Biology subjects

Michel, L. N.

Publications and source records attributed to Michel, L. N..

4 recordsLinked to original sources

bioRxiv2025

Discovery of a chemosynthetic community at the serpentinite-hosted seep on the Quaker Seamount, Mariana Forearc

Deep-sea chemosynthesis-based ecosystems in the Mariana Region include hydrothermal vents on the Mariana Arc and in the Mariana Back-Arc, and serpentinite-hosted seeps on the Mariana Forearc - with the latter being by far the least studied. Here, we surveyed the biodiversity of the serpentine seep on the Quaker Seamount. At first glance, the area appears to be devoid of megafauna, but examination of the carbonates revealed dense aggregations of animals dominated by the limpets Bathyacmaea and Pyropelta on brucite-carbonate chimney structures exhibiting visible fluid venting. Sorting of recovered material yielded a total of 14 species and together with an observation of a Munidopsis squat lobster we report a total of 15 species; six of these are considered endemics of chemosynthetic ecosystems. The occurrence of taxa such as the snail Lurifax cf. japonicus and the limpet Pyropelta ryukyuensis, otherwise only known from distant vents in the Izu-Ogasawara Arc and Okinawa Trough off Japan, strengthens the hypothesis that serpentine seeps may function as dispersal stepping-stones across arc and back-arc systems.

ecology↗

bioRxiv2025

Evolutionary convergence and trophic diversity in hot vent and cold seep shrimps showcase a continuum of symbiosis

Convergent evolution offers a powerful lens through which to examine the selective forces shaping life in extreme environments. In deep-sea hot vents and cold seeps, invertebrates have independently evolved symbioses with chemosynthetic bacteria, but repeated origins of such associations within a family remain rare. Here, we investigate the evolutionary emergence of chemosymbiosis in the shrimp family Alvinocarididae across 22 species collected globally. Electron microscopy identified a gradient of epibiotic bacterial colonization within the cephalothoracic cavity, ranging from absent to dense filamentous mats, suggesting distinct trophic strategies. Isotope and lipid trophic markers confirmed difference in reliance on chemosynthetic production among sympatric species with different bacterial colonization from a single vent. Phylogenetic analysis reveals at least two independent origins of chemosymbiosis, suggesting evolutionary convergence. Microhabitat association data further show that symbiotic phenotypes are most common in shrimps occupying the hottest, most geofluid-enriched microhabitats, though exceptions suggest contributions from additional ecological or physiological constraints. Our findings reveal many alvinocaridids as gradually evolving towards symbiosis, highlighting the importance of intermediate cases to understand the pathways to chemosymbiosis. This study contributes to a broader understanding of the predictability of evolutionary outcomes in distinct habitats such as vents, with broader implications for resilience of deep-sea ecosystems.

evolutionary biology↗

bioRxiv2024

Divergent realized ecological niches of sister species of the Antarctic amphipod genus Charcotia

Climate change and resource exploitation in the Southern Ocean are important Anthro-pogenic pressure on Antarctic food webs. Understanding the eco-functional roles of Antarctic communities is essential for ecosystem management and conservation. Amphipods are among the most dominant and ecologically important benthic taxa in the Southern Ocean. The amphipod genus Charcotia is part of the scavenger guild playing a dominant role in nutrient recycling. To study the trophic habits of two sister species, C. amundseni and C. obesa, stable isotope ratios of carbon and nitrogen were investigated along geographical and bathymetrical gradients. Charcotia obesa belongs to the fourth and C. amundseni to the fifth trophic level, based on significant differences in {delta}15N. Benthic primary producers dominate the diet in both species as derived from their {delta}13C values. Charcotia obesa, the species with the narrowest depth range, did not show a depth-related pattern in isotopic ratios. An increasing geographic gradient of both {delta}15N and {delta}13C values was observed for C. obesa, ranging from the northern most tip of the Western Antarctic Peninsula to the southwestern most part of the Bellings-hausen Sea. This might be linked to nutrient rich glacial meltwater in the latter part of the Southern Ocean. Nitrogen stable isotope ratios of C. amundseni showed a significant difference between Crown Bay and the other locations; this might be explained by the close location of the Filchner Area to nutrient rich upwelling in the Weddell Sea Gyre. Our study provides evidence for niche differentiation between two closely related amphipod species. Incorporation of additional samples from other locations and depth ranges in combination with isotope analysis and DNA-based prey identification might clarify the trophic position of benthic amphipods.

ecology↗

bioRxiv2023

Symbioses of alvinocaridid shrimps from the South West Pacific: No chemosymbiotic diets but partially conserved gut microbiomes

Rimicaris exoculata shrimps from hydrothermal vent ecosystems are known to host dense epibiotic communities inside their enlarged heads and digestive systems. Conversely, other shrimps from the family, described as opportunistic feeders have received less attention. We examined the nutrition and bacterial communities colonizing "head" chambers and digestive systems of three other alvinocaridids - Rimicaris variabilis, Nautilocaris saintlaurentae and Manuscaris sp. - using a combination of electron microscopy, stable isotopes and sequencing approaches. Our observations inside "head" cavities and on mouthparts showed only a really low coverage of bacterial epibionts. In addition, no clear correlation between isotopic ratios and relative abundance of epibionts on mouthparts could be established among shrimp individuals. Altogether, these results suggest that none of these alvinocaridids rely on chemosynthetic epibionts as their main source of nutrition. Our analyses also revealed a substantial presence of several Firmicutes within the foreguts and midguts of these shrimps, which closest known lineages were systematically digestive epibionts associated with alvinocaridids, and more broadly from digestive systems of other crustaceans from marine and terrestrial ecosystems. Overall, our study opens new perspectives not only about chemosynthetic symbioses of vent shrimps, but more largely about digestive microbiomes with potential ancient and evolutionarily conserved bacterial partnerships among crustaceans.

evolutionary biology↗