Friday, March 30, 2012

Alpheid Shrimp/Gobbid – The Landlord and his Tennant


Introduction: The Alpheid shrimp its Gobbid (the goby), engage in a very interesting mutualistic relationship.  While the shrimp burrows in the sand digging a home for the two, the goby keeps an eye out for predators and any sign of danger.  Goby-Shrimp relationships can be found in numerous tropical regions but extensive research has been done in the Red Sea, Japan, and Hawaii.  Over 70 different species of gobies have been associated with shrimp so far [1].  Specific shrimp goby partnerships often change.  When researchers tagged the shrimp and the gobies, often times individual shrimp goby pairs split up and found new partners [1].

Description of the Relationship:  Many researchers have tried to figure out how the shrimp/goby relationship has formed.  Most have come to the conclusion that the relationship evolved as a way for both species to avoid predation [1].  Many Alpheid shrimp are nearly blind, so without their goby partner, they are unable to detect predation [2].  The two find each other in different ways.  The goby relies on vision to find its shrimp partner, where as the shrimp relies on chemical attractions to the goby[1].  While the shrimp digs through the sand, the goby hangs out behind him looking out for danger.  Because the shrimp is nearly blind, he keeps one antenna on the tail of the goby at all times [1].   When the goby detects danger, he slightly flicks his tail, which signals the shrimp to dart into its burrow, with the goby following behind [1].  Because the partnership helps reduce encounters with predators and it does not involve any metabolic processes, this type of mutualism would be considered facultative.  Each, individual could live without the other, but when, paired together, it decreases death caused by predators.

Cost/Benefit Analysis:  There is a fairly even ratio of cost to benefit in the shrimp/goby interaction.  While the shrimp uses a lot of energy to burrow in the sand, he greatly benefits from the protection of the goby because without the goby, the shrimp could not see its predators and would be easy prey.  Although the goby acts as a look out for the shrimp, he gets in return a place to hide from predators.  The shrimp always keeps his antenna in contact with the goby as to not lose his partner.  The shrimp puts more effort into this relationship but also arguably has more to lose without it.