Classification of Chordates Dr K N Nikam M

Classification of Chordates Dr. K. N. Nikam. M. Sc Ph. D Head Department of Zoology R. B. Madkholkar Mahavidyalaya, Chandgad, Dist. Kolhapur 1

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Salient features and classification of Chordates up to order of the following with suitable examples • • • Urochordata Cephalochodata Agnatha Pisces Amphibia 3

Unit-1 1)Protochordates-New General characters and Classification of Protochordata • • • • Protochordata are first chordates. They are primitive chordates. They are intermediate link between invertebrates and chordates. They contain notochord formed of vacuolaed notochordal cells. They are marine. They do not contain a cranium and head. They are called Acraniata. They have no jaws and vertebral column Many gill slits are presents The alimentary canal is straight or U shaped They show filter feeding and ciliary feeding Circulatory system is open or closed type. Development is direct or indirect. Many forms exhibit asexual reproduction. 4

A) Phylum- Urochordata Classes Ascidiacea Thaliacea Larvacea Orders Eterogona Ex. Ascidia Pleurogona Endostylophora Polystylophora Ex. Herdmania Doliolid Phyrosoma Salpida 5

Salient features of Urochordata 1. These are marine & commonly called sea squirts 2. Adults are mostly fixed. 3. They are sessile, solitory, colonial forms. 4. Body is enclosed in a test or tunic hence called tunicates. 5. Pharynx is large, sac like & perforated by gill slits. 6. Notochord confined to the region of larva & hence called urochordates. ( GK. Aura= tail) 7. Larva shows retrogressive metamorphosis ( ie most of chordate characters that are found in larva are lost in the adult. ) 8. Animal show ciliary mode of feeding. 9. Alimentary canal is U shaped. 10. Nervous system is better developed in larva but reduced in adult. 11. They are bisexual & both sexual & asexual reproduction found. 6

Urochordata includes 2000 fixed & 100 pelagic species. It further classified into three sub-classes Sub-class: Ascidiacea • These are fixed or free swimming, • These are solitory or colonial. • Larva are more developed than adult • Gill slits are many • It has two orders Order: Enterogona • Body divided into thorax & abdomen • Neural gland ventral to ganglia. • Single gonad • Larva with 2 sense organs. Ex. Ascidia 7

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Order: Pleuorogona • Body compact, undivided • Neural gland dorsal • Gonds 2 or more in mantle wall • Larva has no eye but otolith. • Ex. Herdmania 9

B) Phylum- Cephalochordata • • Amphioxus These are or free swimming, Body is metmerically segmented Notochord is persistent & extends throughout life in head region. Dorsal nerve cord exists. Midgut diverticulum acts as liver. Many pairs of protonephridia are present. Sexes are separate, external fertilization. 10

Subphylum Cephalochordata includes single class. Leptocardi & 2 genera Leptocardi • It includs small marine fish like acraniates, burried in sand. • Notochord is permanent & extends from tip of snout to tail. • Dorsal tubular nerve cord • Pharynx is large with many gill slits. Ex Amphioxus 11

Phylum-Chordata 2)Agnatha-New • General characters of Agnatha & Classification of Cyclostomes up to classes • Agnatha are vertebrates without jaws , commonly called cyclostomes. • They are Lampreys & hag fishes. 12

Sub-phylum Vertebrata is further classified into two super classes 1) Agnatha without jaws & 2) Gnathostomata with jaws. Salient features • A presence of suctorial, circular mouth without jaws, with horny teeth. • Body is elongated like eel. • Adults are parasite & can live both in fresh water & marine water. • No Paired fins but median fin, no scales on body. • Tongue is muscular & is rasping organ bearing horny teeth. • Heart is two chambered. • They are cold blooded, pineal body sensitive to light. • There are 6 to 14 pairs of gills as respiratory organs. • Fertilization is external. 13

Classification • • Phylum-Chordata. Sub-phylum-Vertebrata Sperclass- Agnatha further divided into two classes. Class: Ostracodermi- Ancient armoured fshes. Class; Cyclostomata- The living Agnatha Class; Cyclostomata- The term cyclostomata has been derived from Greek Word Cyklos=circular + Stoma=mouth. These are the vertebrates which have circular mouth without jaws. • The class cyclostomata further divided into two Orders 1. PETROMYZONIFORMES and 2. MYXINIFORMES 14

