Chapter 9
Tetrapods
Kingdom Animalia
– Sub-Phylum Chordata
• Class Reptilia (reptiles)
• Class Aves (birds)
• Class Mammalia (mammals)
Lobefin fish
Tetrapod origin –
invaded the land 350 million years ago
Early tetrapod – evolved two pairs of
limbs for walking
Tetrapods
Four footed
Breathe air
No True Marine Amphibians
4
Bufo marinus
Class Reptilia
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7000 living species
Dry skin covered with scales
Leathery egg shells
Air breathing
Cold blooded
airbreathing
coldblooded
• Poikilotherms – body temperature varies
with the environment
• Ectotherms – lose metabolic heat to the
environment which affects their body
temperature
Order Chelonia
Sea turtles
9 species
• Bodies enclosed in armor like shell or
carapace
• Carapace is fused to the back bone
• Can’t retract their head
• Forelimbs modified to flippers
Fossil Sea Turtle
Archelon ischyros
(Cretaceous, North Dakota)
Sea turtles
Still tied to land
Sea turtles
Reproduction
• Migrate long distances to lay eggs on remote sandy
beaches
• go where they were born
• Only females go to shore at night
• babies hatch in 60 days
• try to escape to the ocean under the cover of darkness
• they are eaten by: dogs, ghost crabs, wild pigs, birds
and fish
Sea turtles
Conservation and study
Conservation
• nesting areas have been turned into resorts or public
beaches
• artificial lights confuse mom and babies
• Drown in nets
• Eat plastic because they think it is a jellyfish
• Eggs are eaten
• Sea turtle leather
Order Squamata – Sea Snakes,
Marine Iguanas
55 species
Sea Snakes
Sea Snakes
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Found in the Indian and Pacific oceans
Laterally flattened tail
Paddle-like tail
3 to 4 feet
Carnivorous – eat bottom fish
Venom can kill humans
Hunted for their skins
Sea Snakes
•Ovoviviparous – eggs develop
and hatch in female reproductive tract
Marine
iguana
Amblyrhynchus
cristatus
Marine Iguana
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Elegant swimmers
Laterally flattened tail
Warm on rocks
Dive 33 feet to eat seaweed
Live on the
Galapagos
Islands
Marine iguana
Saltwater crocodile
Order Crocodilia
Crocodylus porosus
Saltwater Crocodile
• Found in mangrove swamps and estuaries
• Eastern Indian Ocean, Australia and some western
Pacific Islands
• 20 feet long
• mostly stay near shore
• most aggressive of the marine verts
• attack and eat people
• More feared than sharks
Tetrapods
“Class” Aves
Birds
• Seabirds represent 3% of the 9700 species of birds
• Found pole to pole
• predators of fish, squid, and bottom invertebrates some eat plankton
• Eat a lot to maintain their body temperature
Flight
• Capable of flight an advancement
over reptiles
• Light hallow bones
• eggs have hard shells which make them resistant to
water loss
• Homeotherms – “warm blooded” keep body
temperature constant regardless of environments
• Endotherms – retain metabolic heat which raises body
temperature
Seabirds
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spend a significant part of life at sea
feed on marine organisms
nest on land
Breed in large colonies
mate for life
Care for young
True seabirds have webbed feet for swimming
Penguins
Penguins
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Flightless –wings modified to flippers
“ Fly” underwater
bones are denser to reduce buoyancy
spectacular swimmers
jumps of water
clumsy on land
nearsighted – adapted to underwater vision
layer of fat under skin for warmth
All but 1 of the 18 species live in Antarctic and cold
regions of the southern hemisphere
• Found as far north as the equator
Tubenoses
Tubenoses
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Tube like nostrils
Heavy beaks that are curved at the tip
Salt Glands
spend months or years at sea
skillful fliers
fish at surface – some scavenge
Tubenoses
Albatrosses
Albatrosses
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Magnificent gliders - huge wings that span up to 11 ft
Mate for life
Incubation and care of chick lasts 8+ months
Spectacular migrators – Antartic to Arctic
Tubenoses
Shearwater
petrel
Pelicans
Pelicans
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Large fish eaters
Webbing between all four toes
Unique pouch below beak
Brown pelicans decimated by DDT
Cormorants
Frigate birds
Cormorants
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Black
dive and purse prey
Identified by low flight over water
Float low in the water with only their neck above the surface
Frigate Birds
• Narrow wings
• Long forked tail
• Soar along coast – force other seabirds to regurgitate in midair
• Agile pirates - seldom enter the water
• Feathers are not water proof
A seabird gift
Guano
• Bird excrement
• mined for fertilizer
• very thick on the coasts of Peru, Chile and SW Africa
Gulls and
related birds
Terns
