3/29/2010. Lack of food Extreme temperatures Freezing Heat CHALLENGES/STRESS DUE TO CLIMATE: Strategies for coping with freezing and desiccation

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Conrad Randall
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1 CHALLENGES/STRESS DUE TO CLIMATE: Water Loss Lack of food Extreme temperatures Freezing Heat Strategies for coping with freezing and desiccation Behavioral Reduce skin in contact with air Burrowing Nocturnal lifestyle Dormancy Structural Form cocoons Bind water Seat Patch Skin color Physiological Tolerance to water loss Low metabolic rate Reabsorption of water Water from metabolization of fat Etc 1

A sustained and profound state of behavioral inactivity, entry to and exit from which is governed by internal signals together with exclusively seasonal external cues.

2 A sustained and profound state of behavioral inactivity, entry to and exit from which is governed by internal signals together with exclusively seasonal external cues. High latitudes or altitude Short term vs long term Lower metabolic rate and demands Utilize stored lipids and glycogen Burrowing vs utilization of natural holes Freeze tolerance Aquatic vs terrestrial Anoxic conditions Food? Desiccation Urodelids Fully aquatic species Prolonged larval period: overwinter as immature Semi-aquatic Hibernate on land as adults, active on warm days OR Overwinter in water Most spend one winter in water as larvae Terrestrial Hibernate in natural cavities Usually remain active, eat insects underground Terrestrial hibernation Natural cavities Holes under stones, cellars, logs, etc Small mammal, reptile holes or burrows, nest holes of bank swallows Aggregations of individuals (why?) Burrowing Specifically modified structures Bufonidae, Scaphiopodidae, Microhylidae Hibernate near breeding ponds Freeze tolerance 2

Aquatic hibernation Avoid dessication Water may freeze or become anoxic Massive die-offs Most Ranidae Hibernate in well-oxygenated water Juveniles can be more tolerant than adults (why?

3 Aquatic hibernation Avoid dessication Water may freeze or become anoxic Massive die-offs Most Ranidae Hibernate in well-oxygenated water Juveniles can be more tolerant than adults (why?) True hibernation? Cues Environmental temperature Decrease in oxygen Metabolic supression Use stored lipids and carbohydrates Osmotic/ionic homeostasis Decrease membrane permeability Cheaper to maintain gradient Gas exchange Freeze tolerance and Cryoprotectants Prevent ice from forming in organs Maintain integrity of cell membranes Urea, simple and complex sugars Wood frogs Benefits Range Life history Competition Drawbacks Limit Multiple thawing episodes ofea Also in N.A.: Spring peepers, Western chorus frog, Pacific tree frog, Gray treefrog, Cope s gray treefrog Siberian salamander Found further North than any other species Tolerate up to -35 or 40 o C Found 4-14 m down in permafrost, up to 90 years old 3

Physiology Anti-freeze to depress freezing point of body fluids Glucose Glycerol Tolerate freezing of

Water drawn out of cells into abdomen, around skin and muscles 2.

concentrations of sugars Period of inactivity in warm or dry weather Avoid dessication! 1.

4 Physiology Anti-freeze to depress freezing point of body fluids Glucose Glycerol Tolerate freezing of extracellular fluid, NOT internal organs Repeated cycles of freezing and thawing 1. Water drawn out of cells into abdomen, around skin and muscles 2. Liver begins to convert glycogen to glucose when ice formation begins (6x higher) 3. Heart pumps sugars through organs 4. Extracellular water freezes but internal organs stay just above freezing Organs thaw 1 st : highest concentrations of sugars Period of inactivity in warm or dry weather Avoid dessication! 1. Coccoons of shed skin or mucus Helps control water loss in dry conditions Re-absorb water from bladder 2. Decrease water potential Accumulate urea in plasma Absorb water from more moist surroundings Other ions not affected Sirens Anurans Sirens Dig into wet mud Mucous layer forms protection from dessication Create mud ball 4

Metabolic supression 10-20% Stored lipids, also sugars Use protein if desperate Reserve energy for emergence and

3 hours of resting Spadefoots Dig burrows Explosive breeders Come out in accomodating conditions Fierce larval

urea Metabolize fat during hibernation Water lost from interstitial fluids Use dilute bladder urine to

5 Metabolic supression 10-20% Stored lipids, also sugars Use protein if desperate Reserve energy for emergence and breeding Gas exchange Necessary to efficiently use fuel Pulmonary vs cutaneous Oxygen uptake Decrease 30% within 3 hours of resting Spadefoots Dig burrows Explosive breeders Come out in accomodating conditions Fierce larval compedators Scaphiopus couchi Arid SouthWest Underground 10 months/year High body fluid concentrations, half urea Metabolize fat during hibernation Water lost from interstitial fluids Use dilute bladder urine to replentish water Life history Microhabitat selection Metabolic adaptation Freeze tolerance Organ transplantation Cryogenics 5

Biology 110 Organisms & Environment Desertification Unit Page 1 of 7

Biology 110 Organisms & Environment Desertification Unit Page 1 of 7 Biology 110 rganisms & Environment Desertification Unit Page 1 of 7 Based on Mader, Sylvia S. 1996. Biology - 5th Ed.. WCB and Cox, G.W. 1997. Conservation Biology - 2nd ed. WCB [Chapter 8] and Levine,