Identification of fossil worm tubes from Phanerozoic hydrothermal vents and cold seeps

Abstract

One of the main limitations to understanding the evolutionary history of hydrothermal vent and cold seep communities is the identification of tube fossils from ancient deposits. Tube-dwelling annelids are some of the most conspicuous inhabitants of modern vent and seep ecosystems, and ancient vent and seep tubular fossils are usually considered to have been made by annelids. However, the taxonomic affinities of many tube fossils from vents and seeps are contentious, or have remained largely undetermined due to difficulties in identification. In this study, we make a detailed chemical (Fourier-transform infrared spectroscopy and pyrolysis gas-chromatography mass-spectrometry) and morphological assessment of modern annelid tubes from six families, and fossil tubes (seven tube types from the Cenozoic, 12 Mesozoic and four Palaeozoic) from hydrothermal vent and cold seep environments. Characters identified from these investigations were used to explore for the first time the systematics of ancient vent and seep tubes within a cladistic framework. Results reveal details of the compositions and ultrastructures of modern tubes, and also suggest that two types of tubes from ancient vent localities were made by the annelid family Siboglinidae, which often dominates modern vents and seeps. Our results also highlight that several vent and seep tube fossils formerly thought to have been made by annelids cannot be assigned an annelid affiliation with any certainty. The findings overall improve the level of quality control with regard to interpretations of fossil tubes, and, most importantly, suggest that siboglinids likely occupied Mesozoic vents and seeps, greatly increasing the minimum age of the clade relative to earlier molecular estimates.

Genomic adaptations to chemosymbiosis in the deep-sea seep-dwelling tubeworm Lamellibrachia luymesi

“…5), contrary to recent analyses that indicated that Jurassic tubes from Figueroa deposits were likely to have been made by vestimentiferans [46]. This adds to the growing evidence that the Cenozoic was a key period for the radiation of most dominant invertebrate taxa now occupying in deep-sea chemosynthetic communities [46, 47]. By comparison, the common siboglinid ancestor dates as far back as the Permian (267 mya ± 70).…”

Methanotrophic bacterial symbionts fuel dense populations of deep-sea feather duster worms (Sabellida, Annelida) and extend the spatial influence of methane seepage

“…The suggestion that modern-day serpulids might be endemic to chemosynthetic habitats was proposed early on by other researchers (7,18), calling into question the assumption of obligate suspension feeding (14). By contrast, annelids within Sabellidae inhabit soft mucous and sediment tubes and thus leave only a minor fossil record (19).…”

Microbial-tubeworm associations in a 440 million year old hydrothermal vent community

“…The tube walls are now formed either of framboidal or colloform pyrite, and also retain fine details of the external tube wall ornamentation. Eoalvinellodes annulatus tubes often have thick walls comprising colloform pyrite that is many layers thick, and have external ornament of transverse, bifurcating wrinkles [ 18 , 20 , 25 ]. Small holes in E. annulatus tube walls have been interpreted as moulds of microorganisms [ 18 ].…”