Without some sort of benefit for the epibiotic bacteria, there would be no reason why the bacteria would not seek more preferential habitats. The behaviour of R. exoculata has provided implications of a symbiotic way of life, whereby both individuals benefit from the relationship (Ponsard et al., 2012).
It is, however, widely thought that the epibiotic bacteria benefit greatly from living on and within the body structure of R. exoculata (Gebruk et al., 1993; Petersen et al. 2010; Hugler et al., 2011; Ponsard et al., 2012). In return for the energy supplied by the bacteria, R. exoculata provide beneficial conditions for bacterial growth. The deep sea shrimp can be thought of as bacteria farmers as they give access to the food bacteria need for growth before they are harvested (Gebruk et al., 1993). The shrimp regularly maintain their position in the mixed zone between hydrothermal fluids and the surrounding sea water (Ponsard et al., 2012). This mixing zone contains the chemical compounds the bacteria require for chemosynthesis and, ultimately, survival (Petersen et al. 2010; Hugler et al., 2011; Ponsard et al., 2012). The shrimp also offer bacteria an element of protection from other grazers. Although shrimp may graze the bacteria they harbour the benefit for the bacteria must outweigh or be equal to the cost of an epibiotic way of life (Ponsard et al., 2012). The shrimp’s antennal fanning action adopted to ventilate the bacteria in low flow areas also contributes to making conditions more favourable (Gebruk et al., 1993). The combination of these bacteria benefits makes living on a shrimp more favourable than living out on the substrate, making their relationship truly mutualistic (Gebruk et al., 1993; Ponsard et al., 2012).
In order for the shrimp to provide this bacteria haven R. exoculata must expose themselves to the extreme temperatures of the hydrothermal fluids (Jan et al., 2014). The next section of this blog will investigate how R. exoculata are affected by temperature changes and how they have adapted to cope with them.
Read on to learn about the adaptions to – Temperature