Vertebrtes (fishes)-1......................pptx

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1. Vertebrates: Fish 1

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 Jawless fishes ( Agnatha ) 111 species Cartilaginous fishes (Chondrichthyes) 970 species 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. M arine 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 T he 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 11

12. Superclass Agnatha Class Myxini - hagfishes J awless Entirely marine Feed on annelids, crustaceans, or decaying animals Almost blind Keen sense of smell Attracted to dead whales and fish 13

13. 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

14. 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

15. 16 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 .

16. 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 17

17. Super class Gnathostomes Class chondricthyes Cartiligenous fishes Eg : Sharks, skates, rays Class ostechthyes Bony fishes Teleost

18. 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

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

20. 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) 21

21. 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. 22

22. ray skate

23. 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 24

24. 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

25. 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) 26

26. Class O stecthyes 27 Sub class Sarchoptergii Lobbed fin fishes Sub class actinoptergii Ray finned fish

27. Sub class Sarchoptergii Muscular lobes with fins (fleshy fins) Air sacs changed into lungs Subclass sarcoptergii 1. lung fish 2. Coelacanth 3. Osteolepiforms 1. Lung fishes: Air sacs changed into lungs Present w here seasonal drought are common Use lungs to breath in stagnant and dry freshwater lakes and rivers only three genera survive today 28

28. Neoseratodus inhabit in fresh water Queen land, Australia They survive stagnation by breathing air 2) Propterus T ropical Africa 3 ) Lepidosiren Tropical south A merica They can survive when river or lakes a re dry by burrowing into the mud 29

29. 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 30

30. 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. 31

31. 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 32

32. 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. 33

33. Sub class Actinopterygii 34 Infra class Chondrostean Infra class Neoptergyii

34. 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 35

35. 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) 36

36. 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 37

37. Neoptergyii Flourish in Jurassic period True bony fishes Two genera 1. Lepisosteus 2. Amia Lepisosteus : thick scales (gonoid scales) long jaws Gar pike 38

38. 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 39 Tilapia Catla catla Libeo rohita ( rohu )

39. Movement/locomotion S treamline shape of body M ucoidsecretion lubricate is body F ins 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 40

40. Feeding and Digestion some scavenging Jaws allow for a predatory lifestyle Small, sharp teeth Produced throughout lifetime F ilterfeeder: gill rackers E xternal parasite lamprey Flexible jaws engulf large prey Prey swallowed whole 41

41. 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 S inus venousus A trium V entricle C onus arteriousus 42

42. Reproduction and Development Most dioecious Most with external fertilization C lasper (modified pelvic fin) Marine fish reproduce in large schools Freshwater fish have elaborate mating Some with a high degree of parental care O viparous E gg develop outside female body from stored yolk O vovivparous E mbryo develop in odified ividuct of female eg elasmobrancs V iviparous O viduct modified into placenta lik outgrowthdvelopment ccur in ovarian follicle E g: guppy fish 43

43. 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 S emicircuar canals: receptors for equilirium, balance, hearing present in inner ear O uter ear absent Eyes: lidless 44

44. Excretion T he maintainance of water and salt balance in the body is called osmoregulation Kidneys for nitrogenous wastes N ephron (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

45. 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 46