green hydra, endosymbiotic algae, aposymbiotic algae, adaptation
Green hydra (Hydra viridissima Pallas, 1766) is a classical example of endosymbiosis. Described ultrastructural features of green hydra symbiosis are extensive widening of perialgal spaces, degradation, loss and fusion of symbiosomes. These changes are considered as defensive and protective mechanisms and the endosymbionts show greater viability than their host. Also, a certain degree of independency was noticed and for the first time endosymbiotic algae from green hydra have been successfully isolated and permanently maintained in pure lab culture. Microscopical and molecular analyses of the isolated endosymbionts resulted in the discovery of two hitherto undescribed endosymbiotic species in green hydra. In final conclusion, endosymbiotic algae from green hydra perform as the “stronger” symbiotic partner in green hydra symbiosis. We keep on searching for more evidence and results.