Deep-sea ophiuroids (Echinodermata) from reducing and non-reducing environments in the North Atlantic Ocean

Abstract

The animal communities associated with the deep-sea reducing environment have been studied for almost 30 years, but until now only a single species of ophiuroid, Ophioctenella acies, has been found at both hydrothermal vents and methane cold seeps. Since the faunal overlap between vent and seep communities is small and many endemic species have been found among other taxa (e.g. Mollusca, Crustacea), additional species of ophiuroids were expected at previously unstudied sites. Chemical compositions at reducing sites di¡er greatly from the nearby bathyal environment. Generally, species adapted to chemosynthetic environments are not found in non-chemosynthetic habitats, but occasional visitors of other bathyal species to vent and seep sites have been recorded among many taxa except ophiuroids. This paper presents an analysis of the ophiuroid fauna found at hydrothermal vents and non-reducing nearby sites on the Mid-Atlantic Ridge and on methane cold seeps in the Gulf of Mexico, at Blake Ridge o¡ South Carolina and south of Barbados. In addition to O. acies, four species were found at vents, Ophiactis tyleri sp. nov., Ophiocten centobi, Ophiomitra spinea and Ophiotreta valenciennesi rufescens. While Ophioctenella acies appears to be restricted to chemosynthetic areas, the other four species were also found in other bathyal habitats. They also occur in low numbers (mostly single individuals), whereas species adapted to hydrothermal areas typically occur in large numbers. Ophioscolex tripapillatus sp. nov. and Ophiophyllum atlanticum sp. nov. are described from nearby non-chemosynthetic sites. In a cold seep south of Barbados, three species of ophiuroids were found, including Ophioctenella acies, Amphiura sp., Ophiacantha longispina sp. nov. and Ophioplinthaca chelys. From the cold seeps at Blake Ridge and the Gulf of Mexico, Ophienigma spinilimbatum gen. et sp. nov. is described, likely restricted to the reducing environment. Ophiotreta valenciennesi rufescens occurred abundantly among Lophelia corals in the Gulf of Mexico seeps, which is the ¢rst record of this species from the West Atlantic. Habitat descriptions complement the taxonomic considerations, and the distribution of the animals in reducing environments is discussed.

Tithonia oxfordiana, a new irregular echinoid associated with Jurassic seep deposits in south‐east France

“…The occurrence of ophiuroids in relatively high densities has also been noted (Hecker 1985; Van Dover et al. 2003; Stöhr and Segonzac 2004). Localities at which crinoids are abundant are unknown, but unusually, well‐preserved crinoids have been described from possibly methanogenic carbonates of early Oligocene age (Burns et al.…”

Global Diversity of Brittle Stars (Echinodermata: Ophiuroidea)

“…The scientific effort has varied over the centuries, resulting in patchy knowledge, and brittle stars have received comparatively little attention during the past 50 years. Species inventories are more reliable for better known areas such as the North Atlantic, although, even here they are far from complete, as the discovery of ten new species in the North Atlantic since 2003 shows [42], [68], [69]. Published records for less well known areas, such as the Pacific Ocean, require careful analysis and verification, as many species have been described more than once and need to be revised [70].…”

A hydrothermal seep on the Costa Rica margin: middle ground in a continuum of reducing ecosystems

“…The thiotrophic bacterial symbionts of the two new Bathymodiolus species are 99 per cent similar (based on 16S rRNA) to B. thermophilus from vents of the East Pacific Rise and to those in mussels from the seeps of the Gulf of Mexico ( [36]; electronic supplementary material, table S5). The multiple morphologies of L. barhami at Jaco Scar (spherical bushes and continuous [40], but are known from seeps at Blake Ridge in the Atlantic [41], and as an early stage in organic fall succession [42]. Many of the gastropod genera present such as Lepetodrilus, Bathyacmaea, Fucaria and Neomphalidae new genus (electronic supplementary material, table S6) are most often found at vents [43] but others, including Margarites, Neolepetopsis and Provanna also occur at seeps [44].…”