Scanning electron microscopy (SEM) observations showing epibiont microbe and mineral particles on the internal surface of branchiostegites from brown (A, C, E) and black (B, D, F) morphotypes of Rimicaris kairei from the Edmond and Kairei fields, respectively. (A, B) Aggregations of filamentous bacteria. (C, D) Rod-shaped bacteria on the surface of branchiostegites. (C) Some clusters of mineral particles were visible in brown morph shrimps (arrows). (E) Aggregations of nano- to 1-μm-sized mineral particles formed crusts on the internal surface of branchiostegites. (F) Sheath on filamentous bacteria in a black morph shrimp.