Escaping predators, but, only to get parasites.
It's almost like getting out of the frying pan and into the fire. What
you are seeing in the picture are Daphnia dentifera individuals, that
are small, planktonic crustaceans, between 0.2 and 5 mm in length. The
ones on the top right and bottom middle of this image are uninfected;
the other four Daphnia are infected with Metschnikowia (yeast infecti
on).
It was commonly believed that higher rates of predation must directly
help the species as it removes the weak and diseased individuals from
the population. But in the case of Daphnia at least, it has been
observed that higher rates of predation is actually making them more
susceptible to infection.
When Daphnia sense certain distinct
chemicals exuded by their predators, they grow larger, making it more
difficult for the predators to eat them. But larger Daphnia, it turns
out, also consume greater quantities of a deadly yeast parasite, known
as Metschnikowia. Furthermore, once inside a larger Daphnia, the
parasite appears to release more spores, which go on to infect other
water fleas. (Source 4)
Hence, it has been observed that
Daphnia became more susceptible to the yeast infection in lakes with
fewer resources and higher vertebrate predation, but they evolved
towards increased resistance in lakes with increased resources and lower
predation.
Source:
1) http://www.sciencemag.org/
2) Functional Ecology: Volume 25, Issue 5, pages 945–953, October 2011
3) http://
4) http://www.the-scientist.com/
Image: Credit- Meghan Duffy, from,
http://
Escaping predators, but, only to get parasites.
It's almost like getting out of the frying pan and into the fire. What you are seeing in the picture are Daphnia dentifera individuals, that are small, planktonic crustaceans, between 0.2 and 5 mm in length. The ones on the top right and bottom middle of this image are uninfected; the other four Daphnia are infected with Metschnikowia (yeast infecti
on).
It was commonly believed that higher rates of predation must directly help the species as it removes the weak and diseased individuals from the population. But in the case of Daphnia at least, it has been observed that higher rates of predation is actually making them more susceptible to infection.
When Daphnia sense certain distinct chemicals exuded by their predators, they grow larger, making it more difficult for the predators to eat them. But larger Daphnia, it turns out, also consume greater quantities of a deadly yeast parasite, known as Metschnikowia. Furthermore, once inside a larger Daphnia, the parasite appears to release more spores, which go on to infect other water fleas. (Source 4)
Hence, it has been observed that Daphnia became more susceptible to the yeast infection in lakes with fewer resources and higher vertebrate predation, but they evolved towards increased resistance in lakes with increased resources and lower predation.
Source:
1) http://www.sciencemag.org/
2) Functional Ecology: Volume 25, Issue 5, pages 945–953, October 2011
3) http://
4) http://www.the-scientist.com/
Image: Credit- Meghan Duffy, from,
http://
It's almost like getting out of the frying pan and into the fire. What you are seeing in the picture are Daphnia dentifera individuals, that are small, planktonic crustaceans, between 0.2 and 5 mm in length. The ones on the top right and bottom middle of this image are uninfected; the other four Daphnia are infected with Metschnikowia (yeast infecti
on).
It was commonly believed that higher rates of predation must directly help the species as it removes the weak and diseased individuals from the population. But in the case of Daphnia at least, it has been observed that higher rates of predation is actually making them more susceptible to infection.
When Daphnia sense certain distinct chemicals exuded by their predators, they grow larger, making it more difficult for the predators to eat them. But larger Daphnia, it turns out, also consume greater quantities of a deadly yeast parasite, known as Metschnikowia. Furthermore, once inside a larger Daphnia, the parasite appears to release more spores, which go on to infect other water fleas. (Source 4)
Hence, it has been observed that Daphnia became more susceptible to the yeast infection in lakes with fewer resources and higher vertebrate predation, but they evolved towards increased resistance in lakes with increased resources and lower predation.
Source:
1) http://www.sciencemag.org/
2) Functional Ecology: Volume 25, Issue 5, pages 945–953, October 2011
3) http://
4) http://www.the-scientist.com/
Image: Credit- Meghan Duffy, from,
http://
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