BIO 358 1st Edition Lecture 7 Outline of Last Lecture I Artiodactyls synapomorphy II Pakicetus oldest known cetacean III Ambulocetus IV Graut and Higgens 1994 V 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 ocean B 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 Lecture Marine 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 surface o Moving through the water drag viscosity and density o Breathing onboard oxygen storage o Eating no chance to catch fish density viscosity o 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 mammals These 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 this Comparative approach Compare marine mammals to typical terrestrial mammals We 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 constant body 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 body o Large body size hallmark of being a marine mammal o 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 protein o hair completely keratinized epidermal structure o Sebaceous gland creates oil to water proof skin and conditions hair Dermis o a cellular layer o connective tissue layer o anchors epidermis o blood vessels travel through the o dermis towards the epidermis o carry oxygen nutrients and HEAT to the epidermis Hypodermis o fat filled connective tissue layer o adipose cells Insulating materials o o Hair epidermal Fat Lipid hypodermal Hair 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 it o 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 Blubber thickness in cold water species 2 cm compared to 4 cm Higher lipid content in cold water species 4 times more Insulative blubber than in Stenella conductance 4 times lower Cetaceans and some otariids use blubber fur seals and otters use fur What about polar baers Polar bears lack high density fur Polar bears lack specialized blubber