Marine Mammals Order Cetacea Order Cetacea Two suborders

Marine Mammals Order Cetacea

Order Cetacea • Two suborders – Mysticeti (Baleen Whales) – Odontoceti (Toothed Whales) • One extinct suborder – Archaeoceti (Ancient Whales) Archaeoceti www. seaworld. org/. . . /Killer. Whale/sciclasskw. html • Live, Breed, Rest, and carry out all of their life functions in the water

Cont. • Inhabit all of the world’s oceans – As well as, some freshwater lakes, rivers, brackish waters of estuaries and coastal marshes

Mysticeti • Most of the largest Cetaceans – i. e. Blue Whales (Balaenoptera musculus) which are the largest animal in history • Exceeding 100 feet and weigh as much as 160 tons – Smallest is the pygmy right whale (Caperea marginata) • Measure up to 23 feet – More examples: humpback whale (Megaptera novaeangliae), fin whale (Balaenoptera physalus), and southern right whale (Eubalaena australis) www. nefsc. noaa. gov/. . . /beached_blue_whalebb. jpg

Humpback Whale – Megaptera novaeangliae cas. bellarmine. edu/tietjen/Root. Web/Chiroptera. jpg Fin Whale - Balaenoptera physalus www. exzooberance. com/virtual%20 zoo/they%20 swi

Odontoceti • Largest and most diverse group – i. e. the sperm whale is the largest • Reaching about 60 feet – The largest living predator of warmblooded animals is the killer whale – More examples: Dolphins and porpoises Sperm Whale – Physeteridae animals. nationalgeographic. com/staticfiles/NG. . .

Bottle Nose Dolphin – Tursiops trucatus www. naturescornermagazine. com/Natures. Blog/ima. . . Harbor Porpoise - Phocoena phocoena animals. nationalgeographic. com/staticfiles/NG

Taxonomic History • Hippopotamids are closest living relatives – Followed by ruminants • i. e. cows – Followed by Artiodactyls www. redmills. ie/images/ruminants. jpg www. cbc. ca/gfx/photos/hippo_cp_5128012. jpg cas. bellarmine. edu/. . . /Root. Web/Artiodactyla. jpg

How do Cetaceans reduce drag for fast swimming? • Fusiform body – Tapered at both ends • Paddle-shaped front limbs • No external digits or claws • Tail flattened laterally and bearing horizontal • • • flukes at the tip Vestigial ear pinnae Hairless body Thick subcutaneous blubber layer filled with fat and oil

Cont. • Addition of compressed vertebrae • Shortening of the neck • Lack of sweat glands • Internal reproductive organs • Three chambered stomach • Telescoped skull bones • External nares on top of head – Odontoceti have one blow hole – Mysticeti have two blow holes upload. wikimedia. org/. . . /300 px-Cetacea. jpg

Coping with Cold Climates • Small cetaceans – Have high metabolic rates – Flippers and flukes have a countercurrent heat exchange system • Heat from arterial blood warms venous blood as it returns to the heart • Large cetaceans – Small surface to volume ration www. cresli. org/. . . /2003_WW/breacher_fluke. jpg • Lose little heat to the surrounding environment • Both are insulated by thick blubber layer

Physiological Adaptations for Deep Diving • Rapid exchange in lungs – Enhanced by double capillary layer in the intraalveolar septae – Humans use 4% of Oxygen inhaled, Cetacea use 12% – Twice the number of erythrocytes and myglobin molecules in their blood • Allows for efficient capture and transport of oxygen

Cont. • Alter blood distribution – Rate of flow slows down (Undergo bradycardia) • Heart rate slows by as much as 80 beats per minute – Eliminated at non-critical organs via shunts • i. e. digestive tract – Reserved for critical tissues • i. e. heart and brain • High tolerance to Carbon Dioxide and lactic acid build up in tissue

Physiological Problems with Deep Diving • Increased pressure with increased depth • At high pressure gases go into solution more quickly • Air breathing organisms have a problem with Nitrogen gas absorption into blood – Causes decompression sickness • i. e. Bends or Caisson’s Disease

Physiological Solutions to Deep Diving • Structural Adaptations – Lungs are small • The total amount you take in = the total amount you let out – Dead air spaces are large • i. e. trachea and nasal cavity – Trachea is large and supported by cartilaginous rings – Bronchioles are small but braced by muscles and cartilaginous rings down to alveoli – Ribs are free from sternum Sperm Whale – Physeteridae www. nwf. org/nationalwildlife/article. cfm

