Vertebrates class
- 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
- 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.
- 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.
- 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
- 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.
Editor's Notes
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