Parasites: Site Selection Process Essay

Parasites have evolved in a very specific and selective way throughout generations. Specific parasites have specific factors that influence their site selection process and that work in favor for the parasites. One important component that influences the parasite to become site specific is being host specific, which in turn affects the ability of extracting resources. The more efficient it is in extracting resources the better the chance of reproducing, which then increases the fitness of the parasite. Fitness plays a huge role in determining how successful the parasite may be.

Few other factors that contribute to the site selection process are transmission, survival and reproduction. Since the parasites are in a very predictable environment within the host, they are known to have genetically fixed behaviors inside the host. This fixed action allows us to predict the exact behavior the parasite will make before it makes it to its final destination, which can be anything that will allow for greater fitness. Since parasites are extremely site specific within the host, the parasite to becomes host specific.

As the parasite becomes host specific it allows the parasite to have morphological changes that will aid in the extraction of resources from the host. “It has often been notes that the site selection process often has a connection with the biology of the parasite. We can often relate to this by looking at the strigeoid tremaatodes and the specific sites they tend to occupy in the fish” (Matisz 2010). In order to further test the site selection process a group of research tried to infect different types of fish with metacercariea and see how long it would take them to actually get to the brain.

After monitoring the fish and the metacercarie for 24 hours, they were able to confirm that they migrated to specific places in the brain via spinal cord and then cranial nerves. More specifically they were able to find a lot of the metacercaire in the optic lobe of the fish via an electronic microscope. However, the bigger question is why would the parasites participate in such migration and what benefits does this give the parasite. The major answer behind this phenomenon tends to be the idea of fixed action patterns. Certain stimuli often offer fairly predictable condition within an environment”(sukhdeo 1997). These predictable behaviors often become fixed over time and offer a huge fitness advantage. Due to the genetically fixed patterns, parasites have become site specific. This provides them with resources that will aid their growth and survival. Genetically fixed patterns definitely play a huge role in the site selection process, but morphological changes tend to be just as important. Why may this be?

Well, the parasite may be genetically fixed to get to a specific location within the parasite but, what will aid in the survival of it once it gets to the designated location. One key important change the parasite will go through is morphological changes. Take for example if a parasite were to live on the gills of a fish. It would have to overcome the turbulence of the water to efficiently extract resources and at the same time not get washed off. Therefore, with the specific site a parasite adapts to there are also specific morphological changes that run parallel with the site.

A recent study that was done on ecto-parasite affecting their host had showed that these monogeneans caused some severe damages to the respiratory tract and the heart of the host. The group of researchers went around New Jersey collecting many different fishes and tried to compare the number of metaceraie and the effects it had on the host. The results they had found were quite interesting. They were able to conclude that every time the host had some type of morphological change to overcome the parasite, the parasite responded by developing a counter adaption to the host.

These adaptive changes could have been made to benefit the parasite, benefit the host or to benefit neither and could just be a byproduct of the infection. For example, lets take a look at the gill of the fish where most of the ecto-parasite tend to affect. A possible morphological change that can occur would be the gill tissue of the fish ultimately increasing the surface area. Now why would this occur? Well, it is thought that this might have occurred because the fish is trying to compensate for the loss of oxygen from the affected gill tissue.

Since the ecto-parasite is on ll it is extracting resources from the site making it difficult for the fish to breathe. This particular example shows how extremely site specific the parasite are and also shows how there are morphological and behavioral changes that occur to extract resources efficiently from the fish. In the future, many different approaches could be taken to observe the different patterns site specificity as on the parasite. One factor that is commonly not taken into consideration when talking about site specificity and the behavior of the parasite is the parasites perspective.

A few factors that can affect behavior of the parasite can be age of infection, immune response, increase in size of parasite population or simply a change in the host diet. A lot of the times it is thought that parasites take a certain pathway that lead to their specific site, and it is often misunderstood for that fact that they have two different paths to choose and they end up taking one that becomes fixed. However, there is more involved in this than just simply making a decision. It can be the environment made the parasite choose that path or because it there was a higher reproductive success in that specific path.

I believe there is a lot more involved in the path that parasites take. Furthermore, a important concepts that need to be taken into consideration when talking about reproductive success is specific trade off the parasite has to give. Although the parasite wants to produce more eggs, there is often more pathology also involved with the bigger body. Due to these specific tradeoff that are involved with the increased fitness of the parasite there may be more involved with the specific site and behavior of the parasite.

Next, when it comes to choosing the specific resources within the host there has to be some type of hierarchy the parasite has in deciding which resources is better for them. I believe that different parasites tend to regard different resources in a different manner. For example, certain parasites like the brain better than the heart whereas others may like the lung. This all comes down to what resources are obtained form those specific location in aiding the survival and transmission process. In conclusion, parasites have evolved in such a way that they have predictable behavior within the host.

Also, they are known to be very site specific, which means it is very rare for two parasites to interact within the host. Site specificity offers a few advantages to parasite. First of all, it makes the parasite very host specific. It also aids in the survival and the reproduction process by efficiently extracting resources from the host. In order for those factors to hold true the parasite has to have morphological changes that will allow the parasite to survive in the adverse condition within the host.