Cyprideis torosa (Jones, 1850) in mainland Portugal: what do we know?

Abstract. The distribution of Recent and Holocene Cyprideis torosa (Jones, 1850) from brackish estuaries and lagoons of mainland Portugal is presented; older Cenozoic C. torosa are also briefly mentioned. Around 550 specimens were found alive, in Melides lagoon (456) and salt marshes from large estuaries (90). Thousands of empty valves and carapaces, with different ornamentation, were found in the lagoon, the estuaries and in Holocene samples from boreholes, in the latter with higher concentration in sediments deposited in lagoons. The modern C. torosa was found living mainly in Melides lagoon, associated with brackish and freshwater ostracod species, in soft mud or muddy sand sediments from quiet zones, with salinities from 4.1 to 15.1; it is also found in soft mud to muddy sand sediments whose interstitial waters have salinities from 19.0 to 34.1, on salt marshes (tidal flat and low marsh) of large estuaries, similar to lagoons, in low hydrodynamic areas, together with other brackish ostracods. The main parameters controlling the distribution of C. torosa appear to be the substrate, water dynamics and emersion time, whereas water chemistry is more related to the morphology of valves. In general, C. torosa presents the same ecological characteristics in the Holocene and in modern times.