A vertebrate is an animal with a spinal cord surrounded by cartilage or bone. The word comes from vertebrae, the bones that make up the spine. Animals that are not vertebrates are called invertebrates. Vertebrates include birds, fish, amphibians, reptiles, and mammals

1. Subphylum 4: VertebrataSubphylum 4: Vertebrata
• L. vertebratus, jointed
• Vertebrates have a strong supporting structure called the backbone by
replacing the notochord.
• Backbone is made of individual segments called vertebrae. For this
character this subphylum is called as vertebrata.
• Presence of skull or cranium. For this character this subphylum is also
called as Craniata.
• Dorsal, hollow nerve cord becomes spinal cord and Bones or cartilage
surround the spinal cord
• Unlike invertebrates which have exoskeletons, vertebrates have an
endoskeleton. Endoskeleton continues to grow along with the animal, and
contains living material.
• Body divisible into head, trunk and tail
• L. vertebratus, jointed
• Vertebrates have a strong supporting structure called the backbone by
replacing the notochord.
• Backbone is made of individual segments called vertebrae. For this
character this subphylum is called as vertebrata.
• Presence of skull or cranium. For this character this subphylum is also
called as Craniata.
• Dorsal, hollow nerve cord becomes spinal cord and Bones or cartilage
surround the spinal cord
• Unlike invertebrates which have exoskeletons, vertebrates have an
endoskeleton. Endoskeleton continues to grow along with the animal, and
contains living material.
• Body divisible into head, trunk and tail

2. Vertebrates
 Vertebrates belong to the subphylum Vertebrata of the phylum Chordata.
 A Vertebrate may be defined as a special kind of chordate animal that has a
cartilaginous or bony endoskeleton consisting of a cranium housing a brain
and a vertebral column through which the nerve cord passes.
 Big five diagnostic vertebrate characteristics:
1. Notochord-replaced by vertebral column or backbone
2. Vertebrae- individual segments of vertebral column or backbone.
3. Skull or cranium
4. Dorsal hollow nerve cord
5. Pharyngeal gill-slits
Chordates= Protochordates + Vertebrates

3. Development of Vertebrates

4. Classification of Vertebrates
Subphylum Vertebrata
Agnatha
Class
Gnathostomata
Superclass
Pisces Tetrapoda
Ostracodermi Cyclostomata
Osteichthyes
Chondrichthyes
Placodermi
Reptilia
Aves
Mammalia
Amphibia
Division

5. Phylogeny of Vertebrates
 Evolution is the progressive change in the genetic
composition or heritable traits of a biological population
over successive generations, often resulting in the
development of new species.
 Phylogeny is the history of evolutionary development of a
species or trait of a species or of a group of organisms.
 The concept of phylogeny is used to place animal groups
in proper evolutionary sequence.

6. Geological time
 The geological time (GT) is used by geologists,
paleontologists, and other Earth scientists to describe the
timing and relationships between events that have
occurred throughout Earth’s history.
 The largest defined unit of time is the supereon, composed
of eons. Eons are divided into eras, which are in turn
divided into periods, epochs and ages. The terms
eonothem, erathem, system, series, and stage are used to
refer to the layers of rock that correspond to these periods
of geologic time in Earth's history.

7. Unit of geological time
Unit Subdivision of
unit
Time span
Eon 4 half a billion
years or more
Era 10 several hundred
million years
Period 22 tens to ~one
hundred million
years
Epoch tens of millions of
years
Ages millions of years
Supereon- Precambrian
Eon- Hadean, Archean, Proterozoic and Phanerozoic

8. Eon Era
Time frame (Ma = million years
ago)
Cenozoic
66 million years ago to present
day
Phanerozoic
Mesozoic 252.17 to 66 million years ago
Paleozoic 541 to 252.17 million years ago
Neoproterozoic 1,000 to 541 million years ago
Proterozoic Mesoproterozoic 1,600 to 1,000 million years ago
Paleoproterozoic 2,500 to 1,600 million years ago
Neoarchean 2,800 to 2,500 million years ago
Mesoarchean 3,200 to 2,800 million years ago
Archean Paleoarchean 3,600 to 3,200 million years ago
Eoarchean 4,000 to 3,600 million years ago
Hadean Eon
Formation of Earth to 4,000
million years ago

