Survival of the epigean Dendrodrilus rubidus tenuis (Oligochaeta: Lumbricidae) in a subterranean environment

Abstract

The peregrine earthworm Dendrodrilus rubidus tenuis was regularly sampled in a percolating water drip originating in a habitat inaccessible to humans in the Huda luknja pri Doliču cave, Slovenia. The reconstruction of this habitat includes both a larger passage with bat colonies supplying wet bat guano sediments, on which the earthworms feed, and narrow channels, which drain water from this passage into the sampling drip. Fresh guano is deposited in autumn shortly before the earthworms become inactive. Then, it is exploited by moulds and additionally depleted by water washing out the nutrients before the earthworms reactivate in spring. Thus, this is a rather poor food resource for the earthworms. Despite this, and apart from their short size and delayed maturation, no other disturbance or damage was found caused by malnutrition, which was confirmed in individuals submitted to starvation in captivity. We suggest that Dd. r. tenuis, which shows neither disturbance from nor adaptation to living in a subterranean environment, can subsist there because of its euryoecious character. Nevertheless, in temperate climates, this is rather a harsh habitat for this earthworm.