Animal classes
Terrestrial isopods (Isopoda terrestria)
Terrestrial isopods are the only group of crustaceans that are fully adapted to life on land. Inhabit different biotopes, from the sea shore, high mountains, forests to deserts. Life terrestrial isopods on land allow the so-called pseudotrachea or lungs on abdominal legs. Even though less adapted families still have the same mode of breathing using the gills formed of abdominal legs same as aquatic isopods, and are very dependent on high relative air humidity. As a rule, in the caves the relative air humidity is always very high, therefore the cave habitats are suitable for them. Of 117 species and 32 subspecies so far established for the Croatian fauna 20 species are true cave animals, and 14 species and 7 subspecies are believed to dwell in caves and above-ground habitats. Terrestrial isopods have a number of adjustments to cave habitats, and some have developed a strong ornamentation of the cuticle for defense from predators or pressure when moving through cracks in the soil, eg Herzegovinian Humpback Woodlouse (Cyphoniscellus herzegowinensis). Some species are very widespread, such as white titanic-bug (Titanethes albus) spread from Italy, Slovenia and Croatia, while the most species are spread on a small area or a single site, such as Krk's Iliric Woodlouse (Alpioniscus christiani), found only in Biserujka cave on the island of Krk. Some species have a very interesting distribution, so as Učka's Tiny Humpback Woodlouse (Thaumatoniscellus speluncae) was found only in one cave in Učka Mt, and the only known relative is defined in one locality in Romania.