9. Phanerozoic
eon
Paleozoic
era
Cambrian period Plants like algae and the fauna such as
armored arthropods, Trilobites were
evolve
Ordovician period The first fossils of vertebrates i.e.
ostracoderms were found
Silurian period Some fossil fishes were found
Devonian period The first jawed fish, placoderms arose.
known as "The Age of the Fish“ because
the Devonian features a huge
diversification in fish including armored
fish and lobe-finned fish
Carboniferous
period
lobe-finned bony fishes (Crossopterygii)
gave rise to primitive stem amphibia
(Labyrinthodonts).
known as "The Age of the Amphibians”
The primitive reptiles and synapsids were
also evolved from the primitive
amphibians

10. Mesozoic
era
known as "The Age of the Reptiles“
because in this era reptiles were diversified
and rule the earth from the seas as
ichthyosaurs, the land as dinosaurs, and
even in the air as pterosaurs or flying
reptiles
Triassic The ancestral mammals, Therapsids were
derived from the primitive reptiles
Jurassic The ancestral birds, Pterosaurs,
Archaeopteryx were evolved and
Archaeopteryx had both reptilian as well
as avian characters
Cretaceous A new groups of mammals and birds were
appeared.
Cenozoic
era
Both birds and mammals started flourishing
known as the “Age of Mammals” because
mammals became the most diversified.

14. Amniotes:
Greek, amnion, "membrane surrounding the fetus“
Amniotes are a clade of tetrapod vertebrates comprising the reptiles, birds and
mammals that have an amniotic egg containing specialized extra embryonic membranes
i.e. the amnion, chorion, and allantois that protect the embryo.
They are also called as "higher vertebrates" (reptiles, birds and mammals), which lay
their eggs on land or retain the fertilized egg within the mother.
Formation of these extensive membranes during embryonic development is an
adaptation to lay eggs on land rather than in water as the anamniotes (including frogs)
typically do.
Amnion is an embryonic membrane in an amniotic egg that directly surrounds the
developing embryo in a reservoir of fluid.
Allantois is a membrane sac in an amniotic egg that exchange gases to facilitate
respiration and stores nitrogenous wastes.
Anamniotes:
Anamniotes are group of vertebrate animal comprising the cyclostomes, fishes, and
amphibians that have an anamniotic egg which lacks an amnion and allantois during
embryonic development
anamniotic eggs are jelly-like, instead of calcified and don’t have a nutrient-rich
membranes

16. How Vertebrates Regulate Body
Temperature
• Endothermic – warm-blooded
– An animal that generates its own body heat
– Examples – birds and mammals
• Ectothermic – cold-blooded
– Body temperature is determined by the surrounding environment such as sunlight or a
heated rock surface.
– Examples – reptiles, fish, and amphibians

17. Vertebrate Reproductive Development:
• Oviparous – “egg birth”
– Lay eggs and eggs hatch outside mother’s body
– Examples – Most fish, most reptiles, all birds, and 3
species of mammals
• Ovoviviparous – “egg-live birth”
– Fertilized eggs remain inside of mother
– Nourished by egg yolk – not the mom
– May lay the eggs and then hatch shortly thereafter
OR eggs hatch inside of mother and young are born
live
– Examples – Some fish- Australian angelshark
(Squatina australis), Dogfish (Scoliodon sorrakowah),
some reptiles
• Viviparous – “live birth”
– Young develop within the uterus
– Nourished by placenta
– Example – Golden hammerhead (Sphyrna tudes),
Scoophead (Sphyrna media), Placental mammals
(humans)

