Cetacea [Compatibility Mode]

Cetacea [Compatibility Mode] - 4/26/2010 Three suborders...

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Unformatted text preview: 4/26/2010 Three suborders Order Cetacea Archaeoceti (extinct) Mysticeti (baleen) Odontoceti (toothed) (toothed) The living Cetaceans are a group of large-sized, exclusively aquatic mammals. They occur in all oceans and in some of the larger rivers. The limbs are modified for aquatic life Modifications to the skeleton include: 1. reduced neck - the cervical vertebrae are extremely flattened and/or fused (7 cervicals). 2. articular surfaces of the vertebrae are reduced - flexibility 3. The pelvic girdle is reduced and not in contact with the vertebral column. 4. Externally the elements of the fore limbs are not distinguishable. 1. The hind limbs are absent and the fore limbs are modified into flippers. 2. The radius, ulna, and digital bones are greatly flattened the digits are webbed and greatly flattened, the digits are webbed, and nails are lacking. Killer whale neck bones Innominate (‘no name’) bone: ilium, ischium or pubis? 1 4/26/2010 External features showing adaptation to aquatic life include: Fusiform shape with no constriction at head Tail is laterally flattened down to flukes Ears lack a pinna, and external opening is a tiny pin hole Skin is thick, smooth, and hairless (nearly) A thick layer of blubber under the skin External nares is near vertex of the head Main propulsive organ, the flukes, contain only soft connective tissue, no bone Telescoping In contrast to the Archaeoceti, the skulls of the modern suborders show a progressive phenomenon called telescoping – consists of the backward movement of the bony elements of the rostrum toward the vertex, or the highest point of the skull. The most marked movement is seen in the narial bones. The new location is apparently related to more efficient breathing. Dall porpoise skull, dorsal view Asymmetry and Basining Anatomical features of modern odontocetes Early Odontoceti showed no asymmetry of the dorsal skull bones (right side bigger) – they also lacked the basining of the facial region which in living forms is related to the melon or bulbous forehead structure which plays an important part in echolocation. Dall Dall porpoise skull, lateral view Suborder Mysticeti The baleen whales lack teeth as adults, but teeth buds are found in embryos. The upper jaw has plates of baleen which are cornified epithelial structures The Mysticete skull is epithelial structures. The Mysticete skull is symmetrical and the rostrum is arched to accommodate the baleen. External features include: – 1. blowhole which is divided in two by a longitudinal septum – 2. gular grooves in most forms 2 4/26/2010 Suborder Mysticeti There are three families: 1. Eschrichtiidae 1 genus 2. Balaenopteridae Balaenopteridae 2 genera genera 3. Balaenidae 3 genera Family Eschrichtiidae or Gray whale One species, limited to the North Pacific Recently extinct in the western Pacific Dark gray with some white mottling and the gray with some white mottling and the rostrum is usually covered with barnacles. It lacks a dorsal fin and the head is less than 1/4 the total length. There are 2-4 gular grooves about 6 ft. in length. The baleen color is yellowish and the longest blades are about 18 inches. Family Eschrichtiidae or Gray whale ... Family Balaenopteridae or Fin-back whales 7 species, 6 in genus Balaenoptera and a monotypic genus Megaptera. Species in genus Balaenoptera are also in genus Balaenoptera also known as Rorquals. This family has flat, broad rostrum. Baleen is relatively shorter and broader than gray whale’s, but it may reach 41" in large blue whales. The baleen is black or blue-black in color. The skull has a narrow rostrum and the premaxillae is somewhat arched giving a slightly convex profile to the head. This is the most primitive baleen whale and completely lacks any fusion of the cervical vertebrae. The manus is tetradactylus--the first digit having been lost. Family Balaenidae or Right whales Includes 3 monotypic [? 3 Eubalaena spp ] genera. Baleen is long and flexible and folds on the floor of the closed mouth the floor of the closed mouth. Skull is huge and extremely convex in profile. The head makes up between 1/4 and 1/3 of T.L. There are no gular grooves and there is no dorsal fin except in the pygmy right whale. ‘Right ‘Right whales’ Because these whales: – 1. were formerly abundant, – 2. were slow swimmers, – 3. had buoyant carcasses, and – 4. produced enormous yields of oil, – they were dubbed "right" whales by early hunters. The Rorquals were generally too fast and the sperm whale too belligerent for small boat whaling. 