtle (Dermochelys coriacea) – It has an extensive distribution
around the world. The Gulf of Alaska, Argentina, South Africa, California (USA),
Tasmania and India are just some of the places where it lives.

6. Adaptations
 Modified appendages in the form of flippers.
 They are the only reptiles with hard shells.It is
build out of a bony layer and a keratin
layer.The shell is hydrodynamic in nature.
 The jaw structure is adapted to the specific
feeding habits.
Ex. Strong jaws are present for loggerheads and
serrated jaws are present in green turtle.
 They have salt glands for excreting the
ingested salt.
 They have distinctively shaped beaks for
adapting to different feeding habits.
 Olfaction sense is well developed.

7. Adaptations

8. General Physiology
 The body temperature is regulated by the surrounding
environment.Often they bask under the sun.
 Turtles overcome the constriction in the expansion of its ribs
by muscles that increases the space surrounding their lung as
they breathe in.This provides room for the lungs to expand.
 Turtle’s heart have the ability to control whether blood is sent
to the lungs or the rest of the body.( Depending on the
importance of oxygen uptake or temperature regulation at any
given time).

9. Sea turtle shell
 The shell depends on species.The colour and shape varies with
species.
 The shell consists of a dorsal carapace and a ventral plastron.
 The shell is attached to the body and it grows as the turtle grows.
 The shell protects them from predation and abrasion.
 In all species, except the leatherback,the bony shell is composed of
fused ribs and the backbone is atttached to the carapace.
 The ventral surface – plastron is joined by bridge.
 The bone elements are overlyed by scutes made of keratin.

10. Plastron

11. Feeding
 The diet depends on various
factors – type of turtle, their
environment, their physical
features and their ability to
consume different species.
Ex.A hawksbill has a narrow head
with jaws made for getting food from
crevices.
Loggerheads and Ridley ‘s jaws are
adapted for crushing and grinding.
 Sea turtles change their diet as
age changes.
 Ex.Loggerhead hatchlings are
omnivorous whereas the adults
are carnivorous.

12. Mating
 Females mate with different males
in the breeding season and are
able to nest upto 7 times in two
week intervals.
 They do not bred every year and
the inter-nesting period is called
the remigration period.
 Females come ashore sandy
beaches in the summer and lay
their eggs in holes.They follows
Philopatry.
 Females lay around 100 eggs and
the incubation period last for six
weeks.

13. Juvenile development
 Juvenile turtles remain at open sea for about ten years.This phase is called
pelagic phase.
 The neritic phase begins as they enter into the littoral zone and during this
phase,they can dive into the seabed and can prey upon bottom dwelling
organisms.
 The turtles reach sexual maturity at the age of thirty.

14. Migration
 This is mainly done to give births to young ones .
 For this,they return to the same beach and coast they are
hatched out.
 The turtles rely on Earth’s magnetic field to find their beaches.
( Internal compass).
 Olfaction sense is also used for this.

15. Sea turtle
nesting  Female turtle came ashore on a
sandy beach to nest a few weeks
after mating.This is to build their
nests and lay their eggs.
 Usually nests from May to October (
except leatherback – which nests
during winter).
 The number of eggs in a nest is
called a clutch.This clutch size varies
with species.
 On an average,sea turtles deposit
about 100 eggs in each nest and lay
between 3-7 nests during each
nesting season.

16. Gender determination
 In turtles, Temperature dependent sex determination is
mostly followed.(TSD)
 The temperature of the developing eggs, particularly during
the middle one third of embryonic development,determines
the sex of turtle.
 The turtle eggs,which incubates below 29°C,will be male and
if the eggs hatch above 29°C,the hatchlings will be female.
 Temperature that fluctuate between the two extreme values
will produce a mix of male and female baby turtles.
 The critical period of incubation is known as thermosensitive
period.

17. Life cycle of a sea turtle

18. Sea turtle species
 There are 7 living species of
sea turtles from the families
– Cheloniidae and
Dermochelyidae.
 The Dermochelyidae family
is the largest of all the living
turtles- the leatherback
turtle.
 All the others belongs to
Cheloniidae.

19. Family
 1) Dermochelyidae( 1 genera,1 species)
Genus- Dermochelys Species – Dermochelys coriace(
Leatherback turtle)
 These are the largest and most ancient.
 Appearance is a distinctive balck with white spots.
 Their shell consists of cartilaginous osteoderms .
 Head has two saber like tooth projections.
 They are pelagic and remain in open ocean.

