Congeria kusceri 

Scope: Global, Europe & Mediterranean
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Mollusca Bivalvia Veneroida Dreissenidae

Scientific Name: Congeria kusceri Bole, 1962
Taxonomic Source(s): Graf, D.L. and Cummings, K.S. 2013. The Freshwater Mussels (Unionoida) of the World (and other less consequential bivalves), updated 8 August 2013. MUSSEL Project Web Site. Available at: (Accessed: 15 April 2014).
Taxonomic Notes: Morton et al. (1998) reviewed the status of this genus, and noted that although many had considered the genus to be extinct, there was still one extant species in the cave systems in Slovenia, Croatia and Bosnia & Hercegovina. They regarded this species as a ‘living fossil’, as the species is a single representative of a genus that once had many species during Tertiary times.

Assessment Information [top]

Red List Category & Criteria: Vulnerable A2ac ver 3.1
Year Published: 2011
Date Assessed: 2009-11-26
Assessor(s): Bilandzija, H.
Reviewer(s): Jalzic, B., Seddon, M. & Ward, J.
This species has a restricted range and habitat. It is only found within rivers within cave systems, and appears to have been isolated since the Tertiary era. The conservation assessment of Vulnerable (VU A2ac), is based on the estimated loss of individuals in surviving sub-populations combined with total loss of subpopulations from sites that have been well monitored since the discovery of this living fossil. The loss range is between 25 and 35%, based on the estimated generation length of 25 years, providing an assessment period of up to 75 years. In some parts of the range the loss maybe more severe.

This species has also been assessed at the regional level:
European regional assessment: Vulnerable (VU A2ac)
EU 27 regional assessment: Data Deficient (DD) at the level of the 27 member States of the European Union, as its status in Slovenia is unknown.

Geographic Range [top]

Range Description:This species is known around seven locations is Slovenia, Croatia and Bosnia & Hercegovina. In Slovenia the species is known from one site where it was found as shell deposits. In Croatia there were originally 15 sites described from five sub-populations in the 1960s, but following extensive surveys only three have been rediscovered over the last two years. In Bosnia & Hercegovina it has been described from 13 sites of which four populations have been re-discovered (although not all original sites have been searched). According to Morton et al. (1998) in Bosnia & Hercegovina the species has been recorded from six cave systems at Lusci Palanka, Dabarska Pecina, Tihalijina, Metkovic and Popova Polje as well as from shells in springs at Isvir Krupe and Vrgarac. The main cluster of sites are between Spilt, Mostar and Dubrovnik.
Countries occurrence:
Bosnia and Herzegovina; Croatia; Slovenia
Additional data:
Continuing decline in extent of occurrence (EOO):Yes
Number of Locations:7-10Continuing decline in number of locations:Yes
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:There are few data on population trends. In Bosnia & Hercegovina there is good evidence of serious declines. This species is believed to be long-lived, based on the growth rings in the shell, with an assumption that one growth ring is laid down each year. The estimated age of an individual 12.7 mm in length was 25 years, and the largest known shells are over 25 mm (Morton et al. 1998). Morton et al. (1998) also suggests that sometimes there are years with high juvenile mortality and little recruitment.
Current Population Trend:Decreasing
Additional data:
Population severely fragmented:No
Continuing decline in subpopulations:Yes

Habitat and Ecology [top]

Habitat and Ecology:This species has been recorded from cave systems where it cements onto the rock surfaces. It lives as clusters of shells attached to the cave walls, with the waters having a relatively constant temperature of 9°C and the clusters are not exposed to sunlight. These caves are only accessible during the summer periods, when after periods without rain, water levels within the caves drop, allowing access. This drop in water level is thought to be the trigger for reproduction, when the sperm are released into the water, and then in all probability ‘inhaled’ by the females from the water. The eggs are brooded internally and either released as larva with a short planktonic life, or as ‘crawl away’ juveniles, as is the case with Corbicula fluminea.
Continuing decline in area, extent and/or quality of habitat:Yes
Generation Length (years):25

Use and Trade [top]

Use and Trade: This species is not utilized.

Threats [top]

Major Threat(s): Main threats to the species come from pollution of groundwaters from domestic sources and agricultural runoff.   Although the species is able to withstand a late summer/early autumn drop in water levels, it would also be vulnerable to longer periods of draw-down (water extraction) as would happen if these cave waters were to be heavily exploited as a source of artesian waters for domestic supplies.

Conservation Actions [top]

Conservation Actions: The species is protected in Croatia, however the pollution is still a problem for this species and urgent conservation actions are required to control polluting sources and reduce groundwater use for the extant populations.

Citation: Bilandzija, H. 2011. Congeria kusceri. The IUCN Red List of Threatened Species 2011: e.T171942A6811583. . Downloaded on 23 September 2018.
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