Feeding specialization of bresiliid shrimps in the TAG site hydrothermal community

Abstract

It is argued that the Atlantic bresiliid shrimps Rimicaris exoculata and Chorocaris chacei from a hydrothermal community on the Mid-Atlantic h d g e feed on exosymbiotic bacteiia that form a dense covenng on their mouthparts and the inner surface of the carapace. The associated bacterial community includes different morphological forms and types and is full of sulfide crystals from black smokers. Mouthparts of Atlantic hydrothermal bresiliids are hypertrophied and densely covered with setae to enlarge the attachment surface for associated bacteria. SEM revealed 2 dormnant morphological types of filamentous bactena with trichome width 0.2 to 0.5 pm and 1 to 3 pm, with elemental sulfur inside the cells and with attaching disks; both forms resemble Thlothriv spp. The idea of a bacterial source of food for shrimp was strengthened by carbon stable-isotope analysis, which yielded FI3C = 1 0 . 5 to -12.5%. Presumably, the shnmps keep close to hydrothermal fluid to farm their bacterial symbionts in the moderate current with a low concentration of hydrogen sulfide. The assayed level of ribulose 1,5-bisphosphate carboxylase activity in the bacterial community is low (2.2 pm01 min.' g-' protein), indicating dom~nance of heterotrophic forms among symbionts. The source of pnmary production in the vent community is discussed.

Inorganic carbon fixation by chemosynthetic ectosymbionts and nutritional transfers to the hydrothermal vent host-shrimp Rimicaris exoculata

“…They are in good agreement with previous stable isotope studies (Gebruk et al, 1993;Pond et al, 1997aPond et al, , b, 2000Rieley et al, 1999;Colac¸o et al, 2007) and confirm that R. exoculata depends on its epibionts for its nutrition. They thus strengthen the view that the relationship between bacteria and shrimp is mutualistic: the epibionts supply carbon compounds to the shrimp and the shrimp, thanks to its gill chamber flow and its swimming behaviour, offers them protection and a supply of chemical compounds, maintaining their position at the oxic/anoxic interface around active chimneys Segonzac et al, 1993).…”

“…There is strong evidence, based on stable isotope signatures and essential fatty acid composition, suggesting that the shrimp gets organic matter mainly from its epibionts, rather than from grazing free-living bacteria associated with chimney walls (Gebruk et al, 1993;Pond et al, 1997aPond et al, , 2000Rieley et al, 1999;Colac¸o et al, 2007). Yet this evidence of symbiont-host nutritional relationships is indirect, and how carbon is transferred from bacteria to shrimp remains an open question.…”

Acquisition of epibiotic bacteria along the life cycle of the hydrothermal shrimp Rimicaris exoculata

“…At the ultramafic Rainbow vent field, the end-member was characterized by extremely high concentrations of ferrous iron Douville et al, 2002), explaining the reddish color of the majority of shrimps (Zbinden et al, 2004). At the Logachev vent site, there was a majority of gray/black shrimps, corresponding probably to iron sulfate deposits (Gebruk et al, 1993). For Ashadze, only six black specimens were retrieved.…”

“…One of these invertebrates is the shrimp Rimicaris exoculata (Williams and Rona, 1986). This crustacean, belonging to the family Alvinocarididae, is part of the dominant megafauna at several Mid-Atlantic Ridge (MAR) vent sites (Desbruyères et al, 2001), where it forms dense and motile aggregates around the chimney walls (Segonzac, 1992;Gebruk et al, 1993).…”

Iron oxide deposits associated with the ectosymbiotic bacteria in the hydrothermal vent shrimp <i>Rimicaris exoculata</i>

“…The bacterial community housed in the gill chamber of R. exoculata has been identified as chemoautotrophic bacteria (Wirsen et al, 1993) and phylogenetic analysis revealed that the bacteria could correspond to a single epsilon-proteobacteria phylotype (Polz and Cavanaugh, 1995). Some authors have also hypothesized that the bacteria could acquire their energy from sulphide oxidation (Gebruk et al, 1993;Polz and L. Corbari et al: Bacteriogenic iron oxides Cavanaugh, 1995), but this hypothesis has never been confirmed by any culture experiment. Recently, demonstrated that the bacterial community in the shrimp gill chamber is composed of more than one phylotype and revealed from molecular analysis that three metabolic bacterial types (iron, sulfide and methane oxidation) may cooccur within the symbiotic community associated with Rimicaris exoculata.…”