On pages 100-102, Moalem describes the relationship between the Plesiometa Argyra spider and the Hymenoepimecis argyraphaga wasp. The wasp will sting the spider's abdomen, laying an egg on the spider that will soon hatch into a larva. This larva then feeds off the spider's blood, until it injects the spider with chemicals that will cause the spider to build a web in order to protect the larva's cocoon. Eventually the spider will stop moving and be killed by the larva, who will use the spider's web to build a cocoon for itself. After about a week and a half the larva will emerge from the cocoon as an adult wasp. This section relates to Big Idea #4, "Biological systems interact...". This section of the book shows how two different species can have complex interactions with one another. Moalem describes a unique relationship where a parasite is able to change the behavior of it's own host. This example also relates to Big Idea #1, "The process of evolution drives the diversity and unity of life". The wasp uses a unique process to lay and hatch it's larva, which must have been selected by it's environment over time. By making the spider spin a cocoon for it's larva, the wasp is giving it's larva a better chance of surviving and reproducing, allowing this trait to be passed down to future generations. Is the relationship between the wasp and spider a form of commercialism or parasitism? What process is responsible for the creation of the wasp's unique chemical abilities? In what ways could this relationship be a selective advantage for the wasp? In what ways could this relationship be a selective disadvantage?
(Drew Kyser, akyser4@students.d125.org)
The relationship between the wasp and the larva is parasitism as the wasp places its offspring in the spider without consensus. This is because the wasp feeds off of the spiders blood and lives in the spider which does not benefit the spider in a way that this relationship would be a selective advantage for the spider. This relates to Big Idea 4 because the wasp injects itself to live in the spider to interact by sucking the blood of the spider. Also this wasp matches the Campbell definition of parasitism in which a "parasite eats the cell contents, tissues, or body fluid of its host"(p. 570). The wasp takes the blood of the spider and eventually kills the spider after obtaining its web.
ReplyDeleteThe process of the wasps chemical is that it is produced in the wasp larva and when the larva is ready to cocoon, the chemical is injected which makes the spider make a web to protect the wasp cocoon. Then the chemical stuns the spider so that the larva can devour the spider(Moalem 101). The wasps chemical ability most likely comes from natural selection as a selective advantage trait.
This relationship is a selective advantage to the wasp "Since the larva stage of the wasp is defenseless, the egg is planted on the P. argyra spider where it will hatch. The larva will reside on the spider, virtually free of predation, until it becomes old enough to cocoon into the adult stage" (http://bio390parasitology.blogspot.com/2012/03/hymenoepimecis-argyraphaga.html). This parasite gets free safety on a spiders back and free food from the spiders blood. Then, the best advantage would be the spiders web protection of the cocoon since in the cocoon, the wasp is defenseless. This relationship may also be a selective disadvantage because the wasp is more visible as the spider is larger. Therefore, when the spider gets spotted by the spider's predator, the wasp larva also gets eaten.
(Sam Lee, salee4@students.d125.org)
This is a very simple case of parasitism. The Wasp, or "Lady Macbeth" as Moalem calls it, injects its larva into the spider, without the approval of the spider, as Sam stated. I agree with Sam that the spider does not have any consent in the relationship, because the spider is completely oblivious to the sting, and "goes about his business-spinning webs and trapping prey." (Moalem 101) The spider feels no pain, until the "egg deposited by the adult wasp hatches into larva" (Moalem 101) and "makes holes in the spider's abdomen and slowly feeds off its blood." (Moaelem 101) While this relationship is beneficial for the wasp, so far, the spider feels nothing, continuing to spin on. Finally, the wasp continues to kill the spider, by injecting a lethal chemical into it which completely changes the spider's behavior, eventually leaving it motionless, and easy prey for the wasp. The Wasp then uses the webs built by the spider to enter it's final stage of growth, and build its cocoon. The entire relationship skews in the favor of the wasp, because it gets to grow inside of the spider, and then use the spider's work (the web) to grow in once the spider is dead.
ReplyDeleteThe entire proccess is very complex, as Sam mentions. I disagree with Sam, because Sam states that the chemicals injected by the wasp into the spider make the spider create a web. "The wasp induces its host to build a highly modified, physically stable orb web, to which the larva then attaches its pupal cocoon, and to add an otherwise unusual linear silk stabilimentum to this web that may camouflage the cocoon." (ScienceDirect.com). After the spider creates the web, the larva begin to grow inside of the spider, later releasing chemicals which completely change the nervous system of the spider, and change its behavior, eventually leaving it motionless. After the spider is motionless in the center of the web, the wasp "sucks it dry" and disposes of its carcass.
This is an incredible selective advantage for the wasp, because it is able to invade a host, grow its larva inside the host, then force the host to build a place for the larva to grow, then kill the host. This is an ideal situation for the wasp, because as Sam mentions, it is virtually free of predation inside of the spider, and sometimes, the web that the spider builds is with a certain silk form, which may "camouflage the cocoon." (ScienceDirect.com) This relates to Big Idea #1, because it clearly gives the wasp a higher chance to survive and reproduce, because of this selective advantage assisting it to get through the pre-adult phase of its life.
This may only have one selective disadvantage. As Sam mentions, the spider increases in size when the larva have infested it, therefore it becomes larger and more visible to its predators. If the spider is eaten by a predator, then it can not spin the web for the wasp to grow in. Therefore, if the spider is eaten, then the wasp larvae will not grow, therefore not being able to survive or reproduce. This relates to big Idea #1. Survival of the fittest comes literally in the case of the parasitic relationship between these two organisms, because if the spider is eaten by a more "fit" organism, then whatever parasite is inhabiting it, will also die.
Journal Source:
William G. Eberhard,
Smithsonian Tropical Research Institute and Escuela de Biología, Universidad de Costa Rica, Ciudad Universitaria, Costa Rica
Andrew Komarov, akomaro4@students.d125.org