20.  2) Cheloniidae ( 5 genera,6 species,1 race)
1)Genus- chelonia- a)The green turtle ( chelonia mydas)
b)The black turtle ( chelonia mydas agassizi)-sub species or race
 This genus contains only one living species – green turtle.
 The green turtle has a brownish coloured carapace and scales on
the legs,with yellowish plastron.
 The green term came from the large greenish fat deposit found
under the carapace.

21.  b)The black turtle
 Black turtle is characterised by dark black colour of both the
carapace and plastron in adult form.
 This race is found along the Pacific coastline of Mexico and
extends in smaller populations along the Pacific central
American coastline to Panama.
 They are herbivores.

22.  2) Genus- Lepidochelys : a)Lepidochelys kempii( The kemp’s
ridley)
b) Lepidochelys olivacea( The olive ridley)
 Kemp’s Ridley is the most rarest of the sea turtles and olive ridley is
the most abundant.
 The Ridley’s are smallest sea turtles.
 They both shows a communal nesting called – ‘ arribadas'.Some
are solitary nesters.
 They have high hatching success.
 Kemp’s Ridley turtle have arribadas on only one beach in the world-
Rancho nuevo( Carribean, Mexico).

23. Kemp’s Ridley
Olive Ridley
Olive Ridley
arribada

24.  3) Genus- Eretmochelys imbricata ( Hawksbill)
 They have beautiful carapace.
 The head is distinguished by a narrow, elongated,snout like mouth
and jaw that resembles the beak of a raptor.
 They are solitary nesters.
 Their diet contains 90% sponges.
 They have large clutch size.(130 eggs per nest).
 Habitats include shallow coastal waters and they are found on
muddy bottoms or coral reefs.
 They quickly construct the nests.

25.  4) Genus- Caretta ( Caretta caretta)- Loggerhead turtle
 They have the largest and broadest head and jaw of the
cheloniids.
 They have a beak like snout which is very broad.
 Loggerheads are carnivorous.( crabs,
molluscs,corals,sea anemones,barnacles etc.)
 They inhabit diverse habitats and they shift between
deeper continental shelf and up into shallow river
estuaries and lagoons.
 They make a simple nest at night.

26.  5) Natator ( Natator depressus)- The flatback turtle
 They have a very limited distribution and found only in the waters of
Australia.
 The nesting beaches are in Northern and South central
Queensland.
 Most of the nesting sites are remote and they nest during the
daytime.
 They have a compressed appearance with thin carapace profile and
have oily scutes.
 They does not have extended pelagic phase.
 They lay the 2 nd largest egg of all the sea turtles.

27. Indian scenario
 About 5 species of sea turtles were reported from seas
around India.
 4 species are from Andaman and Nicobar Islands.
 The 5 species are- leatherback, loggerhead, green
turtle,olive ridley and hawksbill.
 A significant portion of olive ridley turtle population nests
at nesting sites along the Eastern coast of India.
 4 out of the 5 species ( except loggerhead) are seen off
the coast of Maharashtra.

29. Nesting sites of Sea turtles in India
 West coast- Gujarat, Maharashtra,Goa, Karnataka
and Kerala.
( Green ,olive ridley and leatherback)
 East coast- West Bengal, Orissa, Andhra Pradesh
and Tamil Nadu.
( Olive ridley)
 Andaman and Nicobar Islands – olive ridley, green
turtle, leatherback and hawksbill.

30. Distribution of Sea Turtles along
the Indian coast
Sea turtle nesting sites
in India

31. Conservation Status

32. Threats
Ghost fishing
Vessel strike
Plastic pollution
Predation

33. Light and Noise pollution
Coastal Development
Flooding
Poaching

34. Bycatch Climate change
Using of turtle shell for making
jewellery

35. Protection Measures

36. Conclusion
 There are 7 different types of sea turtle species.
 These wonderful species are classified as either
endangered or threatened of becoming extinct.
 It is important to protect and conserve these species.
 Various projects and National action plan was
created for the same.

37. References
 Biswas ,K.P.,(2013). Marine Biology.Daya Publishing House,Astral
International Pvt.Ltd.,New Delhi -110002,P- 318-323.
 John H.Steele.,(2009).Marine Biology:A derivative of encyclopaedia of
ocean sciences,Elsevier Ltd.,P-450-457.
 Barry Fell.,(1975). Introduction to Marine Biology., Harper and Row
publishers,New York, Evanston,San Francisco, London,P-226-228.
 https://oliveridleyproject.org/threats-to-sea-turtles
 https://seaworld.org/animals/all-about/sea-turtles/habitat/
 https://ocean.si.edu/ocean-life/reptiles/sea-turtles

38. Thank
you