Takulover. Orca Anatomy. Cetacean Cousins

Transcription

1 Takulover Orca Anatomy Cetacean Cousins

2 WHAT IS A WHALE? Stefan Jacobs Whales are aquatic mammals of the order Cetacea; this includes the dolphin and porpoise. Like mammals, whales are warm-blooded vertebrates that give birth to live young who nurse through the mammary glands. They also breathe air through lungs, maintain a high metabolism to regulate body temperature; generate heat and have little body hair. Whales have a thick, rounded streamlined body; unlike the bodies of fish. They have horizontal tail flukes and rigid flippers that assist in locomotion. They have a mobile rib cage, this allows for the chest to expand when they inhale deeply and the compression of the thorax (upper body) allows for diving into the depths of the oceans; one of the many adaptations to living in the water. Whales also have a unique method of hearing. Unlike other mammals, whales have no tear glands, no skin glands, no olfactory sense, and no external ear openings. Carolus Linnaeus named the Orca in The Orca s scientific name is Orcinus Orca; Orcinus means belonging to the realms of the dead and Orca means kind of whale. Its common name is Killer whale, Orca, Grampus or Blackfish but there are many more names for the Orca world wide as they are world wide creatures. At first the orca was called Delphinus Orca, Delphinus means demon dolphin and Orcus means lower world. Orcas are the world's largest predator of warm blooded animals (endothermic) and they are the fastest swimming dolphins. They live and reproduce about the same time and years as humans. When they hit the grand old age of 60, 70 and even 80 if lucky, they enjoy being grandparents through that time. The Order, Cetacea. All dolphins, whales and porpoises form the scientific Order, Cetacea. Dividing this large group forms two suborders: the Odontocetes (toothed whales) and the Mysticetes (baleen whales).

3 There are branches from this order to different Family s and the one the orca belongs to be the Delphinidae family; including in the Delphinidae family, the dolphin and its present relatives. This family, represented by about 32 species, includes some cetaceans with similar sounding names such as Pygmy Killer Whale (Feresa attenuata) and False Killer Whale (Pseudorca Crassiddens). Orcas are the largest member of the Delphinidae family. The Orca is the largest of all dolphins in the world. It has a wide range of fondness to live in the Tropical waters to the Polar ice; somehow they prefer colder waters. The Orca has other names for instance Grampus, Orc, Orca and Blackfish. The name Killer whale comes from the 18th century when whalers saw these mammals feeding off other whales and dolphins; then they called it whale killer. There is no case of a wild Orca killing a human but there has been only one report that an orca accidentally bit a surfer. The question is why? Maybe they do not see us as a threat. Every time we see orcas, we are reminded how strange and remarkable it is that these creatures, which move with such peace through the three dimensional, a highly active marine world, are mammals like us! That we share the same basic physique and that we both breathe air and we are both global mammals. Bufeo de mascarillia, Spaeknuggure, Sadshi, Mesungesak, Koastka, Innuata, are all local names of Orca in Spanish, Swedish, Japanese, Alaskan, Russian and Korean; yet this is just a few of the hundreds found around the planet. This reflects the mammal s ability to live anywhere in all the oceans and flourish in all types of habitats. Being reported from every corner of the globe; from prehistoric paintings to modern ship based censuses, the orca widely distributed. Although orcas are common in the cooler seas near the north and south poles, very little known about of their movements on a global scale, there is no reliable estimate of the world s populations, only estimates in localised regions. Orcas are opportunistic hunters with an expanse repertoire of predatory skills. Over time they have learned that specialisation is the most efficient way to survive in the wild. They are keen to learn and learn quickly, this makes them different from other predators: most predators stay with one behaviour and do not adapt. Orcas are very curious animals, they will approach a boat with interest and in captivity the orca discovers about human and human discovers about orcas. Sometimes the pair tries psyching each other out with various exercises like reactions when the orca closes its jaws near any part of the human body. With its white eye patch, grey saddle strip, black body, tall dorsal fin, white underneath and striking black pectoral fins make the Orca easy to recognise anywhere around the world. This bold colouring makes the orca hard to see from the preys point of view. To them, the shape of the orca not clear, this makes the colouring a good disguise.

