Due to the high morphological plasticity of shells within the genus Anodonta, Haas (1969) decided to combine the multiple names available for the European forms into a single species, i.e. Anodonta cygnea. Since then, in addition to A. cygnea, another Anodonta species, i.e. A. anatina, has been widely recognised in Europe (Lopes-Lima et al. 2017). More recently, with the help of molecular and morphological work, Anodonta exulcerata has been recognised as a separate and valid species for populations in the Adriatic basin of Italy and the Western Balkan countries (Froufe et al. 2017, Riccardi et al. 2020).

Global and European regional assessment: Endangered (EN)
EU 27 regional regional assessment: Endangered (EN)

Anodonta exulcerata is a European endemic species and is assessed as Endangered (B2ab(iii,v)c(ii)) globally and in the EU27 given that it has a restricted area of occupancy (AOO) of 372 km² globally (which is slightly lower in the EU27 Member States). Additionally, the AOO is highly fragmented by dams and weirs, and its habitat is subject to continuous degradation due to hydrological disturbance, water scarcity and invasive species.

This European endemic species occurs mainly in lakes and other standing or slow-flowing freshwater habitats of the Adriatic river basins of Italy (north of the Apennines) and Switzerland, and along the western Balkans in Croatia, Bosnia and Herzegovina, Montenegro and northern Albania (Riccardi et al. 2020). It may also occur in Slovenia, but this needs to be confirmed.

Most populations of Anodonta exulcerata occur in the pre-alpine lakes of Italy and Switzerland, with some subpopulations occurring in lentic sections of streams and rivers, mainly in the Balkans. The species has also been reported from Lake Trasimeno in southern Italy, but this is most likely due to an ancient human introduction. There are unconfirmed eDNA data from France (upper Loire valley), but further work is required to confirm these records; if confirmed, the native status of the species there is uncertain (V. Prie unpublished data).

Populations of Anodonta exulcerata have declined drastically in lakes in Italy and Switzerland due to the effects of poor water regulation and lake management, causing hydrological disturbances due to floods and especially droughts (N. Riccardi unpublished data). However, the main impact has been the introduction of invasive freshwater bivalve species such as Corbicula fluminea, Dreissena polymorpha and, in particular Sinanodonta woodiana, which have outcompeted and replaced native species in these lakes.

A population reduction of more than 50% has been observed in these pre-Alpine lakes over the last three decades (N. Riccardi pers. data 2022), and due to the predicted rapid expansion of S. woodiana and C. fluminea, the total population is expected to decrease by at least 30% throughout its range.

Anodonta exulcerata occurs in waters with little or no current and substrates typically consisting of mud or muddy sand, often with organic detritus (Riccardi et al. 2020).

This species has the typical unique reproductive features of most Unionidae species, including larval parental care (i.e. brooding) and larval parasitism on freshwater fish (and occasionally other vertebrates) (Lopes-Lima et al. 2017; Modesto et al. 2018). However, the host fish species are not known. Gravid individuals brooding larvae (glochidia) at different stages of development have been observed from early September to late December in Lake Maggiore and Lake Varese (N. Riccardi pers. obs. 2022). Additional information on its biology is scarce due to misidentification with other Anodonta species.

The species is threatened by poor lake and river management, dams, and water over-extraction, which affects the hydrology and water levels of the freshwater systems in which it lives. It is also threatened by the increasing human presence, urbanisation, and intensive agriculture in the western Balkans (M. Lopes-Lima pers. obs. 2022). Another major threat is fouling and competition from other freshwater bivalves such as Corbicula fluminea, Sinanodonta woodiana, and Dreissena polymorpha, which are rapidly replacing native bivalves throughout their distribution. Water pollution from domestic waste and agricultural run-off may also pose a threat to this species, along with habitat alteration caused by increased droughts due to climate change.

No use or trade is known for this species.

This species occurs in the Lake Skadar protected area, and some parts of the Italian and Swiss lakes where it occurs are protected. Apart from this, there are no known conservation actions in place for Anodonta exulcerata, but it would benefit from the development of an action plan to guide future conservation efforts.

It is essential to identify priority populations for conservation in order to establish protected areas, and then to invest in long-term monitoring of these populations using standardised surveys to provide information on population trends. Habitat restoration is also required, with the restoration of connectivity in the rivers, where the species occurs. These areas should be included in order to achieve CBD Target 2 for Italy and the countries in the western Balkans where it occurs. River management practices that involve excavation and disturbance of the substrate, banks and key hydromorphological elements of the channel should be adapted to avoid harming sessile benthic organisms such as freshwater mussels. Control of invasive species such as fouling mussels and macrophytes should also be undertaken in many areas with the hulls of boats and other aquatic vessels being inspected for invasive fouling organisms when they are transported across different waterbodies.

Research is needed to determine its tolerance to contaminants, its detailed distribution, to assess threats, and to understand the basic ecology of the species. Tolerance to traditional and emerging pollutants should be studied in detail and point and non-point sources of pollution identified and eliminated. Outreach and education to relevant stakeholders such as environmental and water management agencies, farmers and farmers' associations, and the general public on the importance of the species and the ecosystem services it provides is also needed.