Population structure and environmental niches of Rimicaris shrimps from the Mid-Atlantic Ridge

P Methou,I Hernández-Ávila,Ma Cambon-Bonavita,F Pradillon,C Cathalot

doi:10.3354/meps13986

Abstract

Among the endemic and specialized fauna from hydrothermal vents, Rimicaris shrimps constitute one of the most important and emblematic components of these ecosystems. On the Mid-Atlantic Ridge, 2 species belonging to this genus co-occur: R. exoculata and R. chacei that differ in their morphology, trophic regime and abundance. R. exoculata forms large and dense aggregations on active vent chimney walls in close proximity to vent fluid emissions, whereas R. chacei is much less conspicuous, living mostly in scattered groups or solitary further away from the fluids. However, the recent revision of Rimicaris juvenile stages from the Mid-Atlantic Ridge shows that R. chacei abundance would be higher than expected at these early life stages. Here, we describe and compare the population structure of R. exoculata and R. chacei at the Snake Pit and Trans-Atlantic Geotraverse (TAG) vent fields. We show distinct population demographics between the 2 co-occurring shrimp species with a large post-settlement collapse in R. chacei populations suggesting high juvenile mortality for this species. We describe important spatial segregation patterns between the 2 species and their different life stages. Additionally, our results highlight distinct niches for the earliest juvenile stages of both R. exoculata and R. chacei, compared with all other life stages. Finally, we discuss the potential factors, including predation and competitive interactions, that could explain the differences we observed in the population structure of these 2 species.

Highlights

Fueled by the chemosynthetic energy arising from the mixing between vent fluids and surrounding seawater, hydrothermal vent ecosystems host dense and lush communities of endemic fauna which are organized in distinct species assemblages along steep thermal and chemical gradients
As in other marine benthic ecosystems (Menge 1991), population demographics of species from hydrothermal vents depend on the number of competent larvae reaching the vent site, the probability of success of their settlement and any mortality events occurring between their successive life stages (Kelly & Metaxas 2008)
Unlike R. exoculata, R. chacei size distribution was skewed towards the smaller sizes, corresponding to the juvenile and subadult life stages (Fig. 1)

Summary

Introduction

Fueled by the chemosynthetic energy arising from the mixing between vent fluids and surrounding seawater, hydrothermal vent ecosystems host dense and lush communities of endemic fauna which are organized in distinct species assemblages along steep thermal and chemical gradients. Mar Ecol Prog Ser 684: 1–20, 2022 tions depends on the dispersal of larvae, their ability to locate suitable habitats, successfully settle on the bottom and enter existing benthic populations or develop into new ones. This implies adaptations at each stage of the life cycle of vent species. Any biotic or abiotic factor affecting one of these 3 steps will likely impact the capacity of individuals to reach sexual maturity and the size of the adult populations These environmental factors act differentially depending on the life stages considered, as each stage can occupy its own ecological niche and differs in its vulnerability to the different mortality factors (Werner & Gilliam 1984)

Methods

Results

Conclusion