Mammalogy Exam 3

BIOL 5760 at Auburn University, includes topics 9-13

What types of constraints are there in form evolution?

phylogenetic, biomechanical

Where is the power for locomotion in mammals?

vertical plane – humerus and femur move vertical, elbows posterior and knees anterior

How does the length, width, and fusions of appendicular bones affect locomotion?

increased length increases speed, increased width increases strength, fusions increase strength and stability

How does the reduction of carpals and tarsals affect flexibility and stability?

decreases flexibility, increases stability

Stride

one cycle of movement, fore and aft

Speed

distance/time

How can you increase stride speed?

shorter time to complete stride, less proximal muscle bulk

How can you increase stride distance?

longer limbs relative to body size, more flexibility in limbs

Adaptation to increase length of stride in plantigrade

arch in foot

Adaptation to increase length of stride in digitigrade

increased length of carpals and tarsals

Adaptations to increase length of stride in unguligrade

fusion of radius-ulna, tibia-fibula and many bones in hands/feet; converge on 1 digit (perissodactyla 3rd digit), converge on 2 digits (cetardiotactyla 3rd and 4th digit), cannon bone

Cannon bone

fused metacarpals or fused metatarsals

Saltatorial adaptations for locomotion

fused cervical vertebrae in some, often long tail for balance, hindlimb elongation, fused long bones (cannon bone common)

Arboreal/brachiator adaptations for locomotion

long forearms, clavicle fused to sternum, digits lengthen, opposable thumbs

Fossorial adaptations for locomotion

short neck, increased size and flexibility of hands and feet, increase width of bones in fore- and hindlimb, elongated scapula

Volant adaptations for locomotion

sternum keeled, elongated digits, membrane forms flight surface

Aquatic adaptations for locomotion

fused cervical vertebrae, long neural spines support tail, chevrons for muscle attachment on caudal vertebrae, vestigial pelvis, decrease length and increase length of appendages, convergence to ‘fin shape’

Amphibious adaptations for locomotion

changes in fins comparable to Cetacea in pinnipeds and sea otters

How do costs of locomotion increase with velocity?

costs generally increase as velocity increases and vary with body mass

Basal metabolic rate

the rate of energy utilization for life sustaining functions; the animal must be at rest, post-absorptive, and not growing or reproducing

Cost of locomotion in small animals

lower maximum speed – the costs of locomotion are greater

Cost of locomotion in large animals

greater maximum speed – the costs of locomotion are lower

Rank from least to most demanding form of locomotion – running, hopping, flying and swimming/diving

flying and swimming/diving (least), hopping (medium), running (most)

Flying and diving benefits

less costly, abundant food, reduced predation

Risks associated with flying

navigation in the dark

Risks associated with diving

navigation in the dark, low oxygen, high pressure, N accumulates in tissues, high heat dissipation

Barotrauma

trauma associated with rapid changes in pressure

How do rapid changes in pressure cause trauma?

pressure forces gas into solution – if pressure reduces too quickly, gasses bubble out of solution and can damage cells, lungs, blood vessels, joints

Nitrogen narcosis

mental hazard, impacts judgement

Oxygen toxicity

ultimately causes cell death, most common impacts on CNS (convulsions, lose consciousness), lungs (difficulty breathing), eyes (visual impairment)

Marine mammal adaptations to high pressure

breathe out before dive (should prevent/reduce oxygen toxicity and N narcosis), allow lungs to collapse, 50-100m (unique surfactant in lungs facilitates reinflation and robust cartilaginous rings around trachea and branches within lungs prevents airway collapse)

Adaptations that support energy demands throughout dive

increased oxygen storage (higher blood volume, hematocrit and hemoglobin), reduced oxygen consumption (bradycardia, hypometabolism, vasoconstriction in extreme cases), use anaerobic metabolism as needed (glycolysis, lactic acid builds up and must dissipate before next dive)

Aerobic dive limit

time at which oxygen is no longer used as fuel

Glycolysis

reduced ATP production/glucose

Echolocation

method of evaluating the environment where an animal evaluates the echoes of its own emitted sounds

