Amphibians: Indicators of Environmental Conditions

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Amphibians Indicators of Environmental
Conditions

• Michael Ellefson
• Joe Ryan

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Why a good indicator?

• Amphibians breath through their skin, which allow
  toxins/chemicals to be absorbed into their body

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Overview

• Salamander Population Decline
• Rising levels of Acid Deposition
• Rising levels of Pesticides (TPT in particular)
• Habitat Loss
• Rising occurrences of Viruses (Particularly RRV
  ATV)
• Rise in levels of Heavy Metals (Particularly
  Cadmium)

• Decline in Frog Populations
• Ultraviolet Radiation
• Rising occurrences of Parasites (Particularly
  Ribeiroia)
• Rising levels of Pesticides (Particularly
  Atrozine and Methoprene)

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Acid Deposition General Information

• Acid deposition includes acid rain, fog, and snow
  and acidic gases and particles.
• Primary causes of acid rain are the increases in
  Sulfur Dioxide and Nitrogen Oxides
• 2/3 of Sulfur Dioxide and ¼ o Nitrogen Oxides
  comes from electric power generation that relies
  on burning fossil fuels

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Sulfur Dioxide and Nitrogen Oxides

• Nitrogen Oxides
• Why worry about it?
• Causes respiratory illnesses in humans
• Sulfur Dioxide
• Why Worry?
• Causes respiratory illnesses and aggravates
  existing heart and lung disease

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Effects of Increasing Acid Deposition on
Salamander Population

• During the last seven years, the Tiger Salamander
  (Ambystoma Tigrinum nebulsun) of the Colorado
  Rockies have declined in population size by 65
• A study showed that salamander eggs had a LD-50
  pH of 5.6, which is within the range encountered
  by eggs at the sites in the Rockies.
• Graph pH levels of 6.1, 5.7, 5.3, and 4.9

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TPT (Triphenyltin)

• Pesticide
• Tennessee State University Study showed that TPT
  made natural killer cells in humans to become
  powerless in their fight against tumors and viral
  onslaughts

• TPT and Salamanders
• Study showed TPT causes mortality and lower
  feeding rates in the Streamside Salamander
  (Ambystoma barbouri)
• Lower feeding rates cause the salamanders to
  metamorphosis later in life, making the age of
  sexual maturity later
• Eggs exposed to 5 ug/L of TPT were killed 93 of
  the time
• Eggs exposed to 1 ug/L didnt have any mortality,
  but decreased their feeding rate

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Habitat Loss

• Professor James Petrankas study compared the
  number of salamanders in habitats left untouched
  by humans to habitats that had had extensive
  logging of trees
• Of the estimated salamander population in North
  Carolina, 80 were found in streams passing
  through undisturbed forests, while 20 were found
  in streams that were next to developed land.

• The dramatic difference is thought to be caused
  by fertilizer runoff which increases the pH in
  the waterways
• Petranka estimates that 14 million salamanders a
  year were killed in North Carolina alone because
  of habitat destruction

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Iridoviruses RRV and ATV

• Iridoviruses are known to infect invertebrates,
  fresh and marine fish, and amphibians
• Regina ranivirus (RRV) was found in salamanders
  in Vonda, Saskatchewan
• Ambystoma tigrinum (ATV) was found in salamanders
  in Southwestern United States
• ATV and RRV were partly responsible for a 77
  decline in the salamander population at these two
  sites.

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Symptoms of ATV and RRV

• RRV- clinical symptoms include loose feces,
  bloody stools, anorexia, vomiting (sometimes with
  blood), raised foci on skin, and erosions
• RRV-Post Mortem inspection affected all organ
  systems besides the muscular and central nervous
  system
• ATV-reported that cells of the epidermis, gills,
  and liver having enlarged nuclear inclusions and
  sloughed skin and mucus (werent found in RRV)

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Where did these new strains come from?

• It is thought that old strains mutated and
  crossed species barrier
• Possible strains that could have mutated to form
  ATV and RRV
• Frog Virus 3 (FV3) found in frogs
• IV29, found in meal worm
• IV30, found in corn earworm
• IV31, found in woodlice
• IV22, found in black fly

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Increase in Heavy Metals such as Cadmium

• Low concentrations occur naturally in environment
• Manure plants, metal refineries, and pesticides
  used on farms are major sources of cadmium
  increase

• Cadmium poses sever implication for humans
• It causes diarrhea, stomach pains, severe
  vomiting, weakened bones, infertility, damage to
  central nervous system, damage to immune system,
  psychological disorders, and possibly DNA damage
  or cancer development

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Cadmium and Amphibians

• LD-50 occurs at 227.3 mu g/L Cd in less than 10
  days and 193.1 mu g/L Cd in less than 24 hours in
  salamander eggs
• During Metamorphosis, these concentrations
  account for stunted growth in the limbs

• At levels of 12.8 mu g/L Cd, no mortalities were
  recorded, nor were any restrictions on growth

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What can we do?

