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Figure 34.14 The origin of tetrapods
Phylum Chordata
Now we move to reptiles
(Class Reptilia) and birds
(Class Aves), then on to
marine mammals
(Mammalia). These are all
re-entry animals – they reentered the marine
environment to exploit
niches there. With birds
we see the advent of true
endothermy.
Nekton
• Free swimmers
Nekton adaptations
• Tend to be large
• The birds, reptiles and mammals breathe air, and are
all re-entry animals
• They have various adaptations for thermoregulation,
breeding, osmoregulation, and movement that evolved
in response to their re-entry into an aquatic
environment
• MANY are K selected, which makes them susceptible
to exploitation, invasive species etc. • r vrs. K selection reproductive strategies
• Breeding on land
• Migrations
• Staying warm (endotherms)
• Osmoregulation (salt and water balance)
• Genetic bottlenecks – what’s this?
Adaptations of marine
mammals
• Hair!
• Internal mammary glands
• Heat retention (blubber/fur) –
endotherms
• Respiratory rates-decreased
• High blood volume
• Fusiform bodies
• K-selected
• Good vision (generally)
• The role of acoustics
• Counter current heat exchange
• Tend to get large (why?) • Some have delayed implantation
(embryo)
Counter current heat exchangers revisited
• Blood in the arteries runs deep (not near the
surface)
• As it passes by cooler veins, it
gives up some of its heat, warming
up the veins. • In this way, heat can be ‘trapped’
within areas where it is needed
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Order Sirenia: Manatees and
dugongs
Dugongs: Dugong dugon
4 species: 3 Manatees and 1 dugong
There used to be the Steller’s Sea Cow – extinct now
?
Natural history of
Dugongs
Live over 70 years, K-selected
Sexually mature between 10 and 18 years!
13-15 month gestation
Nurse for another 14 months
Leave mom when mature!
Sirenia
Manatees Trichechus
IUCN redlisted (close to extinction)
Southeast Asia, Africa, Australia
Monophyletic (closely related to)
elephants
First appeared about 56 million years ago
Eat seagrass
Natural history of
Manatees
Live over 60 years, K-selected
Sexually mature between 10 and 18 years!
12-13 month gestation
Nurse for another 18 months
IUCN redlisted (close to extinction)
Amazon, West Africa, West Indian
45 meter long intestines!
Monophyletic (closely related to)
elephants
First appeared about 56 million years ago
Eat seagrass and mangroves and over 60
species of plants
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Boat strikes
Cetaceans (order Cetacea):
whales and dolphins
Evolution
Feeding and reproduction
Conservation status
Natural history
Physiology
3 families of Mysticetes
Other threats: red tides, habitat degradation, hunting, pollution
Archaeoceti
6 families of Odontocetes
Most Archaeocetes had hind limbs – terrestrial life
They evolved from From Artiodactlyls – even toed ungulates: pigs
hippos, camels. Most likely ancestor were hippo-like (about
65mya)
Its thought that Archaeocetes re-entered the water about 55 MYA
Basilosaurs emerged from the Archaeocetes, about 34mya. They
were truly aquatic
Basilosaurus
Two suborders of Cetaceans
Cetaceans
Mysticetes: baleen whales
3 families: Balaenidae, Balaenopteridae, Eschrichtiidae
Odontocetes: toothed whales
6 families: Physeteridae, Monodontidae, Delphinidae,
Ziphiidae, Platanistidae, Phocoenidae
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Mysticeti: bearded
Baleen
• Baleen
• 2 blowholes
• Largest of the whales: 100 ft, 160 tons!