What mammals use echolocation?

cetacea, chiroptera, soricidae, tenrecs, a few rodents

How does chiroptera produce sound for echolocation?

larynx and vocal chords – projected through mouth and nose in some; focused within nose-leafs of varying complexity in multiple families

Chiroptera hearing range

10-150 kHz

Chiroptera search signal speed

20-30 ms, speeds to 0.5 ms when approaching insects

Echolocation volume of bats foraging in open

100-120 dB

Echolocation volume of bats foraging in clutter

65-75 dB

How is the cochlea modified in bats?

the cochlea has more turns in bats and cetaceans that in terrestrial species, making them more sensitive to a wide range of sounds

Cochlea

the spiral cavity of the inner ear containing the organ of Corti, which produces nerve impulses in response to sound vibrations

How do bats receive echolocation signals (physiologically)?

pinnae receive sound – sound is projected from pinnae to the tragus that produces a produces a second echo and gives directionality

Pinnae

the external, ear-like flaps of a bat, which are crucial for echolocation

Frequency modulated (FM) calls (cetaceans, bats)

sweeps across frequencies in rapid short pulses; provide precise information about the distance to and shape of an object based on the sound quality of the echo; lower range discrimination; best on edges or in clutter

Constant frequency (CF) calls (bats)

relatively constant frequency in longer pulses; frequency of the call increases as they approach an object and they adjust their own frequency to ensure similar return; strong resolution of velocity of target/prey; best in open spaces

How does the doppler effect aid in echolocation?

distance is judged based on time for call to return after bouncing off an object and the frequency of call when it returns

Doppler effect

an increase (or decrease) in the frequency of sound as the source and observer move toward (or away from) each other

What risks are countered by echolocation in cetacea?

reduced visibility with depth and suspended materials (soil, plankton) in water column limit visibility

Whistles

narrow-band fo continuous tones, for intraspecific communication (not echolocation)

Clicks

broad-band pulses used for echolocation

Characteristics of sound produced by cetacea

4-8 cycle clicks, 40-70 ms/click; high frequency signals ~100 kHz, low frequency 30-60 kHz; 210-225 dB sound intensity

How do odontocetes produce sounds for echolocation?

sound produced by nasal system – air forced through two pairs of lips, dorsal bursae–monkey lips complex (3 cm below the blowhole); signals propagate through the melon in special lipid material found only in the melon and the lower jaw

Why is sound detection difficult for cetacea?

sound wave in water is transmitted through entire skull, making it difficult to localize – no pinnae or tragus

Adaptations for sound detection in mysticetes and odontocetes

tympanic bullae detached from skull; bullae and inner ear insulated with air sinuses and fat pads – slows sound, allows for localization

Tympanic bullae

a dense, complex ear bone crucial for underwater hearing (not a skin blister)

Passive sources of heat loss and gain

radiation (transfer of heat from a warm body to a cooler one, without contact), conduction (transfer of heat between objects in contact), evaporative water loss (water/heat lost via evaporation of water from respiratory surfaces or skin)

Active sources of heat loss and gain

endogenous sources, requires ATP

Endogenous sources

origins that arise from within an organism or system, such as the body's own metabolic processes

Endothermy

body temperature determined by endogenous heat production (uses energy to maintain T)

Homeothermy

the regulation of constant body temperature by endogenous heat production

Ectothermy

body temperature determined by exogenous sources (does not use energy to maintain T)

Poikilothermy

type of ectothermy, body temperature varies with temperature over a wide range with environmental conditions, active over a wide range of temperatures

Heterothermy

body temperature varies with region of the body (regional heterothermy) or at different times (temporal heterothermy)

Where does body heat come from?

chemical bonds are broken during metabolism (ATP to ADP, other molecules), breaking down food in gut

Allen’s rule

appendages in endotherm decrease with latitude (limbs, tails, ears, etc); reduces heat loss

Bergmann’s rule

body size in endotherms increases with latitude; occurs within or between closely related species

Why is fur typically white in wintery/snowy habitat?

skin is dark and absorbs energy, energy passes through white layer and is absorbed by skin – dark fur traps heat away from skin and its lost by radiation or convection

