Friday, February 28, 2014

Symbiosis: Relationship Status

Defining Symbiosis 

When it comes to relationships, nobody wants to feel used. Figuring out the perfect balance of give-and-take is quite tricky. For parasites and other organisms, “relationship statuses” are quite complex. The term symbiosis refers to an association that is both close and prolonged between at least two organisms of different species [1]. This association can be further categorized into three forms: mutualism, commensalism, and parasitism [6]. Furthermore, these broad categories also contain subcategories. For example, mutualism can be trophic, dispersive, or defensive [6]. This means two organisms are either equally sharing resources, one is providing resources and the other services, or both are providing services to each other respectively [6]. Given these details, it is evident that deciphering between these three forms can be a bit problematic. 

So, Which Relationship Is It?
When examining symbiotic relationships, one must take into account both costs and benefits of the species involved. In the case of the hermit crab and its sea anemone(s), the advantages that the species gain are difficult to categorize.

Hermit Crabs and Sea Anemones [3]
In “The Art of Being a Parasite”, Claude Combes claims that the hermit crab and its sea anemone(s) have a mutual relationship [2]. The anemone, which is attached to the shell of the crab, provides protection for the crab, while in turn becoming more mobile as a result of its attachment [2]. However, is this trade-off significant enough to label as an example of mutualism? This is where things become complex. Sandy Vigil, author for Demand Media, says these two species actually display commensalism [3]. Why is this important? Well, mutualism refers to two organisms sharing equal benefit in a relationship. On the contrary, when one organism benefits and the other remains unharmed one considers the relationship to be commensalism [3]. Vigil acknowledges the same advantages that Combes presents: protection for the hermit crabs and increased mobility and a subsequent steady food supply for the sea anemones. So, why do they view the interaction differently? It seems that Vigil believes that due to the symbiotic relationship being necessary for the survival of the hermit crab and not the anemone, the two are not equally benefiting. Therefore, the interaction exhibits characteristics of commensalism [6]. If these organisms could talk, the crab would most likely side with Combes and the anemones with Vigil. The type of relationship shared by these organisms all comes down to perception. Thankfully, there are cases where organisms do share a clearly defined symbiotic relationship and the perspective towards their relationship is consistent among observers.

Honey Bees and Flowering Plants

The relationship between Apis mellifera, commonly known as the honey bee, and angiosperms (flowering plants) is a great example; these two species share an undeniably mutualistic relationship [5]. Both the honey bee and the flowering plant rely on each other for survival. There are three different groupings of honey bees which include: the queens, drones (males), and the workers. The worker bees are the pollinators [5]. Pollination is not an active process; instead, it occurs passively as the workers search for food. During this search, the bees fly from one flower to another collecting pollen and nectar. As the bees acquire these necessities, they transfer pollen among the plants which fertilizes them [4]. In this case, it is obvious that both species need each other to survive and working together is in the best interest of them both.

Is There Ever a Right Answer?

Ultimately, when examining the interactions between organisms it is up to the individual to decide which symbiotic relationship is being displayed. In some cases, like the honey bees and flowering plants one will find it easy to decipher between the choices. On the other hand, in cases like the crab and its anemone(s), it will take more effort for one to come to a conclusion. The complex nature of symbiotic relationships is not in the interactions themselves, but in the details of the interaction. Are the organisms equally benefiting by sharing resources, only using another species for transportation, or simply providing shelter [6]? It is up to the spectator to decide.



  1. Another example of mutualism can be found between cleaner fish and their clients. The cleaner fish will eat ectoparasites found on the surface of the client's skin. The cleaner fish receives nutrition while the client benefits by having parasites removed from its body. In the process, the cleaner fish may also consume some mucus from the client's skin. This could be considered parasitism or just a cost the client has to pay in order to get clean. While cleaning the inside of a client's buccal cavity, the cleaner fish risks the possibility of being swallowed. When carried out as beneficial to both organisms, this symbiotic relationship can be classified as mutualistic.

  2. I think that your two examples are great when looking at symbiotic relationships. One question or idea that comes to my mind is which type of relationship allows for the best survival of a species? I think that it depends on the particular species and what each organism requires for survival. In chapter six of "The Art of Being a Parasite", the author discusses the Red Queen Hypothesis, which Van Valen "suggested that the main motor of evolution for all species is the presence of other species with which they compete." After reading this, do you think all symbiosis relationships are important, or just competition? Just some food for thought.

  3. Those are two great examples depicting symbiotic relationships. I would also like to add, that there can also be "cheats" in these associations. In chapter five of "The Art of Being a Parasite", the author explains how false cleaner fish can take advantage of their host by copying the behavior of original cleaners. By looking similar to cleaner fish, these copy cats can get close to their targets and bite off pieces of the host. These mutualistic associations may provide great benefits, but some organisms can exploit these relationships.

  4. I find it interesting on how we classify relationships, whether it be mutualistic, slightly parasitic, overly parasitic, and some species just being plain out jerks to others. We can't realistically keep a tally of "pros and cons" a species poses on another when a relationship occurs, but we can realistically decide if an organism willing to engage in said relationship. I would much rather argue if an organism is engaging in a mutulatisic or commensa-listic relationship vs a parasitic one or in other words group mutualism and commensalism together rather than have 3 separate categories.

    I cannot argue that commensalism does not 100% exist, but I can argue that if one species did another near its personal space, it would do something about it. A common example of commensalism can be seen with cattle egrets that eat insects stirred up when cattle or other livestock walk through fields. In this case, many have argued that the egret gets free food and the cattle gets nothing. But maybe the egrets are helping the cattle by decreasing the amount of bites they will receive when they walk through the field. In the end the cattle allow the egret to follow them (they could easily scare them off ), much like how the anemone willing gets on the hermit crab shells. We did discuss how it seems like the hermit crab was getting more than its fair share in the relationship, but in the end the anemone chooses to stick it out with the crab, and we should avoid trying to labeling it as parasitic.

    My overall question would be should we allow to this to be a separate category in deciding what kind of relationship is being observed? Should the categories with tally marks be pro, cons, and willingness?

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