1. ZLY 304 (AGNATHA & GNATHOSTOMATA) EVOLUTION OF FISH TAXONOMY OF FISH BASIC ORGANIZATION & MODE OF LIFE OF FISH

2. EVOLUTION OF FISH

3. Fish like creatures evolve 480 mya.

4. Origin of Chordates
Early Cambrianperiod - first vertebrates appeared in the ocean
eg: Myllokumingia
respiratory gills formed by pharyngeal gill slits
about 8 gill openings
located in a set of pouches
Myllokumingia

5. Class - Ostracoderms
First fishes Torpedo-shaped , Small (12-35cm), jawless, finless
Shelled = ostraco / skin = derm
polygonal plates around the head and gills  head shield
important group during the Silurian and Devonian periods
filter feeders
Eg Conodonts & Lamprey

6. Class -Ostracoderms

7. Conodonts Late Cambrian Eel like, 1-40 cm in length
They had a notochord, cranium, myomeres, fin rays, and large eyes
No gills, but since they’re little , gas exchange could occur through skin

8. Lamprey - Petromyzontiformes
long, cylindrical bodies
cartilage skeletons
no paired fins
jawless
free-swimming predators on other fish
Extanct groups
Hagfish ex; Mixini
Lampreys
classified in a group called the agnatha (no jaws) or the cyclostomata (round mouth)
HAGFISH

9. Hagfish - Myxini have a partial cranium (skull), but no vertebrae.
Cartilage skeleton
No jaws

10. Lamprey - Petromyzontiformes
LAMPREYS

11. Lamprey - Petromyzontiformes
Lampreys have a sucker-like mouth that lacks a jaw.
They are living since late Devonian

12. Gnathostomata – jawed fish
Middle Silurian - fish with jaws and teeth were evolved
Jaws - adapted from the front elements of the gills
teeth – adapted from bony scales near the skin of the mouth
paired fins - swimming abilities were enhanced
explored more diverse habitats and food
Four groups
Placodermi (extinct)
Acanthodii (extinct)
Chondrychthyes (extant - sharks, rays and chimaeras)
Osteichthyes (extant - more highly evolved bony fishes)

13. Placodermi
Pelvic fin
Pectoral fin

14. Placodermi Carnivores Silurian to Devonian armored with heavy plates
separate head and trunk portions linked by a hinge
Had strong jaws
paired pectoral and pelvic fins
balance and to maneuver
facilitate predation
Extinction event that happen in the Devonian eradicated Placoderms as well as Ostracoderms

16. Acanthodians
stout spines (acanthi =spine) anterior to their well developed fins
6 pairs of ventro-lateral fins in adition to pectorals and pelvic fins
heterocercal tail
Slim body, SMALL SCALES, big mouths
Initially marine but then mostly freshwater
Existed from the Late Ordovician to Early Permian

17. Chondrichthyes Devonian period (416-360 mya) – sharks appeared
Eg; Xenacanthus a freshwater shark
bottom dweller
robust fins
heavily calcified skeleton
appeared in the Devonian and died out in the Triassic ( mya).

18. Ironing
board shark
Stethacanthus sp.
37-45 MYA

20. Chrondrichthyes Current 1200 Spp of Chrondrichthyes are TWO CLASSES
HOLOCEPHALI – EG; Chimera, Ratfish & Elephantfish
ELASMOBRANCHII – Sharks, Skates & Rays
Lateral line from the head to the tail first appeared in sharks and rays – helped locate prey in total darkness
Cartilage skeleton
predators & harmless mollusk eaters
keep swimming because they have no swim bladder

21. TWO FORMS OF SHARKS
two distinct forms of sharks: the pelagic and benthic forms.
pelagic sharks - move constantly through the water & rely on this movement to pass water across the gills for respiration
benthic sharks - sit on the bottom & take in water through a pair of holes at the top of their head called spiracles for respiration

22. TWO MAIN CLASSES OF CHONDRICTHYES
CLASS 1 - HOLOCEPHALI
upper jaw fused to the braincase and a operculum covering the gill slits.
35 spp.
Spiracle absent
Instead of teeth, they have hard grinding plates.
Teeth are plate-like - non-deciduous
Cartilaginous
lacks a true stomach.
They usually feed on small benthic creatures.
feeding on hard shelled invertebrates.

23. HOLOCEPHALI Live In Groups In Deep Waters ( 80 -2,600 M).
Chimaera
Live In Groups In Deep Waters ( ,600 M).
About Odd Looking Species.
Chimera Or The Ghost Sharks,
Ratfish
Elephantfish
Placoid Scales, Large Eyes, Males Claspers
All Are Oviparous - Laying Eggs That Hatch Outside The Mother's Body
Spiral valve present
oil filled liver is present
Ratfish

24. ELASMOBRANCHS The most successful class of cartilaginous fish
sharks, skates and rays
five pairs of gill slits, two small openings on the sides of their heads called as SPIRACLES
HETEROCERCAL tail.