4 Exterior of the Orca In all cetaceans, there is three types of fins, serve to propel the animal and direct it. The pectoral fins and the dorsal fin are to stabilise and direct the creature. Only their front limbs and pectoral girdles of their four legged ancestors remain; the skeletal structure containing a scapula, humerus, radius, ulna, carpus, metacarpus, phalanxes and the back limbs are absent. The pelvis rudiments (vestiges) remain to which the muscles that support and are connected to, the male reproductive apparatus. The dorsal fin and the fluke do not have a skeletal structure but rigid because of connective tissue densely obstacle of interwoven fibres and cartilage. Thermal insulation provided by subcutaneous fat. It is so effective that the body temperature is always adjusted by cooling the blood. This takes place through the fins that have no fatty layer. An orca in captivity named Hyak, his blubber was 9 ½ inches (24 cm) thick, showing he was well insulated from heat loss as heat escapes 25 times faster in water than air. The fins have numerous blood vessels, consequently purpose as heat exchangers. The dorsal surface is mostly black except for a grey saddle behind the dorsal fin which acts like a fingerprint on orcas and is individual to each orca, on the undersides of the body and flukes are white. The males have a large dorsal fin that can grow up to 6 feet (2 metres) tall, making the orca the species with the tallest dorsal fin; yet the female dorsal fin is only 4 feet tall. The head is conical with a distinctive round beak and a white patch above and behind each eye. Orcas have very powerful muscles at the rear of the upper jaw to prevent the escape of large prey and a large throat so they can swallow their food whole and so no need for chewing. The streamlined body saves energy and aids the food storage. Orcas are easy to identify by their striking black and white coloration. Other dolphins have similar coloration, for example Dall's porpoises and False Killer Whales and these similar markings are clearly smaller. Many dolphins have a complex colour pattern though orcas wear a tidy black and white tuxedo. This simple counter-shading is believed to be the most generalised and probably also the most primitive within the Delphinidae family. The white shirt front extends from the lower jaw down to the genital area. Also there is a white zone on the underside of the flukes. The dark, Takulover black coat wrapping around the flippers to lie slightly open over the belly, revealing the genital region. In a trisection cut away that closes very smartly at the base of the fluke.

5 Orcas have a body that offers little resistance to the water. However their bodies differ between sexes. Male Orcas measure between 22 to 30 ft. (6.7-9 m) and usually weigh between 8,000 and 12,000 lb. (3,628-5,443 kg). The largest male ever recorded was 32 ft. (9.7 m) and weighed 21,000 lb. (9,525 kg). As a male Orca approaches adulthood, it gains the typical male characteristics: it gains weight, its pectoral flippers, dorsal fin and flukes grow larger than those of females. Female Orcas measure between 17 to 24 ft. ( m) and usually weigh between 3,000 and 8,000 lb. (1,360-3,628 kg). The largest female recorded was 28 ft. (8.5 m) and weighed 15,000 lb. (6,804 kg). Flukes of a bull can be 8 ft wide and male dorsal fins wobble because of the weight and height of it; some may slightly collapse due to the weight. In captivity, male dorsal tends to flop over more than the females for reasons that are still unknown. The Orcas have a distinct rostrum that is rounded, the teeth are conical and they interlock with the design to grasp and tear more Takulover than to chew their food. The number of teeth varies among individuals. There are usually 14 teeth on each side of the jaw, counting 40 to 58 in total. They typically measure about 3 inches or 7.6 centimetres long and 1 inch or 2.5 cm in diameter. The superior extremities of the Orcas are their pectoral fins. These pectoral fins have most of the bones that make up the front extremities of terrestrial animals, but in the orca, these bones are modified and shortened. These bones are united firmly by connective tissue, thick cartilage pads lay length wise between the bones. The pectoral flippers are round and paddle like. The blood circulation in the pectoral fins helps the animal to maintain a stable body temperature. The arteries within the pectoral fins are surrounded by veins. This way, part of the heat of the blood that travels through the arteries is transferred to the blood that passes through the veins. This heat exchange helps the Orcas to maintain the heat of their body and to regulate its temperature, much like a radiator maintains an automobile engine fresh, but in an inverse way. When the heat of the body exceeds its limits, the circulation of the blood that passes through the veins near the surface of the fin where the surface area increases. When it returns to the body, it returns fresher, allowing the body temperature to return to normal levels. A large male Orca may have pectoral flippers up to 6.5 ft. (2 m) long and 4 ft. (1.2 m) wide. The singular shaped, paddle like pectoral flippers are also proportionally larger than the other dolphins. It contrasts with their sickle-shaped flippers of most delphiniums. They lie about one quarter of the distance from the snout to the flukes. In the males, flippers may reach up to 6 feet wide; about 20% of its body s length. The flipper of a female may reach up to 11-13%. Orcalover

