Marine Mammal Adaptions Adaptation- “An anatomical structure, a physiological process, or a behavior pattern that makes an organism more fit to survive and reproduce in competition with other members of its species.”- E.O. Wilson-

Integument The mammalian integument is a complex, multi-layered structure. Epidermis: Outermost layer, cells are often keratinized and provide water proofing. Epidermal structures include hair, nails, claws, sebaceous (oil) and sweat glands Dermis: Middle layer, formed by two regions of connective tissue Papillary dermis has finger-like projections, each one carries blood vessels and verves toa position near the overlying epidermal cells. Reticular dermis forms a connection with the underlying hypodermis Hypodermis: Bottom layer, a more loosely woven connective tissue layer

Integument

Thermoregulation Mammals are homeothermic endotherms with a high (36 to 38C) and stable body temperature. Water conducts heat away from the body 25 times faster than air.

Adaptations to deal with this Low Surface area to Volume ratio decreases the relative area across which heat is lost. Marine mammals tend to be large, and therefore have a small surface area to volume ratio, thus reducing heat loss.

Insulation Fur: Fat: Many marine mammals use both for insulation. Good in air, but loses most of its insulation when wet Only the sea otter and fur seals have dense enough fur that the skin remains dry under water. Fat: Marine mammals use “blubber”, a thick subcutaneous layer of fat for extra insulation Blubber can be up to 30% of total body weight. Not nearly as effective as dry fur, but better in the water. Many marine mammals use both for insulation.

Mammal Insulation

Hair

Blubber

Hair vs. Blubber

Too Hot Marine mammals, may also face the problem of excess body heat, especially in tropical regions when they are swimming a lot. Bypass insulation by transferring heat to areas of little insulation Pinnipeds: the underside of the flippers. Cetaceans: the fluke, dorsal fin, and flippers

Counter current heat exchanger

Drag Reduction Adaptations to reduce drag Reduce hair, or the guard hairs are the leading hairs, they are flattened and thus for a smooth surface when wetted. Streamlining reduces pressure drag The hydrofoil shape is best at reducing pressure drag.

Flipper

Buoyancy Control When a body is submerged in water, it displaces a volume of water equivalent to its own volume. If the weight of the body is less than or equal to the weight of the water it displaces, it experiences a net upward force and floats. If the weight of the body is greater than the weight of the water it displaces it sinks.

Buoyancy Issues Mammals are made of some stuff, bone and muscle, that are denser than water. Other stuff, like air-filled lungs, body fluids, fats, oils and blubber are less dense than water Two mechanisms to avoid sinking Reduce the amount of muscle and bone Increase the amount of air, body fluid, fat, oil and blubber.

Skeletons

Locomotion Muscles pull on bones, which are attached at joints, thus creating leverage in order to pull water behind the animal and thus thrust it forward. A lever system can be designed to optimize either its force output or the velocity at which it moves. Fource output is increased by increasing The force-in The mechanical advantage of the lever system.

Appendages

Skull Morphologies In pinnipeds, otters and sirenians, the skull morphology is very similar to that of a terrestrial mammal Cetacean skulls are different Both odontocetes and mysticetes have a cranial elongation of the bones that form the rostrum (the snout) and a shortening of the braincase. Mysticetes also have a tremendously elongated maxilla from which the long sheets of baleen hang. The nostrils have migrated farther back on the head, which helps to breathe while in the water.

Skull Morphologies

Respiratory System Pressure increases with depth such that every 10m is an additional atomosphere of pressure At high pressures, nitrogen becomes solvent in body tissues. When it comes out of solution it can rupture the tissue, causing the bends. How do marine mammals avoid this? Oxygen is stored in the blood and muscles and air is kept out of areas that are in contact with blood. For this reason many seals actually exhale before they dive. Marine mammal lungs are reinforced so that they don’t collapse under the pressure and thus trap air where nitrogen could be absorbed into the blood.

Blood vs. Lung O2 Content

O2 in Blood, Lung and Muscle

Lung Morphologies

Breathing in the water. How to keep from choking How do deep diving animals keep water from entering their nostrils? How do they feed without breathing? Nostrils close tightly Odontocetes: the larynx forms an elongated goosebeaklike structure that fits rigidly into the elongated nasal passage. Food passes around the larynx when swallowing and no food or fluids enter the respiratory system. The intranarial (within nose) position of the larynx effectively separates the respiratory tract from the digestive tract to a greater extent than that found in any other mammal. Also allows odontocetes to simultaneously echolocate and swallow.

Dolphin Skull

Feeding Finding food In addition to using sight, Pinnipeds and sea otters use their whiskers to feel for their food. Odontocetes use echolocations, which works even in the dark.

Eating Pinniped dentition is very similar to most carnivores Sirenians use lips and whiskers to gather food and lack incisors. Constantly grind down their molars by chewing. Teeth migrate backward and are constantly being replaced. Odontocetes feed on individual fish and squid. Homodonts (all teeth the same) catch food and chew it. Swallow by creating suction Mysticetes lack teeth and use baleen, plates of keratinized tissue that hang from their upper jaw.

“Teeth”