Some organisms that appear at first glance to be parasites actually provide substantial benefits to their hosts

Saturday, March 15, 2014 by: David Gutierrez, staff writer
Tags: parasites, mutualism, symbiotic relationships

(NaturalNews) The relationships between organisms of different species may be far more complex than they initially appear, and may defy division into the simple categories of "mutualism" and "antagonism/parasitism." For example, at first glance many species of yucca moths appear to be parasites upon the plants (yuccas) from which they take their name. Indeed, the larvae from the genera Tegeticula and Parategeticula are only able to survive by eating the seeds of the yucca. Yet, at the same time, yuccas can only be pollinated by a moth from one of these genera. With this detail, the relationship is transformed from one of parasitism (the moth parasitizing the seeds of the plant) to one of obligate mutualism (in which the relationship provides benefits to both organisms that neither one can survive without).

Biologists have learn that careful observation is needed to determine the nature of any relationship between two species. Thus, while mites are notorious parasites upon honey bees, and varroa mites have been implicated as a major culprit in colony collapse disorder, other varieties of mites have very different relationships with their insect hosts. For example, some mites appear to harmlessly hitch rides on the backs of carrion beetles until the beetle finds a rotting carcass in which to lay its eggs. At this point, some of the mites dismount to feed upon the other insects dwelling within the carcass, such as maggots. This opportunistic behavior actually provides a benefit to the carrion beetle, by reducing food competition for its offspring!

Another example is the American alligator, which digs deep holes in swampy habitats so that it can remain wet even during times of drought. This provides the alligator an added benefit of bringing prey straight to it, since such "gator holes" may provide the only source of drinkable water around for miles at times. Although from the point of view of its prey the alligator is certainly an antagonistic species, the picture is more complicated. Without the concentration of water provided by gator holes, many species -- including the alligator's prey, followed quickly by the alligator -- would surely go extinct.

Sources:

http://www2.mcdaniel.edu

http://www.marietta.edu