Amphibian Malformations Lecture Outline Malformations in amphibians

14 Pages·2008·0.28 MB·English

by  Matt Gray

AAmmpphhiibbiiaann MMaallffoorrmmaattiioonnss
An emerging dilemma with
unsolved issues
LLeeccttuurree OOuuttlliinnee
(cid:122)History of malformations
(cid:122)Three main causes
(cid:122)In depth detail of each cause
(cid:122)Things that you can do to help
(cid:122)References
MMaallffoorrmmaattiioonnss iinn aammpphhiibbiiaannss
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MMaallffoorrmmaattiioonn HHiissttoorryy
(cid:122)Earliest reports of frog abnormalities
– 1700’s
(cid:122)Recently emerged in mid 1990’s
– Minnesota school children
– Attempts to determine root of problem
CCuurrrreenntt ddaattaa
(cid:122) The Northern Prairie Wildlife Research Center
(cid:122) 1,959 malformed frogs
(cid:122) 54 species
(cid:122) 44 states
(cid:122) 4 Canadian provinces
(cid:122) Northern leopard frog is most common
(cid:122) Followed by Green frog and Bullfrog
TTyyppeess ooff MMaallffoorrmmaattiioonnss
Eye abnormalities Incomplete tail resorption
Polymelia(Extra limbs) Polydactyly(Extra digits)
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TTyyppeess ooff MMaallffoorrmmaattiioonnss CCoonntt..
Amelia (Missing limbs) Ectromelia(Missing limb segments)
Ectrodactyly(Missing digits)
Other (abnormal skin webbing, bony triangles,
etc.)
MMoosstt ccoommmmoonn cchhaarraacctteerriissttiiccss
(cid:122)Anurans are most commonly affected
(cid:122)Multiple species are affected
(cid:122)Most occur in hind limbs
(cid:122)Usually involve deletions
(cid:122)Multiple geographic regions
(cid:122)Effects can be consistently observed
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WWhhaatt ccaauusseess mmaallffoorrmmaattiioonnss????
(cid:122)Chemical Contaminants
(cid:122)UV Radiation
(cid:122)Parasitic Trematodes
CChheemmiiccaall CCoonnttaammiinnaannttss
(cid:122)Agriculture chemicals (Roundup)
(cid:122) Industrial pollutants (PCB’s)
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CChheemmiiccaall CCoonnttaammiinnaannttss
(cid:122)Relatively few studies assessing chemical
impacts
(cid:122)Chemical contaminants don’t just have
lethal effects
(cid:122)Amphibian limb defects -69%
– Ouelletet al. 1997
CChheemmiiccaall CCoonnttaammiinnaannttss
(cid:122)Most pesticide-induced malformations
involve hindlimbs
(cid:122)WHY?
(cid:122)Exposure differences
CChheemmiiccaall CCoonnttaammiinnaannttss
(cid:122)Chemical contaminants may not be directly
causing malformations
(cid:122)Temp
(cid:122)pH
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CChheemmiiccaall ssuummmmaarryy
(cid:122)Little work has been done
(cid:122)Plenty of work left to do
(cid:122)Some think that chemical comtaminants
don’t cause malformations
– See Ankleyet al. 2004
(cid:122)Data is still inconclusive
UUVV RRaaddiiaattiioonn
(cid:122)UV-B
(cid:122)280-315nm
(cid:122)Recent increase in radiation
UUVV--BB EEffffeeccttss
(cid:122)Cell death
(cid:122)Slow growth rates
(cid:122)Impair immune systems
(cid:122)Various other sublethaleffects
(cid:122)Amphibians are at high risks
(cid:122)Why would they be?
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UUVV--BB iinndduucceedd mmaallffoorrmmaattiioonnss
(cid:122)Can occur at all life stages
(cid:122)Early exposure can cause delayed effects
SSuubb--lleetthhaall eeffffeeccttss
(cid:122)Blistering
(cid:122)Edema
(cid:122)Scoliosis
(cid:122)Retinal damage
SSyynneerrggiissttiicc eeffffeeccttss
(cid:122)Developmental effects
(cid:122)Decreased hatching success
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AAmmpphhiibbiiaann ddeeffeennsseess ttoo UUVV--BB
(cid:122)Habitat selection: dense forests, muddy
water, deep water, crevices
(cid:122)Egg-laying behavior (Marbled newt)
(cid:122)Egg characteristics (Phyllomedusaspp.)
(cid:122)Melanin
UUVV--BB ssuummmmaarryy
(cid:122)Malformations have been documented
(cid:122)Can occur at all life stages
(cid:122)Defenses have evolved
(cid:122)More data is needed
– Bridges and Boone 2003
(cid:122)See PRIMENet website
TTrreemmaattooddeess
((RRiibbeeiirrooiiaa oonnddaattrraaee))
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RRiibbeeiirrooiiaa oonnddaattrraaee
(cid:122)Phylum –Platyhelminthes (flatworms)
(cid:122)Class –Trematoda
(cid:122)Order –Ribeiroida
(cid:122)Family -Psilostomidae
(cid:122)A.K.A. –flukes
(cid:122)Flattened and oval in shape
(cid:122)Two suckers
MMoorree ggeenneerraall iinnffoorrmmaattiioonn
(cid:122)The most visible and abundant parasites
inhabiting N.A. anurans
(cid:122)Numerous species have been documented
inside amphibians
(cid:122)Complex lifecycle
(cid:122)Interesting fact –no anus
TTrreemmaattooddee HHiissttoorryy
(cid:122)1strecord linked to amphibian
malformations –1990
(cid:122)Johnson et al. in 1999 confirmed trematodes
causing malformations
(cid:122)Present in preserved specimens –1946
– Loeffleret al. 2001
(cid:122)Several other studies have been completed
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HHooww ddooeess tthhiiss Cause this?
With this
LLiiffee ccyyccllee
ooff
TTrreemmaattooddeess
HHaabbiittaatt ttyyppeess
(cid:122)Drying pools
(cid:122)Ephemeral ponds
(cid:122)Permanent Ponds
(cid:122)Large lakes
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