6 The Tail Flukes are flattened pads of tough, dense, fibrous connective tissue, completely without bone. Longitudinal muscles of the back (both above and below the spine) and the caudal peduncle move the flukes up and down. Just like the pectoral fins, the arteries of the tail flukes are surrounded by veins, which help to maintain a stable body temperature. The tail flukes of an Orca of great size can measure up to 9 ft. or 2.7 m from point to point. Like the ends of the tail flukes, the dorsal fin are also made of very dense, fibrous connective tissue that does not contains any bones. As males age the tips of their flukes bend down. This may be to decrease friction as the whale's tail is raised (the down curved tips bend and reduce the surface area as the tail is raised) but then the tips flare out as the tail is pushed down (the power stroke during swimming that needs the greatest surface area). Erin The dorsal fin acts like a keel helping to stabilise to the Orca while swims. As in the pectoral fins and tail flukes, the dorsal fin arteries are surrounded by veins, which help to maintain a stable body temperature. Its tall dorsal fin is proportionally higher than any other dolphin; from one tenth to one fifth of the total body length. The dorsal fins of males can grow up 6 feet (2 m) tall and stand more than twice as those of adult female dorsal fins. The height of the dorsal fin is a useful guide to distinguish adult males with adult females but as it does not begin to grow until they are about 10 years old, it takes at least another 7 years to reach full height in a male Orca. This makes it hard to identify young adults from adult females. In different subspecies of orcas, the dorsal will vary in shape and height. Stefen Jacobs

7 The cut of the dark coat is not quite identical in both sexes. The sex of an orca can be determined in several different ways in Orcas. A distinct white patch on the underside of the Orca covers the anus, genital slit, and the mammary slits (in females). By viewing this (seen when Orcas breach or rolling), one can tell the sex by the presence or absence of the mammary slits, even in babies. Male orcas generally have more of an elongated white patch in the area behind their anus. Several anatomical differences can also be used to tell the sex of the mature adults. This is hard to observe because when the Orcas raise their tails they usually do it quickly, often flopping it around which obscures viewing the drooping fluke tips of the older males. DNA analysis can also tell the sex of the Orcas. This is done by taking a small skin and blubber sample (like a biopsy which means removal of a small living piece of living tissue from an organ or a part of the body) which does not appear to disturb the Orca. Wrapped just behind the dorsal fin, lies the saddle patch. It is a grey strip which is in the shape of a horse saddle and it can be useful for identification. The basic pattern hardly changes through an Orca s life, from birth to death. Very young calves sometimes can be mistaken for porpoises, the saddle patch is quite dark and the light-coloured areas are generally butterscotch or rusty-hued. Before the end of the first year, the saddle patch dims to grey and the colours fade to white. Variations in the basic pattern of the saddle patch are unique to individuals. Researchers working with wild orcas can recognise most individuals by their saddle patch; shape and pattern. It is like a fingerprint. This confirms, in the researcher s notes each individual they observe. Photographic identification is the fundamental tool for following an individual s life, through every day activities. Stefen Jacobs

