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Amphibians In Decline

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Charlene Williams

on 9 April 2013

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Transcript of Amphibians In Decline

Amphibians In Decline Causes, Consequences & Solutions UV-B Radiation Relative to Amphibian Declines Developmental and Behavioral Repercussions of Excess UV-B Exposure. Infectious Disease Relative to Amphibian Declines Differential Susceptibility to Chytridiomycosis Pesticide Use Relative to Amphibian Declines Developmental and Behavioral Repercussions of Excess Pesticide Exposure. Egg Mass Larva Adult Amphibian Life Cycle Accumulating Stressors Geographical Distribution of Factors Affecting Amphibian Decline Infectious Disease UV-B Radiation Infectious Disease Pesticides Egg Mutations & Deformities UV-B in Amphibians Emerging Infectious Disease: Chytridiomycosis -Caused by fungal pathogen Batrachochytrium dendrobatidis (Bd)
-Bd is the only species of chytrid known to parasitize vertebrate species.
-Colonization by Bd results in hyperplasia, hyperkeratosis, hyperemia and cutaneous ulcerations across the amphibian epithelium. Behavioural Changes in Amphibians Pesticides In Our Environment -Underestimate its effects -Tend to ignore
amphibians -Harmful at a range of concetrations

Figure 1. UV-B levels at frog perches and nearby random locations. Distribution May Vary But Effects Do Not Atrazine Hermaphroditism In Rana pipiens Axolotl And Organophosphates Developmental Issues Differential Suceptibility Savage and Zamudio, 2011 -Experimental individuals from 5 geographically distinct populations demonstrating differential chytridiomycosis suceptibility.
Two treatments:
(i) Infection treatment
(ii) Control treatment Figure 2. MHC class IIB PBR allele and heterozygote frequency for Bd infected survivors and non-survivors (Savage and Zamudio, 2011). Presentation by: Colin Adema, Sonya Ramondino and Charlene Williams Factors Affecting Amphibian Decline (1) Habitat loss and modification
(2) Overexploitation
(3) Invasive species
(4) Climate Change and UV Radiation (5) Pesticides and Toxins
(6) Infectious Disease (i) UV-B radiation lowers hatching rate &
affects embryo morphology.
(ii) Pesticides can decimate egg populations. (i) Exposure to UV-B radiation can result in thick corneas & concave spine curvature.
(ii) Pesticides can increase duration of the larval stage.
(iii) Batrachochytrium dendrobatidis (Bd) infection of keratinized epithelium in mouthparts significantly reduces foraging behaviour (negatively affecting survival). (i) UV-B radiation can cause changes in sexual behaviour.
(ii) Pesticides cause mutations in reproductive tissue.
(iii) Bd infection of keratinized epithelium can inhibit essential regulatory function performed by amphibian skin. http://simonthomsett.wildlifedirect.org/files/2008/08/red-eyed-tree-frog.jpg http://2.bp.blogspot.com/-auU0hvB1Shw/UD-xrVl7WqI/AAAAAAAABvY/SdGVYZWBwSY/s1600/strawberry-poison-dart-frog_5869_600x450.jpg http://www.angelfishaquatics.co.uk/ekmps/shops/apd01/images/green-axolotl-2140-p.jpg Understanding Amphibian Decline http://farm3.staticflickr.com/2677/4158542385_ea812b4600.jpg http://www.wri.org/publication/content/8660 Global Distribution of Pesticide Use Ambystoma mexicanum What Have We Learned? -Species disappearing faster than ever
-Must examine all the complex factors
-No silver bullet solution http://images.sciencedaily.com/2007/05/070501075044-large.jpg Population (A) Population (B) Batrachochytrium dendrobatidis (Bd) Batrachochytrium dendrobatidis (Bd) -211x the background rate Why is Differential Suceptibility Important? -Aquatic and terrestrial phases -Used as indicator species -23% mammals, 12% birds, and 32% amphibians
threatened with extinction -Present on a global scale Global Distribution of Chytridiomycosis References Global Altitude Variation UV-B Radiation Pesticides -Of the 99 individuals in the infection treatment, 14 survived.
-Peptide binding regions (PBR) of an expressed MHC class IIB gene were characterized and sequenced for a subset of individuals. (Obtained from Fisher, Garner, Walker, 2009) (Obtained from Bradley, Rosen, Sredl, Jones, Longcore 2002) Obtained from Savage, Zamudio, (2011) http://www.torontozoo.com/adoptapond/frogs.asp?fr=11 http://www.westfield.ma.edu/personalpages/draker/edcom/final/webprojects/sp11/lifecyclefrog/frog_tadpole.gif http://www.edupic.net/Images/ScienceDrawings/frog_eggs.gif Pesticides and Disease Incidence -Malathion exposure affects disease incidence in Bufo woodhousi http://www.frogforum.net/members/john-albums-favourite-frog-toad-photos-picture5965-woodhouses-toad-bufo-woodhousii-woodhousii-male-calling.jpg Figure 1. Skin of Lowland Leopard Frog with Chytridiomycosis Taken from Robles-Mendoza et al. (2009) Initiation of A. mexicanum hatching in the presence of chlorpyrifos Atrazine and reproductive mutations in Rana pipiens Atrazine usage across the United States of America A. mexicanum metamorphosis in the presence of malation Taken from Robles-Mendoza et al. (2009) Taken from Hayes et al. (2003) http://www.myconfinedspace.com/2007/09/12/cute-frog/ (Obtained from Antwis & Browne 2009) Fig. 1. The role of UV-B in the synthesis of calcitriol from its hormonal precursors, including Vitamin D3. Figure 1. Developing long-toed salamander embyo exhibiting anterior dorsal edema and tail malformation. Normal Salamander Embryo (Obtained from Blaustein, Kiesecker, Chivers & Anthony 1997) http://sites.naturalsciences.org/education/treks/amphibian/2007/pages/Spotted%20Salamander%20Embryos.html (Obtained from Kats, Bucciarelli, Schlais, Blaustein & Han 2012) http://people.duke.edu/~jspippen/herps/longtoedsalamander.htm Strawberry Poison Dart Frog Long-toed Salamander -Important effects to consider when looking into remediation efforts http://flatplanet.sourceforge.net/maps/topo.html UV-B Radiation and Disease Incidence Synergistic Effects
(1) UV-B leads to a lower immune response
(2) High altitude areas are prone to invasion by Bd cold-adapted fungus http://funnyanimal4u.blogspot.ca/2012/01/cute-frog-new-photos.html Long-toed Salamanders http://naturalestnaturalist.blogspot.ca/2012/02/herps-are-contagious.html High altitude environments
Tendency to lay eggs in shallow water
Lack of photolyase References Infectious Disease, Pesticides and Amphibian Population Decline References References Infectious Disease, Pesticides and Amphibian Population Decline References CONT'D UV-B Radiation and Amphibian Population Decline References
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