• Acid Deposition use sulfur with less sulfer,
  washing the coal before burning, using scrubbers
  which chemically remove the sulfur dioxide, and
  burning natural gas
• Pesticides Use less and use different types
• Habitat Loss responsible development

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FROGS

• AND
• FROG
• DEFORMOTIES

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• In 1995, a group of children was playing in
  Henderson, Minnesota.
• That day, half of the 22 frogs they found were
  deformed.
• Some had 5 or more legs, no hind limbs, and even
  lacked eyes.

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Frogs

• Malformations have been reported in more than 60
  species.
• Deformed frogs have been found all over the
  world, and 46 states in the US.
• Every species naturally has no more than 5
  deformities in their populations. This statistic
  is higher in frog population.

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Now, I know youre all wonderingWHY?!?

• So, Ill tell you all about it.
• Possible Reasons
• UV radiation
• Pollution (pesticides)
• Parasites

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Ultraviolet Radiation

• Ultraviolet radiation has been known to disturb
  amphibian development by causing damage to the
  immune system and causing genetic disorders.
  This has been getting worse with the decline of
  the ozone layer.

• Ultraviolet rays can kill amphibian embryos,
  larvae, and cause serious eye damage in frogs.
  However, this does not explain the deformities.

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UV effects

• This graph shows the mean population of frog
  embryos surviving to hatching at different
  depths.
• Frogs in shallow waters have a smaller chance of
  surviving because of the UV rays.

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POLLUTION

• Pesticide pollution was put forth as a possible
  solution because Retinoid, which is similar to
  the pesticide methoprene, plays an important role
  in amphibian development, even in hind limb
  development. However, they could not reporduce
  this with methoprene.

• More recently, an endocrinologist from Berkeley,
  Tyrone Hayes, targeted atrazine as a possible
  culprit.
• Atrazine is a weed killer. It has been shown to
  chemically castrate and feminize male frogs.
• Many deformed frogs came from atrazine
  contaminated water.
• Atrazine has also been known to weaken frogs
  immune systems, making them more vulnerable to
  parasites.

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Parasites

• Parasites, especially a flatworm trematode called
  Ribeiroia Ondatrae, explain frog deformations
  better than the other possible solutions.
• Ribeiroia forms cysts on the body of frogs,
  especially around the hind limbs, which cause new
  legs to grow in different places.
• Ribeiroia is almost always found where frog
  deformities are present, even where the kids were
  playing in Minnesota.
• It has now been identified in WI, IL, PN, and NY.

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Deformity Frequency and Ribeiroia presence

•  The frequency of deformities rose in relation to
  the frequency of parasite infections measured in
  amphibians dissected.

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Ribeiroia Process
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Rib makes frogs easy targets

•  Johnson et al. exposed tadpole Pacific tree frog
  (Hyla regilla) to the cercaria of a trematode
  parasite, Ribeiroia. They found that as the
  number of parasites per tadpoles rises, the
  percentage of abnormalities increases while
  survival decreases.

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Why does Rib attach to the back legs?

• Hind limb malformations 80 of total
  malformations.
• They have remarkable accuracy of the anatomical
  site where the penetrate their hosts. They can
  even specify whether they are going to infest the
  right or left side of the tadpole.
• The reason for this accuracy is that there is an
  arms race between the parasite and the host.
  After the parasite tries to infect the frog, the
  tries to shake them loose through evasive action.

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Rib attachment cont

• So, the frog needs to attach to a place where it
  will be able to hang on.
• High speed videography of staged encounters
  between the parasite and host.
• Showed that frogs could more easily dislodge from
  sides of tadpole.
• Conceptual fluid-dynamic models show that water
  in the recess immediately behind the torso, next
  tail is realatively stagnant. Called the dead
  water zone.
• Parasite attaches here because it decreases on
  water drag, making it easier to hang on.

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Deformed Tadpole
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Synergistic deformities

• Pesticides and Ribeiroia
• As mentioned, pesticides weaken frog immunity.
• This makes them less resistant to ribeiroia.
• This is because pesticides have been shown,
  through models of locomotion, to reduce frog
  activity. Reduced frog activity makes them more
  vulnerable to parasites because they are less
  likely to initiate fast, repetitive starts.

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More about tadpole activity

• Frogs in the presence of predators, even when
  separated by a screen, can significantly increase
  the number of parasites in the water.
• Tadpoles also reduce their activity in the
  presence of predators, causing more parasite
  infections.

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The Human Factor

• Human impacts compound the effects of these three
  natural factors.
• Destruction of ozone and UV rays
• Fertilizers such as nitrogen and phosphorus leak
  into the water, causing algal blooms to become
  larger.
• This creates more food for snails, giving Rib
  more hosts to infect.
• More fertilizers cause tadpoles to move around
  less
• Human stocking of ponds create more tadpole
  predators
• Majority of wetlands infected are artificial
  bodies of water
• Artificial bodies are more likely to be close to
  human influnce and consequently more polluted.

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Why should we care?

• Frogs occupy a very unique place in our
  ecosystem.
• They are very sensitive to environmental
  fluctuations because their respiration happens
  through their skin. Their soft eggs are also
  very sensitive
• Frogs are developing deformities now in places
  and at rates unheard of in the past. The
  potential that the frogs are a signal of things
  to come is so great that answers must be found.