PHYLUM CHORDATA

Chordata: Main Characteristics

– Pharyngeal Slits» Series of openings connecting inside of neck to outside;» Sometimes in form of gills;» For terrestrial groups: only exist during embryonic stages.

– Dorsal Nerve Cord» A bundle of nerve fibres running along dorsal area;» Connects brain to lateral muscles and other organs;

– Notochord» Cartilage rod that supports nerve chord;» For some: disappear during adult stage;» Vertebrata: notochord during embryo, vertebra (backbone)

during adult;

– Post Anal Tail» Tail located beyond anus;

Chordata: General Characteristics

• Closed circulatory system;• Almost all with a heart;• Most with blood containing haemoglobin• Muscles segmented into blocks call myotomes• All chordates are Deuterosomes (just like

Echinodermata): ie anus formed before mouth• 2 Classes (Urochordata and Cephalochordata) are

important oceanic filter feeders

CLASSES IN PHYLUM CHORDATA

Urochordata:

• Adults do not have chordate features except for gills

• Some Families have spicules• 3 Classes:

– Ascidiascea (Sea Squirts) – Thaliacea (Salps) – Larvacea

UROCHORDATA: Ascidiascea

• Most common class• Common name: ‘sea squirt’• Body in form of basket;• Possesses 2 siphons (side-

by-side)• Larva (resembles tadpole):

free swimming;• Larva swims and attach to

hard substrate; and• Larva looses tail and ability

to swim.

UROCHORDATA: Thaliacea (salps)

Almost exactly like Ascidia except for a few features:

– Siphons on both ends (not side-by-side)– perforated pharynx replaced by two funnel-

shaped holes– No larval stage

UROCHORDATA: Larvacea

• Different from other 2 classes;

• Only non stationary group;

• Tadpole shaped larvae never lose their tail;

• Average size only 5 mm (including tail);

• Possess a transparent gelatinous 'house‘

• eg Oikopleura sp.

Oikopleura (without housing)

Oikopleura (with housing)

EXAMPLES OF UROCHORDATA:Ascidia

Ciona sp.

CEPHALOCHORDATA

• Known as amphioxus or lancelet• Only 25 known sp.• Found in shallow seas esp. buried in marine sand;

– Eg. 5000/m2 at Discovery Bay, Jamaica • Possess chordate features even in adults• Different from true vertebrata: small brain• No true vertebrae• Developed circulatory system;• Excretory system – paired nephridia

CEPHALOCHORDATA -Feeding

• Water ‘sucked’ into mouth thro’ ciliary movement around mouth;

• Water filtered by oral cirri and then thro’ gills;

• Food in water caught by mucus;• Hepatic caecum - secretes digestive

enzymes;• Actual digestion done at the digestive

area of intestine called ciliocolonic ring)• Sexes are separated;• Larva resembles fish

CEPHALOCHORDATA (Amphioxus)

CLASS MYXINI (Hagfish)

• Found in cold aceans;• Resembles an eel• Pinkish in colour• Secretes a lot of sticky mucus• 3 heart accessory;• No cerebrum and cerebellum• No jaws or stomach;• Feeds on dead or dying fish.

CLASS MYXINI (Hagfish)

• Also preys on small vertebrata;

• Almost blind;• Developed sense of smell

and touch;• 4 tentacles located

around mouth, used as sensory organ;

• Direct reproduction, no larval stage;

• Juveniles resemble adults

CLASS MYXINI (Hagfish)

• Juvenile Myxini are hermaphrodite

• Eggs – about 1 in diameter• No. of eggs not many but rate

of mortality low;• Possesses a cranium (skull);• Some without vertebra• Skeleton from cartilage

SUBPHLUM VERTEBRATA

• Well recognized: not because of large number of taxa or individuals but because relates to humans

VERTEBRATA – Fossil Records

• Exists > 500 million years ago (late Cambrian Era)• Original form without jaws (as in hagfish and lamprey• First species identified – Anapsis• Cartilagenous fish, bony fish and tetrapod (vertebrata

with true feet) evolved during late Devonian Era (360 M years ago)

• Terrestrial amphibians appeared during late Mississippi Era

• Amniots (ancestor to reptiles, birds and mammals) evolved during early Pennsylvanian Era

VERTEBRATA – Life History

• Can be found from the tropics to the poles, from the deep ocean to the highest mountain, and in the air.

