Symbiotic Relationships

This topic submitted by Laura Broseke ( at 12:06 AM on 6/10/04.

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Symbiotic Relationships
Marine Ecology Summer 2004
Laura Broseke

Symbiotic relationships are extremely prevalent everywhere in our world. They occur within our ecosystems, our homes, and our bodies. These relationships are crucial in the maintenance of the intricate system that we live within. A major place where symbiotic relationships occur is in the ocean. A very minute, but spectacular part of the ocean is the coral reef. Symbiotic relationships are responsible for the existence of the coral reef because of the relationship between the coral polyps and the zooxanthellae algae that form the actual living coral reef (Rattner, 2001). It is this life from symbiotic relationships that makes the coral reef so attractive to other life forms, and thus makes it such a spectacular place.
Symbiotic relationships can be categorized into three different parts. The first type of relationship is the mutualistic relationship. This type of relationship describes a living characteristic of two different organisms that live in close proximity to each other, and each organism benefits from the effects of the other organism’s activities. A second type of relationship is a commensalistic relationship. This type of relationship is present when two different organisms live in close proximity to each other, and one organism benefits from the other organism’s activities, while the other organism is not harmed nor helped by the activities of the other organism. The third type of relationship is a parasitic relationship. This relationship is characterized by two different organisms that live in close proximity to each other, and one of the organisms, the parasitic organism, benefits at the expense of the other organism, or the host (Fenner, 2004). The presence of these three different types of relationships is very important to the balance of life on the coral reef.
There are many species that are involved in one or more of these types of relationships. In fact, every species on the coral reef is involved in a sense that the life of the actual coral of the reef assists in the maintenance of the other life forms on the reef. Mutualistic relationships may be the most common type of relationship on the coral reef. This relationship is exhibited by many different species in many different ways. An example of a mutualistic relationship would be the cleaner fish that works with larger fish to remove parasitic fish and diseased or nerotic tissue from their scales, gills, or mouths. This cleaning may take place casually or appear to happen in certain “stations” like a car wash, except the cleaner fish are the soap, and the larger fish are the cars. The relationship may take place between species that are closely related phylogenetically, or more distantly related. One species of fish that act as cleaners when they are young is a hogfish, and another species is a wrasse (Fenner, 2004).
Commensalistic relationships occur very often on the coral reef, many times for camouflage and the protection against predators. This relationship is important for the organism that is being camouflaged, but does not aid in the life of the other organism, but does not harm it either. Examples of species that work in this type of commensalistic relationship are the pygmy seahorse, and a sea fan. The fan works are a camouflage for the seahorse, and the seahorse benefits because of the deception from the predators (Fenner, 2004).
Parasitic relationships are also common on the coral reef, but usually occur in a more destructive manner. One of the organisms will use the host’s nutrients or energy in order to aid in its own life, and slowly kill the host, or allow it to maintain its like in order to maintain the parasite’s life. An example of a parasitic relationship is the goby fish that is the host to a copepod crustacean (Fenner, 2004). Another example is a type of barnacle, the Sacculina carcini, which infests a host crab. This barnacle actually finds a hole in the exoskeleton of the crab, so microscopic hairs can penetrate the hole and inject a few cells, and then has a “slug” appearance on the underside of the crab, eventually covering most of the crab’s body. The barnacle dissolves nutrients from the crab’s blood, but ceased to trigger any immune responses, so the crab continues with daily life. The female Sacculina lays her eggs in the crab’s brood pouch, and the instinct of the crab is to continue nurturing the contents of the pouch, and aid in the dispersal for future fertilization, which allows the parasite to continue on with the cycle (Zimmer and Bregman, 2001).