Order (1): Petromyzontiformes • Commonly called as lamprey and is marine as well as freshwater. • It is ecto-parasitic, on other fishes. • They live in sea and migrate to. the river for spawning. In river built nest by using stones or pebbles from river bed. Fertilization is external. After spawning parents die. • Body is distinguished in to head, trunk and tail. • Head and trunk is cylindrical and tail is laterally compressed. • Anterior end bears a ventrally directed cup like sucker or funnel surrounded by oral papillae lined by radiating rows of horny teeth. • The apex of the buccal funnel bears a small circular mouth opening behind which is found tongue with large horny teeth. • Single nostril, seven pairs of external gill slits on lateral side of the head. • Cloacal aperture is located at the junction of trunk and tail. • Small sensory pores of lateral line system extend along the lateral side of the body below the head.

Order (1): Myxiniformes • • • Commonly called as hag fish or slime eels and is exclusively marine in habitat. Body is soft, without scales, elongated worm like and differentiated in to head trunk and tail. Eyes are degenerate and covered with a thick skin. Mouth is terminal and surrounded by six cirri or tentacles. There is a single median nostril present close to the mouth. Six pairs of gill pouches, located far behind the head but open outside by a single pair of external gill slit. Dorsal fin indistinct. Caudal fin and ventral fin confluents. Hermaphrodite. They are injurious to fish industry. 16

3)Pisces-New A)General characters & Classification up to orders; Respiration in Fishes 17

Class: Pisces Salient Features • • • They are cold blooded strictly aquatic, fresh water & marine water. Body is stream lined with paired & unpaired fins. Gills are organs of respiration. Dermal scales forms exoskeleton Fins are supported by fin rays. Mouth has true jaws with teeth. Internal ear has three semicircular calals. Heart is two chambered. & single circulation. Bony or cartilagenous endoskeleton support the body Sexes are separate some males have copulatory organs Fertilization is external ( except few) Development is direct. Migration & parental care is seen. 18

Class pisces is further divided into two groups 1. Chondrichthyes or Elasmobranchi- Cartilagenous fishes 2. Osteichthyes or Telostomi- Bony fishes 1. Chondrichthyes- Cartilagenous fishes Salient Features • • • • They have cartilagenous endoskeleton. Microscopic placoid scales are present. Mouth is present on ventral side. Teeth with enamel caps. Five pairs of gill slits are present & open outside separately. Tail is heterocercal or asymmetrical. Males have claspers. Air bladder & operculum absent. Spiracles are present. These are cold blooded. Heart is two chambered. Intestine has scroll valve These are oviparous or ovovivipoarous. Fertilization is internal. Caecum & cloaca are present 19

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2. Osteichthyes or Telostomi- Bony fishes • • • Bony endoskeleton present Large ganoid, cycloia or ctenoid types of scales present Mouth is terminal with teeth. Four pairs of gills which covered by operculum. Tail is homocercal. There are no claspers in male. Air bladder is present & no spiracle. They are cold blooded. Heart is two chambered. Scroll valve absent in intestine These are oviparous usually but some are vivipoarous. Fertilization is external. 21

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B)Respiration in Fishes 23

C)Structure of gills in Cartilaginous and Bony Fishes Gill Structure in Cartilaginous Fish- Scoliodon There are five pairs of gill pouches containing gills. Adjacent gill pouches are separated from each other by the interbranchial or gill septum. The inner or pharyngeal border of each gill septum is supported by a cartilaginous visceral arch or gill arch with its slender branchial rays. A gill arch also gives out rigid structure called gill raker in pharynx which prevents food particles in the internal bracnhial aperture. The endodermal mucous membrane of a septum is raised into numerous horizontal leaf like folds, called gill lamellae or filaments. The interbranchial septum bears two sets of gill filaments, one on its anterior face & other is on posterior face, Each set is called half gill. Both set is called complete gill or holobranch. The posterior hemi branch of a septum has longer filament. Each gill pouch has two set of gill filaments, one on its anterior wall and one on its posterior wall. In cartilaginous fishes, the interbranchial septa extend well beyond their gill filament and then bent posteriorly

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Structure of gills in Cartilaginous T. S. of holobranch of scoliodon

