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10/18/12
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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 re-entered the marine environment to exploit niches there. With birds we see the advent of true endothermy.
Nekton • Free swimmers
• 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.
• Genetic bottlenecks – what’s this?
Nekton adaptations
• r vrs. K selection reproductive strategies
• Breeding on land
• Migrations
• Staying warm (endotherms)
• Osmoregulation (salt and water balance)
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
4 species: 3 Manatees and 1 dugong
There used to be the Steller’s Sea Cow – extinct now
?
Dugongs: Dugong dugon
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!
IUCN redlisted (close to extinction) Southeast Asia, Africa, Australia
Monophyletic (closely related to) elephants First appeared about 56 million years ago Eat seagrass
Sirenia Manatees Trichechus
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
Other threats: red tides, habitat degradation, hunting, pollution
Cetaceans (order Cetacea): whales and dolphins
Evolution Feeding and reproduction Conservation status Natural history Physiology 3 families of Mysticetes 6 families of Odontocetes
Archaeoceti 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 Mysticetes: baleen whales 3 families: Balaenidae, Balaenopteridae, Eschrichtiidae
Odontocetes: toothed whales 6 families: Physeteridae, Monodontidae, Delphinidae, Ziphiidae, Platanistidae, Phocoenidae
Cetaceans
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Mysticeti: bearded
• Baleen • 2 blowholes • Largest of the whales: 100 ft, 160 tons!
Baleen
Humpback baleen
Gray whale baleen
Feeding • Gulp feeding • Bubble nets: Humpbacks
http://www.youtube.com/watch?v=vJvfjiCTvq4
Straining/Skimming
Blue Whale: Krill
Bowhead: copepods (fine baleen) http://www.youtube.com/watch?v=r8DuJy27OjI
http://www.youtube.com/watch?v=fOMzFFh3rEA
http://www.youtube.com/watch?v=k2lAf5j4ou0
Balaenidae:right whales
• No ventral grooves • No dorsal fin • Polar waters • Moderate migrations • Heavily exploited
Bowhead Right whales Pygmy right whale
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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
Balaenopteridae: rorquals
Blue whales
Balaenopteridae: Humpbacks
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Eschrichtiidae: gray whales • Few ventral grooves • Dorsal knuckles • Bottom feeders • extensive migrations
Gray whales: �Eschrichtius robustus
The only whales to feed on the bottom (on benthic amphipods)
Mysticetes 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
Remember those blow holes?
Odontoceti • Teeth • Smaller (ex. sperm whale) • Highly social • Sophisticated sonar • deep divers • One blowhole • Predators • short or no migrations • temperate/tropical
6 families of toothed whales
Odontocetes: the human factor
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http://www.youtube.com/watch?v=TMCf7SNUb-Q
The human factor
http://www.youtube.com/user/XcaretPark?v=4-CUA7dQKdg
The other side of the story
Delphinidae (dolphins) in particular have complex social systems and tight knit alliances
They have very large brains
Private lives of Dolphins…
http://www.youtube.com/watch?v=T7AlinxwVAg
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
Its about those giant squid…
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Odontocete whales Monodontidae: Narwhals and white whales (beluga)
• Flexible head • Cold arctic waters
Monodon monoceros – the narwhal
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*
What about that tusk anyway…
Lives in the arctic ocean
Still hunted by Native Americans/Alaskan/Canadian tribes
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’
Porpoises: • Spade shaped teeth • triangular dorsal fin • blunt head • less social
Risso’s dolphin
Delphinidae: dolphins
• Highly social • Sophisticated sonar • Includes killer whales and dolphins
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Oceanic Dolphins Delphinidae
Phocoenidae: Porpoises • Less social than delphinidae • travel in smaller groups • tend to be small in size
Phocoena phocoena Harbor porpoise
Porpoises
Platanistidae: river dolphins
• Highly endangered • poor eyesight • long rostrum (beak) • good sonar • small groups
River dolphins 4 living species in fresh water
Baiji – Chinese river dolphin – extinct 2006
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Other marine mammals
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