Lesson 2: Parasites, YUM! An example of mutualism and its effects on coral reefs

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Lesson 2 Parasites, YUM! An example of
mutualism and its effects on coral reefs

• Researcher
• Thomas Adam
• Doctoral Student
• University of California, Santa Barbara

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In this lesson, we will be exploring the
symbiotic relationships found between parasites,
host fish, and cleaner fish, and how this may
affect the surrounding environment.
Gnathiid Parasite. Feeds on fish blood (like a
mosquito)
Cleaner Wrasse Cleaner fish. Feeds on
invertebrates, especially gnathiids
Parrotfish Host fish. Herbivore, feeds on algae
it scrapes off the reef
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Background

• Cleaner fish remove and eat parasites found on
  the scales, fins, or mouths of other fish. They
  are said to eat about 1,200 parasites a day!²
• The parasites are mostly small crustaceans called
  gnathiid isopods.
• Many different kinds of fish visit the cleaner
  station to have parasites removed. The station
  is usually located in front of a reef that an
  individual cleaner fish rarely leaves.
• The different kinds of fish that visit a cleaner
  fish are called client fish because they get
  cleaned.

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Key Term Parasitism

• Parasitism is a relationship
• between two organisms in
• which one organism benefits
• at the other organism's
• expense.
• The gnathiid isopod (right) is a parasite
• to fish because it sucks the fishs blood
• and could transmit diseases. Only the
• gnathiid benefits from the interaction.

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Key Term Mutualism

• On the other hand, cleaner fish and client fish
  have a mutualistic relationship because they both
  benefit from the cleaning interaction.
• CLEANER FISH benefit client fish because they
  get rid of their parasites.
• CLIENT FISH benefit cleaner fish because they
  provide them with a food source (parasites).

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Organism of interest Bluestreak Cleaner Wrasse
Species name Labroides dimidiatus

• Bluestreak Cleaner Wrasses are commonly found in
  the tropical Pacific. The study we discuss in
  this lesson was conducted in Moorea, French
  Polynesia.
• Cleaner Wrasses use the coral reef as a habitat,
  and find a territory that they rarely leave.
• Cleaner Wrasses are often seen alone or in pairs.

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Developing a Scientific Question

• Since the Bluestreak Cleaner Wrasse stays in
  small territories where it is visited by many
  different kinds of fish, Tom (lead researcher)
  began asking questions, such as
• Do the visiting client fish have an effect on
  the coral reef habitat near the cleaner station?

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A Question for YOU

• What are some ways these visiting client fish
  might affect the coral reef?
• Hint Think of all the different kinds of fish
  in the ocean. How could they positively or
  negatively effect the coral reef? Take some time
  to brainstorm and record your ideas.

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I hope you got creative! Some examples might
include

• POSITIVE EFFECTS
• Client fish might eat algae from the reef so the
  coral can have access to sunlight to grow
  (photosynthesis).
• Client fish might release feces (waste) which
  could be food for some coral reef dwellers.
• Some client fish might travel in schools,
  bringing more yummy parasites for the cleaner
  fish.

• NEGATIVE EFFECTS
• Some client fish might be corallivores and feed
  on the coral itself!
• Some client fish might be carnivores and feed on
  the cleaner fish and/or other client fish.
• Some client fish might be so large that they
  damage the reef as they pass through a cleaner
  station.

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Further Developing a Scientific Question

• Tom observed various species of butterflyfishes
  being cleaned at cleaner stations. Many of these
  butterflyfishes prey on coral polyps
  (corallivores), including the ornate
  butterflyfish shown below.

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Main Research Question

• Do cleaner fish have a negative effect on corals
  by attracting and concentrating coral predators?
• Assignment Create an educated prediction
  (hypothesis) of what you would expect the
  results of this experiment to be and explain WHY
  you are making that prediction.

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Compare your Hypothesis to the Scientists
Hypotheses

• The bluestreak cleaner wrasse is attracting
  butterflyfishes.
• 2) The increase in the abundance of
  butterflyfishes at reefs with cleaner fish has a
  negative impact on coral because the
  butterflyfishes are feeding on the corals.
• Did you notice that Tom needs to go beyond his
  initial observations and actually quantify
  whether butterflyfish are being attracted to the
  reef by cleaner wrasses? Then he can go on to
  investigate his main question.

