Croatian Brackish Karst Spring Lake Jezero Blaca in Pelješac Peninsula Reveals Interesting Truncatelloid Gastropods Assemblage

ABSTRACT Jezero Blaca is a unique spring lake situated at the northern coast of the Pelješac Peninsula near the village Duba Pelješka in South Dalmatia, Croatia. The lake supported by a karstic spring located near the Adriatic seashore is inhabited by unusually rich brackish water truncatelloid assemblage. The position of the lake near seashore evokes a model of sea invertebrate gradual adaptation to freshwater spring head allowing them to further invade the stygobiont karst conduits. Similar lakes could be the marine gateways of the extraordinarily rich Dinaric stygobiont fauna. The main aim of this study was to sample and barcode the aquatic snails found in this locality to check their species affiliation and describe conservation needs. The results confirmed that the locality hosts four interesting representatives of the gastropod superfamily Truncatelloidea, which has never been found syntopically so far. One of the species characterized by unique COI sequences and was described herein as Truncatella dalmatica new sp. The conservation need of this unique and understudied habitat type is discussed.