Biology Sperm whale

1 biology

1.1 external appearance
1.2 skeleton
1.3 jaws , teeth
1.4 brain
1.5 biological systems
1.6 senses

1.6.1 spermaceti organ , melon
1.6.2 eyes , vision


1.7 sleeping
1.8 genetics

biology
external appearance

the sperm whale largest toothed whale, adult males measuring 20.5 metres (67 ft) long , weighing 57,000 kilograms (56 long tons; 63 short tons). contrast, second largest toothed whale (baird s beaked whale) measures 12.8 metres (42 ft) , weighs 15 short tons (14,000 kg). nantucket whaling museum has 5.5 metres (18 ft)-long jawbone. museum claims individual 24 metres (80 ft) long; whale sank essex (one of incidents behind moby-dick) claimed 26 metres (85 ft). similar size reported jawbone british natural history museum. 20m specimen reported soviet whaling fleet near kuril islands in 1950. there disagreement on claims of adult males approaching or exceeding 24 metres (80 ft) in length.

extensive whaling may have decreased size, males highly sought, after world war ii. today, males not exceed 18.3 metres (60 ft) in length or 51,000 kilograms (50 long tons; 56 short tons) in weight. view holds exploitation overwhaling had virtually no effect on size of bull sperm whales, , size may have increased in current times on basis of density dependent effects. old males taken @ solander islands recorded extremely large , unusually rich in blubbers.

it among sexually dimorphic of cetaceans. @ birth both sexes same size, mature males typically 30% 50% longer , 3 times massive females.

unusual among cetaceans, sperm whale s blowhole highly skewed left of head

the sperm whale s unique body unlikely confused other species. sperm whale s distinctive shape comes large, block-shaped head, can one-quarter one-third of animal s length. s-shaped blowhole located close front of head , shifted whale s left. gives rise distinctive bushy, forward-angled spray.

the sperm whale s flukes (tail lobes) triangular , thick. proportionally, larger of other cetacean, , flexible. whale lifts flukes high out of water begins feeding dive. has series of ridges on s caudal third instead of dorsal fin. largest ridge called hump whalers, , can mistaken dorsal fin because of shape , size.

in contrast smooth skin of large whales, skin wrinkly , has been likened prune whale-watching enthusiasts. albinos have been reported.

skeleton

the ribs bound spine flexible cartilage, allows ribcage collapse rather snap under high pressure. while sperm whales adapted diving, repeated dives great depths have long-term effects. bones show same pitting signals decompression sickness in humans. older skeletons showed extensive pitting, whereas calves showed no damage. damage may indicate sperm whales susceptible decompression sickness, , sudden surfacing lethal them.

like cetaceans, spine of sperm whale has reduced zygapophysial joints, of remnants modified , positioned higher on vertebral dorsal spinous process, hugging laterally, prevent extensive lateral bending , facilitate more dorso-ventral bending. these evolutionary modifications make spine more flexible weaker spines of terrestrial vertebrates.

as other toothed whales, skull of sperm whale asymmetrical aid echolocation. sound waves strike whale different directions not channeled in same way. within basin of cranium, openings of bony narial tubes (from nasal passages spring) skewed towards left side of skull.

jaws , teeth

the lower jaw long , narrow. teeth fit sockets along upper jaw.

the sperm whale s lower jaw narrow , underslung. sperm whale has 18 26 teeth on each side of lower jaw fit sockets in upper jaw. teeth cone-shaped , weigh 1 kilogram (2.2 lb) each. teeth functional, not appear necessary capturing or eating squid, well-fed animals have been found without teeth or deformed jaws. 1 hypothesis teeth used in aggression between males. mature males show scars seem caused teeth. rudimentary teeth present in upper jaw, these emerge mouth. analyzing teeth preferred method determining whale s age. age-rings in tree, teeth build distinct layers of cementum , dentine grow.

brain

the brain largest known of modern or extinct animal, weighing on average 7.8 kilograms (17 lb), more 5 times heavier human s, , has volume of 8,000 cm. although larger brains correlate higher intelligence, not factor. elephants , dolphins have larger brains humans. sperm whale has lower encephalization quotient many other whale , dolphin species, lower of non-human anthropoid apes, , lower humans .

the sperm whale s cerebrum largest in mammalia, both in absolute , relative terms. olfactory system reduced, suggesting sperm whale has poor sense of taste , smell. contrast, auditory system enlarged. pyramidal tract poorly developed, reflecting reduction of limbs.

biological systems

the sperm whale respiratory system has adapted cope drastic pressure changes when diving. flexible ribcage allows lung collapse, reducing nitrogen intake, , metabolism can decrease conserve oxygen. between dives, sperm whale surfaces breathe 8 minutes before diving again. odontoceti (toothed whales) breathe air @ surface through single, s-shaped blowhole, extremely skewed left. sperm whales spout (breathe) 3–5 times per minute @ rest, increasing 6–7 times per minute after dive. blow noisy, single stream rises 2 metres (6.6 ft) or more above surface , points forward , left @ 45° angle. on average, females , juveniles blow every 12.5 seconds before dives, while large males blow every 17.5 seconds before dives. sperm whale killed 160 km (100 mi) south of durban, south africa after 1-hour, 50-minute dive found 2 dogfish (scymnodon sp.), found @ sea floor, in belly.