18. Lower vertebrata (Anamniota) Higher vertebrata (Amniota)
Cyclostomata, Chondrichthyes,
Osteichthyes and Amphibia
Reptilia, Aves and Mammalia
Predominantly Aquatic Predominantly terrestrial
Body consists of three parts. Neck
absent
Four parts
2 pairs of fins or limbs Fins never present. 2 pairs of
pentadactyle limbs
Pharyngeal gill clefts persist
throughout their life
Disappear in th eadult
Notochord persists Replaced by a vertebral column
Poikilothermous Homoiothermous

19. • Gr. a, not; gnathos, jaw
• Without true jaws
• Paired appendages absent
• Inner ear with two semi-circular canals
• cartilaginous skeleton
• Notochord persistent in adults
• rasping mouth to suck blood
• Gr. a, not; gnathos, jaw
• Without true jaws
• Paired appendages absent
• Inner ear with two semi-circular canals
• cartilaginous skeleton
• Notochord persistent in adults
• rasping mouth to suck blood
Division: AgnathaDivision: Agnatha

20. • Gr. Ostrakon, shell; derma, skin
• Palaeozoic, world’s first vertebrates
• Their body form was fishlike, usually flattened dorso-ventrally with huge head
and gill region
• No jaws, pectoral or pelvic fins but had only median fins
• Their body were very bony and heavily armoured.
• The head was encased in a solid shield made of broad bony dermal plates
• The rest of the body is surrounded by a series of smaller plates often called
dermal plates
e.g. Pteraspis rostrata
• Gr. Ostrakon, shell; derma, skin
• Palaeozoic, world’s first vertebrates
• Their body form was fishlike, usually flattened dorso-ventrally with huge head
and gill region
• No jaws, pectoral or pelvic fins but had only median fins
• Their body were very bony and heavily armoured.
• The head was encased in a solid shield made of broad bony dermal plates
• The rest of the body is surrounded by a series of smaller plates often called
dermal plates
e.g. Pteraspis rostrata
Class: OstracodermiClass: Ostracodermi

21. Biological Significance:
 Ostracoderms are espicially interesting because they represent the oldest known vertebrate
fossils which are found in the late cambrian and Ordovician rocks. They are the remote
ancestors of all the vertebrate including man
 Microscopic examination of their fossilized bony tissues reveals a great complexity of
structure and implying that these vertebrates were far advanced and had undergone a
considerable period of evolution before becoming fossilized
 They developed heavy bony armours for survival against the attacks of giant arachnid
predators. As the enemies disappeared, the descendants of ostracoderms, the cyclostomes,
also lost the unwanted heavy armour which was hinderance in rapid progression
 The cartilage of cyclostomes and sharks and skates (Chomdrichthyes) was previously
considered a precursor to bone and more primitive. Since the ostracoderms had bony
skeletons, the bone is now considered more primitive and the cartilage is interpreted as a
degenerate condition.

22. Class: OstracodermiClass: Ostracodermi

23. • Gr. cyklos, circular; stoma, mouth
• Body eel shaped
• Without scales, jaws and lateral fins
• Mouth rounded and suctorial
• Gills 5-16 pairs
• Parasites and scavengers
• 45 species
• Gr. cyklos, circular; stoma, mouth
• Body eel shaped
• Without scales, jaws and lateral fins
• Mouth rounded and suctorial
• Gills 5-16 pairs
• Parasites and scavengers
• 45 species
CyclostomataCyclostomata

24. Classification of Cyclostomata
Order 1. Petromyzontiformes (Gr., petros-stone+ myzon-suck)
 Freshwater and marine
 Mouth ventral, within a suctorial buccal funnel beset with many horny teeth.
 Gill pouches and gill slits 7 pairs each
 Dorsal fin well developed
 Branchial basket complete
e.g. Lamprey (Petromyzon)
Order 2. Myxiniformes (Gr., myxa-slime+ oidea-type of)
 All marine
 Mouth terminal with 4 pairs of tentacles and few teeth. No buccal funnel
 Gill pouches 6-15 pairs. Gill slits 1-15 pairs
 Dorsal fin feeble and absent
 Branchial basket poorly developed
 Large mucous glands open along the sides of the body and secrete enormous
quantity of slime, hence called slime eels
e.g. Hagfishes (Myxine)