Sterna paradisaea
Gulls
• includes a large variety of seabirds
• predators and scavengers - eat anything
• Successful in the company of humans
Terns
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Graceful fliers
hover over prey and then plunge
have slender beaks
eat small fish
Shorebirds
Shorebirds
plover
avocet
Shorebirds
sandpiper
killdeer
Shore Birds
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wade
no webbed feet
not seabirds in the strict sense
common in estuaries and coastal marshes
Body form and beaks adapted
to niche and function
Class Mammalia
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Evolved 200 million years ago from reptiles
4600 species
Endotherms – “warm blooded”
Homeotherms - same temperature
have hair to retain body heat
Viviparous – embryo develops in the mom and
receives nourishment from the mom
Mammary Glands – secrete milk to feed the baby
Brain is larger relative to body size than other
vertebrates
Live anywhere there is air to breath and food to eat
Five groups of land mammal have invaded the oceans
Five Marine Mammal Lineages
Order Pinnipedia
Seals, sea lions, walrus
Order Pinnipedia – Seals, Sea Lions and
Walrus
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Paddle Shaped Flippers - still need to rest on land
19 or 20 families
Predators of fish and squid
Streamlined bodies for swimming
Live in cold water
Have a thick layer of fat - blubber
Blubber serves as a food reserve, conserves heat and
provides buoyancy
• Conserve heat with:
– blubber
– bristly hair
– Size – low surface area to volume ratio
• Need to breed on land
Sea lion skull
California Sea lions –
sunning
Leopard seal -- Antarctic
Conserving heat
Pinnipeds give birth on
land (or ice)
Pinniped birth
Seals
Seals
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19 species
Rear flippers cannot move forward
when on land they pull with their front flipper
swim with their rear flippers
Seals are highly
adapted for
aquatic life
Crabeater seal
An Antarctic seal that filter feeds on krill
Elephant Seal
(Mirounga)
Ano Nuevo
State Park,
California
Harbor seal pup
Phoca vitulina
Hawaiian monk seal
(Monachus schauinslandi)
Mediterranean monk seal
(Monachus monachus)
Caribbean monk seal
(Monachus tropicalus)
Harp seal
Phoca groenlandica
Seals hunted
for blubber
and fur
Seal lions
Sea lions and Fur Seals
• 5 species
• Eared seals
• move rear flippers forward so they can walk or run on
land
• front flippers can be rotated so they can sit on land
• graceful and agile swimmers
• females are called cows
• males are called bulls
California sea lion
Zalophus californianus
California sea lion
Zalophus californianus
California sea lion
Zalophus californianus
Walrus
Odobenus rosmarus
Walrus
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Eat bottom invertebrates like clams
Suck up food – no tusks
whiskers act as feelers
Tusks – are used for defense and to haul out on the ice
Walrus
Walrus
Order
Carnivora
Sea otter
Enhydra lutris
Sea otter
Order Carnivora - Sea Otter
• smallest marine mammal
• Males are 60 to 80 pounds
• No blubber
• insulation comes from air trapped in their fur
• almost killed to extinction because of their fur
• playful and intelligent
• spend most of their time in the water
• need to eat 15 to 20 lbs a day
• eat: sea urchins, abalone, mussels and crabs
• live around and protect kelp beds
Sea otter
Polar bear
Ursus maritimus
Polar bear
Polar Bear
• Semi-aquatic
• good part of their lives is spent drifting on ice in the
Arctic
• Eat seals
• stalk and kill seals when they come up to breath or
rest
Polar bear
Polar bear
Order Sirenia
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relatives of elephants
Pair of front flippers - no rear flippers
swim with up and down stroked from the tail
wrinkled skin with few hairs
well padded body with blubber
Gentle creatures
Live in groups
Only Strict vegetarian
large lips used to feed on sea grasses
West Indian
Manatee
Trichechus manatus
Amazon Manatee
Trichechus inunguis
West African River Manatee
Trichechus senegalensis
Manatee – (four species)
• all endangered because of loss of habitat
–Exploited for: meat, skin, oil rich
blubber
 reproduce slowly – one calf every three
years
Dugong
Dugong dugon
Dugong
• Found from east Africa to some western pacific
islands
• Critically low numbers
Steller’s Sea Cow
largest sirenian – now extinct
(Hydrodamalis
gigas)
up to 7.5 m long
Convergence in body form among
marine vertebrates
Marine Vertebrates - converge in body form
Superficially resemble fish
Order Cetacea – whales, dolphins, porpoises
Perceptions of
whales
Order Cetacea
• largest group of marine mammals
• 90 species- all marine except for five species of river
dolphins
• most complete transition to aquatic life
• spend entire lives in water
Humpback whale
Megaptera novaeangliae
A bit of anatomy….