8 Each population bears slight difference to the general outfit. Orcas hunted off the coast of Australia and New Zealand has been described as dark, purplish brown with ivory shaded areas. Those orcas in Antarctica area smaller, more distinctly more yellow than their northern relatives and those off the coast of Mexico and in the Southern hemisphere. The Resident orcas have plain, featureless saddle patches, characteristics and significantly different from the Transients in the area. Such variations in appearance come from long-term isolations of Orca communities; presumably first isolated geographically than reproductively scenario is thought to have began evolving 2 million years ago. The most likely scenario is that adaptations were developed for food exploits certain food types; fish verses marine mammals. Type B Antarctica Orcas Marty and Carol Levin

9 Inside the Orca The cetacean brain has a shape of a balloon and the anteroposterior compression of the cranium is probably caused by evolution. The cerebral hemispheres almost completely covered the cerebellum and have more convolutions (helixes) than any other mammal. Some researchers say the convolutions are similar in humans. The volume being equal, the brain surface in some Odoncetes is greater than the human s. For example, the Bottlenose dolphin has a surface area of 580 inch 2 (3,745 cm 2 ) and humans have a surface area of 352 inch 2 (2,275 cm 2 ). The density of the cortex in cetaceans average 0.05 inches (1.4 mm) thick, whilst in humans it is 0.11 inches (2.9 mm) thick so primates have a thicker cortex than cetaceans. Figure 1: Wűrtz & Repetto The total volume in the Bottlenose dolphin is 220 inch 3 (560 cm 3 ), humans 259 inch 3 (660 cm 3 ), still more than a chimpanzee. One example of the weight of an orca is the weight of Hyak s brain. It was 14 ½ pounds, Hyak was a 25 year old male. A cetacean heat is capable to store oxygen by using a pigment known as myohemoglobin. The red corpuscles are larger and more numerous than land mammals. The corpuscles are inches ( mm) in diameter and 27, 5590 inches 3 to per inches 3 (7 to 11 million per mm 3 ), in humans inches ( mm) in diameter and per inch (5 million per mm). Blood weight varies from 5% to 9% of body weight. The weight of Hyak s heart was 34 ½ pounds. On surface, heart beats per minute, underwater per minute. It uses a rete mirable system, a network of capillaries located at various strategic points. Figure 2: Wűrtz & Repetto

10 Cetaceans have a stomach with a number of chambers, each with their own functions and have bacteria to help aid digestion of food. The stomach has a front chamber, a main chamber, a pyloric chamber and the duodenal ampulla. The chamber numbers can vary between species. In length, the intestine is nine to ten times the length of the animal s body; it is less developed in Odoncetes.. Figure 3: Wűrtz & Repetto Skeleton All the outlines of possible hidden extremities have disappeared, except for two smalls cleared pelvic bones that are well hidden between muscles of the body; these small bones are not connected to the spine. The skeleton in most cetaceans is made up of spongy bone filled with fat; this is to improve hydrostatic balance. The spinal column is nearly straight, due to weakness of the pelvis; the sacral vertebrate cannot be distinguished. In Odontocetes, the cranium has many characteristics which are related to the presence of special organs associated with sound creation, reception and diving. The pre-jawbones and jawbones are lengthened to the front and back, extending over the orbital region. In addition, there is a strong unbalance between the right and left sides due to the development of a fatty organ known as the melon. The flippers, or pectoral fins, are supported by bones - the same types of bones as are found in the human arms (upper arm bone, two lower arm bones, wrist bones, hand bones, and finger bones).

11 SKELETAL SYSTEM Temporal and palatine vomer Cranium symmetry Pterygoid bone Choane margins or posterior spout holes Occiput condyles Teeth in the embryo Teeth in adults Well developed mandible symphysis Mouth closing Mandible concavity Hyoid bone Sternum composition Segments between ribs and sternum Number of ribs articulated with sternum Thorax Pelvic bones DEVELOPED / NON-DEVELOPED hardly developed unbalanced complex formed by the Pterygoid bone turned to the back teeth teeth yes complete towards the outside with mobile articulation several bones present minimum of 3 ribs mobile columnar Number of digits 4

12 Full list of references coming soon Whale and Dolphins: Guide to the biology and behaviour of cetaceans (Wűrtz & Repetto 1998 Swan Hill Press) Whales and Dolphins (Cardawine, Hoyt, Fordyce, Gill 1998 Collins Publishers)