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How would you TEST these hypotheses?

• Assignment Write a step by step PROCEDURE that
  would allow you to investigate these questions.
  Be detailed and creative.
• When you are done writing a procedure, create a
  MATERIALS LIST of supplies you would need to
  conduct the experiment.

Teachers Please give students ample time to
brainstorm and develop their ideas. This is an
excellent group activity.
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Toms Materials Listto investigate question 1

• Scuba gear (including dive buddy)
• Underwater paper/pencil to record data
• Small nets to catch fish
• Clove oil (slows down fish so they are easier to
  catch but does not harm them)
• Ruler or calipers to measure fish
• Ziploc bags/buckets to transport fish
• Watch/Timer

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• EXPERIMENTAL REEFS
• Bluestreak cleaner wrasses were caught from
  another reef and transferred to this reef.

• CONTROL REEFS
• 1) The patch reef had no cleaner fish to begin
  with.
• 2) The cleaner fish was removed from the patch
  reef.

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Toms Methodsto investigate question 1

• To test whether cleaner wrasses were attracting
  corallivores to their cleaning stations, Tom
  IDENTIFIED, COUNTED and took SIZE ESTIMATES of
  every fish that passed both experimental and
  control patch reefs.
• Patch reefs are small, isolated reefs that are
  often cleaning stations for cleaner fish. The
  patch reef in the background photo is one of
  Toms study sites.

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Results for Experiment 1

• EXPERIMENTAL
• The abundance of butterflyfish visiting reefs
  INCREASED when a cleaner was added to the reefs.

• CONTROL
• The abundance of butterflyfish visiting the
  reefs with no cleaner wrasses stayed CONSTANT
  throughout the experiment

This means that the increase in butterflyfish
abundance was caused by the addition of a
cleaner!
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Toms Materials Listto investigate question 2

• Scuba gear
• (including dive buddy)
• Small pieces of Porites rus coral
• Numbered square tiles
• Z-SPAR (clay-like substance,
• used to stick coral to tiles)
• Mass balance for buoyant weight
• Ziploc bags, buckets and coolers
• to transport corals

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Toms Methodsto investigate question 2

• Porites rus was used because it is a species of
  coral that is particularly important in
  reef-building.
• Pieces of this coral (240 total!) were placed on
  tiles using sticky Z-SPAR and then buoyant
  weighed.
• Twenty reefs were used for the experiment
• Ten EXPERIMENTAL reefs WITH a cleaner wrasse Ten
  CONTROL reefs with NO cleaner wrasse
• At each reef, the coral pieces were either
• CAGED (6 corals) NO access for corallivores
• PARTIALLY CAGED (6 corals) corallivores CAN
  access coral
• After a month, all of the same corals were
  buoyant weighed again to see if their weight
  increased, decreased, or stayed the same.

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A Questions for YOU

• Tom used 240 corals total. He surveyed 20 reefs,
  each with 12 corals. Why would he use so many
  corals and reefs?
• Hint Why not just test two corals, one at an
  experimental reef and one at a control reef?

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• And the winning answer is
• Science is so much fun that Tom wanted to spend
  ALL of his free time on his project
• What, you dont believe me?
• Okay, the real reason is that REPETITION is very
  important in science. Scientists must repeat
  their experiments over and over again to be sure
  they get similar results every time.
• If a hypothesis statement holds true for each
  experimental trial, the statement can develop
  into a scientific LAW or THEORY. If another study
  can prove the statement wrong, then usually a new
  hypothesis must be written and tested before it
  can become a law or theory.

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• BUOYANT WEIGHING
• This method is used because it allows scientists
  to measure corals in seawater. Since corals are
  mainly tissue, their weight changes drastically
  if exposed to air. Here is how it is done
• Individual coral piece is placed in a wire
  basket.
• The wire basket is attached to fishing line by a
  hook that hangs from the bottom of the scale.
• The basket is placed in seawater so that coral is
  fully submerged and the weight is recorded
  digitally.

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A Question for YOU

• What is the difference between the words mass
  and weight?
• Hint Think about why the method shown in the
  previous slide provides us with weight data
  instead of mass data.

