Journal of The Malacological Society of London Molluscan Studies Journal of Molluscan Studies (2013) 79: 90–94. doi:10.1093/mollus/eys037 RESEARCH NOTE Downloaded from https://academic.oup.com/mollus/article-abstract/79/1/90/1029851 by IFREMER user on 14 November 2018 PROGENETIC DWARF MALES IN THE DEEP-SEA WOOD-BORING GENUS XYLOPHAGA (BIVALVIA: PHOLADOIDEA) Takuma Haga1 and Tomoki Kase2 1Marine Biodiversity Research Program, Institute of Biogeosciences, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, Kanagawa 237-0061, Japan; and 2Department of Geology and Paleontology, National Museum of Nature and Science, 4-1-1 Amakubo, Tsukuba, Ibaraki 305-0005, Japan Correspondence: T. Haga; e-mail:
[email protected] Sunken plant debris (sunken wood, hereafter) in deep-sea absence of pelagic larval development implies a low capacity environments harbours an idiosyncratic fauna that is based dir- for dispersal and for finding ephemeral resources in the deep ectly or indirectly on wood decomposition (Turner, 1973, sea (Knudsen, 1961; Scheltema, 1994; Voight, 2009). 1978). This resource is ecologically comparable with deep-sea An alternative hypothesis concerning the association of tiny whale-falls, because of its ephemeral nature (Distel et al., individuals with larger conspecifics in many Xylophaga species 2000). The obligate wood-boring and wood-consuming (xyl- is that, instead of externally-brooded offspring, they represent ophagous) bivalve genera Xylophaga, Xylopholas and Xyloredo, mating partners in the form of dwarf males. Dwarf males are, all belonging to the family Xylophagaidae (Turner, 2002;we in general, tiny individuals (50% or less of the normal body here regard it as an independent family based on unpublished size) that attach to large individuals in gonochoristic organ- molecular phylogenetic data of TH), occur primarily in the isms.