25. Lamprey
 Three species are found in both salt and freshwater.
 Petromyzon marinus (Sea lamprey) is the marine species,
Lampetra fluviatilis is the freshwater lamprey
 Their name means stone lickers (lambere-to lick and petra=stone)
 They are external parasites

26. Systematic position:
Kingdom Animalia
Phylum Chordata
Class Cyclostolata
Order Petromyzontiformes
Family Petromyzontidae
Genus Petromyzon
Species Petromyzon marinus

27. Lamprey characteristics
 Oral disc/buccal funnel, with epidermal denticles and rasping tongue; active
"predatory parasites”
 No bone
 Nostril on top of head
 Well-developed vertebrate eyes
 Well-developed Lateral Line system
 Best developed pineal “eye” of any aquatic vertebrate;
 2 pairs of semicircular canals;
 Uniformly 7 pairs of gills
 Cartilaginous
 Eggs deposited in freshwater; freshwater larva; many species have
freshwater adult, but most migrate to sea and have marine adult stage
(anadromous).

28. External features
 The body is divided into three divisions-head, trunk and tail
 Greenish-brown in color
 It is without exoskeleton, soft and slimy by secretations from epidermal glands
Fins:
Paired appendages are absent
Two unequal median dorsal fins-first and second, caudal fin
Buccal funnel:
 The anterior end of the body or head bears a ventrally directed large cup-like
depression, the sucker or buccal funnel
 Surrounded by a marginal membrane beset with numerous soft small projections,
the oral papillae which help in attachment to a fish
 The longer sensory processes are project out from the papillae-cirri
 The inside of buccal funnel is beset with rows of conical yellow, horny, epidermal
teeth.
 A small circular mouth opening is situated at the apex of the buccal funnel
 The tongue bears large horny teeth

31.  The two eyes lack eyelids and are covered by a transparent
area of skin
Apertures:
(1)Mouth
(2)Nostril
(3)7 small rounded openings of external gill slits
(4)Cloaca
(5)Numerous small sensory pores of the lateral line
system

32. Habits
 It is a rather unpleasant animal
 The larval phase is a freshwater, sedentary and filter-feeding
 The adult lives in the sea and external parasites on fishes
 It clings to fishes, turtles etc. with its powerful suctorial mouth and cut the
scales and skin using their teeth to get to the blood and body fluid and
secreting an anticoagulant onto the tissue.

33. Reproduction
 Sexes are separate.
 Mature sea lampreys migrate into rivers or streams in April to July for
breeding
 Peak spawning occurs in June and July before the death of the adults
 Males move pebbles from a sandy bottom by their buccal funnel and make a
nest in the form of a horseshoe shaped depression or pit
 Females will anchor themselves by their oral disc to a stone in the nest and
a male winds his tail around her and eggs and sperm are discharged.
 Once the reproductive cycle is over, both females and males die within days
 Also, adults do not spawn, die due to degeneration of internal organs, lack
of essential substances and the acculmulation of poisonous metabolites

36. Sedentary phase
The eggs hatch after approximately 13days and attained a
length of approximately 6.4 mm. The blindworm-like larval
lamprey is known as ammocoetes
Small wormlike larvae swept downstream andwhen they
locate suitable habitat- usually slit/sand stream bottoms and
banks in slower moving waters- they burrow in and take up
residence and undergo a sedentary phase
The larvae feed micro-organisms, ciliates and diatoms from
the water through filter-feeding
Last from 3-17 years

