BIO 358 1st Edition Lecture 7Outline of Last Lecture I. Artiodactyls synapomorphyII. Pakicetus – oldest known cetaceanIII. Ambulocetus IV. Graut and Higgens 1994V. Shimamura et al. VI. Reconciling molecular and fossil data a. 2001 new fossil of Pakicetus Outline of Current Lecture I. What is challenging about living in water? A. Imagine yourself in the oceanB. Physical properties of water C. Heat conductivity coefficient II. Solutions to living in water A. Structure of the integument B. Fur Density (fur seals and otters) C. Blubber (cetaceans and other otariids) D. What about polar bears? Current LectureMarine Mammals =Diverse group of mammals – what is so tough about being a wet mammal?Visualize:- You are at the beach, bi-pedal, nearly hairless body thrown into north Atlantic- Challenges:o Cold – heat conductivity coefficient o Staying at the surfaceo Moving through the water –drag (viscosity and density)o Breathing – onboard oxygen storage o Eating – no chance to catch fish… density/viscosityo Seeing where your going – hard, water attenuates light- LIVING IN WATER IS CHALLENGING Physical Principles of water –- Identify characteristics of water that pose a functional problem to marine mammalsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Identify morphological and physiological solutions to thisComparative approach –- Compare marine mammals to “typical” terrestrial mammalsWe are comparative functional morphologists, that is how we look at the world… REVIEW: - Order Carnivora – Mustleids, Phocids, Otariids, Ursids- Order Cetacea – whales, dolphins, porpoises Physical characteristics of water: The heat conductivity coefficient of water is 25x highter than that of air at the same temperature- What does this mean?- Water conducts heat away from the body minimally 26 times faster than air at the same temperature- Functional problem = heat loss from the body! o Mammals are endotherms o They maintain a high (36-38 degree Celsius) and relatively constant body temperature. o Endotherms generate heat at the same rate it is lost, that is how you maintain a constantbody temperature.o Does that mean that the metabolic rates of marine mammals are 25 times higher than terrestrial mammals?! NOT LIKELY. NO. then what are they doing? What influences heat loss from a body?- H’=(Tb-Ta)(SA)( C )- H’ = rate of conductive heat loss from a body in Watts (W = energy/time; J/s)- Tb = body temperature (degrees Celsius)- Ta = ambient temperature (degrees Celsius) - Ta-Tb = temperature differential- SA = surface area of body (m2) - C= thermal conductance of body (W/m2( degree C) - Heat loss is dependent on these 3 things. Surface area of the body, the difference in temp between the environment and the body and the thermal conductance.Is lowing the body temperature to that of the ambient temperature and option for a killer whale? NOOOO it maintains a high and constant body temperature. Decreasing surface area… is that an option? YES! Marine mammals can modulate the surface area that they expose.- SA = ratio relative to body volume (SA/V) - As body size increases SA/V ratio decreases o Ie newborns have higher surface area relative to the volume of the bodyo Large body size = hallmark of being a marine mammalo When you increase your body size you decrease your SA/V ratio which decreases heat loss from the body!!!- LARGE BODY SIZE IS A MORPHOLOGICAL SOLUTION TO DECREASE HEAT LOSS FROM THE BODY - Modified reduced appendages = decrease in SA And decreasing conductance?!- Yes- Conductance is the inverse of insulation - Decrease conductance = increase insulation - Layering clothes is our solution- Animals have their skin (integument) - Insulative properties of the integument are the most important morphological solution to decreasing heat loss in marine mammals Features of the integument - multi layered tissue- epidermis, dermis, hypodermis- epidermis = outer layer, multi layered o As cells grow and migrate to the surface they fill with keratin: a water proofing proteino hair = completely keratinized epidermal structureo Sebaceous gland – creates oil to water proof skin and conditions hair- Dermis = o a-cellular layero connective tissue layero anchors epidermiso blood vessels travel through theo dermis towards the epidermis o carry oxygen, nutrients and HEAT to the epidermis- Hypodermis = o fat filled connective tissue layero adipose cells- Insulating materials =o Hair - epidermal o Fat (Lipid) – hypodermalHair Structure in a single follicle: - Primary/Guard hair = one single bigger, thicker and coarser - Underhairs= multiples, analogous to down, soft fluffy. TRAPS IN AIR. Comparing the cross section of a follicle across species: - Dog 0-5 underhairs per follicle - Seal 5-20 underhairs per follicle - Otter 50-100 underhairs per follicle - Sea otters increase the density of their fur by increasing the # of underhairs per follicle Insulator graph: - STILL AIR IS THE BEST INSULATOR, especially at high volumes- Dry fur is a good insulator BECAUSE IT TRAPS DRY STILL AIR next to your body- When fur gets wet its insulating qualities plummet- Except for the sea otter!! Because of the density of fur. Fur Density –- only the densest furs can maintain trapped air even when it is wetted - # of hairs per cm squared of fur- cetaceans have 0- sirenians have 1 o sensory hairs - odobenids- phocids- fur seal 60,000- sea otters 130,000!!!- Only these two groups that use fur as insulation Are fur seals and sea otters deep divers? - No why?!- As you increase your depth you increase the pressure and decrease the volume of trapped air = less Insulative material - Is it important to keep their fur clean?o Yes o Sea otters spend 7-9 percent of their daily energy budget cleaning their fur o They clean it and then blow air into ito Enhanced vulnerability to oil spills - Is dense fur a Synapomorphy?!o NO it is a convergent (homoplastic) character - EVERYBODY ELSE RELIES ON BLUBBER Blubber = specialize hypodermis- Adipose rich- Thickened - Balaenid whale – 20-25 cm thick (thickest blubber of all cetaceans)- Phocid seal Increase Insulative quality of blubber: - Increase thickness - Increase fat (Aka lipid) content Worthy and Edwards 1990: - Compared phocoenaphocoena (cold water 13 C) and spotted dolphins (stenella) from the eastern tropical pacific (warm water 28 C) -