Parasitology Lec 6: Annelida (Part 2)

What does the study focus on?

A population of oligochaetes from Foundry Cove in 1989.

What is Foundry Cove?

A freshwater bay on the Hudson River in New York.

What happened at Foundry Cove until 1979?

A battery factory discharged large quantities (53 tons) of cadmium (Cd) and other heavy metals into the bay.

When was Foundry Cove declared a Superfund Hazardous Waste site?

1984.

What family of oligochaetes is the study based on?

Tubificidae.

How do members of the family Tubificidae respond to pollution?

Members of the family Tubificidae are highly resistant to pollution.

Where are Tubificidae found in high numbers?

In wastewater treatment plants.

What are members of the family Tubificidae referred to as?

Sludge worms.

Where were worms collected?

From Foundry Cove and from a control site, South Cove.

How did worms from both sites survive in uncontaminated South Cove sediments?

Worms from both sites survived well in uncontaminated sediments from South Cove (control).

How did worms from Foundry Cove survive contaminated sediment?

Worms taken from Foundry Cove survived a 28-day exposure to the contaminated sediment.

What does the book state about South Cove worms exposed to contaminated sediment?

No worms collected from the South Cove site survived exposure to the contaminated sediment.

What does the original research state about South Cove worms exposed to contaminated sediment?

The South Cove worms exposed to contaminated sediment mostly died.

What does each bar represent?

Three replicates of 10 worms each (n = 30).

Why is n = 30 a small sample?

It is a small sample when compared to the number of tubificid worms located at Foundry and South Cove.

What does a small sample reduce the chance of finding?

The small number of resistant tubificid worms that would be located in South Cove.

What did the authors do with offspring from Foundry Cove adults?

They reared them to a second generation in clean water and uncontaminated sediment and then tested the offspring's tolerance to cadmium.

What does each point represent?

The mean of three replicates of 10 worms each (n = 30).

What did the study authors and the book's author conclude?

This is evidence of evolution.

What is natural selection?

The process by which populations become adapted to their environment.

What are the components of natural selection?

Variation, inheritance, differential adaptedness, and differential reproduction.

What is variation?

Members of a population differ from each other.

What is inheritance?

Some of these differences can be inherited as genes.

What is differential adaptedness?

Differences affect how well the individual adapts to the environment.

What is differential reproduction?

Individuals with better adaptedness leave more offspring in the next generation.

How did Edward Blyth describe ideas of natural selection?

In terms of stabilizing a characteristic in an animal population.

What was Darwin's proposal about natural selection?

Natural selection could explain a naturalistic creation of all organisms.

What would provide new alleles and what would natural selection favor?

Mutations would provide new alleles and natural selection would favor “good” mutations to create new organisms.

When was remediation of Foundry Cove completed?

1994–1995.

What did remediation reduce cadmium levels to?

Less than 10 µg Cd/g, as opposed to 7,000 µg Cd/g.

What study was initiated in 1996?

Another study on the tubificids of Foundry and South Coves.

What happened to tubificids from Foundry and South Coves each year?

They were placed on high cadmium-concentration sediments.

What was measured in the 1996 tubificid study?

The number of hours until there was 50% mortality.

How long did it take Foundry Cove populations to converge with South Cove populations?

Only 9 years (generations).

How vulnerable are Foundry Cove worms to cadmium today?

They are as vulnerable to cadmium as the worms in South Cove.

What are the three forms natural selection can take?

Stabilizing, disruptive, and directional.

What does stabilizing selection favor?

The middle ground, or intermediate phenotype.

What does disruptive selection favor?

Two or more extremes.

What is an example of disruptive selection?

The British snail that lives in two very different habitats: low vegetation versus forest.

How do snail shells differ between the two habitats?

Snails in one habitat have a dark shell; snails in the other habitat have a light shell.

What does directional selection favor in the temperature example?

If the temperature goes up 10 degrees, an individual that can thrive at high temperature will leave more offspring than one that can also thrive at this temperature.

What is microevolution?

A change in the gene frequencies within a population over time.

What is one example of microevolution?

Insect resistance to pesticides.

What is another example of microevolution?

Different breeds of dogs.

What allows tubificid worms to resist cadmium?

Tolerant worms produce higher concentrations of a metal-binding protein in response to high levels of Cd concentrations.

How does the metal-binding protein help worms survive cadmium?

The protein binds to the Cd, detoxifying the metal and allowing the worm to survive higher levels of intracellular Cd.

Where is protein-bound cadmium deposited?

In the chloragogen tissue.

What is chloragogen tissue?

Excretory tissue located in the intestinal wall of annelids.

What does the white in the cross section of L. hoffmeisteri indicate?

Solid cadmium granules in the chloragogen tissue.

What is the black area on the lower left of the L. hoffmeisteri cross section?

The gut lumen.

What do annelids use chloragogen tissue to sequester?

Silica they naturally take up from the environment.

What else does the chloragogen system appear to allow annelids to sequester?

Heavy metals.

What is hyperdominance?

The overabundance of certain species in a community.

What does hyperdominance usually indicate?

A polluted waterbody.

What does hyperdominance of oligochaete worms indicate?

The water is polluted.

What can species-level identification of tubificid worms determine?

The type of pollutants.

Which pollutants can species-level identification of tubificid worms determine?

Copper, hexavalent chromium, cadmium, lead, and poly aromatic hydrocarbons (PAHs).