Molecular phylogeny and classification of the chemosymbiotic bivalve family Lucinidae (Mollusca: Bivalvia)

Abstract

A new molecular phylogeny of the chemosymbiotic bivalve family Lucinidae is presented. Using sequences from the nuclear 18S and 28S rRNA genes and the mitochondrial gene cytochrome b, 105 specimens were analysed representing 87 separate species classified into 47 genera. Samples were collected from a wide range of habitats including mangroves, seagrass beds, shallow sands, offshore muds, and hydrocarbon seeps at depths ranging from the intertidal to over 2000 m. A chronogram, derived from the combined molecular tree, was calibrated using ten lucinid fossils. The trees show five well-supported clades and two single branches of Fimbria fimbriata (Linnaeus, 1758) and Monitilora ramsayi (Smith, 1885). A new classification of Lucinidae is proposed with seven subfamilial divisions: three new subfamilies -Pegophyseminae, Leucosphaerinae, and Monitilorinae -are introduced and Codakiinae, usually treated as a synonym of Lucininae, is revived to include the Lucinoma, Codakia, and Ctena subclades. Membership of the Lucininae and Myrteinae is considerably revised compared with Chavan's commonly employed 'Treatise' classification. Previously considered as a separate family, Fimbriinae is now regarded as a subfamily within Lucinidae. The status of Milthinae is presently equivocal pending further analysis and Divaricellinae is recognized as polyphyletic, and is therefore abandoned, with species and genera now grouped in various places within the Lucininae. Deeper water Lucinidae mainly belong to Leucosphaerinae, Codakiinae (Lucinoma clade), and Myrteinae, with Lucinoma species being most frequently associated with hydrocarbon seeps. Species occurring in seagrass habitats derive largely from Pegophyseminae, Codakiinae, and Lucininae, and species from mangrove habitats derive from the Pegophyseminae and Lucininae.

Investigating the Bivalve Tree of Life – an exemplar-based approach combining molecular and novel morphological characters

“…Choice of taxa was also coordinated with past and ongoing taxon-driven work in sub-branches of the bivalve tree (e.g. work on lucinids (Taylor and Glover 2006;Taylor et al 2011), unionoids (Graf and Cummings 2006;Whelan et al 2011) and anomalodesmatans (Dreyer et al 2003;Harper et al 2006)) as well as with parallel studies on other aspects of bivalve biology and anatomy (e.g. Simone et al in press).…”

Chemosymbiotic bivalves from Miocene methane-seep carbonates in Italy

“…Thus, if the inclusion of Meganodontia in Pegophyseminae (cf., Taylor et al, 2011Taylor et al, , 2014) is correct, it would be the third lucinid subfamily to have a considerable fossil history at methane seeps (Taylor et al, 2014;Kiel and Hansen, 2015).…”

“…Most Cretaceous to extant lucinids at methane seeps belong to either the Codakiinae or the Myrteinae (Taylor et al, 2011;Kiel, 2013). Thus, if the inclusion of Meganodontia in Pegophyseminae (cf., Taylor et al, 2011Taylor et al, , 2014) is correct, it would be the third lucinid subfamily to have a considerable fossil history at methane seeps (Taylor et al, 2014;Kiel and Hansen, 2015).…”

“…perinaequilatera Sacco, 1901 represent deformed specimens of Meganodontia hoernea and should therefore be considered as synonyms. Taylor et al (2011) tentatively assigned Meganodontia to their new subfamily Pegophyseminae, whose species are united by some unusual morphological characters, including thin, globular, smooth shells, a narrow edentulous hinge with an internal and laterally extended ligament in most species (Taylor et al, 2011). Meganodontia hoernea is a common and widespread species in the Miocene of Italy, associated with 'Calcari a Lucina' limestones and reducing deep-sea marly sediments.…”

An overview of chemosynthetic symbioses in bivalves from the North Atlantic and Mediterranean Sea

“…Lucinidae are burrowing bivalves occurring over a wide range of depths, from coastal to at least 2500 m, and in latitudes from 60 • N to 55 • S. More than 400 (330 living) species have been described, 85 in the area investigated here. They are the most diverse of the chemosymbiotic bivalves (reviewed in Taylor and Glover, 2006;Taylor et al, 2011). All investigated Lucinidae harbor chemoautotrophic, sulfur-oxidizing Gammaproteobacteria located within vacuoles occurring in gill epithelial cells from the lateral zone of the gill filament, suggesting obligatory association (Frenkiel and Moueza, 1995).…”