Many species interact in these types of relationships because they need to do so in order to maintain their lives. The actual process that occurs within one of these relationships would vary greatly from one species to another, but the reason for parting in this process is essentially the same for all species—survival. Some species may have a relationship that requires direct contact with another species, such as the cleaner fish, and these fish, both the cleaners and those being cleaned, are very trusting. The cleaner fish must depend on the bigger fish not to take advantage of them being in their mouths and eating them, while the larger fish must depend on the smaller fish not to take advantage of them, and eat more than just parasites. There are cases in the cleaner fish scenario where “sneaking” fish may act as a cleaner, but actually partake in some of the flesh of the larger fish (Davidson, 1998).
Other species need not be in direct contact with other organisms, such as the small pilot fish that usually swims with barracudas or sharks in the open ocean in order to be protected from other predators that may be lurking in the open water. A clown fish’s survival is aided by the sea anemone, which has stinging cells within the tentacles to help keep predators away. The clown fish are immune to the sting from the tentacles of the anemone, so they are able to live in the anemone without harming the organism, or being harmed by the organism (Bolin, 2004).
There are also species that use the help of other species for not only protection against predators, but also for transportation. The large humpback whale serves as a playground or mollusks that form barnacle encrustations on the humpback whale’s back. These mollusks gain a method of transportation from the whale, and also are able to filter feed from the ocean currents as the whale travels. Another species that uses larger organisms for transportation is the remora fish. This fish has a fin that actually acts as an organ for suction. The fin enables the remora to attach to the sides of larger fishes and turtles, which allows them to have a method of transportation and a chance at the remnants of food from the larger organism (Bolin, 2004).
Some species even incorporate other species of algae in their tissue systems in order to take advantage of the benefits of photosynthesis that the algae perform. These types of organisms include some jellyfish, and sometimes different types of giant clams.
Other species live together in one dwelling in order to make use of each of the organism’s primary characteristics to maintain survival. Small goby fish and bottom dwelling shrimp live in this type of situation, and the shrimp does most of the digging and maintenance of the dwelling, while the goby’s sharp eyesight is useful to keep watch over the dwelling. As the goby watches for predators, it will flick its tail at the first sign of danger and both organisms will take cover (Fritz, 2004).
The most amazing relationship on the coral reef is the coral itself. The coral polyp is an amazing organism that is able to work with algae in the water to use the energy from photosynthesis, and in turn give the ability to accrete calcium carbonate from the seawater, and build stony protection around itself. This ability to form protection as a result of relationships with other organisms makes the coral polyp an essential part of the coral reef, and a “cornerstone” to the community. The life of the coral polyp attracts other species, and these organisms then live in symbiotic relationships with the coral, and thus make the coral reef so diverse (Fritz, 2004).
These mutualistic and commensalistic relationships are hypothesized to have originated from parasitic relationships. This is supported by the idea that as certain organisms served as parasites on other organisms, the hosts developed ways to make use of the metabolic and digestive wastes, and thus begin to form a mutualistic relationship. This would have occurred over a long period of time while many organisms of one or several species maintained the parasitic relationship with the host, and over the long period of time, the host was able to evolve and maintain the parasite’s presence, and thus live in a mutualistic relationship with the other organism. Through this evolution, many species live in very intricate in interesting ways together, and contribute to the beauty of the coral reef (Yamamura, 1996).
Coral reefs are very peculiar environments that almost seem to be mysterious. The creatures and ways of life that exist on the coral reef are like none that we may encounter on our terrestrial environment. The amazing relationships that exist between so many of the species on the coral reef add to the complexity of life that goes on under water on the mysterious coral reef.

Work Cited.
Bolin, R. 2004. ‘Symbiosis’ Courier Journal. No Vol.: No page.

Bregman, M and Zimmer, C. 2001. ‘Animal Parasites’. Science World. No Vol.: No page.

Davidson, OG. 1998. ‘The Enchanted Braid’. No Vol.: Page 89.

Fenner, B. 2004. ‘Cleaning Symbiosis Among Marine Fishes’. Web access:

Fritz, S. 2004. ‘The Living Reef’. Smithsonian Ocean Planet. Popular Science. No Vol.: No page.

No author listed. 2004. ‘Forming Partnerships’. Web access:

Rattner, R. 2001. ‘Good Neighbors?’ Zoogoer. Vol. 30: Issue 4. No page.

Rudman, WB. 1998. ‘Symbiosis and commensalism’. Sea Slug Forum. No Vol.: No page.

Yamamura, Norio. 1996. ‘Evolution of mutualistic symbiosis: a differential equation model’. Res. Popul. Ecol. Vol. 38: No. 2.

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