Comparative anatomy of chordate

Subphylum Vertebrata or

CraniataLect. 4

Assist. lec. Sawsan S. Hameed

Biology Department

Tishk international University

2021-2022

Objectives

- Understand the general characteristics of Vertebrata

- Differentiate between super classes of Vertebrata

- Understand the features of super classes of

Vertebrata

- Describe and classify different classes of Agnatha

- Understand the classes of Agnatha, characteristics,

their classification with examples of each

➢ Called craniata due to presence of cranium,

➢ The names of Vertebrata is due to the change of

notochord to vertebral column

➢ Basic features

➢ A complex brain encased by a cranium, which protects and

supports it.

➢ Advanced nervous and sensory structures.

➢ Have endoskeleton

➢ Males and females are separate

➢ Gill slits are few in number, when present

➢ Variety of feeding strategies: herbivores, carnivores,

omnivores, filter feeders, parasites.

Subphylum Vertebrata or Craniata

Features of vertebrate

➢ Variety of habitats including freshwater, salt water,

terrestrial.

➢ Specialized epidermal structures; scales, feathers, hair,

fur, spines.

➢ True kidneys.

➢ Efficient respiratory system of gills or lungs

➢ Body is bilaterally symmetrical and of three parts - head

trunk and post-anal tail.

➢ Divided into 2 superclass

➢ Agnatha (Jawless Vert.)

➢ Gnatha (Jaw Vert.)

Class Ostracodermi

fossil

Class Myxini

Hag fishesClass

Cephalospidomorphi

(Lampery)

Agnatha

jawless vert.Gnatha

jaw Vert.

Super class Super class

Superclass Agnathan (jawless)

vertebrates➢ lack jaws hence the name agnatha (without jaw)

➢ Vertebral spine is cartilaginous in nature • head with a cranium

that encases a brain

➢ Mouth is generally round/ circular

➢ No scales or exoskeleton.

➢ Divided into 3 classes

➢Class Ostracodermi (fossil)

➢Class Myxini Hag fishes

➢Class Cephalospidomorphi (Lampery)

Agnathan (jawless) vertebrates

Class I : Ostracodremi ("shell-skinned") (extinct)

The earliest known vertebrates appear in fossils records of jawless primitive fish-like animals

Important features

➢ Primitive vertebrates, small to medium sized

➢ Body were fish-like, usually flattened dorso-ventrally, with a huge head and gill region

➢ No pectoral and pelvic fins but had only median fins

Exapmles : Cephalaspis , Pteraspis

➢ The head was encased in a solid shield made of broad bony dermal plates.

➢ This has led to their names Ostrochoderms (armoured fishes) or (bony skin) (Gr., orstracon= shell, derma = skin).

➢ Most kinds had a pair of large lateral eyes and median pineal eye on top of head

Agnatha (jawless) vertebrates

Dorsal fin

Dermal plater

Cephalaspis Pteraspis

➢ This group include two classes; Myxini (hagfishes), and Cephalaspidomorphi (lampreys).

➢ Members of this group lack jaws, internal ossification, scales, and paired fins.

➢ Both groups share pore like gill openings and an eel-like body form.

➢ In other respects, however, the two groups are morphologically very different.

➢ Notochord persists in adults

Living Agnathans (Jawless Vertebrates)

lampreys

Characteristic

➢ elongated eel-like body, lack jaws, true teeth, paired fins and bones

➢ Notochord remain throughout the life

➢ Lack vertebrae, but considered vertebrates because they have cranium and cartilagenous endoskeleton.

➢ Have single nostril loads to olfactory sac.

➢ Eyes are vestigial and covered by skin

➢ Have gill pouches

➢ All the hagfish are belong to one order Myxiniforms

Scientific classification

Kingdom: Animalia

Phylum: Chordata

subphylum vertebrate

Superclass Agnatha

Class: Myxini

Order: Myxiniformes

Class 2; Myxini

Scientific classification

Kingdom: Animalia

Phylum: Chordata

Class: Myxini

Order: Myxiniformes

Genus: Eptatretus

Genus. Eptatretusis a large genus of hagfish. It has at

around 48 described species at

present

Species: Eptatretus

stoutii➢ Is a species of hagfish.

➢ A jawless fish, lives in the

mesopelagic, near the ocean

floor.

➢ Produce large amounts of slime

➢ Eaten in Korea and other Asian

countries, along with its eggs and

its slime

Eptatretus stoutii

Eptatretus

➢ Agnatha vertebrates, lack jaws,

➢ Notochord remain through the

life and have primitive vertebral

column

➢ Have cartilaginous cranium &endoskeleton

➢ single median nostril

➢ Parasitic form prey on fishes

Scientific classification

Kingdom: Animalia

Phylum: Chordata

Subphylum: Vertebrata (Craniata)

Superclass Agnatha

Class Cephalaspidomorphi

Order Petromyzontia

Examples: marine lamprey Petromyzon marinus ,

freshwater lampreys Lampetra fluviatilis and L. planeri.