37. Free swimming stage
 After sedentary phase, the larvae undergo metamorphosis. This begins
in mid July and lasts until the end of September
 Obvious external changes occur in the sea lamprey including the
development of functional eyes, a oral disc lined with teeth and a
grasping tongue. Sea lamprey also change its color. Also their kidneys
change to allow them to live in seawater
 Then lampreys leave the streams and enter the sea
 The lamprey parasitizes host fish by using their oral disc to suck blood
and body fluids
 Once this parasitic stage is over, lamprey return to streams and the
lifecycle begins all over again

38. Uses
 Lampreys have been used as food for humans
 In southwestern Europe, larger lampreys are still a highly prized delicacy
 In Britian, lampreys are commonly used as bait

41. Affinities of Cyclostomata:
Resemblances with Cephalochordata (Branchiostoma):
 Lack of jaws, exoskeleton, paired fins and gonoducts
 Persistent and continuousnotochord
 Numerous gill slits
Resemblances with Ostracoderms:
 Absence of biting jaws
 Single nasal opening
 Pineal eye
 No paired fins
 Pouch-like branchial sacs
 Internal ear with 2 semi-circular canals
 Lateral line system

42. Differences from fishes:
Absence of bitting jaws, scales, true teeth, paired
appendages, true fin rays,girdles, ribs, stomach, spleen and
gonoducts
Diphycercal caudal fin
Continuous median dorsal fin
Incompletely or poorly developed cranium, vertebral,
pancreas, brain and lateral line organs

43. PiscesPisces
• L. piscis, fish
• Exclusively aquatic, cold-blooded, oviparous and
ovoviviparous vertebrates
• Paired and unpaired fins and supported by dermal fin rays
• Skin usually moist and scaly
• Exoskeleton of dermal scales, denticles or bony plates
• Endoskeleton cartilaginous or bony
• Respiration by gills
• L. piscis, fish
• Exclusively aquatic, cold-blooded, oviparous and
ovoviviparous vertebrates
• Paired and unpaired fins and supported by dermal fin rays
• Skin usually moist and scaly
• Exoskeleton of dermal scales, denticles or bony plates
• Endoskeleton cartilaginous or bony
• Respiration by gills

44. Types of fins
1. Unpaired median fins
2. Paired lateral fins
Uses of fins:
 Caudal fin or tails are used for swimming
 Others fins are used as steering and rudders
 When the body is at rest, the paired lateral fins serve to
maintain equiibrium
 Lungfishes use them legs in walking
 The flying fish use their large and extended pectoral fins for
glding
 Pelvic fins of Chondrichthyes male modified into claspers
 In remoras, anterior dorsal fin forms an adhesive disc or sucker
on head

45. Types of Caudal fin

47. Types of scales
Scales are external coverings that grows out of
an animal’s skin to provide protection
Two types-epidermal and dermal
Dermal scales are small, thin, cornified,
calcareous and bony plates which fit closely
together or overlap each other on the body of
fish

48. Cosmoid Scales:
Do not found in living fishes
Found in ostracoderms, placoderms and extinct
sarcopterygians (lobe finned fishes and lung fishes)
4 distinct layers-
Upper layer is thin enamel-like ganoine
Second layer is thick, dentine like cosmine
Third layer is spongy bone
Lowest layer is compact bone
This scales grow along with the fish

50. Placoid scales:
Found in elasmobranch fishes-shark, skate and rays
Each placoid scale consists of a backwardly directed spine
arising from a rounded or rhomboidal basal plate
embedded in dermis
Spine is made of enamel-like and basal plate of dentine-like
bony material
A pulp cavity inside spine opens through basal plate
This scale donot grow with the fish. When the shark gets
longer, new scales grow to fill the gaps between the scales

52. Ganoid scales:
 Found in the chondrosteans such as gars, bichirs and reed fishes
(Polypterus, Acipencer, Leipidosteus)
 They are thick, flat and diamond-shaped scales
 They closely fitted side by side like tiles or pieces of jigjug puzzles,
instead of overlap each other.
 They provide a bony armour to the fish
 In Polypterus, This scales composed of 3 layers-
 Upper layer is enamel like ganoine
 Middle layer is dentine-like cosmine
 Inner layer is bony isopedine
 In Leipidosteus, two layers-
 Upper layer is enamel like ganoine
 Inner layer is bony isopedine

