Download - Order Cetacea Characteristics
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Order Cetacea Characteristics:
• All completely aquatic – many marine, some freshwater • Fusiform body = cigar-shaped • Lack sebaceous glands • (nearly) hairless • Thick insulation; blubber • Forelimbs = flippers; tail forms flukes • No clavicle; no external digits/claws • No mucous membrane = no sense of smell • No outer visible ears • No vocal chords – but still emit high-frequency sound (?)
o Air exhaled across air sacs in nasal passage, producing clicks?
o Melon (oil-filled frontal sac) may help direct clicks forward o Sound waves bounce off higher-density objects back to inner
ear • Modified skull
o Shifting external nares to top and back o Premaxillary & maxillary bones cover roof of skull
• Reduced differentiation of vertebrae; high neural spines; compressed cervical vertebrae
• “pinhole camera” type of eye o Good for depth of field, but not fine adjustment
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Suborder Odontoceti (Odontocetes = toothed whales, dolphins, porpoises)
• Many, homodont teeth • Well developed brains • Echolocation
• Toothed whales emit a variety of sounds ranging around 280,000 Hz • Baleen whales emit a variety of sounds ranging around 20,000 Hz (human
range, reach volume of 8 decibels, carry hundreds of km underwater
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Family Delphinidae (dolphins, orca whales)
• Cone-shaped teeth • Off shore/deeper waters • Curved or hooked dorsal fin
Family Phocoenidae (porpoises)
• Spade-shaped teeth • Near shore/shallower waters,
including estuaries • Triangular dorsal fin
Family Physeteridae (sperm whales)
• 1,100+ m deep for 1.5 to 2 hrs! • Mollusk & fish feeders
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Family Platanistidae (river dolphins)
• Amazon River, Ganges River
Suborder Mysticeti (Mysticetes = baleen whales) • Lack teeth • Baleen plates extending from palate (100-400 each side of
mouth); sieves
• No echolocation; but ultrasonic sounds (navigation,
communication) • Historically high mortality rates due to whaling
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Family Balaenidae (right whale, bowhead whale)
• Long, finely fringed baleen plate • Plankton feeders, skim surface or
swim through
Family Balaenopteridae (blue whale, finback whale, humpback
whale)
• Throat grooves elongate • Shorter, triangular, coarser comb
structure to plates • Krill & fish feeders
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humpback migration Family Eschrichtiidae (gray whale)
• Bottom feeder? (abrasions) • Scoop/filter food material from
bottom • Long migration (Siberia, Korea,
Alaska, down to Gulf of CA)
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Diving Adaptations of Mammals (namely deep divers) 1) Breathing
• Often exhale before dive (reduces buoyancy & risk of decompression sickness)
• Low lung capacity relative to non-diving mammals • Collapse of thorax results in collapse of alveoli; pushes air
into non-collapsible trachea (reduces decompression sickness – maintain pressure)
2) Circulation
• Bradycardia (drop in heart rate) • Vasoconstriction of peripheral blood vessels (maintain blood
flow to brain) • Increased blood volume relative to body size • Increased hemoglobin / oxygen carrying capacity • Increased myoglobin oxygen carrying capacity; more oxygen
in muscle 3) Metabolism related
• Muscles function under anaerobic conditions (20+ min) • Lactic acid tolerance
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Low Frequency Active (LFA) Sonar
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http://www.nrdc.org/wildlife/marine/sonar.asp