Abstract
Cocconeis sawensis Al-Handal & Riaux-Gobin (2014: 217), first described from a saline lake in Southern Iraq (Middle East), is observed for the first time in South America attached on Cladophora sp. from Peixe lagoon in Southern Brazil. Specimens were examined with light and electron microscopy and some morphometric variations were observed in relation to the type material. Valves from Peixe lagoon exhibit rhombo-elliptic outline with broadly cuneate to rounded apices with slightly smaller dimensions. The number of striae shows a broader range of variation on both valves and areolae density in the raphe valve is lesser. The fimbria of the raphe valva valvocopula are elongated with unequal length and shape. Different arrangement of the hymenes were also observed in the sternum valve. More information on the environment where the species was found and its relation to the populations of the species from Florida and Napuka Atoll are provided.