Earthworm fauna of Cape Kamenjak (Istria, Croatia) with a focus on the endemic species Octodrilus istrianus Mršić, 1991

Abstract

The area of Donji Kamenjak (Istria, Croatia) is locus typicus for the species Octodrilus istrianus Mršić, 1991. However, the whole earthworm fauna has not been investigated. Given that O. istrianus is an endemic species to the Istrian region, this fact inspired our research in this small, but unique location. Field samplings were conducted over a two-year period (2020–2021), with biannual collections in both spring and autumn. In total, we identified nine earthworm species, including eight from the Lumbricidae family and one from the Acanthodrilidae family. We confirmed the presence of O. istrianus Mršić, 1991 and, for the first time in Croatia, documented the presence of Microscolex dubius (Fletscher, 1887). The most abundant species was Octodrilus kvarnerus Mršić, 1987, also an endemic species for this area. The endemic species O. istrianus in this surveyed area faces threats from habitat degradation, mechanical land cultivation practices, wild boars foraging and the impact of tourism during the majority of the year.