How are microbial and detrital sources partitioned among and within gastropods species at East Pacific Rise hydrothermal vents?

Abstract

For the last few decades, trophic ecology has usually been investigated by using stable isotopes. However, the isotopic signatures of potential food sources in hydrothermal vent ecosystems are often unknown and so their relative contribution to the consumers' diet, as well as resource partitioning, are then difficult to estimate. Here, we used a recent Bayesian mixing model (stable isotope analysis in R, SIAR) based on d C and d 15N to estimate the contribution of multiple food sources to the diet of eight vent gastropods that can reach high densities at hydrothermal vents (Lepetodrilus elevatus, Lepetodrilus pustulosus, Lepetodrilus ovalis, Eulepetopsis vitrea, Cyathermia naticoides, Peltospira delicata, Peltospira operculata and Rhynchopelta concentrica). These species, known as primary consumers (mostly bacterivores and detritivores), were sampled on the South-East Pacific Rise at 17°25 0 S and the North-East Pacific Rise at 9°50 0 N and 12°50 0 N. Several potential food sources were sampled according to the gastropod habitat on the chimney wall, or mussel beds (proxies of Gammaproteobacteria form I RubisCO, Gammaproteobacteria form II RubisCO and Epsilonproteobacteria, biofilms of siboglinid and alvinellid tubes, biofilms of mussel shells and particulate organic matter). Some of these microbial and detrital sources were confirmed as present in the gut content of some small specimens by transmission electron microscopy. Distinct stable isotopic signatures of the potential food sources allowed calculation of their relative contributions to primary consumers' diets. This revealed that gastropod species living on siboglinid or bathymodiolin habitats are usually generalists, feeding on various pools of microbial or detrital origins. For a particular habitat, sympatric gastropod species partition the food sources, thus avoiding being in competition. Only for the alvinellid habitat Peltospira spp. appeared to be more specialists as the choice of food sources is more reduced.

The Evolutionary Ecology of Animals Inhabiting Hydrogen Sulfide–Rich Environments

“…Shifts in trophic resource use and expansion of trophic niche widths in fishes inhabiting freshwater sulfide springs have been linked to changes in resource availability and competitive release (Tobler et al 2015). In contrast, competition and resulting niche partitioning among species have been documented in other H 2 S-rich environments (Gaudron et al 2015, Levesque et al 2003. Accordingly, evidence that competitive release provides an advantage for H 2 S-tolerant species is mixed.…”

A molluscan class struggle: exploring the surprisingly uneven distribution of chemosymbiosis among two major mollusk groups

“…This species is endemic to the East Pacific Rise vents and is often found in abundance on Riftia tubes (Wareń and Bouchet, 1989). Campylobacteria have been reported extracellularly on gill tissue of this species in association with lysosomes, indicating possible endocytotic digestion (Zbinden et al, 2015).…”

Integrated Study of New Faunal Assemblages Dominated by Gastropods at Three Vent Fields Along the Mid-Atlantic Ridge: Diversity, Structure, Composition and Trophic Interactions

“…The abundance and large distribution of this genus may be related, among other factors, to its feeding plasticity and high mobility. In fact, these limpets exhibit various feeding strategies including grazing with their radula, active suspension feeding and even symbiotic relationships (Bates, 2007;Gaudron et al, 2015) and they are able to adjust their position in response to environmental changes (Bates et al, 2005). Their continuous reproduction and planktonic dispersal strategy also make them effective early colonizers (Kelly and Metaxas, 2007;Matabos et al, 2008;Tyler et al, 2008;Bayer et al, 2011;Nakamura et al, 2014) as observed by their rapid colonization after an eruption at the EPR (Bayer et al, 2011).…”