B9 vertebrates marine mammals

Question 1

Order Sirenia (4 species)

Answer 1

Includes manatees and sea cows. Arose in the Eocene (50mya) in sea of Tethys (was around where the med is now). Evolved from the proboscideans (elephants). Features: herbivores (only marine mammal group that eats plants), very low metabolic rate, tropical/warm shallow water, heavy bones, flipper like forelimbs, reduced hindlimbs, blubber and sparse hair, fleshy lips. Often live in cloudy water, so don’t see very well.
Families (2): Trichechidae (manatees) 3 species) new world. Dugongidae (dugongs) 1 species, Steller’s sea-cow, hunted to extinction) Indo-pacific.

Question 2

Order Carnivora (36 species)

Answer 2

Seals, sea lions, walruses. Pinnipedian (3 families) 33 species). Marine otters (2 species). Polar bear (1 species).

Question 3

Pinnipedia

Answer 3

From late Oligocene (27-25mya, semi-aquatic, carnivorous, fur/hair and blubber, very sensitive whiskers (vibrissae), mobile neck (unlike dolphins), swim side to side (like fish, lateral undulations).

Family (3): Otariidae (eared/fur seals + sealions) 14 species). Phocidae (true/earless seals) 18 species). Odobenidae (walruses) 1 species). These are though to be monophyletic families, could be generic arctoid mammals.

Question 4

Family Otariidae

Answer 4

Ability to rotate pelvis (walking on hind flippers), 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. Includes fur seals and sea lions.

Question 5

Family Phocidae

Answer 5

Unable to rotate pelvis (move by undulating body), no external ear flabs, blubber (insulation), pelvic flippers (propulsion), pectoral flippers (stability + steering), excellent divers.

Question 6

Family Odobenidae
(two subspecies today)

Answer 6

Ability to rotate pelvis, no external ears, blubber for insulation/virtually hairless, pelvic/pectoral flippers for propulsion, large canine tusks.

Question 7

Superorder Certartiodactyla

Answer 7

Includes whales, dolphins, porpoises

Question 8

Order Cetacea (90 species)

Answer 8

Fully transformed back to ocean. Arose in Eocene (53-54mya) in sea of Tethys. Entire life, almost no hair (blubber). Shortened neck with fused vertebrae, no hind limbs, powerful tail (horizontal flukes), paddle-like forelimbs. Blow holes, specialised ear bones and semicircular canals. Origins = Artiodactyls (even toed ungulates) Deer, antelope, camels, pigs, giraffes, hippos).

Major groups (2): Mysticetes, Odontocetes

Question 9

Group Mysticetes

Answer 9

Feeding: mouth flexible/capacious, lack teeth (have baleen plates), eat small fish/krill. 2 blowholes, small eyes point sideways.

Major families (4): Balaenopteridae (fin/humpback), Balaenidae (right/bowhead), Neobalaenidae (pigmy right), Eschrichtiidae (gray).

Question 10

Group Odontocetes

Answer 10

‘Toothed whales’ = peg-like, uniform teeth, eat fish/mammals. High frequency sound (echolocation, communication, melon on skull). Fused nostrils = one blowhole.

Question 11

Extinct groups

Answer 11

Desmostylia (related to elephants), Kolponomos (marine bear-like carnivoran), Thalassocnus natans (aquatic sloth).

Question 12

Enaliarctos

Answer 12

Earliest known pinnipeds. Mid-Oligocene- late Miocene (30mya) from California and Oregon. Aquatic features: distinct, highly modified flippers, streamlined, reduced tail. Still retained terrestrial features: inner ears adapted to air hearing, heterodont definition (need to bring prey to shore to chew it). Coastal species, similar to sea otter, only in pacific.

Question 13

Puijila darwini: Rybczynski et al. (2009)

Answer 13

Late Oligocene = early Miocene, Canadian lakes, similar to land dwelling arctoids (no flippers, long tail, proportionally long limbs like skunk/marten)
A swimmer: all in muscle attachment sites, long shoulder blades down to back, big shoulder muscles, large muscle (teres) that allows shoulder rotation, robust forelimbs, enlarged webbed feet and flattened finger ends.
Not an otter: hand and foot proportions are unlike otters, long first finger and long phalanges, shorter and slimmer tail not used in swimming, uses all four limbs to swim (otters only use back and tail)

Question 14

Mammalian lungs

Answer 14

Back to tidal lungs again (1/3 – 1/20th tidal vol, 5% body vol), finely divided  very high surface area, surfactants prevent bubbles, negative pressure ventilation.

Question 15

Bird lungs

Answer 15

Completely divided, no cutaneous respiration (how does right side get O2)

Question 16

Diving

Answer 16

Record = 137.5 minutes, 2992m. Challenges: O2 decrease, lactate build-up, pressure change, changes in gas chemistry.
-Retia mirabilia, myoglobin-rich muscles, increased haematocrit, blowhole muscles, blood buffering.
-Heart (similar size + structure to terrestrial, glycogen stores, aortic bulbs)
-Respiratory systems (collapsible chest, reduced lobulation, supported trachea)
-Diving response (decline in heart rate, regional vasoconstriction, reduction in core temp, regional reduction in metabolic rate).

Question 17

Marine mammal adaptations (senses)

Answer 17

Sound travels quickly underwater, communication/echolocation. Low frequency (long distance), high frequency (fine resolution). Sound production (larynx, inflatable throat pouches, phonic lips/melon. Sound reception (auditory canal, lower jaw and throat).

Question 18

Marine mammal adaptations (self-management)

Answer 18

Have lungs, but have some problems with salt. Internal fluids are hypo-osmotic to seawater. Derive water from food (preformed and metabolic). Large, reniculate kidneys (excrete concentrated urine).