Cont. • Mechanism – Total exhalation before diving gimp-savvy. com. – Diving pressure forces collapse of lungs • Forces air into dead air spaces, including nasal passages – Dead air spaces devoid of vascular tissue – Nitrogen is six times more soluble in oils then in water • Blubber is highly vascular and serves as Nitrogen reservoir • Oil also present in nasal sinus and may absorb nitrogen there as well

Mating • Usually have one mating season per year • Gestation is about 10 to 17 months • Females give birth to a single calf every one to six years • Calves are born tail first and must swim from the moment of birth • Mysticetes nurse for about six months • Odontocetes nurse for over two years

Social behavior • Highly sociable within their respective species; often forming pods – Pods often collaborate in hunting, playing, traveling, and taking care of young – Usually remain in pods throughout their life – Pods are beneficial because hunting is easier in a group; also pods decrease predation

Communication • Flukes or Flippers – Slap the surface • Breaching – Leaping from the waters surface – Helps them to attain an elevation of several yards • Spy-hopping – Raise head out of water to investigate objects or potential prey

Cont. • Emit various sounds from their head’s – Sperm whales have simple clicks – Humpback whales have complex “songs” – These sounds and echolocation help them navigate, investigate their surroundings, and hunt

Echolocation in Mammals • Four orders of mammals use echolocation – Order Cetacea (Whales, Dolphins) – Order Soricomorphia (Shrews) – Order Carnivora (Pinnepeds) – Order Chiroptera (Bats)

northern short-tailed shrew- Blarina brevicauda clackhi. nclack. k 12. or. us/. . . /cute%20 sea%20 lion cas. bellarmine. edu/tietjen/Root. Web/Chiroptera. jpg

Echolocation in Cetacean • Important means of navigation • Very well developed in Odontocetes • Very Rapid – Size, shape, and distance of the object can be determined • Anatomy of nasal regions – Ducts and diverticula – Nasal plugs – Air cycled back and forth • • All are used to siphon air to create different sounds Hearing the return echo – Mandible • Small thin bone, that allows the animal to hear through the lower jaw in front

Food • Mysticetes – Filter feeders • Use their baleen to strain plankton and other tiny organisms • Odontocetes – Feed on fish, squid, and crustaceans • Larger species eat aquatic birds and mammals (which include other cetaceans)

Prey debilitation by Odontoceti • Spermaceti organ – “Shocks” prey so they can eat

Ecosystem Roles • Vital roles as consumers • Host a range of internal parasites – Cestodes in their intestines (Tetrabothrium and Diplogonoporus) – Plerocercoids in their blubber (Phyllobothrium and Monorygma) – Trematodes in their stomachs, livers, intestines, and sinuses (Bolbosoma) • Host a range of external parasites – Cookie-cutter sharks (Isistius brasiliensis)

Cont. • Cetaceans are mutualists with animals that feed • on ectoparasites Birds have a commensal relationships with cetaceans – Seagulls often follow schools of dolphins and consume small fish stirred up by the feeding cetaceans – Pilotfish (Naucrates ductor) sometimes accompany killer whales and eat scraps from their kills

Economical Importance for Humans • Disadvantage – Impact commercial fisheries due to competition for fish • Advantage – Hunted for meat, oil, and blubber in 19 th century • Oil is used for lighting and heating – Important for entertainment and tourist industries Killer Whale – Orcinus orca www. destination 360. com

Human Impact on Cetaceans: Negative • Commercial whaling in the 19 th th • and 20 th century decreased the populations of mysticeti Many small odontocetes threatened by commercial fishing operations – Become entangled in nets and drown, or killed by explosives – They are killed on purpose because fishermen see them as competition www. chinadaily. com. cn/world/2006 -10/18/xin_46 • Use of military sonar in the ocean • and increase in ocean noise threatens cetaceans All cetaceans face threats of pollution and global climate change www. wwf. org. ph/_content/bycatch. jpg

Human Impact on Cetaceans: Positive • Commercial whaling was banned in 1986 • Captive breeding programs help critically endangered odontocetes www. onevoice-ear. org/. . . /dolphins_jobs. jpg members. greenpeace. org/. . . /source/action_129. jpg

References • De Maddalena, Alessandro. June 2004. Giants of the Deep. World and 1, 19: 6 • Ellis, E. and A. Poor. 2006. “Cetacea” (on-line), Animal Diversity Web. September 30, 2007 http: //animaldiversity. ummz. umich. edu/site/accounts/information/Cetacea. html • Werth, Alexander J. June 2006. Mandibular and Dental Variation and the Evolution of Suction Feeding in Odontoceti. Journal of Mammalogy. 87: 3, 579 -588