8/12/2019 Swimming and Diving 2 mamalia laut

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Precent of the air in the lungs in less thah a second. Exhalation often leave a clound of

condensed water ( up to 6 m high in blue whale ). Whales can be indentified by the particular

shape ang size of their exhalation. nhalation is e!ually rapid" and the full brething cycle can

be completed without brea#ing the swimming pace. $etaceans" especially the large whales"

use the oxygen in the air of the lungs more efficiently than land mammals. %he greater

number of capillaries in cetacean lungs allowns &' percent of the oxygen to be removed in abreath" compared to ' perecent in terrestial mammals.

ost cetaceansare negatively buoyant" and sin# when dead. %he details of buoyancy

control are not well #nown. n some way" the combined buoyancy of the blubber and the air

in the lungs provides neutral buoyancy ( *ig. +., ). Water contributesgreatly to the buoyancy

of cetaceans. -arge whales for example the blue whale cannot support their body mass with

out the aid of the high density water. ut of the water" the s#eleton and internal organs are

crushed under their own body weight.

$etaceans are able to stay under water at moderate depths for prolonged periods.

ost cetaceans stay in the top &' m ( ,6/ ft ) of the water column" where their food is

concentrated. 0eeper dives are fre!uent" however. Porpoises have been trained to retrieveob1ects at 22' m" and baleen whales can dive over 2&' m. %he sperm whales regularly

feeds down to depths ,'''m ( 2+' ft )" and has been recorded feeding to a maximum

depth of '' m. While diving" sperm wahles have become entangled in undersea cables

and have drowned. %hese unfortunate incidents have provided the best information on the

maximum dives of sperm whales.

%he lenght of dives varies. 3enerally" the baleen whales in the relatively shailow

dives remain submerged for &4,& min" but can stay down for up to &' min. %he sperm whale

can stay submerged for 5&4' min in its deep sea dives ( %ab +. ). ne of the problems

humans have in air assisted diving is that the pressrized air causes a buildup of nitrogen gas

in the blood. f a diver retruns to the surface too !uic#ly" whitout ade!uate decompression"the nitrogen dissilved in the blod froms bubbles that cause a condition #nown as the bends.

7ince cetaceans do not have any air in their lungs while diving" they do not suffer from the

bends. $etaceans have adaptations that seal off the blow hole while diving. n porpoises

( *ig +.5 )" there is a strong sphincter muscle that helps #eep the trachea closed.

%he physiology of cetaceans is also ad1usted to diving. %he blood has a higher

concentration of red blood cells than that of terrstrial mammals" and therefore can carry

more oxygen. When a cetacean dives" the heart rate slows and circulation to the muscle

mass of the body is decreased. *or example" some seals have a heart rate of ,''4,&'8min

on the surface. %his drops to around ,'8min while diving. While diving" blood is directed

primarily to the brain" and only a small amount goes to other vital organs. %he muscles"

however" are not whitout oxygen. $etaceans have up to nine times more myoglobin ( similarto hemoglobin ) in their muscle compared to land mammals. %his myoglobin provides

oxygen to muscle during diving. *inally" when the oxygen of the muscles is depleted"

cetaceans rely on anaerobic matabolism to provide a continual energy source. 9naerobic

metabolism is less efficient than aerobic ( see the special feature at the end of this chapter)"

and cetaceans have a higher tolerance for its by product" lactic acid" that do land mammals.

arine mammalsalso are more tolerant of high carbo dioxide concentrations. n land

mammals" elevtaed carbon dioxide concentrations automatically cause breathing cetaceans

do not have this reflex.