Wednesday, March 23, 2005

Societal values and attitudes: their history and sociological influences on amphibian conservation problems.

This chapter was written by J. W. Gibbons. He talks about the views that society has about amphibians, for example, that some people think that they cause warts, or that they associate them with snakes (or as some people, especially girls, have told me, that they are disgusting, putting and ugly face…). For people to care about amphibian conservation, education is important, especially hands-on experience. One important fact to use in public education is that amphibians are indicators of environmental stress (“canary on the mine”).

Sunday, March 20, 2005

Human exploitation of amphibians: direct and indirect impacts

This chapter was written by Jensen and Camp. Direct impacts are use for food, pets, education and research, medicine, bait, and leather trade. Indirect impacts include the release of exotic amphibians in the wild by researchers, teachers and pet-owners; the effect of the decrease of amphibian in other animals, such as an increase the insects that they eat, and the decrease of the animals that eat them. Also the methods for catching amphibians can be very harmful, for example, pouring liquid bleach into streams to drive salamanders from under rocks. Most of the amphibians used for food are wild-caught. Possible solutions are to decrease amphibian consumption: in Germany they had a campaign “let the frogs keep their legs”; replace the use of amphibians used for dissections in schools by computer models, and educate amphibians pet owners and bait users not to liberate them into the wild (Please..don’t turn it loose is available at: http://www.parcplace.org/DontTurn.pdf)

Global change: challenges facing amphibians

This chapter was written by Blaustein et al. They talk about global changes, like increase UV-B radiation (ozone depletion), pollution (CO2, CFCs, organofluorocarbons) global warming, and the effects that these have on amphibians. Some amphibians might be affected by global warming, for example, some are breeding earlier due to the increase in temperatures, and some have lost their habitat, like some amphibians in the cloud forest of Costa Rica. Drier weather makes breeding ponds shallower, so amphibians are more exposed to UV radiation, which can cause mutations and affect the immune system. Some amphibians respond negatively to increase UVB radiation, but some don’t: this can be explained by different capacities to repair UVB damage. UVB caused DNA damage is repaired by a photolyase enzyme (CDP-cyclobutane pyrimidine dimer) that has been found in higher levels in amphibians that are not affected by UVB. They talk about the research of Merila et al, which combines climate change, UV and amphibian breeding. They say that if amphibians are breeding earlier, then they are less exposed to UV radiation. The solution to all these global problems will come the day that pollution levels decrease. Some international treaties have the intention to decrease or end these problems, but, without the signature of the Kyoto Protocol by the US, it is less likely that CO2 levels will decrease soon. Also CFCs are very stable: estimates suggest that those in use today will continue to deplete the ozone layer for 50 to 150 years.

Friday, March 18, 2005

What is causing deformed amphibians?

Today I finished reading the chapter about amphibian deformations by S. Sessions. There is no consensus in the literature if the correct name would be malformations (caused by developmental errors) or deformations (caused by trauma), because on amphibians a trauma can cause a developmental error. There are different possible causes of deformities: Pollution (retinoids), UVB radiation, predation, parasites (trematode infections). Pollution and UVB radiation haven’t been well proved yet, but predation and parasites are the most probable causes. Predation in tadpoles, including cannibalism, (especially in early stages, when they haven’t lost the ability to regenerate tissues) has been proved to cause deformations. Parasites, specially the trematode Ribeiroia, forms cyst in tadpoles, which changes the arrangement of developing limb cells, causing polymelia (numerous limbs) and other deformities observed in natural amphibian populations. The reason why more deformations have been reported recently is not very clear: one hypothesis is that pollution or another type of habitat perturbation could be affecting the trematode cycle, increasing the number of parasites.