• have a dorsal fin
• Muscular tail ends in a pair of fin like horizontal
flukes
• blubber for insulation and buoyancy
• Nostrils on top of head forming a blowhole (single or
double)
Cetacean swimming
• swim with strong up and down movements of the tail
and flukes
• Front flippers only
• rear limbs fail to develop (vestigal)
Vestiges of
terrestrial
ancestry
Dolphin
embryo
Vestigial pelvic girdle
Cetaceans are divided into two groups
(suborders)
1.Suborder Mysticeti – Baleen Whales
2.Suborder Odontocetti – Toothed
Whales
Baleen whales
Toothed whales
Baleen whales
Suborder
Mysticeti
Baleen whales
Feeding
• whale feeds by taking a big mouth of water and then
squeezing out the water
• whale licks off the food that is left behind and
swallows it
• 13 species
– Largest – blue whale
– 2nd largest – fin whale
• blowhole has two openings
Baleen whales
Feeding in baleen whales
Baleen
•Fibrous plates that hang from the
upper jaw
•Inner edge has bristles that form a
dense mat
•Made of keratin
Baleen
Whale bone corset,
ca. 1890
Whale bone
corset stays
Krill (a euphasid shrimp)
Rorquals
Blue whale
Family Balaenopteridae
(Balaenoptera musculus)
• Roquals - some baleen whales are classified into this
group
– Examples – Blue, minke, humpback
– Feed by gulping up schools of fish and swarms of krill
– Lower part expands when feeding hence the distinctive
grooves
Some other Rorquals
Minke whale
Balaenoptera acutorostrata
Bryde's whale
Balaenoptera edeni
Humpback whale
Megaptera novaeangliae
Humpback whale
Megaptera novaeangliae
Feeding
Balaena mysticetus (bowhead)
Right
whales
Eubalaena australis (southern right
whale)
Eubalaena glacialis (northern right whale)
Right Whale
• Feed by swimming along the surface with their
mouths open
• Have the largest baleen plates but the smallest bristles
• Allows them to filter small plankton-like copepods
and krill
Bowhead whale Eskimo fishery
Bowhead whale
Grey Whale
Eschrichtius robustus
Eschrichtiidae
Grey Whales
• Primarily bottom feeders – amphipods in the mud
• Stir up the bottom with their pointed snouts and then
filter the sediment
• Most feed on right some – some left
Such close contact is not
allowed in US waters
Whale
barnacles
Toothed whales
Suborder
Odontoceti
Toothed
whales
Suborder
Odontoceti
Toothed
whales
Suborder
Odontoceti
Suborder Odontocetti – Toothed
Whales
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80 species
teeth adapted to a diet of fish, squid and other prey
teeth are used to catch and hold - not chew
food is swallowed whole
one blowhole
Cetacean
blowholes
Mysticeti
Odontoceti
Sperm Whales
Family Physeteridae
3 species in 2 genera
Physeter catodon
Sperm whales
– largest toothed whale
– most numerous of the great whales
– eat squid, sharks, lobsters and marine mammals
Sperm whale
spermaceti
Sperm whale
ambergris
Ambergris
–Large globs of sticky material made of
squid beaks and other debris
–Ingredient in fine perfume
Sperm whale
pygmy sperm whales
Genus Kogia
Kogia skull
Family
Delphinidae
killer whale
dolphins
Orcinus orca
killer whale
Family Delphinidae
• Predators of sea lions, penguins, fish, sea otters and
other whales
• White bellies used to flash and frighten herring
schools
• Flukes stun fish
• Most common in cold water
Killer whale
Killer whale
Dolphins
Family Delphinidae
Dolphins
– Small toothed whales
– Distinctive snout or beak
– Perpetual “smile”
– Playful, highly social and easily trained
– Travel in large groups – pods, herds or
schools
Porpoises – small group of blunt nosed
whales
Dolphin skull
Trained dolphins
Biology of Marine Mammals
•Our knowledge is limited
•Hard to keep in captivity
Cetaceans are
hard to study
Radio tags
Swimming and Diving
•Streamlined body for swimming
•Pinnipeds swim with flippers so do sea
turtles
•Sirenians and cetaceans – tails and flukes
move up and down
Whale Spouts
• Cetaceans – blowhole on top – can
breathe with body still in water
• To avoid inhaling water can empty and
refill lungs quickly – less than 2 sec.
• Fin whale – half the time of a human
breath but 3000 times more air
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Whale spouts
• Spout – warm water condenses when
breathe out
• Mixes with sea water and mucus spouting
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Diving
Diving