• Vertebrata and insects use energy for flying;

• Evolution began in the ocean;

• Ancestor with gill slits but for filtering for food, respiration via skin;

• Later gills use for respiration

VERTEBRATA – Life History (cont)

• Almost all with separate sexes;

• Almost all oviparous (lay eggs)

• Some fish and reptiles maintain eggs in body. Eggs hatch internally – ovoviviparous;

• Some (incl. Sharks and dogfish) and almost all mammals retain embryos in the mother and feed via a special connector (viviparous)

What differentiates Vertebrata from other Chordata?

Vertebrae• Centrum – bony

structure in the form of a disc. Formed around and replacing the notocord

• Neural arch – long hole through which the nerve cord passes

centrumneural arch

What other forms are unique of the Vertebrata?

Neural crest cells• During early development, ie. when nerve cord is being

formed, neural crest cells leave nerve cord and move around body forming various important nerves, nerve ganglia, and other nerves in the head and face

DIFFERENT BONES FOUND IN VERTEBRATA

2 kinds of bones• Dermal Bones

– Bony forms (plates and scales) that develop into skin;– example: bony shield of early jawless fish, scales of sharks,

shoulder blade, top of the skull

• Endoskeletal Bone– Originally : cartilage form and later calcified;– For cartilaginous fish true bones never formed.– example: vertebrae, ribs, appendages, jaws

DIFFERENT BONES FOUND IN VERTEBRATA (cont)

• Cartilage– All vertebrata have cartilage– Cartilage are flexible – nose, ears– Hard cartilage – larynx– Calcified cartilage (sharks teeth); not true

bones as they are not alive.

CLASSIFICATION OF SUBPHYLUM VERTEBRATA

• Petromyzontidae - lampreys• Placodermi – extinct• Chondrichthyes – cartilaginous fish• Acanthodii – extinct• Actinopterygii – fin fish• Actinistia – coelacanth• Dipnoi – lung fish• Amphibia• Reptilia• Aves • Mammalia

PETROMYZONTIFORMES (Lampreys)

• Also called Agnatha• Resembles eels but with differences

– Lack both jaws and paired fins

• Almost 50 species• Found in rivers and coastal areas of temperate region• Some remains in freshwater througout life• Others (eg Petrmyzon marinus): are anandromus ie stay

in freshwater during early stage and return to sea during adults

• Live for 1 – 2 years, lay eggs and die• Larva trap food using gills

Petromyzontiformes (Lampreys)

Lamprey sucking blood from fish

PETROMYZONTIFORMES (cont)

• With rounded jawless mouth which resembles a sucker

• Preys on fish but also on invertebrates

• Now a major fisheries problem in the Great Lakes

PLACODERMI – FIRST JAW FISH

PLACODERMI

• Extinct• Thick bony shield around head and neck • Teeth replace by bony plates • When in existence represents a very diverse and

successful group

PLACODERMI - Examples

• Dunkleosteus – marine predators• Found in Ohio, USA• Lived during Devonian Era• Very diverse• Size – 20 feet• Width of head – 4 feet

• Bothriolepis• From Quebec, Canada• Head – 4 inches wide

CHONDRICHTHYES

• Including sharks, skates, rays and chimaeras

• First appeared 450 M years ago

• No true bones; only cartilages

• Teeth and vertebrae calcified• Sharks prey on fish, squids,

and marine mammals• Skates and chimaeras feed

on crustaceans and mollusks

• Thick heterocercal tail

• Fin fish with homocercal tail

Shark

Salmon

CHONDRICHTHYES - Clasification

• Elasmobranchii– Upper jaws not fused and with a braincase;– Gill openings resemble slit;– eg Sharks

• Brandyodonti– Upper jaws fused and with a braincase;– Gills covered by operculum– eg – Chimaera, ratfish

ACTINOPTERYGII

ACTINOPTERYGII

• 20,000 species still living;• Fins – skin membrane supported by bony thorns;• All with true bones except for some primitive forms; • Largest teleost group;• Operculums cover gills;• Most with homocercal tail;• With swimming bladder;• Most lay eggs but some will wait until hatch. (guppy,

swordtail)

ACTINOPTERYGII (Classfication)

• Used to be categorized into 3 groups;