54. Cycloid scales:
 These type of scales are found in lung fishes, some
holosteans (Amia), and the most of the teleostean fishes
which have soft fin-rays such as carp, Hilsha, salmon etc.
 The word cycloid comes from the Greek word cyclo
meaning circle
 These scale are roughly circular in outline with smooth
outer edge
 Cycloid scales increase in size with the increasing the size
of that fish
 They are marked with several concentric lines of growth
which are called circuli, used for the determining the age of
the fish

55. During the cooler months of the year the scale grows more slowly and the
circuli are closer together leaving a band called an annulus. By counting the
annuli it is possible estimate the age of the fish.

56. Ctenoid scale:
 Found in those fishes with spiny fin rays such as perch, bass etc.
 Their outer edge (exposed part) have numerous small comb-like
teeth or spines.
 The word ctenoid comes from the Greek word cteno meaning comb
and refers to the comb-like ctenii on the margin of the scale
 Cycloid and ctenoid scale overlap each other which gives the fish
greater flexibility than those species with ganoid and cosmoid scale
 Some species of flatfishes such as soles, flounders bear two types,
ctenoid scale dorsally and cycloid scale ventrally

58. Functions of scales:
 Form a protective covering of exoskeleton on the body
 The age of the fish is also determined from the growth rings of the
scales
Modifications of scale:
 In eels, scales are minute and deeply embedded in dermis
 In some fishes (chimaeras), they become localized
 In globe fish (Tetradon) and porcupine fishes (Diodon), they
develop it into large protective spines making it difficult to be
swallowed.
 Shark teeth are modified large placoid scale
 Sting (barb) of a sting ray is a modified large placoid scale
 The teeth on the elongated rostrum of sawfish (Pristis) are formed
by placoid scales

60. PlacodermiPlacodermi
• Several early primitive jawed fishes
• Bony head shield movably articulated with
trunk shield
e.g. Dinichthyes
• Several early primitive jawed fishes
• Bony head shield movably articulated with
trunk shield
e.g. Dinichthyes

61. • Gr. Chondros, cartilage; ichthys, fish
• Mostly marine
• Cartilaginous endoskeleton
• Skin with placoid scales
• Mouth ventral and teeth are modified placoid
scales
• Gill slits not covered by operculum
• Pelvic claspers in male
• Sexual reproduction with internal
fertilization
e.g. sharks, rays, skates
• Gr. Chondros, cartilage; ichthys, fish
• Mostly marine
• Cartilaginous endoskeleton
• Skin with placoid scales
• Mouth ventral and teeth are modified placoid
scales
• Gill slits not covered by operculum
• Pelvic claspers in male
• Sexual reproduction with internal
fertilization
e.g. sharks, rays, skates
Class: ChondrichthyesClass: Chondrichthyes

63. Classification
Subclass Elasmobranchii
 Cylindrical or flattened body
 5-7 pairs of gill slits
 An upper jaw not fused to the cranium
 Have placoid scales
Superorder Selachii (Gr., selachos, a shark)
 Multiple gill slits on either side protected by individual skin flaps
 A spiracle behind each eye
 Cloaca present

64. Order 1. Squaliformes or Pleurotremata (Gr., pleuro-side+trema-
opening)
 Body typically spindle-shaped.
 Gill-slits lateral, 5-7 pairs
 Spiracles small
 Pectoral fins moderate, constricted at base
 Tail heterocercal
e.g. Dogfish shark (Scoliodon)

