The shells of the Congeria jalzici cave shells or Jalžić's shell were first discovered in the source of Krupa river in 1970. In 2010 the first living animals were found. The shell is a living remnant (relic) of the Cenozoic era (66 million years ago to today). Shellfish live in underground streams and are frequently found in large colonies.
The cave shell can grow to 13 mm in size. Its surface is brown in color. It has two genders. Shellfish are fed by filtering organic matter from groundwater. Reproduction works at lower water levels. The life expectancy of a Jalzic shell is between 30 and 40 years. The cave shell source is a small water cave, which was explored to a depth of 6 m and a length of about 60 m. The trench is covered in fine sand. Shellfish live alongside Marifugia cavatica cave worm.
Where to discover
The cave shell source is only accessible by foot. When driving on the Semič – Gradac road, heading towards Semič, turn right after arriving in Stranska vas. After about 300 m park your car and head down the road on foot. Cross the bridge over the Krupa river and continue to Karst cave Jewish house. Walk past the small hayrack and watch for a small signpost for »Jamska školjka« and continue on the forest road. The cave shell source is located about 10 – 15 minutes walk.