25. SKATES
pelvic fin divided into two lobes 
stocky tail w/o stinging spine 
enlarged, thorn-like scales ('bucklers') along the midline of back
males have rows of enlarged scales near the eyes and wingtips
RAYS
one-lobed pelvic fin 
whip-like tail, usually with stinging spine 
no bucklers along back or tail 

26. TEETH
Most vertebrate have teeth that are locked into sockets in their jaws
The teeth of cartilaginous fish are simply attached to the jaw by fleshy tissue

27. SHARK SENSES AND SEX normal five senses smell/taste is extremely good.
LATERAL LINE present
Ampullae of Lorenzini located in their snouts. They are connected by pores to their surroundings. These organs can detect electrical impulses. Theoretically they could detect the electric field produced by a 12 volt battery being dropped into the middle of the Atlantic Ocean.
Internal fertilization
OVIPAROUS, meaning that laying leathery eggs (mermaid’s purses)
OVIVIVIPAROUS meaning that the eggs hatch inside the mother and the young are born live.

29. Class - Osteichthyes Consists of all the bony fish = 30000 species
Tilapia and catfish
Jaws present & have paired fins
Heterocercal caudle fin
Gas filled airbladder
Single gill slit on each side - Operculum protect the gills
Skin is protected by scales
external fertilization of egg
have sharp eyesight
Mucous glands and embedded dermal scales are present in the skin

30. Class Osteichthyes two sub-classes: Sarcopterygii - LOBE FINNED FISH
with lobed, fleshy fins
muscular fins supported by bones
lungfishes and lobefins
Actinopterygii - RAY FINNED FISH
thin, flexible skeleton rays
the higher bony fishes

31. Sarcopterygii - LOBED-FINNED FISHES
End of Devonian - sea levels dropped at the end of the life became difficult for fishes
some fish developed fins that were stiff, rounded and well muscled.
Those who had rounded well muscled fins are now called as lobed finned fishes, and as SARCOPTERYGII in Latin.
fleshy fins supported by central bones, homologous to the bones in your arms and legs. These fins underwent modification, becoming the limbs of amphibians and their evolutionary descendants such as lizards, canaries, dinosaurs, and humans.

32. Sarcopterygii - LOBED-FINNED FISHES
This group includes six species of lungfishes and one species of coelacanth that has muscular fins with large, jointed bones attaching the fins to the body.
The lungfish are a small group found mostly in freshwater stagnant water or ponds that dry up in Africa, South America, and Australia.
Current thinking agrees that one of these lobe-finned fishes adapted to moving on the land and was the ancestral amphibian.
Although the rest are long extinct are, few Lobed -finned fish still living in the sea such as THE COELACANTH

33. Sarcopterygii - LOBED-FINNED FISHES
COELACANTHS were thought to have become extinct 70 million years ago
1938 -off Madagascar
more than 200 have been captured since 1938.
Several other populations of coelocanth have now been found, but large numbers being caught are threatening this relic species.
Their lobed fins can move alternately, like a walking land animal.
They live in deep water and feed near the seabed.

34. Subphylum - Vertebrata
Kingdom - Animalia
Phylum - Chordata
Subphylum - Vertebrata
Super class - Pisces
Class - Agnatha
jawless fish (50 sp)
Hagfish
Lampreys
Class –Chrondrichthyes
cartilaginous fish (600 sp)
Sharks
Skates
Rays
Class- Osteichthyes
bony fish (30000 sp)
2 sub classes
Lungfish, Eels, Carps, Lizardfish, Silversides & Salmon
Sub class - Sarcopterygii
Lung fish and lobed fin fishes
lobed, fleshy fins
muscular fins supported by bones
Sub class - Actinopterygii
ray finned fish
thin, flexible skeleton rays
the higher bony fishes
21 orders

35. TELEOST VARIETY
Although most teleost fish are fusiform (torpedo) - shaped not all are
Seadragon – its shape helps to camouflage it amongst seaweeds

36. TELEOST VARIETY
Sargassum fish

37. TELEOST VARIETY
Sunfish – extremely flattened – swims like a manta ray on its side
Marlin – has a long spike (modified upper jaw) that they use for attacking prey and defiance

38. TELEOST VARIETY Flatfish – effectively a teleost fish on their sides
They are born looking like normal fish - but one of their eyes migrates to the other side of the body
Some have chromatophores – pigment cells that allow quick camouflaging of animals

39. TELEOST VARIETY
Some teleosts have extra large pectoral and pelvic fins
When trying to avoid predators flying fish extend their fins and fly for 10s of meters over the sea surface