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1. Vertebrates: Fish
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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. Fishes
Groups of fish
1. Jawless fishes (Agnatha)
○ 111 species
2. Cartilaginous fishes
(Chondrichthyes)
○ 970 species
3. Bony fishes
(Osteichthyes)
○ 27,000 species
○ Separated into ray-
finned (Actinopterygii)
and lobe-finned
(Sarcopterygii) 5

6. • Gr. a, not; gnathos, jaw
• Without true jaws
• Paired appendages absent
• Cartilaginous skeleton
• Notochord persistent in adults
• rasping mouth to suck blood
• Scales absent
Division: Agnatha

7. 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
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

8. Lamprey
 jawless
 Three species are found in both salt and freshwater.
 Marine
 Their name means stone lickers
 They are external parasites
 The tongue bears large horny teeth
 7 small rounded openings of external gill slits
 Cloaca

9. Habits
 It is a rather unpleasant animal
 The larval phase is a freshwater 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.

10. 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 accumulation of poisonous metabolites

11.  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 and when they locate suitable habitat- usually slit/sand stream
bottoms and banks in slower moving waters- they burrow in and take up residence
 The larvae feed micro-organisms, ciliates and diatoms from the water through filter-feeding
 Last from 3-17 years
 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
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13. Superclass Agnatha
Class Myxini - hagfishes
- Jawless
- Entirely marine
- Feed on annelids, crustaceans, or
decaying animals
- Almost blind
- Keen sense of smell
- Attracted to dead whales and fish
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14. Scales
 Scales are external coverings that grows out of an animal’s skin to provide
protection
Types of scales
 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

15. Types of scales
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

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Ganoid scales:
 Found in the chondrosteans such as gars, bichirs
 They are thick, flat and diamond-shaped scales
Cycloid scales
 Greek word cyclo meaning circle
 These type of scales are found in lung fishes,
 soft fin-rays such as carp, Hilsha, salmon etc.
Ctenoid scale
Greek word cteno meaning comb
 Perch, bass etc.
 Their outer edge (exposed part) have numerous small
comb-like teeth or spines.

17. Superclass Gnathostomata
Jaws represent a major advancement for vertebrates
● Hinged jaws
Jaws are used in feeding
● Paired appendages
● Pectoral fins present behind head: paired
● Pelvic present ventrally and posteriorly: paired
● Dorsal fin : unpaired
● Anal fin: unpaired
● Caudal fin: unpaired
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18. Super class Gnathostomes
Class chondricthyes
Cartiligenous fishes
Eg: Sharks, skates, rays
Class ostechthyes
Bony fishes
Teleost

19. • 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: Chondrichthyes

20. Class Chondrichthye
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Sub class
elasmobranchii
(sharks, skates, and
rays)
Sub class
Holocephalii
(rat fish)

21. Class Chondrichthyes
Sub class Elasmobranchii - sharks, skates, and rays
- Sharks
- Evolution: Devonian period
- Body wall: Dermal palacoid scales
- Sand paper texture
- Teeth: rows of teeth
- Modified palacoid scales
- Teeth replacement: 7-8 days
- Size: less than one meter to 10 meter
- Largest shark: 10 meter
- Filter feeders: pharyngeal arch for filter feeding
- Great shark: extinct
- Reproduction: may be oviparous (lay eggs), ovoviviparous (eggs hatched within body), or viviparous
(give birth)
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22. Skates and Rays
● Large teeth
● Body expanded laterally
● Wing like appendages
● Colorful
● Dorsoventral muscles
Help in locomotion
Rays: viviparous
without spines
Stingrays have whip-like tail with spines and venom glands
Electric rays have electric organs on sides of head
Skates: oviparous
spines present
Skates look like kites with a sharp tail.
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23. ray skate

24. Class Chondrichthyes
Holocephali
- chimaeras or ratfish
- Split from elasmobranchs 380 MYA
- Operculum present
- Gills covered by single operculum
- Lack scales
- Teeth modified to crushing plates
- 30 species
- Jaws bear flat plates instead of teeth
- Lateral line receptors
- Eg rat fish
- Large head
- Small mouth
- Large lips
- narrow tapering tail
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25. Lateral line receptor
“The lateral lie found alongside a fish body from the operculum
to the tail sense vibration or movement in the water, locate
predator and find prey”
Made of series of mechanoreceptors (neuromast) arranged in row

26. Class ostycthes (bony fishes)
● Having at least some Bones in their Skelton and scales, bony
operculum, covering the gill openings, and lungs or swim
bladder
● 20,000 species
● Silourian period (443 million years ago)
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27. Class Ostecthyes
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Sub class Sarchoptergii
Lobbed fin fishes
Sub class actinoptergii
Ray finned fish