3 4/26/2010 Great whales Baleen from Rourqual, Right, and Gray whales Gray whale upper lip and exterior edge of baleen Gray whale Gray whale spy-hopping behavior spy- Gray whale, full-term fetus full- 4 4/26/2010 Gray whales in migration Males compete for access to females Gray calf killed by killer whales Gray whale hairs, barnacles and amphipods 5 4/26/2010 Gray whale population trajectory History of Rourqual Fisheries Shore-based whaling in Iceland Explosive harpoon and gun Useful products Right whales 6 4/26/2010 Biscayne Right Whale on Vancouver Island Station Right whale harvest in Pacific Suborder Odontoceti These are the toothed whales. All members of this suborder possess teeth as adults although they may be teeth as adults, although they may be reduced to a single pair or may not erupt. The skull is asymmetrical on the dorsal surface, especially in the region of the blowholes. Externally there is only a single blowhole. Odontocete Families Physerteridae, Sperm whale Kogiidae, Pigmy sperm whales, 2 spp Ziphiidae, Beaked whales, 19 spp Monodontidae, White and narwal, 2 spp Plantanistidae, river dolphins (4 spp in monotypic families?) Delphinidae, Ocean dolphins, ~33 spp Orcaelidae, Killer whale, 1 spp Grampidae, Grampus whale/Risso’s dolphin, 1 spp Globicephalidae, Pot-headed whales, various Phocoenidae, Harbor porpoises, 6 spp Odontocete families The number of families in this suborder varies with the authority (see pgs 238-473). You have been given is the splitter's version-that is opposed to the lumper's version. Lumpers are prone to include the last five families on your list in the Delphinidae--that is the Delphinidae, Orcaelidae, Phocoenidae, Grampidae, and Globicephalidae are included in the Delphinidae, but the Phocoenidae is usually given at least subfamilial status. Pygmy sperm whale skull: Kogiidae 7 4/26/2010 Cuvier’s beaked whale: Ziphiidae Beluga (white) whale: Monodontidae Narwhale tusk: Monodontidae Amazon dolphin: Platanistidae Family Delphinidae The five remaining families of odontocetes are frequently lumped together in the Delphinidae Phocoenidae includes 6 species known as porpoises--lack beaks, GK name for pig GK 2 families monotypic: Orcaelidae & Grampidae Delphinidae popularly known as dolphins-jaws extend beyond the contour of the head, forming a beak Globicephalidae lack beak but have melon Killer whales 8 4/26/2010 Killer whale and shark bites on juvenile Gray Whale flipper Dall porpoise riding bow: Phocoenidae Dall porpoise flukes with algae Harbor porpoise fetus with hairs on snout Female harbor porpoise fetus with umbilical cord Dolphin giving birth: flukes first 9 4/26/2010 Pacific right whale dolphin: Delphinidae ShortShort-finned Pilot Whale : Globicephalidae Sperm whale: Physeteridae Largest of the toothed whales In the past, males reached a length of 20 (65 ft) but today males greater 20 m (65 ft), but today males greater than 18 m (60 ft) are rare Female maximum length is 12 m (40 ft) Calves at birth are 4 m (13 ft) Maximum age attained is 50+ years Historic shore whaling picture Sperm whale blowing & sounding Sperm whale schooling and Socialization Schooling is common and of 3 types: – 1. females and young – 2. young males – 3. mixed ages and sexes Older adult males are often solitary and tend to migrate to higher latitudes than do females and younger animals Communicate and form defensive rosettes when under attack by killer whales 10 4/26/2010 Hunted by man and killer whales The head contains the spermaceti organ They were hunted for: Deep diving Sperm whales are known for their ability to make prolonged deep dives. Dives of large adult males may be greater than 1 hr. Females and young dive for 15-20 min Off South Africa (Durban, S.A.) – – – – spermaceti oil low grade blubber oil flesh for animal feed human food and pharmaceuticals They were once prized for high-grade machine oils and for ambergris, but these products are now replaced by synthetics 2 adult males, over water 3,193 m (10,476 ft) deep. Dives lasted 82 & 83 minutes. Later when captured their stomachs contained bottom dwelling sharks. Sperm whale skeleton, Hilo, Hi Sperm whale tooth (ageing) Unique echolocation mechanism in sperm whales Why do sperm whales not have the same mechanism as other odontocetes? At 2500 m, well within the maximum recorded depth, available air for echolocation is 1/250 of the surface volume Advantages to sperm