Sub Phylum Vertebrata By - PowerPoint Presentation

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Sub Phylum Vertebrata

By

Dr.

Preetha

Karnaver

Assistant Professor in Zoology

Christian

College,

Chengannur

They possess vertebral column- hence the name

vertebrata

Also possess a brain case (Cranium)- hence also known as craniates

Possess all basic chordate characters

General characters

Veretebral

column

:

Notochord in embryo gets replaced by vertebral column.

Vertebrae are serially arranged to form a column

Inside that column, spinal cord is protected

Head:

distinct head is present.

Brain enclosed within brain case(Cranium)- hence craniates

Integument:

Outer epidermis and inner dermis

Epidermis derived from ectoderm and dermis derived from mesoderm

Endoskeleton

Internal cartilage or bony skeleton

Specialised tissue composed of compactly arranged collagen fibres

Bone contain crystals of calcium phosphate

Muscular Pharynx

Possessed by all vertebrates

In fishes, pharyngeal pouches opens out as gill slits bearing gills

In

tetrapods

, they are sources of several glands

Digestive system

Completely muscular

Distinct liver and pancreas present

Circulatory system

Closed type

Heart

multichambered

and ventrally placed

Erythrocytes contain Haemoglobin

Coelom

: divided into two

1) Pericardial cavity (

sorrounding

heart )

2)

Pleuroperitoneal

cavity (

sorrounding

lungs and viscera)

Excretory system

Paired Kidneys and associated ducts to drain waste

Endocrine system

Consists of ductless glands scattered throughout the body

Appendages

Two pairs

Limbs

Limb girdles

Appendicular

skeleton

Classification

DIVISION (SUPER CLASS) AGNATHA

Agnatha

(Greek A= without;

gnathos

-jaw)

Comprises Jawless fishes

Evolved in

ordovician

period

Fossil remains of only one group

Ostracodermi

is available

Very few number of species survive as evolutionary relicts

Salient features of Agnatha

Jaws, teeth, paired appendages, ducts etc absent

Roof of cranium is membranous

Vertebral column consists of persistent notochord

Single median nostril

7-14 pairs of gill slits

1-2 semicircular canals in internal ears

Elongate kidneys with long

archinephric

ducts

Well developed pineal apparatus

Larval stage is

microphagous

Possess

endostyle

Class Myxini

Class

Cephalaspidomorphi

Consists of Hagfishes

Terminal mouth

Four pairs of tentacles

Buccal

funnel absent

Nasal sac opening to pharynx

Pharyngeal pouches 5-15 pairs

About 65 species identified

sofar

Eg

:

Myxine

Consists of Lampreys

Circular and

suctorial

mouth with keratinised teeth

Nasal sac not connected to

buccal

cavity

Pharyngeal pouches – 7pairs

About 41 species identified

sofar

Eg

:

Petromyzon

But, according to another classification, hagfishes and lampreys are included under class

Cyclostomata

Cyclos

= circle; Stoma= Mouth)

Primitive jawless vertebrates commonly called Lampreys

Elongate , round, eel like body

Soft, smooth skin

Exoskeleton absent; cartilaginous endoskeleton present

Jaws absent Mouth circular and

suctorial

Single, median nasal opening

Persistent notochord

2 chambered (auricle & Ventricle) heart

Gonad single; without

Gonoducts

Development- direct/ indirect

Eg

:

Petromyzon

PETROMYZON

Jawless aquatic vertebrate

Commonly called Lamprey

Found in North America, Europe, West Africa, Japan, Chile, Australia,

Newzealnd

and Tasmania

Body elongate, laterally compressed (eel like)

Head, trunk and tail present

Neck absent

Buccal

funnel/sucker directed down wards at anterior end of head

Buccal

funnel is

sorrounded

by lips supported by cartilage

Lips carry sensory papillae

Mouth lies at the base of sucker

Many horny teeth are present inside the sucker

Horny

protrusible

tongue is also present

Attaches to the body of fish by sucker and feeds on blood

Eyes lateral; without eyelids

There is a median transparent area behind eyes- Pineal organ

Single median nasal aperture

7 gill clefts on either side of head behind each eye

Gill clefts do not open into pharynx

Anus lies at base of tail

Urinogenital

opening lies on a papilla behind anus

Skin slimy, scale less

Lateral lines present

Presence of 2 dorsal fins and an anal fin

Pectoral and pelvic fins absent

Presence of cartilaginous endoskeleton

RBC contains nucleus and haemoglobin

Sexes separate

Females lay eggs (oviparous)

Fertilisation external

Characteristic larval stage called

Ammocoete

larva

3 species of Lamprey found in Northern hemisphere

Petromyzon

marinus

Petromyzon

fuviatilis

( river lamprey)

Petromyzon

planeri (Brook lamprey)

Ammocoete

larva of

Petromyzon

Very much similar to

branchiostoma

in organisation

Thin, laterally compressed body

They also possess;

Unconstricted

notochord

Oral hood

Endostyle

Epipharyngeal

groove

Peripharyngeal

bands

Velum

Class Ostracodermi

Extinct jawless vertebrates

Fossil jawless

agnatha

of fresh water

Fish like body

Heavy head armour

Skin bears heavy , bony, dermal plates

Single nostril on top of head

Mouth- slit like opening at extreme tip of head

Scoops decaying matter with mouth from bottom of

frewsh

watre

bodies

Axial endoskeleton/ vertebrae absent

Sometimes, a pair of fins are seen behind head

Cephalaspis (Head shield)

Palaeozoic, armoured, jawless fishes

Medium sized

Detritivorous

fish – in fresh water streams and estuaries (in

devonian

period)

Heavy armour- to defend enemies and also as calcium source in the calcium poor fresh water

envt

.

Sensory patches in head shield to sense presence of burrowing worms and other organisms in mud

Mouth beneath the head-

bottom feeder- moves head side to side- stirring sand- revealing hiding places of worms in mud