First seep-dwellingDesbruyeresia(Gastropoda: Abyssochrysoidea) species discovered from a serpentinite-hosted seep in the Southeastern Mariana Forearc

Abstract

2016): First seep-dwelling Desbruyeresia (Gastropoda: Abyssochrysoidea) species discovered from a serpentinite-hosted seep in the Southeastern Mariana Forearc, Molluscan Research, ABSTRACTThe South Chamorro Seamount (13°47'N, 146°00'E) on the southeastern Mariana Forearc is one of a series of serpentine mud volcanoes in the area, and hosts an active fluid seepage area on its summit. During a recent research cruise three specimens of a small rissoid-like gastropod were collected with chemoautotrophic bivalves. Subsequent morphological and molecular investigations revealed it to be a novel species of Desbruyeresia (Abyssochrysoidea: Provannidae), described herein as Desbruyeresia chamorrensis n. sp. Although all known specimens had a heavily corroded apex, so the protoconch could not be observed, its radular characteristics are very similar to those of other Desbruyeresia species. Phylogenetic reconstruction using the cytochrome c oxidase subunit I (COI) gene also supports its placement within Desbruyeresia. The new species is distinguished from all other described congeners by having more numerous (17-20) axial ribs on the teleoconch, and a broad shell for the genus (shell width to height ratio 0.6-0.65). Living Desbruyeresia were previously only known from hydrothermal vents and this is the first species known to inhabit seeps or serpentinite-hosted chemosynthetic habitats.

Gastropod fauna on organic falls at the Southwest Atlantic deep-sea

“…Provannidae snails are often found in chemosynthetic environments, such as organic falls (Smith and Baco, 2003;Johnson et al 2010;Lundsten et al, 2010a;Sumida et al, 2016, this study), hydrocarbon seeps (Warén and Bouchet, 2009), hydrothermal vents (Bouchet and Warén, 1991;Warén and Ponder, 1991;Warén and Bouchet, 1993;Suzuki et al, 2006b;Sasaki et al, 2010;Johnson et al, 2015;Sasaki et al, 2016), cold seeps (Kaim et al, 2008a;Sasaki et al, 2010;Sasaki et al, 2016) and serpentinite-hosted environment (Chen et al, 2016a(Chen et al, , 2016b. The genus Cordesia was found only at hydrocarbon seeps in west Africa, and this is the first time it is reported on food falls.…”

“…The clade including Rubyspira, Desbruyeresia and Abyssochrysos is well supported on other phylogenetic studies and seems to have radiatde 26-90 million years ago. The same could be said for the basal clade formed by the genus Provanna alone and a third brach with species of Alviniconcha and Ifremeria nautilei (Johnson et al, 2010;Chen et al, 2016aChen et al, , 2016b.…”

“…Abyssochrysidae is monotypic and the Abyssochrysos is mainly found on deep-sea sediments off Brazil, West and South Africa, Oman and Indonesia, presenting mainly carnivorous and parasitic behaviors (Houbrick, 1979;Bouchet, 1991;Warén and Bouchet, 2009). The family Provannidae comprises a recent and well-known group of gastropods from deep-sea hydrothermal vents, hydrocarbon seeps, food falls and serpentinite-hosted ecosystems (Bouchet and Warén, 1991;Warén and Ponder, 1991;Warén and Bouchet, 1993;Warén and Bouchet, 2009;Johnson et al, 2015;Chen et al, 2016aChen et al, , 2016b. It is formed by 5 genera, Provanna (Dall, 1918), Alviniconcha (Okutani and Ohta, 1988),…”

“…They are medium sized snails (generally less than 15 mm in shell height), that are mostly deposit feeders and bacterial mat grazzers (Warén and Bouchet, 1993;Sasaki et al, 2010). Provanna cingulata was the first abyssochrysoid snail found on serpentinite-hosted ecosystems (Chen et al, 2016a) along with a Desbruyeresia species (Chen et al, 2016b). Desbruyeresia encompasses six described species, five of them are known from hydrothermal vents from Western Pacific and Indian Oceans (Kaim et al, 2008a;Sasaki et al,2010), together with a specie from serpentinite-hosted vents (Chen et al, 2016b).…”

“…Kaim et al (2008a) associated some of the fossil specimens described as Hokkaidoconcha as being possibly of the superfamily Cerithioidea, but the relationship beetwen these families are not supported by genetic studies (Colgan et al, 2007). Morphological analyses indicate that provannids were part of the superfamily Abyssochrysoidea (Warén and Bouchet, 2009), what was later reinforced by molecular data by Johnson et al (2010) and Chen et al (2016aChen et al ( , 2016b. Provannidae is probably paraphyletic because the Abyssochrysoid is rooted at the same clade, making the genus Rubyspira to remains unassigned at family level (Johnson et al, 2010).…”