The bolas spider, Mastophora hutchinsoni, attracts Lacinipolia renigera and Teta

Question

The bolas spider, Mastophora hutchinsoni, attracts Lacinipolia renigera and Tetanolita mynesalis males by mimicking the female moth sex pheromones. However, as the prey species use different pheromone blends we conducted experiments to determine how this is accomplished by the predator. The periodicity of L. renigera mate-seeking activities occurs early in the scotophase, whereas male T. mynesalis are active late at night, corresponding with periods when these moths are captured by the spider. The pheromone blend of early-flying L. renigera interferes with attraction of late-flying T. mynesalis to its pheromone in a dose-dependent manner, suggesting the spider must always produce a single sub-optimal "compromise" blend for both species or that it adjusts its allomonal blend to optimize capture of the respective prey species at different times during the night. We delayed (L. renigera) or advanced (T. mynesalis) the periodicity of male activity through photoperiodic manipulation and found that the bolas spider attracted both prey species outside their normal activity windows. These results support the idea that bolas spiders the produce components of both species at all times rather than producing the pheromone of each prey species at different times of the night. However, using couple gas chromatography-electroantennography, we also demonstrated that the spider decreases its emission of the L. renigera pheromone over the course of the night. This modification should reduce the behavioral antagonism of the L. renigera pheromone on T. mynesalis males and increase the predator's success of attracting T. mynesalis during this prey's normal activity window late at night.

Explanation / Answer

In a research study, researchers have a research question in mind which they want to solve and hence, that is the reason that they are doing the study in the first place. This research question is framed in the form of a sentence or statement that can either be proved or disproved. For example, say, I want to know at what time the early bird catches the worm.

My research question would be: At what time does the early bird catch the worm?

The statement would be: The early bird catches the worm at 5 am.

Now, as a researcher, my job would be to set up an experiement to find out if the early bird does catch the worm at 5 am or not.

In this example, the statement under testing or experiementation is called the Null hypothesis. In the event that I prove that the early bird does catch the worm at 5 am, it is considered that the null hypothesis is accepted. However, if I find out that the early bird catches the worm not at 5 am but at 6 am, then the null hypothesis is rejected. And another hypothesis called the Alternative hypothesis is accepted, which is a statement that is expected (or hoped) to be true instead of the null hypothesis.

In the research summary posted in your question, the scientists want to figure out how it is possible that the spider can imitate the female sex pheromones (which are different for different species) of 2 different types of moths, which are active at different times of the night and without causing any intereference to the attraction of the moths to it. The scientists have stated that the pheromones of the early active moth (L. renigera) interferes with the attraction of the late flying moth (T. mynesalis), in a dose-dependent manner. This means that more the amount of early flying moth pheromone, more is the interference.

Hence, the null hypothesis would be: The spider produces a single sub-optimal (that is, quantity less than the quantity of pheromone required to get best/optimum attraction) compromise blend for both species (so that there is no interference in attraction) OR the spider adjusts the allomonal blend (chemical substance that one species emits to cause a favourable reaction in another species) to optimize capture of each moth at different times of the night.

Through experimentation, the scientists have found that even if the pheromones are produced at different time intervals outside the active time window, the spider can still attract the moths. Hence, they have concluded that the spider produces both pheromones of both moths all the time. Consequently, the null hypothesis is rejected and the alternative hypothesis is accepted.

The alternative hypothesis would be: The spider produces both pheromones of both species at all times.

The scientists have also mentioned that as it gets later into the night, the spider decreases the release of the early flying moth pheromone so that it doesn't interfere with the attraction of the late flying moth. This is in support of the alternative hypothesis because even though the amount of the pheromone is decreased, the spider doesn't stop producing it and thus, the spider produces both pheromones of both moths all the time. And it is able to capture both moths (as reported in the summary).

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