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Mass vs. Weight

• Mass A measure of the amount of stuff or
  matter in an object.
• Example When you place an object on a mass
  balance, the scale is balanced by the mass of
  another object that is already known.
• Weight A measure of the pull of gravity on an
  object.
• Example In buoyant weighing, the object (coral)
  is attached to fishing line that was hanging from
  the scale. Gravity is pulling the line and the
  object. There is no balancing!
• So, the weight of an object changes when the
  pull of gravity changes, but the objects mass
  remains the same.
• FURTHER DISCUSSION If you were in outer space,
  where you are not subjected to Earths
  gravitational force, would it be more productive
  to collect data on the mass or weight of an
  object?

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Results for Question 2

• Corals left in PARTIAL CAGES grew more slowly
  when placed at cleaner stations than at a similar
  reef without cleaner wrasses. DOES THIS SUPPORT
  TOMS HYPOTHESIS?
• YES! This means more corallivores were attracted
  to the experimental reefs, most likely because of
  the presence of cleaner wrasses. The corallivores
  probably found the open sides of the cage and ate
  some or all of the coral inside, so they ARE
  negatively affecting the coral reef.
• FULLY CAGED corals did equally well at cleaner
  stations and control reefs. DOES THIS SUPPORT
  TOMS HYPOTHESIS?
• YES! The corallivores could not get inside the
  cage at any of the reefs, so there should be no
  change to the weight of the corals.
• Toms evaluation The difference between the
  growth rate of the fully and partially caged
  corals was positively related to the abundance of
  butterflyfish, strongly suggesting that
  butterflyfish were responsible for the decrease
  in the growth rate of corals at cleaner stations.

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Conclusions

• Cleaners can actually have a negative effect on
  the corals that provide habitat for them and many
  other fishes.
• However, this is likely only one of many effects
  that cleaners have. For example, it is possible
  that cleaners also benefit corals by attracting
  fish that eat algae (herbivores), which leaves
  behind less algae that will compete for space
  with the corals.
• Further research on cleaner-client interactions
  will help us to better understand some of the
  processes that are important for structuring
  coral reef communities.

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End of lesson
Hey, wait up! Dude, youre coated in parasites.
Its LUNCHTIME!
Cleaner Wrasse
Parrotfish (herbivore)
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VOCABULARY CHECK

• Parasitism A relationship between two organisms
  in which one organism benefits at the other
  organism's expense.
• Mutualism A relationship between two organisms
  in which they both benefit from the interaction.
• Organism Any living thing.
• Photosynthesis The process in which green plants
  combine carbon dioxide and water in the presence
  of light energy and chlorophyll to produce
  carbohydrates (see lesson 1).
• Schooling Bunching or grouping of fish all
  orienting in one direction and keeping equal
  spacing.
• Corallivore An organism that feeds primarily on
  coral polyps.
• Carnivore An organism that feeds on other
  consumers (meat eater).
• Hypothesis An educated prediction.
• Hypotheses More than one hypothesis.
• Quantify To express observations as a number or
  measure.
• Calipers An instrument used to accurately
  measure length or thickness of an object.
• Buoyant Weigh A technique used to find the
  weight of an object while submerged.
• Repetition Repeating a scientific experiment
  until there is enough data to support the
  validity of the outcome.
• Theory A former hypothesis that has been tested
  with repeated experiments and observations and
  found to always have the same result.
• Law Similar to a theory. Usually describes, but
  does not explain, one phenomena. Laws often
  include a mathematical equation.
• Mass A measure of the amount of stuff or
  matter in a thing.
• Weight A measure of the pull of gravity on an
  object.
• Herbivore An organism that feeds on producers
  (plant eater).

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Work Cited

• Text
• Adam, Thomas, researcher. Personal contact.
• Grutter, A. S. Mar. Biol. Prog. Ser. 130, 6170
  (1996).
• Photos
• Laman, Tim. www.nationalgeographic.com (slide
  11).
• Parks, Peter. www.lexagrutter.com (slide 4)
• Pelc, Robin. University of California, Santa
  Barbara (slides 1, 2, 3, 6, 7, 11, 28).
• Withy-Allen, Kira. University of California,
  Santa Barbara (slides 15, 17, 19, 23).