First record of the Ponto-Caspian amphipod Chaetogammarus trichiatus (Martynov, 1932) (= Echinogammarus trichiatus) (Crustacea, Gammaridae) in Lake Geneva

The Ponto-Caspian amphipod Chaetogammarus trichiatus was recorded for the first time in Lake Geneva. The identification of the collected specimens was established through morphological examination and independently confirmed by DNA barcoding based on the mitochondrial COI gene. The present observation in Lake Geneva is noteworthy, as C. trichiatus has only rarely been reported from lake ecosystems, most records originating from large rivers. In addition to addressing sampling aspects, we describe the habitat of C. trichiatus in Lake Geneva, detail the morphological identification criteria used to distinguish the species, and discuss the probable implications of this newly recorded species for the interpretation of previous findings in the lake.