Evolution of sensory adaptations across the life cycle of the hydrothermal vent shrimp Rimicaris exoculata: from genotype to functional phenotype
Hydrothermal vents are dynamic habitats scattered along mid-ocean ridges. They are characterized by the absence of sunlight, high pressure, and steep thermal and chemical gradients resulting from the mixing of hot fluid, rich in reduced and toxic compounds, with seawater. These conditions have allowed the establishment of an endemic and specialized macrofauna that depends on fluid emissions for its trophic supply.
Among this biodiversity, the shrimp Rimicaris exoculata is one of the emblematic species and the numerically dominant one on the Mid-Atlantic Ridge. It forms dense aggregates in direct proximity to the walls of active chimneys and relies on autotrophic symbiotic bacteria for its nutrition. The fact that it is found at most sites all along the ridge reflects its high dispersal potential and suggests that it possesses efficient mechanisms involved in detecting and orienting toward and within sites.
Throughout its life cycle, it faces multiple constraints that vary radically from one stage to another. During the earliest life stages, larvae disperse in the water column. After this phase, during which they rise high enough to feed on photosynthetically derived food, they must detect the signature of hydrothermal activity in order to recruit to new sites. Juveniles, located on the periphery of the chimneys, must then detect environments favorable to the acquisition of symbionts, which will provide their main food source in adulthood. Finally, adults must remain close to the fluids while avoiding extreme temperatures, in order to maintain their symbionts. In short, the very different environments and lifestyles of these three stages probably require different sensory modalities. Although these remain hypothetical in larvae and juveniles, they have been partially characterized in adults.
Previous work, carried out largely by the BOREA laboratory, has revealed three main sensory modalities in adults: chemoreception, photoreception, and thermoreception. However, these modalities remain unexplored in the other life stages, and some, such as mechanoreception, have not yet been studied in this species.
My research therefore aims to identify the players involved in the sensory modalities of R. exoculata across its life cycle.
To address this, the project is built around three complementary objectives, carried out in parallel across the entire life cycle, in order to reconstruct the complete scenario of R. exoculata in relation to the distinct lifestyles and environments of the different stages:
- The first, molecular objective will identify all candidate receptors involved in thermo-, chemo-, photo-, and mechanoreception, then quantify and compare their expression across different tissues and life stages;
- The second, tissue-level objective will map the distribution of these candidates while analyzing the morphology and structure of their target tissues, in order to track their reconfiguration across the life cycle;
- Finally, the third, functional objective will precisely characterize the function of these candidates, to determine whether the nature of the detected stimuli and the sensitivity thresholds differ during development.
Beyond its fundamental aspect, this project is set in a context of growing pressure on deep-sea mineral resources and their possible exploitation. These activities could cause major disturbances to the sensory systems of R. exoculata at all life stages. A better understanding of its sensory capacities would therefore also make it possible to assess the ability of this species to detect, avoid, or recolonize disturbed habitats.
