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[BPT05-03] Variation in mineral precipitates in the gill chamber and digestive tract of Rimicaris from Kairei and Edmond fields, Central Indian Ridge
Keywords:Hydrothermal vetnt , biomineralization, Rimicaris kairei
Filamentous and rod-shape bacteria were observed on the inner surface of the branchiostegites (in the gill chamber) in both types of individuals from both sites; which suggests that coloration and site had little influence on the microbial community in the gill chamber. In brown individuals, the brownish precipitate were aggregations of mineral particles 1 µm or less in diameter, which covered the overall inner surface of branchiostegites. Conversely, the black precipitates in the black individuals, which mainly contained phosphorous and sulfur, was colloidal rather than particulate in nature and enveloped the surface of filamentous bacteria growing from branchiostegites but not the surface of branchiostegites themselves. In the digestive tract, iron oxides, sulfur [S], pyrite [FeS2], marcasite [FeS2], chalcopyrite [CuFeS2], and sphalerite [(Zn,Fe) S] were detected in specimens from the Edmond Field; while Anhydrite was additionally detected in specimens from the Kairei Field. The metal sulfides decreased in density through the digestive tract from the mouth towards the anus in specimens from Edmond, and for Kairei specimens a trend of decreasing Anhydrite and increasing sulfur was found throughout the digestive tract.
To summarize, we revealed that gill chamber precipitates differed in Rimicaris specimens obtained even from the same site; while mineral compositions in the digestive tract differed between the sites. These results indicate that gill chamber precipitates likely depend on microhabitats of Rimicaris within a vent field, while the composition of digestive tract minerals are likely controlled by chemical compositions of vent fluids which is consistent within each site but differ among different sites.