Filinia species in brackish waters at St. Maarten (Dutch Caribbean)

From a brackish lagoon on St. Maarten (Dutch Caribbean) plankton samples were collected from 2003 to 2005. The samples were taken and physical-chemical data were measured by the second author. The samples were analyzed by the first author. Three rotifers belonging to the Filinia terminalis-group were found. They differ in morphology from described species. The physical-chemical results show that the brackish habitat in which they are found is very deviating from their normal freshwater habitat. These differences suggest the presence of cryptic species. The results contribute to the knowledge of the morphology and the ecology of the Filinia terminalis-group. It is stressed that records of animals found outside the known geographical and ecological range should be accompanied with a good descriptions to prevent force fitting and, a priori, creating very eurytopic cosmopolitan species.