Interactions

Symbioses

          Some other species can be found living inside of or on Stichopus chloronotus. One of these species is the pearlfish Carapus homei (also known as Encheliophis homei). This fish can be found in both the respiratory trees and coeloms of these sea cucumbers, but it is not thought to be parasitic (Trott 1970; Trott and Trott 1972). These fish can be sexually paired in some other holothurians hosts, however they are not generally found in sexual pairs within Stichopus chloronotus (Trott 1970).

         Another species that is symbiotic with Stichopus chloronotus is the polychaete Gastrolepidia clavigera. This polychaete is generally found near either end of the sea cucumber’s body, and when disturbed it crawls into the mouth or cloaca (Britaev and Lyskin 2002). The polychaete is parasitic in that it feeds on the tissues of the host, but it is also slightly mutualistic in that it eats copepods (such as Nanaspis moluccana and Chauliolobion forcipatum), which are also parasitic to holothurians (Britaev and Lyskin 2002). Although there are some mutualistic tendencies in this relationship, G. clavigera is generally considered a parasite, since the impacts of it feeding on S. chloronotus are much greater than those of copepods feeding on S. chloronotus (Britaev and Lyskin 2002).


Image: E. homei, a pearlfish often found living inside of S. chloronotus

Nutrients

          While feeding on sediments, sea cucumbers consume significant amounts of microalgae (Uthicke 2001b). At very high densities of holothurians this grazing can be harmful to the microalgae communities, but at moderate densities the presence of holothurians may actually be beneficial (Uthicke and Klumpp 1997). This is possible because of the nutrients carried in S. chloronotus waste products (Uthicke and Klumpp 1997; Uthicke 2001b). The water that passes through the digestive system of Stichopus chloronotus carries forms of nitrogen (Mukai et al. 1989; Uthicke 2001b), usually in the form of ammonium (Uthicke 2001b), as well as small amounts of phosphate (Pomeroy and Kuenzler 1969). The addition of waste to surrounding water has the ability to significantly raise ammonium levels, and this is thought to increase the production of microalgae (Uthicke 2001b). For this reason holothurians are generally seen as beneficial to their ecosystem (Uthicke 2001b).