Amphibian Unit 1
What is Batrachology?
the study of amphibians
Why are amphibians and reptiles often studied together?
1. historical inertia
2. tradition
3. many aspects of their lives are complimentary
4. similar modes of investigation
5. biological similarities
Amphibian Skin
moist and scaleless
Amphibian skeleton
ossified but flexible, some have more cartiledge
Amphibian reproduction
internal/external, indirect and direct development
Amphibians are what kind of "therms?"
Poikilotherms - they adjust temp based on external environment
What kind of heart do amphs have?
3-chambered heart
What is heterochrony?
(embryonic) heterochrony refers to alterations in the timing and rate of developmental processes that change the body form of adults
What is ontogeny?
the process of a single cell (egg or zygote) to an adult organism
Which two organisms' larvae resemble their adult stage in appearance and organization?
Salamanders and caecilians
Anurans
frogs/toads
All larval amphibians share what traits?
1. promote aquatic existence (thin, highly vascular skin, gills)
2. lidless eyes and large nonvalvular nares
3. the body is muscular and adapted for undulatory swimming
4. skeleton is mostly cartilaginous
5. well-developed lateral line system
What natural processes affect physiological processes of juveniles and adults, especially embryos?
Temperature, gas exchange, and water availability
Metamorphosis
signals the completion of embryogenesis and is initiated internally by thyroxine - env factors can initiate early release
Only a few amphibians hatch eggs. This process is driven by glands that secrete what
proteolytic enzymes that weaken and dissolve egg capsule
Growth
both indeterminate (attenuated) and determinate (asymptomatic)
Size of an amphibian is determined by
1. genetic potential
2. size at hatching
3. abundance and quality of food during growth
4. sex
How long do amphibians live?
Most less than 7 years, but can live up to 25 years
Amphibian sense organs
1. 10 cranial nerves
2. cutaneous sense organs
--mechanoreceptors (lateral line and tactile)
Amphibian respiratory surfaces
1. skin
2. gills
3. lungs
4. buccopharyngeal (cheek, mouth, pharynx)
Amphibian lifecycle
1. physically tied to water to reproduce
2. mostly internalized fertilization (salamanders)
3. both direct and indirect development *
4. biphasic and biennial ****
1/3 salamander species are found in
North America
The highest concentration of salamanders is found in
the Appalachian Mountains
Amphibian declines due to
1. habitat destruction
2. invasive species
3. pollution
4. unsustainable use (subsistence, commercial exploitation)
5. Disease/parasitism, climate change
Two qualifications to be considered a hotspot region
1. at least 1500 vascular plant species as endemics (naturally occurring)
2. lost at least 70% original habitat
Why are amphibians better bioindicator species?
1. permeable skin
2. found in and around water
3. reproduction is tied to water
4. complex life cycle
5. physiology makes them more sensitive to env changes
Issues in political ecology
1. habitat loss and pollution
2. invasive species
3. global climate change
4. unsustainable use
5. disease
Why are amphibians traded?
1. pet trade
2. skin trade
3. bushmeat
current issues in amphibian ecology
1. political ecology
2. trade in exotic wildlife
3. sport/commercial hunting/fishing
Human effect of habitat modification/fragmentation/loss...
urban sprawl, wetland mitigation banking - wolf in sheep's clothing
Promises v Problems of pesticide use
Promise is quick but dirty fix, economical fix; Problem is development of resistance, secondary pest outbreaks, adverse human and env health problems
Alternative pest control methods
1. cultural control
2. biological control (natural enemies)
3. genetic control
4. chemical ecology (hormones)
5. physical + natural barriers
6. control w sterile males
7. biotechnology (resistant strain of crop/plant)
8. IPM (integrated pest management) - long term management
Direct take v indirect take
Direct take shows intent, indirect take does not show intent
Max sustained yield
a population declines once this value is exceeded
optimum sustained yield
level of sustained yield determined by species interaction, esthetics, and land use problems
Sustainability
process or state that can be maintained indefinitely
what is urban blight
general deterioration of structures and facilities in addition to a decline in quality of services (education, etc)
the lifeboat ethic
the argument to the effect that we should limit amount of food-aid to high-population countries to prevent further population growth