Thursday, March 17, 2005

recap

Since I started reading months ago, first I will try to quickly summarize what I know to date. Hopefully one day before my comps I will come back to those readings and talk about them more extensively. The topics for my comps are: ECOPHYSIOLOGY, COMMUNITY ECOLOGY, AMPHIBIAN CONSERVATION, STREAM ECOLOGY, and POPULATION BIOLOGY. First, I started reading:

Ecophysiology:
From the book Vertebrate ecophysiology (Bradshaw, 2003):
Chapter 5: Case studies of stress: incidence and intensity. From the book Behavioral approaches to conservation in the wild (Clemmons & Buchholz, 1997) Chapter 6: Conservation and the ontogeny of behavior (McLean) Chapter 11: The importance of social behavior studies for conservation (Komdeur & Deerenberg). As a quick summary: mostly what they talk about how corticosteroids are high when animals are stressed. Immune system is affected by stress…that’s why stressed people get sick. Mc Lean talked about behavioral responses to stress: choosing burrow places, e.g.

Community Ecology:
Null hypotheses in Ecology (Strong) from the Journal Synthese. Talked about how different is Ecology from other “hard” sciences (organismal, lots of different variables, high variability among individuals). Null hypothesis must be explicit in ecology, and most of the time that doesn’t happen at all. Research should be more experimental than observational or corroborative, where they don’t use null hypothesis.

Amphibian conservation:
I am almost finishing the book with that name, edited by Ray Semlitsch. About all the problems that amphibians are facing, and possible solutions. Pond breeding amphibians, N. America stream amphibians, terrestrial salamanders with direct development, amphibians in the new and old world tropics (sad stories: low budget for conservation and research, high treath by unsustainable use of natural resources, endemic unique species, etc, etc), natural population fluctuations and again null models to prove real declines, habitat destruction and alteration, invasive species, pathogens, infectious diseases and immune defenses, ecology and evolution of infectious diseases, effects of pesticides and deformations (I haven’t finish that chapter, so I will post more about it tomorrow).

Stream Ecology:
Principles of Terrestrial Ecosystem Ecology Chapter 12: Community effects on ecosystem processes. Functional types, Abundance effects on ecosystems (Keystone species). Effects on resources (e.g. nitrogen fixing tree-Myrica), climate, disturbance regime, mutualism, top-down controls, diversity in functional types enhances efficiency of resource use and retention and stabilizes ecosystem processes, temporal variations, complementary use of resources.

Stream Ecology: Structure and Function of running waters
Chapter 2: Streamwater chemistry: determinants of riverwater chemistry: geology, rainwater, volcanic activity, pollution. Materials in river: Dissolved & Suspended; Organic & Inorganic. Dissolved gases: O2 y CO2. CO2 more soluble in water than O2. Concentrations change seasonally and daily. O2 higher in cold waters. High rainfall and runoff have less concentrated waters. Groundwater is more concentrated and has less O2 than surface water, and is less variable.
More CO2, less pH. Hardness relates to Mg and Ca concentration. Number of species commonly increases with hardness. Water of low ionic concentration support fewer fauna.
Chapter 3: physical factors of importance to the biota.
Current: physical adaptations, flow (laminar, transitional, turbulent), behavior, equations to describe streamflow (Re: UL/v= Bulk flow, Reynolds number).
Substrate: inorganic, organic, importance of detritus (more spp), Lithophilus (stones), psammophilus (sand), xhylophilus (wood), phytophylus (plants). Higher abundance in detritus, leaves, and cobbles.
Temperature: in small streams shading can alter summer temp. Stenothermal (narrow temp range animals), Eurythermal (wide range). Less temp, less 02, restricts organisms. Temp triggers development, influences egg developmental rate, juvenile growth, productivity. Less temp, high body mass (insects)
Oxygen: current influences 02, some animals have behaviors to have more O2 in slow moving waters or high temp.

That’s it for today…from tomorrow I will try to summarize less and write a little every day.


why

The purpose of this blog is to help me study about the topics for my comps. I started reading in December, and I just had the idea to start this journal about the things I read every day, as a way to help me memorize and understand better, in a “fun” way. Also, I think it will be easier for me to find and read my old postings, than to read a notebook. My native language is Spanish, but since I am studying in the US and my exam will be in English, writing this will also help me to practice for my exam.

Test1

The intention of this blog is to help me to study for my comprehensive exam. If it's too boring...I am sorry! If it's interesting...good for you!