A hypocystal archeopyle in a freshwater dinoflagellate from thePeridinium umbonatumgroup (Dinophyceae) from Lake Nero di Cornisello, South Eastern Alps, Italy

This study presents the first record of a living dinoflagellate cyst with a hypocystal, antapical archeopyle. It is also the first detailed account of the archeopyle of a living freshwater cyst from the genus Peridinium. The cysts were isolated from sediment traps deployed in Lake Nero di Cornisello, a low-alkalinity high mountain lake of the Adamello mountain range (2233 m above sea level, South Eastern Alps, Italy). The archeopyle is large, clearly hypocystal, polygonal, and slightly peanut-shaped. The species producing this cyst belongs to the Peridinium umbonatum group and is described based on scanning electron microscopy and light microscopy. Partial sequences of SSU rDNA were obtained and compared with previously published sequences from the P. umbonatum group. The taxonomic position of the species is discussed.