Counter-current exchange in cold climate

arteries and veins of appendages lie close enough together to hold in heat more effectively

What are examples of behavioral regulation of body temperature?

move to microclimates that are closer to thermal neutrality, build larger nest, huddle, stay out of cold through burrowing underground or foraging under snow (subnivean), reduce activity

Dormancy

period of inactivity characterized by reduced metabolic rate (MR) and lower Tb

Torpor

a short-term metabolic suppression that typically lasts less than 24 h, facultative response to insufficient energy; found in echidna, bats, many rodents (not voles), some primates, hedgehogs, badgers, elephant shrews, many small marsupials

Hibernation

prolonged period of torpor typically extended for weeks or months; typically obligate, occurs regardless of circumstances; in most species, Tb remains 2-3 degrees C above freezing (5-10 degrees C in warmer climates); deep hibernation exhibited by small animals

What process is the most costly part of hibernation?

arousals – rewarming, euthermia, or cooling (83% of costs of hibernation)

What behaviors increase thermogenic capacity

exercise, shiver, non-shivering thermogenesis

Challenges associated with heat

proteins typically denature at ~41 degrees C, narrow window between euthermy and death, dehydration due to high evaporative water loss

How do desert species reduce water loss?

reduce body size, concentrate urine, lower fecal water loss, produce low water and high fat milk, re-ingest feces of suckling pups, unique nasal passages

How do animals increase their body water content?

target high water food items and high fat food items, metabolize stored body fat

Sweating

loss of water via eccrine glands – found in species with limited fur, primates and several ungulates

Panting

rapid, shallow breathing that increases evaporation from respiratory tract – many carnivores and small ungulates

Saliva spreading

active licking and spreading saliva across fur to facilitate greater heat loss by radiation or convection – many rodents

Behavioral regulation of Tb

nocturnal or limit activity to morning and evening, fossorial, seek shade, reduce use of energy overall

Estivate

period of dormancy due to high temperatures; many retain low level of activity and may forage

Counter-current exchange in heat (brain cooling in Artiodactyla)

blood in vessels of nasal passage cooled by evaporative water loss; warm blood from heart carried to cavernous sinus in nasal passages; arteries cross network of cool veins where heat exchange occurs; blood temperature reduced by 2-3 degrees C before entering brain

Somatic cells (soma)

building cells that compose everything in body; from an evolutionary perspective, it is the sole job of the soma to support the replication of the gametes

Gametic cells (gametes)

egg and sperm cells only

Oviparity

lay eggs, little or no other embryonic development within the mother (monotremes)

Viviparity

development of the embryo inside the body of the parent, eventually leading to live birth (all therian mammals)

Hormone

a regulatory compounded produced by an endocrine gland and transported in blood to stimulate specific cells or tissues into action

What organs produce hormones relevant for reproduction?

hypothalamus, anterior pituitary, ovaries, testis

GnRH (gonadotropin releasing hormone)

produced by hypothalamus, regulated FSH and LH, sensitive to environmental stimuli

LH in males (luteinizing hormone)

produced by the anterior pituitary, stimulates the Leydig cells to produce testosterone

FSH in males (follicle-stimulating hormone)

produced by the anterior pituitary, stimulates Sertoli cells to produce androgen-binding protein (ABP), which localizes testosterone for sperm maturation

Testosterone

triggers spermatogenesis, libido, secondary sexual characteristics

FSH in females(follicle-stimulating hormone)

produced by the anterior pituitary, stimulates the maturation of the follicle by stimulating the production of estrogen by the granulosa cells

LH in females (luteinizing hormone)

produced by the anterior pituitary, induces progesterone production in the theca cell, ovulation, and the transition of the follicle to a corpus luteum

Estrogen (estradiol most common form)

produced by developing follicle (granulosa cells), promotes proliferation of the endometrium, induces estrus behaviors

Progesterone

produced by developing follicle (theca cells), promotes growth of the uterine lining in preparation for implantation; stimulates development of the mammary glands, maintains pregnancy

Preputial gland

produces pheromones