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Wide range of abilities
Sea otters – 4 to 5 minutes – 180 ft
Pinnipeds – 30 minutes – 490-820 ft
Baleen whales – rarely venture below 300 ft –
eat plankton
• Toothed whales – excellent divers
• Sperm whales – dive 7,380 ft – under water for
an hour
• Dolphins dive 990 feet
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Adaptations to Reduce Oxygen
Use
• Heart rates slow
• Northern Elephant Seal – 85 BPM down to
12 BMP
• Blood flow reduced to non-essential body
parts
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Diving
• To get as much oxygen as possible hold
breathe for 15 to 30 sec then rapidly
exhale and take a new breath
• 90% of oxygen in lungs is exchanged
• Humans only exchange about 20%
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• Better at absorbing oxygen from the air
and storing in the blood
• More blood
• More RBC which carry more hemoglobin
• Muscles rich in myoglobin (stores oxygen
in the muscles)
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The Bends
• When pressure is released quickly
• Dissolved nitrogen comes out the blood
and forms bubbles in the blood
• Bubbles lodge in joints
• Block flow of blood to brain and other
organs
• Painful condition
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• Have adaptations that prevent nitrogen
from dissolving into the blood in the first
place
• Lungs collapse
• Reduce need for oxygen
• Store oxygen with hemoglobin and
myoglobin
• Reason why marine mammals do not get
the bends
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Cetaceans underwater
Senses
Olfaction
Vision
Depend little on the sense
of smell
Vision is excellent
Senses
• Depend little on the sense of smell
• Vision is excellent
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Echolocation
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Sensory system based on hearing
Nature’s version of SONAR
Find prey
Orientate to surroundings
Toothed whales and pinnipeds
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• Emit sounds waves that travel 5x faster in
water
• Listen for echoes which are reflected back
from surrounding objects
• Echoes analyzed by brain
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• Time it takes the echoes to return tells
them how far it is
• Sounds – short burst of sharp clicks
• Repeated at different frequencies
• Low Frequency Clicks – high penetrating
power – travel long distances – info on
topography – stun prey
• High Frequency Clicks – more detailed –
locate prey
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• Air forced through air passageways and
several air sacs as blowhole is closed
• Contracting and relaxing muscles changes
frequency
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Beluga whale
Delphinapterus leucas
• Melon or Spermaceti Organ – focuses out
going sound
• Incoming sound – received through the
lower jaw into the inner ear
• Do not hear much from the outside
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Melon
• Fatty structure on the forehead of toothed
whales
• Focus and direct outgoing sound waves
• Gives them their characteristic round
foreheads
• Beluga – in Russian means “White Melon”
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Echolocation
Melon or spermaceti organ
(outgoing sound)
Incoming sound – through the lower jaw, into the
inner ear
Behavior
• Mammals rely mostly on past experience,
stored and processed in the brain to
respond to changes in the environment
• Highly social animals
• Live in groups at least part of the time
• Pinnipeds – huge colonies during breeding
season
• Cetaceans – highly organized pods
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Communication
• Sound important
• Sea lions and fur seals communicate with
loud barks and whimpers
• Seals – sedate grunts and whistles and
chirps
• Pinnipeds – important in maintaining
territory and finding pups
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• Cetaceans – rich variety of vocalizations
that are different from the sounds used in
echolocation
• Can produce both at once
• Social vocalizations are low-frequency
sounds that humans can hear
• Sounds associated with moods
• Used in social and sexual signaling
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• Humpback whale males produce songs to