65. Order 2. Rajiformes or Hypotremata (Gr., hypo-below+ trema-
opening)
 Body depressed, flattened dorso-ventrally
 Gill-slits ventral, 5 pairs
 Spiracles large, highly functional
 Pectoral fins enlarged, fused to sides of head and body
e.g. Skate (Raja), Electric ray (Torpedo), Sawfish (Pristis)

66. Subclass 2. Holocephali (Gr., holos-entire+ kephale-
head)
 Single gill opening on either side covered by a fleshy operculum
 Upper jaw fused to the cranium
 No spiracles, cloaca and scales
 Jaws with hard, flat plates instead of tooth
 Single nasal opening
e.g. Rat fishes or chimaeras

67. Shark
 About 300 living species
 Most of them are marine with a few exceptions such as the bull shark
and the river shark which can live both in seawater and freshwater
 They are distinguished by their muscular strength, agility of
movements, well-developed sense organs and powerful jaws
 Largest living vertebrates, after whales, reaching up to 12 m in length
 A mature whale shark (Rhincodon typicus) may reach 15-17 m in
length

68. No anal fin
Body flattened, ray-like
and mouth terminal
Snout elongated,
saw-like
Body not flat, ray-like and
mouth ventral
Snout short , not
saw-like
Squatiniformes
Triassic
Pristiophoriformes
Jurassic
Squaliformes
Jurassic
Hexanchiformes
Permian
Anal fin
6-7 gill slits,
1 dorsal fin
5 gill slits, 2
dorsal fins
No fin
spines
Dorsal fin
spines
Mouth behind
front of eyes
Mouth in
front of eyes
Nictitating eyelids,
spiral intestinal valve
No Nictitating eyelids,
ring intestinal valve Lamniformes
Jurassic
Orectolobiformes
Jurassic
Heterodontiformes
Triassic
Carcharhiniformes
Jurassic

69. Orders of Shark
Squatiniformes - Angel sharks
Pristiophoriformes - Sawsharks
Squaliformes - Dogfish shark, Bramble shark
Hexanchiformes: Cow sharks and Frilled sharks
Carcharhiniformes – Tiger shark, Bull sharks, Hammerhead shark,
Milk shark
Lamniformes-- White shark, Basking shark, Great white shark
Orectolobiformes—Carpet shark, Whale sharks, Zebra shark
Heterodontiformes: Bullhead or Horn sharks.

70. Angel shark
Dogfish shark

71. Sharks

72. More Sharks

73. External features
 Body is divisible into three regions- head, trunk and tail
 Head is dorso-ventrally flattened and produced in front into a
pointed rostrum or snout.
 Trunk is almost oval and gradually tapers to the tail
 Tail forming the posterior half of the body is slightly bent
upwards
 Body surface is rough due to backwardly projecting spines of
placoid scales

74. Body Structures of a Shark

75. Fins:
 Fins are flap-like outgrowths of bodywall and internally supported by
cartilaginous rods and horny finrays.
Median fin- 1st
and 2nd
dorsal, anal, caudal fin
Lateral fin- Pelvic fin, Pectoral fin
Eyes
Body apertures
Mouth:
 Mouth is a crescentic opening lying ventrally on head near its anterior
end
 Each jaw bears one or two rows of sharply pointed and backwardly
directed teeth adapted for holding and tearing.
 Teeth are polyphyodont
Nares or nostrils: Olfactory organs

76. External gill slits:
Cloacal aperture:
Abdominal pore:
Caudal pits:
 At the base of caudal fin, one
ventral and dorsal caudal pits
Lateral line
Ampullae of Lorenzini

77. Feeding
 Most sharks are carnivorous
 Sharks such as Whale shark (Rhincodon), Basking shark
(Cetorhinus maximus) are filter feeder and have reduced or
nonfunctional teeth.
 Sharks those eat mollusks and crustaceans have dense flattened
teeth for crushing
 Those eat larger preys have pointed lower teeth for gripping and
triangular upper teeth with serrated edges for cutting

