Sunday, March 21, 2010
Mimicry Through Coloration
On pg. 171, Coyne explains that there are 7 species of mosquitoes that all look very like except for slight microscopic differences. Each species has a distinct niche, but only one species, Anopheles gambiae carries malaria. As a result, it has been difficult for humans to fight malaria by targeting the mosquito carriers because the resemblance to the harmless mosquito species. Give another example of cryptic coloration. Why is cryptic coloration a selective advantage for these species? What type of mimicry is this? Furthermore, explain the differences between cryptic coloration and aposematic coloration. It will be helpful to cite Campbell or other outside sources in your answer.
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Wouldn’t the malaria mosquito imitating the normal mosquito be like, reverse Batesian mimicry? Not cryptic coloration? Because the malaria mosquito would be a harmful specie mimicking a harmless specie (instead of a harmless specie mimicking a harmful one, which is normal Batesian mimicry). Because cryptic coloration is when an animal uses camouflage to hide itself and blend into the environment and background, not to disguise itself amongst similar species. On that note, aposematic coloration is different from cryptic coloration, because aposematic coloration is when an animal is brightly colored to warn and ward off potential predators. The purpose of aposematic coloration is the exact opposite of cryptic coloration; aposematic coloration is used to stand out and be extremely recognizable. It is usually animals with strong chemical defenses that display aposematic coloration. (Campbell 1201).
ReplyDeleteOne example of cryptic coloration is the Indonesian Mimic Octopus. Not only does this mollusk change color to blend in with the background, it also changes color, shape, and behavior to mimic other, more harmful animals in the ocean. This is another example of Batesian mimicry. The octopus mimics poisonous and unpalatable species in order to deter predators. The mimicry of the octopus is a selective advantage, because if the octopus mimics harmful species, then it is not likely that the octopus will be eaten, therefore augmenting the octopus’s chances at survival.
http://www.youtube.com/watch?v=H8oQBYw6xxc
At first, Sam's point about reverse mimicry didn't make sense, but upon rereading chapter 54 of Campbell on community ecology, I see what she means. For example, Hawkmoth larva display Batesian mimicry because their defensive coloration mechanism is to look like the green parrot snake, something dangerous. (Campbell 1200-1201) What is happening here with Anopheles gambiae is the opposite; it would be like if the snake was pretending to be a harmless larva to avoid being targeted by snake traps. That being said, cryptic coloration is different from both batesian mimicry and aposematic coloration (which is where instead of trying to look like something else the organism wants to stand out and seem threatening (like the poison dart frog, which is brightly colored to detract predators)) because in this case the organism is using camaflouge. This is a selective advantage because this way, prey like the Canyon tree frog can blend with surroundings and be harder to spot. Arguably, what Anopheles gambiae is doing can be considered cryptic coloration, if someone thinks of other species of mosquitoes as an environment or surroundings with which this species is trying to blend in. Like Coyne points out, we still differentiate between the species of mosquitoes because the groups of organisms are “reproductively isolated” from each other (172), and in not interbreeding with other ‘safe’ mosquitoes, Anopheles gambiae finds relative safety from humans trying to combat malaria; these organisms stay comfortably hidden among other species while we try to figure out which organisms we actually need to target to fight this disease. This relates to the theme interdependence in nature, because one species of mosquito is relying on other species to look similar to ensure a successful cover, which enables the mosquitoes to survive and reproduce.
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ReplyDeleteI agree with Samantha's post that scenario in the prompt is reverse Batesian mimicry is when "a non-harmful species mimics a harmful species" (Campbell 1201). A non-harmful species will want to mimic a harmful because then predators will not want to eat this harmful specie. The scenario with the mosquitoes in Sam's prompt is reverse Batesian mimicry because a harmful species is pretending to be a non-harmful species.
ReplyDeleteCryptic coloration is the same thing as camouflage and makes the organism difficult to spot. Being difficult to spot is a natural selection because predators will have a harder time finding the cryptic colored organism and the cryptic colored organism will be able to live longer and reproduce. Aposematic coloration is when animals exhibit bright colors on their skin to warn other animals that they are poisonous. "Predators are particularly cautious in dealing with potential prey having bright color patterns" (Campbell). Aposematic coloration is having bright colors to warn off predators, and cryptic coloration is being camouflaged with the surroundings to hide from predators.
An example of batesian mimicry is when different butterflies in the rain forest mimic the toxic Heliconid butterflies. By doing so, less predators will want to eat them because the predators think the non-harmful butterflies are toxic. Another example of batesian mimicry is with snakes. The coral snake is really dangerous and is avoided by many predators. The coral snake has a distinctive ring pattern that is mimicked by many harmless snakes so predators will think they are a coral snake and won’t eat them (http://www.wisegeek.com/what-is-batesian-mimicry.htm). An example of cryptic coloration is the uroplatus geckos of Madagascar. The geckos blend in with their habitat that most organisms can't see them (http://rainforests.mongabay.com/0306.htm). Another example of cryptic coloration is the stick insect. The stick insect looks like a stick and when predators come by, the predator can’t thinks the insect is a stick and doesn’t eat the stick insect (http://www.firstpr.com.au/stick-insect/). An example of aposematic coloration is the poison dart frog. The bright colors, like orange, on the frog's skin warn the frog's predators that the frog is poisonous and has chemical defenses. Another example of aposematic coloration is bees. Bees have bright yellow and black stripes on their body. The bright colors warn predators that they have a stinger so predators won’t go towards the bees.
This prompt relates to the theme interdependence in nature. With batesian mimicry, harmless animals have to depend on harmful animals that look like them to avoid predators. With cryptic coloration, the camouflaged animal depends on its surrounding because it has to look like its surrounding to escape predators. With aposematic coloration, the animals depend on its predators to know that bright colors mean that they are toxic.