whale in using burst pulse: AmphitheaterAmphitheater-like structure of dorsal skull Contains – Spermaceti organ – ‘Junk’ – Air sacs – Nasal passages – Monkey’s muzzle Single click reflected many times – 1. Need to produce only one click on limited air (1/250 of surface volume) – 2. Summation effect; pistol shot – 3. More information (size and texture) 11 4/26/2010 Head structure of sperm whales unique (inc f. Kogidae) blow hole frontal sac spermaceti organ Echolocation According to Ken Norris (1969), "If an animal listens to the echo of its own sound and then uses that echo to determine a bearing, range, or the characteristics of an echoing object, it is echolocating.” postulated for whales, pinnipeds and seabirds - only good evidence for odontocetes skull left bony nares Monkey’s muzzle Odontocete larynx ‘goosebeak’ Relaxation oscillations used to produce click and burst-pulse signals burst- Purves (1966) tested transmission: strongest at tip of snout Transmitted sound strongest at tip of snout 12 4/26/2010 Received sound strongest at rear of lower jaw rear of lower jaw is dense thin bone Tursiops skull: Reception area on Diving Adaptations Weddell seal well studied (page 166) because they home to breathing hole Three physical factors have profound effects on the anatomical and physiological characteristics of marine mammals: – Temperature (excursions & thermoregulation) – Light (natural ~ 1000m & bioluminescence) – Pressure (10 m = 1 atm, gas laws apply) Humans, as free or SCUBA divers, face same problems, may be solved by technology Special problems of orientation. Under the fast ice, breathing holes are few and the seals run the risk of exceeding their abilities and drowning. They may swim considerable distances under water, up to 2.5 nm. On exploratory dives into unfamiliar territory, the seals are most likely to become disoriented and exceed critical limits. On these dives, seals invariably return from the same direction they set out on. Weddell Seal Diving Behavior Vision Enormous size of eyes Rods for black and white vision Feeding in midwater, between 300 & 400 m, even though the water depth was 600 m. Factors favoring midwater feeding include: – 1) greater probability of finding fish – 2) dive is of short duration – Cones for color for color -less likely to exceed critical limits -navigational errors less significant – 3) one direction is always certain; hole is above – 4) vertical approach provides best angle for locating hole by vision (or echolocation ??) Trade off between acuity and summation Information on absorptive spectra lacking 13 4/26/2010 Acuity vs Summation Species Man Harbor porpoise Fin whale Walrus Harbor seal So. Elephant seal Rods/mm2 80-100,000 200000 62000 110000 110000 90000 Rods/optic fiber 110-125 4850 5095 2300 1544 920 Body Body Air Spaces Subject to great changes in pressure and volume – at 10 m volume is half, pressure doubled Ribs, true ribs reduced, flexibility true ribs reduced flexibility Lungs, diaphragm, retia and trachea – allow equilibration of pressure – isolate nitrogen gas in non-absorptive spaces non- In human free divers, lung squeeze results in pulmonary edema and rupture of capillaries Deep divers have collapsible trachea walrus harbor seal Ross seal CardioCardio-vascular adjustments to diving Blood – high volume – high oxygen capacity rigid flexible very flexible Tracheal Ring Cartilages stored in circulating blood (see table, pg 151) bl 151) muscle (myohemoglobin) lungs of seals Cardiac function – heart rate (bradycardia) – cardiac output (stroke volume constant) – pressure remains high in sensitive tissues Harbor seal experiment Vascular Bundles and Plexiform Structures 14 4/26/2010 Tuna Porpoise Interactions: Medina panel 3 phases in releasing porpoises Boat 1 All three predators share prey Purse seine Medina Panel fine mesh 2 Boat backing down direction against current 3 cork tender currnet direction cork line sinks and porpoises escape Definition for ‘Dolphin Safe’ labeling Through international conservation efforts, < 2000 dolphins killed in eastern tropical Pacific purse seine fishery since 1998 – Old rule: yellowfin tuna not from intentional set on dolphins – New rule: no dolphins killed or seriously injured in set New treaty limits total mortality to < 5000/yr and protects individual stocks 15 ...
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This note was uploaded on 09/13/2010 for the course OCS 4012 taught by Professor Baltz,d during the Spring '08 term at LSU.

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