Progenetic dwarf males in the deep-sea wood-boring genus Xylophaga (Bivalvia: Pholadoidea)

摘要

Sunken plant debris (sunken wood, hereafter) in deep-sea environments harbours an idiosyncratic fauna that is based directly or indirectly on wood decomposition (Turner, 1973, 1978). This resource is ecologically comparable with deep-sea whale-falls, because of its ephemeral nature (Distel et al., 2000). The obligate wood-boring and wood-consuming (xylophagous) bivalve genera Xylophaga, Xylopholas and Xyloredo, all belonging to the family Xylophagaidae (Turner, 2002; we here regard it as an independent family based on unpublished molecular phylogenetic data of TH), occur primarily in the deep sea, extending down to the hadal zone, from polar to tropical regions (Knudsen, 1961; Schitte, 2005). They have been recognized as the most important organisms that convert refractory sunken wood into a food source available to other members of the community (Turner, 1973; Distel & Roberts, 1997; Distel, 2003). However, Xylophagaidae remain little studied, as they are difficult to find due to their patchy distribution at great depths. Therefore, many species are known only from the type localities (see Voight, 2007).