The Dinaric Alps are known worldwide as the richest subterranean fauna region. The karst areas in Croatia, part of the Dinarides , have been defined biospeleologically as an area of high biodiversity in world terms, covering 26 thousand km2 in all. The diversified geomorphology, hydrology and climate have resulted in a remarkable range of different underground habitats in Croatia, inland and coastal caves, superficial and deep phreatic networks, interstitial – hyporheic substrates and other infiltration zones, etc.
To date about 470 aquatic and 860 terrestrial subterranean taxa from the Dinaric alps have been described. About one third of these described taxa come from Croatia. In Croatia more than 500 obligate subterranean species and subspecies are known from caves and interstitial habitats. The majority of subterranean species in Croatia are terrestrial biota. There are 316 troglobiont and 170 stygobiont taxa (species and subspecies) recorded. Most subterranean species have very restricted ranges, almost 70 % of them endemic to Croatia. Cave fungi are poorly known. Among them there are several important parasitic troglobionts and troglophilic species on cave coleopterans and troglophilic moths in Croatian caves. Some saprotrophic species could be troglobiotic too but their taxonomic and/or ecological status must be clarified in future research.
With a respect to the number of troglobionts, the five largest animal groups are beetles (Coleoptera), falsescorpions (Pseudoscorpiones), spiders (Aranea), snails (Gastropoda) and centipedes (Diplopoda). The beetles are predominant. More than 100 cavernicolous beetles (species and subspecies) are known in Croatia. Among stygobionts, the Crustacea predominate. At least half of species described in Croatia are Crustacea. Numerically, among crustacean stygobiotic Amphipoda dominate in caves and Copepoda in interstitial habitats.
The only known stygobiotic sponge Eunapius subterraneus Sket & Velikonja inhabits several caves in Croatia in Ogulin area. Also, the only known stygobiotic clam Congeria kusceri Bole inhabits few of caves in Croatia. Other important groups include hydrozoa, planarians (Temnocephalida and Tricladida), snails (Mollusca: Gastropoda) and the only European stygobiotic Chordata olm Proteus anguinus Laurenti. The high taxonomic diversity of the subterranean biota of Croatia can be attributed partly to the geographical heterogeneity and a rather unique combination of various geological and ecological phenomena.
Bibliography: Gottstein Matočec, S. (ed.), 2002: An overview of the cave and interstitial biota of Croatia. Natura Croatica, Vol. 11, Suppl. 1, p. 1-112.