Caro A. auteur aut IRD Got P. auteur aut IRD Bouvy Marc auteur aut IRD Troussellier Marc auteur aut IRD Gros O. auteur aut IRD text journalArticle eng text/pdf born digital access The bivalve Codakia orbicularis, hosting sulfur-oxidizing gill endosymbionts, was starved (in artificial sea-water filtered through a 0.22-mu m-pore-size membrane) for a long-term experiment (4 months). The effects of starvation were observed using transmission electron microscopy, fluorescence in situ hybridization and catalyzed reporter deposition (CARD-FISH), and flow cytometry to monitor the anatomical and physiological modifications in the gill organization of the host and in the symbiotic population housed in bacteriocytes. The abundance of the symbiotic population decreased through starvation, with a loss of one-third of the bacterial population each month, as shown by CARD-FISH. At the same time, flow cytometry revealed significant changes in the physiology of symbiotic cells, with a decrease in cell size and modifications to the nucleic acid content, while most of the symbionts maintained a high respiratory activity (measured using the 5-cyano-2,3-ditolyl tetrazolium chloride method). Progressively, the number of symbiont subpopulations was reduced, and the subsequent multigenomic state, characteristic of this symbiont in freshly collected clams, turned into one and five equivalent genome copies for the two remaining subpopulations after 3 months. Concomitant structural modifications appeared in the gill organization. Lysosymes became visible in the bacteriocytes, while large symbionts disappeared, and bacteriocytes were gradually replaced by granule cells throughout the entire lateral zone. Those data suggested that host survival under these starvation conditions was linked to symbiont digestion as the main nutritional source. specialized 034 084 75 10 3304-3313 2009 0099-2240 https://www.documentation.ird.fr/hor/fdi:010046068 10.1128/aem.02659-08 0099-2240 [F B010046068] https://www.documentation.ird.fr/hor/fdi:010046068 https://www.documentation.ird.fr/intranet/publi/2009/05/010046068.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2009-06-08 2017-08-23 fdi:010046068 fre