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Subterranean community from Lukina jama – Trojama cave system, the deepest cave in Dinaric Karst (Northern Velebit Mt., Croatia)

First biological research of deep pits in the Northern Velebit area started in 1992 with discovery of the cave system Lukina jama – Trojama. It is the deepest pit of the Dinaric Karst (-1421 m), situated in the Northern Velebit National Park. From its entrance zone to the 320 m of depth it is filled with ice and snow and therefore not suitable for the majority of cave- dwelling fauna. The temperature range (measured in 2010) gradually increases from bellow 0°C (entrance) to 4, 9°C (depth of 1381 m). Deepest part of the pit reaches phreatic zone which is explored up to 40 m in depth. During high water stands water can rise more than 100 m. Altogether 29 taxa are recorded in Lukina jama – Trojama cave system, 20 troglobionts (Gastropoda 1 ; Palpigrada 1 ; Acari 2 ; Opiliones 2 ; Pseudoscorpiones 1 ; Isopoda 2 ; Chilopoda 1 ; Diplopoda 1 ; Collembola 5 ; Diplura 1 ; Coleoptera 3) ; 7 stygobionts (Porifera 1 ; Bivalvia 1 ; Hirudinea 1 ; Polychaeta 1 ; Amphipoda 2 ; Decapoda 1) ; 1 tentative troglophile (Diptera) and 1 trogloxene (Chiroptera). Almost total absence of troglophiles can be explained with low temperatures in the entrance parts of the pit. The number of collected specimens of most taxa is extremely low considering the collection effort. In total 16 troglobionts and 2 stygobionts found in the cave system are endemic for Velebit Mt. and Lika region. However, several troglobionts recorded in deep pits only few kilometers away from Lukina jama – Trojama have not been found (Hirudinea 1 ; Araneae 2 ; Pseudoscorpiones 1 ; Isopoda 1 ; Collembola 1 ; Coleoptera 1). Along with a species of Coleoptera adapted to hygropetric habitat, extremely troglomorphic representatives of Collembola and Isopoda terrestria were found. In comparison to the world's deepest subterranean community from Krubera – Voronja cave (Western Caucasus), Lukina jama - Trojama has higher species richness (29 vs. 16 taxa) probably as a result of more frequent collection effort but also biogeographical position. The vertical distribution of species richness is different where the highest number of collected taxa in Voronja-Krubera is in the entrance zone (60 m deep) and in Lukina jama – Trojama in a chamber at 1000 m depth. About half of the taxa collected in Lukina jama – Trojama are still undescribed, including several new genera, but more specimens are needed for the taxonomical studies.

subterranean community ; Dinaric karst ; species richness

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