Humpback
baleen
Gray whale baleen
http://www.youtube.com/watch?v=fOMzFFh3rEA
Straining/Skimming
Feeding
• Gulp feeding
• Bubble nets: Humpbacks
http://www.youtube.com/watch?v=vJvfjiCTvq4
Balaenidae:right whales
• No ventral grooves
• No dorsal fin
• Polar waters
• Moderate migrations
• Heavily exploited
Blue Whale: Krill
http://www.youtube.com/watch?
v=k2lAf5j4ou0
Bowhead
Right whales
Pygmy right whale
Bowhead: copepods (fine baleen)
http://www.youtube.com/watch?v=r8DuJy27OjI
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Northern Right Whales
Eubalaena glacialis
300-400 left
Major cause of mortality: ship strikes
Balaenopteridae
• Numerous ventral grooves
• Fast swimmers
• Small dorsal fin, far back on the back
• Extensive migrations
Balaenopteridae: rorquals
Balaenopteridae
Balaenopteridae: Humpbacks
Blue whales
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Eschrichtiidae: gray whales
Gray whales: Eschrichtius robustus
• Few ventral grooves
• Dorsal knuckles
• Bottom feeders
• extensive migrations
The only whales to feed on the
bottom (on benthic amphipods)
Mysticetes
Remember those blow holes?
Are LARGE
Are endangered
Are K-selected
Undertake long migrations (most)
Feed with baleen in a variety of ways
Are not particularly social…
We looked at three families
Odontoceti
• Teeth
• Smaller (ex. sperm whale)
• Highly social
• Sophisticated sonar
• deep divers
• One blowhole
• Predators
• short or no migrations
• temperate/tropical
Odontocetes: the human factor
6 families of toothed whales
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The human factor
http://www.youtube.com/watch?v=TMCf7SNUb-Q
The other side of
the story
http://www.youtube.com/user/
XcaretPark?v=4-CUA7dQKdg
Private lives of Dolphins…
http://www.youtube.com/watch?v=T7AlinxwVAg
Delphinidae (dolphins)
in particular have
complex social systems
and tight knit alliances
They have very large
brains
Its about those
giant squid… Physeteridae: sperm whales
• Deep divers
• Large spermaceti organ in head
• Matriarchial (female) societies
• Largest of the odontocetes
• Temperate waters
http://www.youtube.com/watch?
v=_NpZLhqly8s
Can dive up to 7,000
feet, and stay for
more than an hour
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Odontocete whales
Monodontidae: Narwhals and white
whales (beluga)
• Flexible head
• Cold arctic waters
Monodon monoceros – the narwhal
Lives in the arctic ocean
Lack of dentition other than the tusk – only
found in males!
Like the beaked whales – probably ‘suck’ up
their prey. Eat cod and other fish and squid*
Still hunted by Native Americans/Alaskan/Canadian tribes
What about that tusk anyway…
Delphinapterous Leucas – Beluga whale
Delphinapterous Leucas – Beluga whale
Lives in the Arctic
7 neck vertebrae are not fused –flexible neck!
Still hunted
Opportunistic feeders: fish, invertebrates, squid
Extremely high levels of contaminants in their fat
PCBs, and pesticides like DDT, HCB, HCH, chlordane and toxaphene
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Ziphiidae:
beaked whales
• Least known group
• Very deep divers
• In some only the
males have teeth
• Some known only
from strandings
Erupted teeth are a secondary
sexual charcteristic (males)
Northern Bottlenose whale Hyperoodon ampullatus
Beaked whales
Can dive to over 6,000 feet
Can stay down for over 80
minutes
Only 3 or 4 species of 21 are
reasonably well known
Most have only one pair of
teeth
Females usually have none
Teeth may be the key to female
attention…
Sexual maturity is at about 15
years
Age? 56yrs? 84 yrs?
Dolphins and porpoises
Dolphins:
• conical teeth
• falcate dorsal fin
• usually have a more prominent beak Delphinidae: dolphins
Porpoises:
• Spade shaped teeth
• triangular dorsal fin
• blunt head
• less social
Risso s dolphin
• Highly social
• Sophisticated sonar
• Includes killer whales and dolphins
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Oceanic Dolphins
Phocoenidae: Porpoises
• Less social than delphinidae
• travel in smaller groups
• tend to be small in size
Delphinidae
Porpoises
Phocoena phocoena
Harbor porpoise
Platanistidae: river dolphins
River dolphins
4 living species in fresh water
• Highly endangered
• poor eyesight
• long rostrum (beak)
• good sonar
• small groups
Baiji – Chinese river
dolphin – extinct 2006
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Other marine mammals
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