attract females
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Grey whale vocalization
Sei whale vocalization
Play Behavior
• Pleasurable activities with no serious goal
• Play with food and floating objects
• Dolphins play with rings of bubbles and
surf
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Breaching
• Leaping up in the air and loudly crashing
on the water
• Warning signal
• Scanning the surface
• Getting rid of parasites
• fun
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Humpback whale
Megaptera novaeangliae
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More examples of complex
behavior
• Members of a pod may come to assist a
member who is in trouble
• Pod members refuse to leave an injured or
dying pod member
• Dolphins help member surface to breath
• Work together to herd fish and hunt
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Migrations
• Pinnipeds and cetaceans make seasonal
migrations
• Travel thousands of miles from feeding
(Arctic) grounds to breeding grounds
(warm water)
• Most tooth whales do not migrate
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Reproduction
• Reproductive system is similar to that of
land mammals
• Some unique adaptations to life in the
water
• Males have an internal penis and testes to
keep the body streamlined
• Penis is kept rigid by a bone – can be 10 ft
long in blue whales
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• Pinnipeds breed on land or ice
• Seals - Each adult male breeds with one
female
• Sea lions, fur seals and elephant seals –
male breeds with many females –
establishes a territory by constant violent
fighting – could have 50 females
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• Strongest males hold harems
• Bachelor groups contain the other males
who spend their time trying to sneak into
harems
• Subordinate males live longer
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Sea lions
Elephant seals
• Seal pups are born on land
• Moms must go to sea to get food
• Need to find pup when return by smell and
sound
• Nursed for 4 days to two years
• Two pairs of mammary glands that
produce fat rich milk ideal for rapid
development of the pups blubber
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Sea lions
Pregnancy
• A female can only become pregnant for a
brief period during ovulation (release of
eggs by ovaries)
• Females return to breeding grounds once
a year
• Gestation – length of time it takes for the
embryo to develop
• Gestation is less than a year
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• Delayed implantation – can take up to four
months for the embryo to attach to the
inner wall of the uterus
• Keep babies from being born too soon
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Cetacean Reproductive Behavior
• Intensely sexual animals
• Seem to use sex for procreation and
pleasure
• Reach sexual maturity at the ages of 5 to
10
• Sexual behavior appears to have a role in
the establishment and maintenance of
bonds among individuals
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• Sexes are usually separate in pods
• Males often perform elaborate courtship
displays to attract females
• Fights between rival males are common
but cooperation also occurs
• Groups matings
• Males help in copulation of grey whales
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• Gestation lasts 11 or 12 months in most
cetaceans
• Sperm whale – 16 months
• Development is relatively fast for their size
• Human – 9 months for a 7lb baby
• Blue whale – 11 months for a 3 ton calf
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• Born tail first
• Remain attached to placenta longer to
breath
• Calf immediately swims to surface
• Fat rich milk is responsible for their fast
growth
• Born without blubber so fat rich milk is
very important
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Humpback
whale and calf
Killer whale
and calf
• Milk is produced by two mammary glands
with nipples located on both sides of the
genital slit
• Milk is squirted into the calf's mouth which
allows it to drink under water
• Close bond between mother and calf
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Bowhead and calf
Right whale and calf
Dolphin and calf
Cetaceans
nursing
The End