28. Sub class Sarchoptergii
● Muscular lobes with fins (fleshy fins)
● Air sacs changed into lungs
Subclass sarcoptergii
1. 1. lung fish 2. Coelacanth 3. Osteolepiforms
1. Lung fishes:
 Air sacs changed into lungs
 Present where seasonal drought are common
 Use lungs to breath in stagnant and dry freshwater lakes and rivers
 only three genera survive today
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29. 1) Neoseratodus
 inhabit in fresh water
 Queen land, Australia
 They survive stagnation by breathing air
2) Propterus
 Tropical Africa
3) Lepidosiren
 Tropical south America
They can survive when river or lakes are dry by burrowing into the mud
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30. Aestivation
A dormant state that help animals to withstand hot dry period
● Lungfishes remain in aestivation for six months
● Can survive when rivers or lakes are dry
● They form burrows in mud
● They keep an air pathway
● They open this pathway by bubbling air to the surface
● Small opening in earth are produced after substrate dries
● These openings are only evidence of presence of lung fish
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31. 2. Coelacanths
● A second group of sarcotergeons
● Fossils of 70 million years old
Latemeria chelomnea
● Is closest living fish relative of terrestrial vertebrates
● Numerous other specimens have been found in deep water around Comoro
Island off Madagacar
● It is large group up to 80 kg
● Heavy scales (Ctenoid scales)
● Ancient coelacanth live in fresh water lakes and river thus the ancestor of
letmeria must have moved from fresh water habitat to deep sea.
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32. Osteolepiformes
● A third group of sarcopterygians became extinct before the close of the
Paleozoic period
● They are believed to have been the ancestor of ancient amphibians
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33. Sub class Actinopterygii
● Contain fishes that are called ray finned fishes because their fins lack
muscular lobes
● Homocercal tail:
○ equal upper and lower lobe
● Hetrocercal tail:
○ unequal upper and lower lobe
○ Upper lob large lower lobe short
● Possess swim bladder, gas filled sac along the dorsal wall of the body cavity
that regulate buoyancy.
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34. Sub class Actinopterygii
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Infra class Chondrostean Infra class Neoptergyii

35. Infra class Chondrostean
● Ancestral chondrosteans had a bony but living members the
sturgeon and paddle fish have cartilaginous Skelton
● Tail with large upper lobe (heterocercal tail)
1. Sturgeon 2. Paddle Fish
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36. ● Most sturgeons live in sea
● Migrate into river to breed
● Small mouth weak jaws
● Heavy scales cover the tail
Importance:
● Valued for their caviar (eggs)
● Swim with open mouth (filter)
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37. Paddle fish
 Large in size
 Paddle like rostum
 Rostum contain sensory organs detect weak eclectric
fields
 Filter crustaceans and small fshes
 Present in lakes and rivers of Mississppi basin
 China and America
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38. Neoptergyii
● Flourish in Jurassic period
● True bony fishes
● Two genera
1. Lepisosteus 2. Amia
Lepisosteus:
 thick scales (gonoid scales)
 long jaws
 Gar pike
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39. Amia: 20,000 species
● Symmetrical caudal fin
● Teleost or modern bony fishes
● Swim bladder
● Symmetrical caudal fin (homocercal tail)
● Great diversity
● Tuna, seahorses, flatfish, pufferfish, tilapia, catla catla etc
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Tilapia
Catla catla Libeo rohita (rohu)

40. Movement/locomotion
Streamline shape of body
Mucoidsecretion lubricate is body
Fins
Bundles of segmented muscle tissue (myomeres)
- Have W-shaped arrangement
- Mostly used for swimming
- Very efficient form of locomotion (don’t have to fight
gravity)
- Myomeres produce s-shaped swimming motion
- Fish push on water
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41. Feeding and Digestion
- some scavenging
- Jaws allow for a predatory lifestyle
- Small, sharp teeth
- Produced throughout lifetime
Filterfeeder:
gill rackers
External parasite
lamprey
- Flexible jaws engulf large prey
- Prey swallowed whole
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42. Respiration
- Some have cutaneous respiration
- Some can breathe air
- Water: 2.5%oxygen
- Pumping mechanism
- Ram ventilation
Circulation
- 2 chambered heart with single circuit
- Blood pumped through gills then to body
- Sinus venousus
- Atrium
- Ventricle
- Conus arteriousus
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43. Reproduction and Development
- Most dioecious
- Most with external fertilization
- Clasper (modified pelvic fin)
- Marine fish reproduce in large schools
- Freshwater fish have elaborate mating
- Some with a high degree of parental care
- Oviparous
- Egg develop outside female body from stored yolk
- Ovovivparous
- Embryo develop in odified ividuct of female eg elasmobrancs
- Viviparous
- Oviduct modified into placenta lik outgrowthdvelopment ccur in ovarian follicle
- Eg: guppy fish
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44. Nervous system
- Small brain compared to other vertebrates
- CNS: brain and spinal cord
- Sense organs
- Evolved because light doesn’t travel far in water and sound and pressure waves
travel very far
- Lateral line system
- Eyes
- Chemoreceptors
- Hearing: bony ossicles
- Semicircuar canals: receptors for equilirium, balance, hearing present
in inner ear
- Outer ear absent
- Eyes: lidless
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45. Excretion
The maintainance of water and
salt balance in the body is called
osmoregulation
Kidneys for nitrogenous wastes
Nephron
(osmoregulation too)
● Primitive marine fishes are
isotonic
● Most marine fishes are
hypotonic
○ Loose water and gain salt
● Freshwater fishes are
hypertonic
○ Gain water and loose salts 45

46. Diadromous fishes
● The fishes which migrate between fresh water and marine environment are
called diadromous fishes
Catadromous fish
• Spent most of adult in sea
● Migrate from sea to fresh water to spawn
● Salmon and lamprey
Anadromous fish
• Spend mos of adult in fresh water
• Migrates from freshwater to marine environment to spawn
• Fresh water eel
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