Structure of gills in Bony Fishes • • There are five pairs of gill clefts opening in pharynx by internal branchial apertures in bony fishes. The operculum is present on each side which cover the gill cleft opening. They are present on either side of the pharynx in common gill chamber. Just behind mouth, in buccal cavity, there are two oral valves. These allow water to enter the mouth and do not allow water from phyrynx to out through mouth. Each gill consists of two rows (hemibranchs) of slender gill filaments'. Inter branchial septum is extremely reduced so that the gill filaments hangs freely in the gill chambers. Therefore this type of gill is called filiform or pectinate. Every gill filament bears several minute transverse plates or lamellae covered with thin epithelium containing capillaries. The inner or pharyngeal border of each arch bears teeth – like processes called gill rakers which prevent the entry of food particles entering the gill chambers

Structure of gills in Bony Fishes- T. S. of holobranch of labeo

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Class : Amphibia-New General characters & Classification up to orders; Parental care • Amphibians are first vertebrates that occur in fresh water & on moist land. • They inhabiting in all places except in the regions of extreme cold & extreme hot. • Regeneration is well known phenomenon. • Being cold blooded they show hibernation & aestivation. • About 2500 living species are known. • The first amphibian appeared about 300 million years ago. 34

• • • • Salient Features They can live both in water & on land. . These are cold blooded Skin is smooth, slimy & without endoskeleton. Skin, lung, gills & buccal cavity. Are the respiratory organs. Unlike fishes nasal cavity opens in buccal cavity. Heart is three chambered. Middle ear has rod like columella. Sexes are separate & show sexual dimorphism. Males have no copulatory organs. Fertilization is external. Parental care is fascinating Development is indirect with larval stage. Larva undergoes metamorphosis. 35

Parental Care 36

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Parental Care • The nursing of eggs and embryos by the parents is called parental care. • 1) Nest • A. Mud Nests • Hyla faber, Female makes a nest in mud in shallow water • Heptadactylus ocellatus, It builds small mud bunds near the edge of pond water & spawns in that enclosure. • Rhacophorus schlegeli, Spherical hole in Mud banks of pond. • Desmognaths fucus, Underground burrow 39

• B) Tree Nests • 1) Phyllomedusa deposits the egg in the leaf nests. The leaf nest are constructed by folding the margin of leaves 7& glued together by cloacal secretion. Leaf nest are overhanging the water. • 2) Triton constructs the nest using the shoots of trees. • 3) Chiromantis- Female deposits eggs on foamy mass on trees • 4) Hyla resinfictrix- Collects bee wax from hives of stingless bees applies it on inner surface of shallow cavity on the tree. When this cavity is filled with rain water, female lays egg. 40

• C) Foam Nest • 1) Rhacophorus sclegeli- Foam mass on which eggs lays • D) Gelatinous bags • 1) Phrynixalus birol- Secretes sausage shaped transparant gelatinous membranus bag on eggs are lays. 41

• 2) Direct Caring by parents • 1) Desmognathus fucus- Taile amphibbia, male carries eggs around neck in the form of string • 2) Dendrobatus- Carry tadpoles on their back • 3) Phyllobatus- males carry tadpoles on their back • 4) Alytes obstetricans (Mid-wife toad)- After fertilization eggs are wrapped round back of thigh of male & carries to water bodies. • 5) Hylla goeldii- Female carries eggs on back • 6) Pipa pipa- Skin on dorsal side has small pockets into which eggs are placed • 7) Pipa dorsigera- Small cutaneous pit deveope on dorsal skin of female. Male place eggs on pits, pit has operculum. • 8) Rhinoderma darvini- Vocal sacs of male have 2 slits and eggs are put in it 42

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• 9) Nototrema marsupium- Eggs are deposited in pouch on the back with one opening at the posterior end. • 10) Ichthyophis- It is burrowing limbless amphibia coils around the eggs untill they are hatchd • 11) Ovoviviparity- Female retain their eggs in the oviduct and they give birth to young one, Toad like Nectophrynoides. 44

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Deadly Poisonous frog 57

Unit-2 58

Reptiles-New • General characters & Classification up to orders; Venomous & non-venomous snakes 59

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Aves-New • General characters & Classification up to orders; Digestive & Respiratory system 61

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Mammals-New • General characters & Classification up to orders; Circulatory system of mammals 66

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Arterial system of human 68

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