Perrine SALVI

Comparative study of life history traits of four amphidromous goby species (Teleostei: Gobiinae: Sicydiinae) from the Indo-Pacific Basin using a multidisciplinary approach: A key to understanding endemism

In the Indian and Pacific Oceans, river biodiversity is based mainly on amphidromous species, among which the endemic gobies Cotylopus acutipinnis (Mascarene Archipelago, Indian Ocean), C. rubripinnis (Comoros Archipelago, Indian Ocean) and Sicyopterus pugnans (French Polynesia, Pacific Ocean) live in sympatry with the widely distributed goby Sicyopterus lagocephalus. These amphidromous species are characterised by a life cycle in which adults reproduce in rivers; larvae hatch from the eggs and are flushed down rivers within hours to reach the sea where they disperse for several months before returning to colonise island rivers. In the cosmopolitan species, the duration of this marine phase may allow dispersal on the scale of the south-western oceanic basin, as attested by genetic studies showing possible flows between Reunion and Mayotte for example. Nevertheless, the migration trajectories of the larvae at sea remain mysterious, as does the geographical origin of the larvae recruiting in a given river. The proposed study aims to investigate the inter-annual variability of life history traits, including the age of post-larvae of the four species at the time of their recruitment in the rivers of three islands (Reunion, Moheli (Comoros) and Tahiti), according to the seasons. It will thus be possible to verify whether the endemism vs. cosmopolitanism of the species can be linked to different larval dispersal durations and migration patterns. We plan to investigate the possible migration trajectories of the different species according to the seasons by a hydrodynamic modelling approach, coupled with the analysis of elements and traces included in the otoliths by scanning or transmission electron microscopy coupled with an EDX detector. The elements included in the otolith should provide information on the environment crossed during dispersal, which will enable us to identify the most probable trajectories, among those proposed by the hydrodynamic model.