engleski

Green hydra symbiosis and symbiogenesis

Symbiotic associations are of a wide significance in evolution and biodiversity. Symbiosis is a long-term close relationship between two or more species which belong to differently named categories. Green hydra is a typical example of endosymbiosis. In its gastrodermal myoepithelial cells it harbors individuals of unicellular green algae. Each alga is placed inside one vacuolar membrane forming the symbiosome. Symbiogenesis denotes new form, function or metabolic capability that one symbiotic partner gained from the other. Newly described mechanisms of the hydra-alga symbiosis are widening of perialgal space, degradation and loss of symbiosome, fusion of symbiosomes and perialgal spaces, and their role in regular re-assembling of the symbiosis (1). For the first time endosymbiotic algae from green hydra have been successfully isolated and permanently maintained in a clean lab culture. By microscopical, morphometrical and molecular analyses it was established that different genera of unicellular green algae could be present as symbionts in green hydra, only one at a time. Endosymbiotic alga performed as the “ stronger” symbiotic partner in green hydra symbiosis, but once isolated, endosymbiotic alga proved to be less resistant to environmental conditions than the aposymbiotic one. The results referred to the fact that symbiogenesis in green hydra has probably not been finished yet.

green hydra; symbiosis; symbiogenesis; endosymbiotic alga

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