Interactions

            The rainbow darter, similar to numerous other animals, lives every day in response and according to its interactions with other species. Take for example, the Ptychobranchus occidentalis and Venustaconcha pleasii, parasites that attach to the gills of the darter and encapsulate themselves in the host's tissue. These glochidia larvae of some freshwater mussels cling onto the fish for a period of anywhere from a few days to multiple weeks, or anytime after they develop into free-living juveniles. These parasites often times increase ventilation rates of the Etheostoma caeruleum species, restricting their activity levels. In some cases, the darters have lost body size and have showed significantly weaker responses to predation risk (Crane et al., 2011).              

            Additionally, it is important to consider the interactions the rainbow darter has with the human population, rather than just other parasitic species. One study in particular was performed in a stream by snorkeling biologists in order to determine the fish's responses to chemical alarm cues. They exposed the species to skin extracts that served as cues, and in the presence of the alarms, the rainbow darters showed a significantly higher amount of latency to move. This experiment and interaction between the Etheostoma caeruleum and humans indicates that the fish can sense alarming signs and respond with the appropriate behaviour like, in this case, freezing and resisting movement (Crane, Mathis, and Woods, 2009). Although considered an experiment, this is actually a beneficial interaction since it provides scientists with information in regards to the rainbow darter species and how it would respond in similar situations.              
           
            Another study was performed on the rainbow darters, however in this case, to collect information that would pertain and help in the understanding of another species of fish, the yellowcheek dater, also known as Etheostoma moorei. Since this fish is extremely endangered, biologists did not want to test their hypotheses in fear of harming them more, so instead they used the rainbow darters, a fish which is surprisingly abundant in population. This surrogate species assisted in proving the hypotheses correct, therefore allowing scientists to work with the yellowcheek darter without fear of harming the fish (Johnson and Weston, 2008).              

            Ultimately, the rainbow darter has and will continue to prove itself useful in both human interactions as well as illustrating relationships between itself and other species. Much information can be sought out and obtained by analyzing this type of data and conducting similar experiments.

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