Evolutionary relationships of deep-sea vent and cold seep clams (Mollusca: Vesicomyidae) of the "pacifica/lepta" species complex

The smaller vesicomyid bivalves in the genus Isorropodon (Bivalvia, Vesicomyidae, Pliocardiinae) also harbour chemoautotrophic symbionts

“…The level of divergence among COI sequences from the three Isorropodon species is within the range of values documented between distinct populations of the species Archivesica gigas which may, in fact, be a species complex (Osborn 2001). Goffredi et al 2003 study on the "pacifica/lepta" species documented divergence levels between 0.2 and 2.8 % (intraspecific) and between 3.9 and 10.3 % (interspecific), levels that were consistent with the ones reported for other described species of vesicomyids (Peek et al 1997(Peek et al , 2000. Baco et al (1999) and Kojima et al (2006) documented much lower intraspecific levels of COI variations (from 0.1 to 1.8 %) in Calyptogena kilmeri, Calyptogena elongata and Calyptogena solidissima.…”

“…Indeed, because genera were initially poorly defined in Vesicomyidae, recent work has attempted to clarify the taxonomy of the family (see Krylova and Sahling 2010 for review). However the taxonomic and phylogenetic study of this group is still in progress, and the incongruence between clades and named genera is fairly evident from our, as well as from other authors' phylogenies (Peek et al 1997;Goffredi et al 2003;Kojima et al 2004;Decker et al 2012). …”

“…Genome sequencing of symbionts has emphasized several traits typical of maternallytransmitted bacteria, including genome size reduction coupled with the loss of certain genes (Kim et al 1995;Harada et al 2009;Kuwahara et al 2008;Stewart et al 2008). The systematics and evolution of Pliocardiinae hosts have also been studied but their taxonomy is still under debate as genera are typically found non-monophyletic in phylogenetic reconstructions (Kojima et al 1995;Baco et al 1999;Osborn 2001;Goffredi et al 2003;Kojima et al 2004Kojima et al , 2006Decker et al 2012). Yet, apart from large-sized Pliocardiinae vesicomyids, there are in this subfamily smaller-sized species which have been overlooked, and for which very little data is available, both for hosts and associated symbionts.…”

“…Recently, we recovered a few specimens of three Isorropodon morphospecies from the Eastern Mediterranean, Gulf of Cadiz and Gulf of Guinea cold seeps. In order to verify the monophyly of Isorropodon, we sequenced cytochrome oxidase I (COI), a molecular marker previously used in vesicomyid studies (Baco et al 1999;Peek et al 1997;Goffredi et al 2003;Decker et al 2012). In order to characterize potential bacterial partners associated with Isorropodon species, we used comparative 16S rRNA gene sequence analysis and fluorescence in situ hybridization (FISH).…”

Deep-sea food bonanzas: early Cenozoic whale-fall communities resemble wood-fall rather than seep communities

“…The two late Oligocene whale-fall assemblages described by Nesbitt (2005) from the upper part of the Pysht Formation are not included here because all reported species are rather common in these sediments (Nesbitt 2005; J. L. Goedert 1990, personal observations), thus providing little evidence for trophic relationships between them and the whale bones. The communities were compared using genus and family level identifications; species level comparison was not feasible due to the limited number of species-level identifications, and due to the difficulties of distinguishing fossil species among bivalve groups like vesicomyids that are known for their cryptic species (Goffredi et al 2003). Faunal similarities were calculated pair-wise and using the Dice, Jaccard and Raup-Crick indices, all of which delivered very similar results.…”