Epibiotic association between filamentous bacteria and the vent-associated galatheid crab,Shinkaia crosnieri(Decapoda: Anomura)

Abstract

The galatheid crabShinkaia crosnieri, is the sole member of the subfamily Shinkaiinae. It is abundant and forms dense beds around active hydrothermal vents in the Okinawa Trough. Thousands of filamentous bacteria attached to the plumose setae on the ventral surface of this crab were observed using field-emission scanning electron microscopy and transmission electron microscopy. Nucleic acids were extracted from the filamentous bacteria, and the phylotypes of 16S rRNA genes were identified from 81 clones. These phylotypes were divided into three groups: Epsilonproteobacteria (74%); Gammaproteobacteria (20%); and Bacteroidetes (6%). Gamma- and major phylotypes of Epsilonproteobacteria were also detected using fluorescencein situhybridization analysis. These Epsilon- and Gammaproteobacteria were closely related to cultured and uncultured bacteria from hydrothermal vent fields including episymbionts of vent-associated invertebrates such asRimicaris exoculata, Alvinella pompejana, the scaly-foot snail,Kiwa hirsutaetc. The carbon isotopic compositions of the muscle ofS. crosnieriand in filamentous bacteria were similar. The muscle ofS. crosniericontained monounsaturated C16and C18fatty acids, which are known to be characteristic of sulphur-oxidizing bacteria in H2S-rich marine habitats. Through the video images transmitted by a submersible and a remotely operated vehicle,S. crosnieriwas observed to comb out its ventral setae using the third maxilliped and appeared to consume the contents. These evidences suggest the epibiotic association betweenS. crosnieriand the filamentous bacteria attached to the ventral setae of the crab, but the details of role and function are still unclear at the present study.

In Situ Determination of Bacterial Growth in Mixing Zone of Hydrothermal Vent Field on the Hatoma Knoll, Southern Okinawa Trough

“…The clade of Epsilonproteobacteria consists of many ecotypes include symbiont with marine invertebrates (Dubilier et al 2008;Tokuda et al 2008;Tsuchida et al 2010), pathogen or normal flora of animals, and free-livings (Campbell et al 2006). In this study, the 16S rRNA gene sequences of Epsilonproteobacteria from a digestive tract of the Bathymodiolus have either possibility of a feed from mixing-zone bacterial population or a member of normal flora (Egas et al 2012;Van Horn et al 2011) .…”

Dancing for Food in the Deep Sea: Bacterial Farming by a New Species of Yeti Crab

“…An example of this is R. exoculata , as this shrimps' bacteria have relatively unique 16∶2(n−4) and 18∶2 (n−4) FAs that can be traced into the shrimp's tissue [25]. Perplexingly, these same (n−4) FAs were also present in S. crosnieri 's epibionts but they were not found in S. crosnieri 's tissue as would be expected if the crab's bacteria were its main food source [18]. Isotopic and FA analyses of K. puravida n. sp.…”

“…Only the vent crab Shinkaia crosnieri, has been observed to scrape off its epibiotic bacteria and transfer them to its mouth, providing a clear mechanism for symbiont harvesting [17]. Isotopic evidence further supported S. crosnieri 's consumption of its epibionts [18]. Yet the importance of S. crosnieri 's symbionts to its overall nutrition remains unknown [18].…”

Microdistribution of Faunal Assemblages at Deep-Sea Hydrothermal Vents in the Southern Ocean

“…sp., and S. crosnieri has been observed “combing out” these setae using its third maxilliped to transfer epibiotic bacteria to its mouth [68]. Carbon radioisotope uptake and stable isotope studies confirm that S. crosneiri obtains nutrition from harvesting epibiotic bacteria in this fashion [69], [70]. Kiwa hirsuta and K. puravida are thought to harvest epibiotic bacteria similarly from the setae on their chelipeds, although this has only been demonstrated for K. puravida [57].…”