The Evolutionary History Of The Behavior

How did this partnership evolve? What evolutionary benefit is there to needing another species to survive?

Phylogeny describes changes in a species over many generations. In goby-shrimp relationships, phylogeny relates to how these partnerships evolved over time. Before the invention of S.C.U.B.A., researchers lacked the ability to accurately observe and document goby-shrimp relationships. Now, divers can more easily collect specimens and observe these partners’ behavior in marine environments, and delve into how and why these animals choose to associate with each other. Although not much is known about this particular pairing, there has been a lot of research conducted on the phylogeny of symbiotic relationships in general. Most researchers have come to the conclusion that, like many other symbiotic relationships, the shrimp-goby pairing evolved as a way for both species to avoid predation (Karplus 1987.)

Above: A visual representation of the three types of symbiosis (via

Symbiotic relationships in general have arisen out of the need of two (or more) organisms to achieve certain separate survival aims. Developing a symbiotic relationship increases the chances of at least one of the organisms achieving those aims. In populations, some organisms will have traits that are more advantageous to successful reproduction than others. Individuals with these traits are favored by natural selection. The success or failure of traits depends on population pressure -- circumstances that make it more difficult for individuals to survive. Most symbiotic relationships probably started out as facultative [Grabianowski], but eventually, the symbiosis became more useful in finding food, shelter or whatever else the symbiotes derived from one another. Over evolutionary time, it became more advantageous for the symbiotes to work together. If this goby/shrimp pairing kept occurring, coevolution would then have occured since the pairing would result in higher survival rates for both species. Therefore, both organisms would eventually incorporate the symbiotic relationship into their life histories.