POLYCHAETES OF <i>MARENZELLERIA</i> GENUS (SPIONIDAE) IN THE SOUTH-EASTERN BALTIC SEA (RUSSIAN EEZ)
The habitation of two closely related polychaete species of Marenzelleria genus is proved in the South-Eastern Baltic Sea with the use of a morphological approach for the first time. M. neglecta lives in the shallow, euthrophic, oligohaline Vistula and Curonian lagoons. M. arctia dwells in relatively deep, mesothrophic and mesohaline marine waters up to the depth of 70-80-meters. Spreading and distribution of the species in the South-Eastern Baltic Sea are described.