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

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