New Data on the Distribution and Relation to Environmental Factors of the Alien Branchiura sowerbyi Beddard, 1892 (Oligochaeta: Naididae) in Bulgaria

New data on the distribution of the Asian alien species Branchiura sowerbyi (Oligochaeta: Naididae) were reported for Bulgaria. During the period 2012-2020, the species was found in 40 lotic and lentic water bodies (17 rivers and 23 reservoirs and lakes). Eight new inhabited water bodies of different types (4 reservoirs, 2 natural lakes and 2 rivers) were registered. The spread of the species in relation to environmental parameters was analysed. The ecological preferences of the B. sowerbyi showed a great adaptability and tolerance towards water temperature and oxygen concentration as well characteristics of the water bodies' type. The highest number of individuals was recorded in silt-sand, natural organic matter and coarse detritus substrates.