– Chondrostei– Holostei– Teleostei

• Present– Cheirolepis– Polypteridae– Redfieldiidae– Chondrostei– Neoterygii : Holostei dan Teleostei

Chondrostei

• Two chondrostean lineages survive today– sturgeons of Eurasia and North America– paddlefish (shown here) of North America and China

• have secondarily lost a number of actinopterygian traits– lack scales on most of the body– cartilaginous skeleton– shark-like, heterocercal tail – rostrum extending past the mouth

Chondrostei: example

Paddlefish

Holostei:

Only 8 species survive:

• Lepisosteidae – – Gar Pikes - 7 species, North and Central America

• Amiidae – – the Bowfin - 1 North American Species - Amia

calva

Holostei: examples

Alligator gar

Manjuari

SARCOPTERYGII

• Include Actinistia, Dipnoi and Tetrapod;

• Tail formed earlier – heterocercal

• Now (lung fish, cealocanth) – homocercal

• Lobed-fins - containing bones and muscle;

• Front fins can be used to support body.

• Dipnoi – lung fish – From South Amerika

• Coelocanth– from Sulawesi

AMPHIBIA

• Order Urodela – Body usually long and cylindrical; – head, trunk, and tail are separate;–  legs, if present, usually all equal in size. – Salamanders and Newts.

• Order Salientia – Body usually short and stout; – head and trunk usually combined, – with no tail; – legs often smaller in front. – Frogs and Toads. 

Salamander

REPTILIA• Order Testudines

– Body is covered by "shell" of fused hardened scales; – have toothless beaks. – turtles and Tortoises

• Order Crocodilia– Have legs and movable eyelids; – mouth without "lips";– found mostly in or near water. – Alligators, Crocodiles and Gavials.

• Superorder Squamata – May or may not have legs; – teeth hidden by "lips"; – common on land but sometimes in water; – Scales often small– Lizards and snakes

Marine Turtles in Malaysia

Hawksbill turtle (Eretmochelys imbricata)

The leatherback turtle (Dermochelys coriacea)

The green turtle (Chelonia mydas)

Olive-ridley turtle (Lepidochelys olivacea

MARINE TURTLES OF MALAYSIA

AVES (Birds)

• extremely distinctive and successful • estimated 9000 species • evolved remarkable specializations for flight

– unique "one-way" breathing system– light yet strong hollow bones– skeleton in which many bones are fused or lost– powerful flight muscles– feathers.

OstritchFlamingos

Snow owl Hawk

MAMMALS: Characteristics not found in other animals

• Middle ear bones

• Hair

• Mammary gland – milk production

Mammalia

Subclass Metatheria (Marsupials)

Youngs born in immature stageMost have pouch

Major Groups:

•Order Didelphimorphia - opossums •Order Paucituberculata - shrew-like insectivores •Order Dasyuromorphia - Tasmanian wolf •Order Diprotodontia - (10 families and 117 species) kangaroos,

wallaby, wombats, koalas

Subclass PrototheriaOrder Monotremata

• Lay eggs with leathery shells• Nourish young with milk• 2 Families:

– Family Ornithorhynchidae, duck-billed platypus– Family Tachyglossidae, spiny anteater

Platypus Echidna

EUTHERIA

Major Orders of Mammals:

Subclass Eutheria (Placental Mammals)

Order Artiodactyla (even-toed ungulates: antelope, deer, camels, pigs, cows, sheep, hippos, etc.)

Order Carnivora (carnivores: cats, bears, dogs, polar bear, Order Cetacea (whales, dolphins) Order Chiroptera (bats) Order Insectivora (insect-eaters: hedgehogs, moles, shrews) Order Logomorpha (rabbits, hares) Order Perissodactyla (odd-toed ungulates: horses, rhinos, tapirs)

Major Orders of Mammals: (cont)

Subclass Eutheria

•Order Pholidota (the pangolin) •Order Primates (apes, monkeys, lemurs, people) •Order Proboscidea (elephants, mammoths, mastodonts•Order Rodentia (rodents: rats, mice, squirrels, hamsters, •Order Sirenia (sea cows, manatees)

MARINE BIODIVERSITY

• Plankton– Phytoplankton– Zooplankton

• Benthos– Coral species– Polycheates– Molluscs– Crustaceans

• Nekton– Fish– Squids– Mammals