In 2019, as part of a 2-month mission funded by the IRD, Hervé Macarie (team HEALTH-IMBE), accompanied by Professor Daniel Martinez (Pomona College, USA), has shown for the first time that freshwater hydra, small cnidarians, were ubiquitous in Guadeloupe and Martinique, and found in 50 % water points surveyed (rivers and ponds). This discovery was unexpected, as these organisms, which are adapted to freshwater, do not naturally cross saltwater bodies.
This result reinforced the relevance of using the’hydra as a model for studying the impact of chlordecone, an insecticide responsible for an environmental and health crisis in the French West Indies. Genomic analysis of hydra from the French West Indies revealed two distinct groups one close to the American hydras and a second that could be linked to the African hydra populations, the hypothesis being that this second group could have been the first. introduced by man from Africa during the slave trade.
To test this hypothesis, a AOI funding IMBE mission to the south gave Hervé Macarie the opportunity to visit the Senegal in 2025, accompanied by’Hervé Jourdan (team POPCO) and Mamadou Sylla Barry. On 2560 km of prospecting, They explored the Senegal River, Lake Guiers, the Gambia River and several waterholes around Dakar. No hydra was found, This suggests a very low density in the environments surveyed, with unfavourable factors such as brackish or excessively warm water.
This research paves the way for a better understanding of biogeography and history of West Indian hydras, and their role in island ecosystems.
Next step: to continue our exploration in Africa, to lift the veil on the little-known history of these freshwater micro-inhabitants. We'll keep you posted on progress!
