return to the ocean 2

Question 1

marine mammals

Answer 1

Order Sirenia
* Includes manatees & sea cows
* 4 sp.
Order Carnivora
* Includes seals, sea lions & walruses
* Pinnipedia (3 families) 33 sp.
* Marine otters 2 sp.
* Polar bear 1 sp.
Superorder Certartiodactyla
* Includes whales, dolphins & porpoises
* Cetacea (Order) 90 sp.
Extinct groups
* Desmostylia (related to elephants), Kolponomos (marine bear- like carnivoran), Thalassocnus natans (aquatic sloth)

Question 2

Order Sirenia

Answer 2

• arose in the Eocene (50 mya) in the sea of Tethys
• evolved from the proboscideans (elephants)

Question 3

Sirenian features

Answer 3

• Herbivores
• Very low metabolic rate
• Tropical / warm shallow water
• Heavy bones
• Flipper like forelimbs
• Reduced hindlimbs
• Blubber and sparse hair
• Fleshy, almost prehensile lips
• 2 families:
  * Trichechidae (manatees)
  * 3 sp.
  * New World
  * Dugongidae (dugongs)
  * 1 sp. (+ Steller’s Sea Cow)
  * Indo-Pacific

Question 4

Pinnipedia (order carnivora)

Answer 4

From late Oligocene (27 – 25 MYA)
* 3 monophyletic families:
* Otariidae (eared / fur seals & sealions, 14 sp.)
* Phocidae (true or earless seals, 18 sp.)
* Odobenidae (walruses, 1 sp.)
* Semi aquatic
* Carnivores
* Fur/ hair and blubber
* Very sensitive whiskers (vibrissae)
* Mobile neck
* Swim side to side like fish (lateral undulations)

Question 5

family Otariidae

Answer 5

Ability to rotate pelvis (walking)
* Small external ear flaps (pinnae)
* Dense fur for insulation
* Long coarse guard hairs
* Thick under-fur to trap air
* Large fore flippers for propulsion
* Sexual dimorphism

Question 6

family Phocidae

Answer 6

• Unable to rotate pelvis: move by undulating body
• No external ear flaps
• Blubber: insulation
• Pelvic flippers: propulsion
• Pectoral flippers: stability & steering
• Excellent divers

Question 7

family Odobenidae

Answer 7

Previously diverse, two subspecies today
* Ability to rotate pelvis (O)
* No external ears (P)
* Blubber for insulation (virtually hairless) (P)
* Pelvic / pectoral flippers for propulsion (O & P)
* Large canine tusks (Neither)

Question 8

Enaliarctos - earliest known pinnipeds

Answer 8

• Mid-Oligocene – late Miocene (~30
  MYA) from California and Oregon
• Aquatic features
  
  • Distinct, highly modified flippers
  • Streamlined
  • Reduced tail
• Still retained many terrestrial features
  
  • Inner ears adapted for hearing in air
  • Heterodont dentition: must bring prey to shore to handle + chew it
• A coastal species
• Similar to sea otter
• Ancestral to all pinnipeds?
• Only in Pacific

Question 9

Puijila darwini: Rybczynski et al. (2009)

Answer 9

Late Oligocene  early Miocene, Canadian lakes
Similar to land dwelling arctoids
* No flippers
* Long tail
* Proportionally long limbs like a skunk or marten

A swimmer
* Its all in the muscle attachment sites
* Long shoulder blades (extend down back)
* Big shoulder muscles
* Large muscle (teres) that allows rotation of shoulder
* Robust forelimbs
* Enlarged webbed (?) feet (flattened finger ends)

Not an otter
* Hands & feet proportions are wrong: big hands unlike otters
* Long first finger, long phalanges
* Shorter, slimmer tail not used in swimming
* Uses all four limbs to swim (otters use only back and tail)

Question 10

order Cetacea (Superorder Cetartiodactyla)

Answer 10

• Arose in Eocene (53- 54MYA) in Sea of Tethys
• Entire life in water
• Blubber
• Almost hairless
• Shortened neck: fused vertebrae
• No hind limbs
• Powerful tail, horizontal flukes
• Paddle-like forelimbs
• Blow holes
• Specialised ear bones
• Specialised semicircular canals
• 2 major groups: Mysticetes and Odontocetes

Question 11

Cetacea origins

Answer 11

Artiodactyls (even toed ungulates):
* Deer
* Antelope
* Camels
* Pigs
* Giraffes
* Hippos

Question 12

Mysticetes

Answer 12

• Baleen plates
• Eat small fish or krill
• Mouth is flexible and capacious
• Lack teeth
• 2 blowholes
• Small eyes point sideways
• Major families:
  
  • Family Balaenopteridae: fin, humpback
  • Family Balaenidae: right, bowhead
  • Family Neobalaenidae: pigmy right
  • Family Eschrichtiidae: gray

Question 13

Odontocetes

Answer 13

• “Toothed whales”
• Peg like, uniform teeth
• Melon on skull
• High frequency sound:
  
  • Echolocation
  • Communication
• Fast: eat fish and mammals
• Fused nostrils  one blowhole

Question 14

mammalian lungs

Answer 14

• Back to tidal lungs again
  
  • Dead space = 1/3 – 1/20th tidal vol
• 5% body volume
• Finely divided -> V. high SA
• Surfactants prevent bubbles
• Negative pressure ventilation

Question 15

diving : marine mammal adaptations

Answer 15

• Record dive: 137.5 min, 2992m (Cuviers Beaked Whale)
• Challenges: O2 decrease, lactate build-up, pressure change, changes in gas chemistry
• Heart:
  
  • Similar size & structure to terrestrial
  • Glycogen stores
  • Aortic bulb
• Retia mirabilia
• Myoglobin-rich muscles
• Increased haematocrit
• Blowhole muscles
• Respiratory system:
  
  • Collapsible chest
  • Reduced lobulation
  • Supported trachaea
• Blood buffering
  
  • Diving response:
  • Decline in heart rate
  • Regional vasoconstriction
  • Reduction in core temperature
  • Regional reduction in metabolic rate

Question 16

senses : marine mammal adaptations

Answer 16

• Sound travels quickly underwater, light readily attenuated
• Sound used for communication & echolocation
• Low freq: long distance
• High freq: fine resolution
• Sound production
  
  • Larynx (pinnipeds)
  • Inflatable throat pouches (pinnipeds)
  • Phonic lips + melon (cetaceans)
• Sound reception
  
  • Auditory canal (pinnipeds)
  • Lower jaw and throat (cetaceans)

Question 17

salt management : marine mammal adaptations

Answer 17

• Have lungs, but not immune to problems of high salt:
  
  • May ingest water accidentally
  • Diet is salty (esp. invertebrates and plants)
• Internal fluids are hypoosmotic to seawater
• Derive water from food- preformed and metabolic
• Large, reniculate kidneys- excrete concentrated urine