Figure 4. Clown fish and anemone. Figure 5. Sea spider. Page 2 of 6. Saylor URL:

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1 Symbiosis The phrase symbiotic relationship simply refers to a close ecological relationship between two different species. These relationships differ along a spectrum from positive to negative interactions. If both species benefit from the interaction, the relationship is considered to be a mutualism. Figure 1. Coral reef When one species benefits and the other is not impacted, the relationship is considered to be a commensalism. When one species benefits and the other species is harmed, the relationship is considered to be either parasitic or predatory or herbivorous. If both species are impacted negatively through a competition over limited resources, the relationship is considered to be competitive. i Figure 2. Coral feeding Symbiotic relationships can vary in intensity. If the organisms are dependent upon each other, the relationship is termed obligate. However, when the organisms can survive with or without this relationship, it is termed facultative. Symbiotic relationships come in many forms that span the tree of life, and they can be found in all ecosystems, from terrestrial to aquatic. One of the most diverse ecosystems which easily contains examples of each relationship type can be found in the ocean, specifically coral reefs. Page 1 of 6

2 Coral reefs are considered to be among the most ecologically diverse systems in the world. Coral reefs are created from small coral animals which are classified in the cnidarian group. As adults, corals are stationary and are considered sessile. They have small soft bodies, each protected by a hard Figure 3. Aerial view of coral reef calcium carbonate skeletal structure that is secreted continuously at the base of the body over the animal s lifetime. ii As coral feed, they use their tentacles to reach out and capture small plankton and fish. Once a potential threat swims by, the coral retreat into their protective skeleton. Coral animals live in communities, and once old coral animals die off and new ones settle on top of the dead skeletons, the coral reef structures will build up substantially over time. iii Figure 4. Clown fish and anemone Corals are not the only animals that live within their reef structures. Many species of fish, fungi, sea turtles, algae, sponges, oysters, clams, shrimp, crabs, sea stars, urchins, and even other cnidarians like jellyfish and sea anemones all call these reefs home. iv With such a diverse assemblage of organisms, it is easy to see how a variety of ecological interactions would evolve Figure 5. Sea spider Page 2 of 6

3 over time. In the coral reef system, a classic example of a mutualistic relationship exists between clown fish and sea anemones. Made famous by Pixar s movie, Finding Nemo, clown fish often hide within the stinging tentacles of sea anemones. The clown fish get protection, while they also scare off potential predatory fish of the anemone and therefore provide protection for their protectors. A commensalism exists commonly in the coral reef between glass shrimp and chocolate chip sea stars. Glass shrimp, as they are named, are almost completely transparent. To hide from predators, they often hop on the back of a chocolate chip sea star for camouflage, while the sea star is completely unaffected. v Parasitic interactions are common in any ecosystem, and the coral reef is no exception. Sea spiders are considered parasites to table coral. Sea spiders often seek protection and will pierce the body of the coral (called the polyp) and live inside them. Herbivory is illustrated in coral reefs by several species, including the long-spined sea urchin as well as herbivorous fish species. These urchins and fish will graze on algae that are commonly found throughout the reef, which will essentially take over and negatively impact the community if populations are not kept in check. vi Predation is also common in these reef communities, and a classic example involves the barracuda fish and the parrotfish. Barracuda fish are fierce predators and regularly seek out prey such as the colorful herbivorous parrotfish. Another example, which reveals some Figure 6. Barracuda fish Page 3 of 6

4 complexity in the coral reef, involves the saddled butterflyfish and the sea anemone. We mentioned earlier that clownfish protect the anemone against their predator, which happens to be a saddled butterflyfish! vii Figure 7. Saddled butterflyfish There are many more types of interactions within not only the coral reef community but in communities all over the world. However, these examples give a glimpse of the complexity that can arise over a long and complex evolutionary history! i Marietta College, Symbiosis, n.d., ii University of Michigan, Ecological Communities: Networks of Interacting Species, 2008, ol_com.html. ii Environmental Protection Agency (EPA), Coral Reef Protection: What Are Coral Reefs? n.d., iii Ibid. iv Ibid. v Canisius College, Canisius Ambassadors for Conservation, Mutualism, n.d., vi The Nature Conservancy, Coral Reefs, 2012, vii The Nature Conservancy, Coral Reefs, 2012, Page 4 of 6

5 Pictures: Figure 1. Coral Reef t_palmyra.jpg Figure 2. Coral Feeding %28soft_coral %29_with_extended_polyps.jpg Figure 3. Aerial View Coral Reef Figure 4. Clown fish and Anemone g Figure 5. Sea Spider pg Figure 6. Barracuda Fish Figure 7. Saddled Butterflyfish Page 5 of 6

6 erflyfish_1.jpg Page 6 of 6