81. Unio tumidus Philipsson, 1788

Findings in Serbia.

Unio tumidus tumidus: Dokić (1882); Droüet (1881, 1884); Tadić (1960).

Unio tumidus solidus: Tadić (1960) .

Unio tumidus: Arambašić (1994); Živić et al. (2001); JDS-ITR Report (2002); Paunović et al. (2005, 2006, 2007 a, 2012 a); Simić et al. (2006); Tomović et al. (2010 b, 2012, 2013, 2014, 2016); Raković (2015); Novaković (2012); Savić (2012); Martinović-Vitanović et al. (2013); Lucić et al. (2015), Zorić et al. (2020).

Common name. Swollen river mussel.

Morphology. Large bivalve. Solid, ovoid tumid shell with a very rounded ventral margin. Its dimensions reach 80 mm (rarely up to 120 mm) in length, 40 mm in height and 35 mm in depth. For more details see Welter-Schultes (2012: 15, figure on the top of the page).

Distribution and ecology. Western Palearctic species widespread in Europe. It has similar habitat requirements as U. pictorum, and generally occurs in slow-flowing large rivers, less frequently in lakes and reservoirs, with a dominance of a muddy substrate. In Serbia, this is one of the most common and widespread bivalves. It has been recorded along almost the entire courses of the Danube, Sava, Tisza, Velika Morava, Zapadna and Južna Morava Rivers.

Other remarks. Due to pollution and habitats destruction this species is critically endangered in Austria and endangered in Germany and Spain. It has 90 nominal species as synonyms (Graf &Cummings 2021). It has been assessed as LC, yet with decreasing population trend, on the IUCN Red List (Vavrova 2011 d).