78. Digestive system
Alimentary canal:
 Mouth
 Buccal cavity
 Pharynx
 Oesophagus
 Stomach
 Intestine
Glands of alimentary canal:
 Liver
 Pancreas
 Rectal gland
 Spleen

79. Digestion
Food is swallowed without mastication
No digestion occurs in buccal cavity which lacks salivary
glands.
The gastric juice in stomach contains pepsin and
hydrochloric acid
Proteins into syntonin, proteoses and peptones, but cannot
digest chitin
Liver secretes bile which makes the semidigested food
alkaline in intestine
Pancreas secretes trypsinogen, amylopsin and lipase for
digestion of proteins, starches and fats
Spiral valve in intestine serves to delay the passage of
food and offers a large surface for absorption of the products
of digestion.

80. Male reproductive organ
 Testes-attached to the bodywall by
a peritoneum fold called
mesorchium
 Fine tubules-Vasa efferentia
 Vas deferens or Wolffian duct
 Seminal vesicle- storage of
spermatozoa
 Opens separately into urogenital
sinus

81. Female reproductive
organ
A pair of ovaries
Mesovarium
Oviducts
Oviducal funnel
Shell gland
Uterus

82. Reproduction and development

83.  Sharks may be oviparous, ovoviviparous and
viviparous
 Oviparous sharks deposit their eggs in the
ocean that will hatch later
 Parents does not guard the eggs
 Tough leathery membrane covers shark eggs
which are called mermaid’s purse
e.g. Cat shark, Horn shark, Leopard shark

84. Viviparous shark:
 These give birth to live young
 The eggs hatch inside the female’s body
and get nourishment from the mother
through the placenta (via an umbilical
cord which is connected to the pup
between the pectoral fins)
e.g. Bull shark, Hammerhead shark, Mako
shark

85. Ovoviviparous shark:
 Most sharks are ovoviviparous
 The eggs hatch inside the female body but they don't
nourish through the placenta
 The pups are nourished from the egg’s yolk and fluids
secreted by glands in the walls of the oviduct
 The pups have cannibalistic behaviour
e.g. Great white shark, Saw shark, Tiger shark

86. Senses
• Olfactory organs can detect
chemicals diluted 1/10 billionth their
original concentration
• Lateral line senses low frequency
vibrations of prey over large
distances
• Excellent vision, even in dim water,
used at close range
• At close range, sharks are guided
to prey by electric fields
surrounding all animals
• Buoyancy

87. Shark Attacks
• Only 32 species ( of 350) have been documented
to attack humans with another 36 considered
potentially dangerous; these typically are the larger
size sharks; 80 % of sharks are harmless
• Great white, tiger, and bull sharks are the more
aggressive species
• 50-75 attacks occur each year, with 8-12 fatalities;
in contrast 30-100 million sharks are killed every
year
• Attacks usually occur by sandbars, steep drop offs,
or by river inlets and are associated with mistaken
identity,territorial behavior, or feeding behavior

88. Economic importance of Shark

89. Skates and Rays
Make up half of all species of Elasmobranchii
Order Rajiformes—skates
Order of Rays
 Order Myliobatiformes- Dasyatis (Stingrays), Mobula (Devil rays),
Himantura (Haushpata) etc.
 Order Torpediniformes- Torpedo (Electric rays)
Order Pristiformes- Pristis pristis ( Common sawfish)

91. Form and Function
• Specialized for benthic life
• Flattened dorso-ventrally; enlarged pectoral fins are used as swimming
wings
• Water used in respiration enters large spiracles in head
• Teeth adapted to act as rollers to crush invertebrates and sometimes
small fish
• Stingrays have whip-like tail with spines and venom glands
• Electric rays have electric organs on sides of head
• Skates look like kites with a sharp tail.

94. Economic importance of ray
Flesh of ray is delicious food.
The oil produced from liver of ray is good food
They are also used for producing fish meal,
fish flour for the poultry feeds
The fins of Blue-spotted string ray are sun-
dried and exported to other countries for used
in much relished soups.