Class 3; Cephalaspidomorphi

➢ Median fins include two dorsal fins and caudal fin

➢ Seven pairs of gill pouches open separately to the exterior via gill slits

➢ larval stage are free living nonparasitic, mouth with upper

and lower lips.

➢ The larva is called Ammocoeta larva after 3 years then become adult after change in morphology and anatomy

Class III: Cephalaspidomorphi

Scientific classification

Kingdom: Animalia

Phylum: Chordata

Subphylum Vertebrata

Superclass: Agnatha

Class Cephalaspidomorphi

Order: Petromyzontia

Genus: Petromyzon

Species: P. marinus

The sea lamprey (Petromyzon marinus)

➢ Is a parasitic lamprey found on

the Atlantic coasts of Europe and North

America

➢ It is brown, gray, or black in color

➢ Can grow up to 90 cm (35.5 in) long.

➢ Prey on a wide variety of fish.

➢ The Secretions in the lamprey's mouth

prevent the victim's blood from clotting.

➢ Victims typically die from excessive

blood loss or infection.

Petromyzon marinus

River Lamprey (Lampetra

fluviatilis)

➢ known as the European river Lamprey

or Lampern, Jawless lamprey

➢ Found in coastal waters around almost

all of Europe.

➢ Feeds as ectoparasites on fish.

➢ Migrate upstream from the sea

to spawning grounds in autumn

& winter

Scientific classification

Kingdom: Animalia

Phylum: Chordata

Subphylum Vertebrata

Superclass Agnatha

Class: Cephalaspidomorphi

Order: Petromyzontia

Genus: Lampetra

Species: L. fluviatilis

Lampetra fluviatilisscientific name Lampetra

fluviatilis

Petromyzon marinus L. planeri

Lampetra fluviatilis

Sea Lamprey

1-Terminal mouth with four pairs of

tentacles. Buccal funnel absent. 5 to 16

pairs of pharyngeal pouches. About 65

species.

Hagfishes

2- No paired appendages,

3- No dorsal fin (the caudal fin extends

anteriorly along the dorsal surface.

4- Dorsal nerve cord with differentiated

brain, no cerebellum.

5- No larval stage.

6- Marine

1. Suctorial mouth with keratinized teeth.

Seven pairs of pharyngeal pouches. 41

species.

Lampreys: (Petromyzontes)

2. No paired appendages,

3. One or two dorsal fins.

4. Dorsal nerve cord with differentiated

brain, small cerebellum present.

5. Long larval stage (ammocoete).

6. Freshwater and marine

Class Myxini Class Cephalospidomorphi

Larval stage of lamprey

1. Ammocoete, is the larval stage of lamprey.

2. Its resemble amphioxus in many way.

3. Ammocoete do have several characteristics lacking in amphioxus that are homologous to those of vertebrates; these include:

➢ Chambered heart, well-developed brain, special sense organs, and pituitary gland.

Ammocoete

Oral hoodPharyngeal bars

Pharyngeal gill slits

Eye

brainOptic vesicle

anus

Post anal tail

Dorsal nerve cord

notocord

Larvae of lamprey Ammocoete

Jawless

mouth

Vestigial eye

Caudal fin

No scale

Buccal funnel First dorsal fin

Second dorsal fin

(Myxini Form)

Cephalaspidomorphi

Living Jawless Vertebrate

➢ In this lab, study all of the slides, reserved samples and pictures.

Starting by;

➢ Lamprey whole specimen

➢ Identify some chordates characteristics in a lamprey

➢ Pharyngeal slits, tail

➢ Draw it with all the labelling

➢ Slide of Ammocoetes, region of pharynx, gills and tail

➢ Study the chordates characteristics using the slide of

Ammocoetes. Notice the following;

➢ Notochord

➢ nerve cord.

➢ Region of gills

➢ Postanal tail

➢ Based on your information from the previous lab, how to differentiate

between the Amphioxus and the Ammocoetes?

➢ Draw all the slides, and whole specimen. Label all the structures that

you identify.

Lab study: Agnatha

References

For further reading please see:

Charles K. Weichert (2017). Elements of chordate anatomy. 3rd edition.

The McGraw−Hill Companies, New york.

Comparative anatomy | Definition, Examples, & Facts |

Britannicahttps://www.britannica.com › science › comparative-anatomy

Kardong, Kenneth V. (2019). Vertebrates: comparative anatomy, function,

evolution (8th edition). New York.

De Iuliis, G., & Pulerà, D. (2019). The dissection of vertebrates. 3rd

edition. Academic press. Elsevier, London.

Kenneth, S. S. (2017). The unity of form and function. 8th edition. The

McGraw−Hill Companies,. New york.

Comparative Anatomy. wwww.health.zone/