title: Symbiosis between hydra and chlorella: molecular phylogenetic analysis and experimental study provide insight into its origin and evolution.
abstract: Although many physiological studies have been reported on the symbiosis between hydra and green algae, very little information from a molecular phylogenetic aspect of symbiosis is available. In order to understand the origin and evolution of symbiosis between the two organisms, we compared the phylogenetic relationships among symbiotic green algae with the phylogenetic relationships among host hydra strains. To do so, we reconstructed molecular phylogenetic trees of several strains of symbiotic chlorella harbored in the endodermal epithelial cells of viridissima group hydra strains and investigated their congruence with the molecular phylogenetic trees of the host hydra strains. To examine the species specificity between the host and the symbiont with respect to the genetic distance, we also tried to introduce chlorella strains into two aposymbiotic strains of viridissima group hydra in which symbiotic chlorella had been eliminated in advance. We discussed the origin and history of symbiosis between hydra and green algae based on the analysis.
authors.affiliation: Graduated School of Sciences, Kyushu University, Hakozaki 6-10-1, Higashi-Ku, Fukuoka 812-8581, Japan.
authors.forename: Hitomi
authors.initials: H
authors.lastname: Kawaida
authors.forename: Kohki
authors.initials: K
authors.lastname: Ohba
authors.forename: Yuhki
authors.initials: Y
authors.lastname: Koutake
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Shimizu
authors.forename: Hidenori
authors.initials: H
authors.lastname: Tachida
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Kobayakawa
mesh_terms: D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D002708:Chlorella / Q000235:genetics*; D016000:Cluster Analysis; D017931:DNA Primers / Q000235:genetics; D004272:DNA, Mitochondrial / Q000235:genetics; D049810:Genetic Speciation; D006829:Hydra / Q000235:genetics*; D016013:Likelihood Functions; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010802:Phylogeny; D012337:RNA, Ribosomal, 18S / Q000235:genetics; D017422:Sequence Analysis, DNA; D013559:Symbiosis / Q000235:genetics*
chemical_list: D017931:DNA Primers; D004272:DNA, Mitochondrial; D012337:RNA, Ribosomal, 18S