the sperm whale has longest intestinal system in world, exceeding 300 m in larger specimens. similar ruminants sperm whale has four-chambered stomach. first secretes no gastric juices , has thick muscular walls crush food (since whales cannot chew) , resist claw , sucker attacks of swallowed squid. second chamber larger , digestion takes place. undigested squid beaks accumulate in second chamber – many 18,000 have been found in dissected specimens. squid beaks vomited whale, make hindgut. such beaks precipitate formation of ambergris.

the arterial system of sperm whale foetus.

in 1959, heart of 22 metric-ton (24 short-ton) male taken whalers measured 116 kilograms (256 lb), 0.5% of total mass. circulatory system has number of specific adaptations aquatic environment. diameter of aortic arch increases leaves heart. bulbous expansion acts windkessel, ensuring steady blood flow heart rate slows during diving. arteries leave aortic arch positioned symmetrically. there no costocervical artery. there no direct connection between internal carotid artery , vessels of brain. circulatory system has adapted dive @ great depths, as 2,250 metres (7,382 ft). myoglobin, stores oxygen in muscle tissue, more abundant in terrestrial animals. blood has high density of red blood cells, contain oxygen-carrying haemoglobin. oxygenated blood can directed towards brain , other essential organs when oxygen levels deplete. spermaceti organ may play role adjusting buoyancy (see below). arterial retia mirabilia extraordinarily well-developed. complex arterial retia mirabilia of sperm whale more extensive , larger of other cetacean.

senses
spermaceti organ , melon


anatomy of sperm whale s head. organs above jaw devoted sound generation.

atop whale s skull positioned large complex of organs filled liquid mixture of fats , waxes called spermaceti. purpose of complex generate powerful , focused clicking sounds, sperm whale uses echolocation , communication.

the spermaceti organ large barrel of spermaceti. surrounding wall, known case, extremely tough , fibrous. case can hold within 1,900 litres of spermaceti. proportionately larger in males. oil mixture of triglycerides , wax esters. proportion of wax esters in spermaceti organ increases age of whale: 38–51% in calves, 58–87% in adult females, , 71–94% in adult males. spermaceti @ core of organ has higher wax content outer areas. speed of sound in spermaceti 2,684 m/s (at 40 khz, 36 °c), making twice fast in oil in dolphin s melon.

below spermaceti organ lies junk consists of compartments of spermaceti separated cartilage. analogous melon found in other toothed whales. structure of junk redistributes physical stress across skull , may have evolved protect head during ramming.

running through head 2 air passages. left passage runs alongside spermaceti organ , goes directly blowhole, whilst right passage runs underneath spermaceti organ , passes air through pair of phonic lips , distal sac @ front of nose. distal sac connected blowhole , terminus of left passage. when whale submerged, can close blowhole, , air passes through phonic lips can circulate lungs. sperm whale, unlike other odontocetes, has 1 pair of phonic lips, whereas other toothed whales have two, , located @ front of nose instead of behind melon.

at posterior end of spermaceti complex frontal sac, covers concave surface of cranium. posterior wall of frontal sac covered fluid–filled knobs, 4–13 mm in diameter , separated narrow grooves. anterior wall smooth. knobbly surface reflects sound waves come through spermaceti organ phonic lips. grooves between knobs trap film of air consistent whatever orientation or depth of whale, making excellent sound mirror.

the spermaceti organs may adjust whale s buoyancy. hypothesized before whale dives, cold water enters organ, , blood vessels constrict, reducing blood flow, and, hence, temperature. wax therefore solidifies , reduces in volume. increase in specific density generates down force of 392 newtons (88 lbf) , allows whale dive less effort. during hunt, oxygen consumption, blood vessel dilation, produces heat , melts spermaceti, increasing buoyancy , enabling easy surfacing. however, more recent work has found many problems theory including lack of anatomical structures actual heat exchange.

herman melville s fictional story moby dick suggests case containing spermaceti serves battering ram use in fights between males. few famous instances include well-documented sinking of ships essex , ann alexander attackers estimated weigh one-fifth as ships.

eyes , vision


like other toothed whales, sperm whale can retract eyes.

the sperm whale s eye not differ of other toothed whales except in size. largest among toothed whales, weighing 170 g. overall ellipsoid in shape, compressed along visual axis, measuring 7×7×3 cm. cornea elliptical , lens spherical. sclera hard , thick, 1 cm anteriorly , 3 cm posteriorly. there no ciliary muscles. choroid thick , contains fibrous tapetum lucidum. other toothed whales, sperm whale can retract , protrude eyes 2-cm-thick retractor muscle attached around eye @ equator.

according fristrup , harbison (2002), sperm whales eyes afford vision , sensitivity light. conjectured sperm whales use vision hunt squid, either detecting silhouettes below or detecting bioluminescence. if sperm whales detect silhouettes, fristrup , harbison suggested hunt upside down, allowing them use forward parts of ventral visual fields binocular vision.

sleeping

for time researchers have been aware pods of sperm whales may sleep short periods, assuming vertical position heads below or @ surface. 2008 study published in current biology recorded evidence whales may sleep both sides of brain. appears whales may fall deep sleep 7 percent of time, between 6 p.m. , midnight.

genetics

sperm whales have 21 pairs of chromosomes (2n=42). genome of live whales can examined recovering shed skin.