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Marine Ecology Progress Series

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MEPS 320:89-99 (2006)  -  doi:10.3354/meps320089

Symbiosis of epi- and endocuticular bacteria with Helicoradomenia spp. (Mollusca, Aplacophora, Solenogastres) from deep-sea hydrothermal vents

Sigrid Katz1,*, Colleen M. Cavanaugh2, Monika Bright1

1Department of Marine Biology, Faculty of Life Sciences, University of Vienna, Althanstr. 14, 1090 Vienna, Austria
2Department of Organismic and Evolutionary Biology, Harvard University, 16 Divinity Avenue, Cambridge, Massachusetts 02138, USA

ABSTRACT: Two species of Solenogastres (Mollusca, Aplacophora) from deep-sea hydrothermal vents of the East Pacific Rise, Helicoradomenia cf. acredema and a second as yet undescribed species of the same genus, were discovered to harbor epibiotic and endocuticular prokaryotes along their entire bodies. Helicoradomenia sp. 1 additionally harbored intracellular rods in the epidermis. TEM (transmission electron microscopy) and SEM (scanning electron microscopy) observations revealed 4 different bacterial morphotypes: rod-shaped, helical, unsheathed and sheathed trichomes. One conspicuous rod was found to contain membranes typical for type II methanotrophs. Applying in situ hybridization with group-specific Bacteria and Archaea probes, the majority of the prokaryotes associated with Helicoradomenia sp. 1 were identified as α-Proteobacteria, while others belonged to the γ-Proteobacteria or could not be associated with a definite bacterial clade. While solenogastres usually lack microbial epigrowth, the 2 Helicoradomenia species consistently are associated with similar epi- and endocuticular bacteria, indicating these are symbiotic associations.

KEY WORDS: Symbiosis · Helicoradomenia · Solenogastres · Alphaproteobacteria · Gamma-proteobacteria · Hydrothermal vents · East Pacific Rise · Chemosynthesis · Aplacophora

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