A review of the diversity, adaptations and groundwater colonization pathways in Cladocera and Calanoida (Crustacea), two rare and contrasting groups of stygobionts
Brancelj, Anton; Dumont, Henri J.
published: Jan 1, 2007
ArtNo. ESP141016801002, Price: 29.00 €
Cladocera and calanoid Copepoda are ubiquitous in surface freshwater, each with about 500-600 species and subspecies distributed worldwide. Both groups also contain some subterranean species, which occur in karst and porous aquifers. The first stygobiotic calanoid, Microdiaptomus cokeri, was described in 1942, and the first cladoceran, Alona smirnovi, in 1973. Currently, seven species of Cladocera are confirmed and three more are possible stygobionts. In Calanoida, nine species are recognized stygobionts and three more are possible. In the last few years the number of described stygobiotic taxa has increased and may continue to do so, as caves and gravel-beds are more intensively studied. Stygobionts are probably derived from a Miocene fauna that, under the constraint of a worsening climate, took advantage of the development of caves and found subterranean refugia. The Pleistocene glaciations accelerated this colonization process, which persists to the present. Both groups do not contribute much to the overall subterranean biodiversity, but they exhibit adaptations that may help to reveal the mechanisms of colonization of the subterranean realm. Some of their characteristics are related to feeding and to maintaining their position during cave floods, and are shared with other stygobionts. In addition, stygobiotic Cladocera and Calanoida have distinct life-histories and morphological adaptations. In karst-dwelling Cladocera, parthenogenesis supports fragmented populations, whereas karst-dwelling Calanoida are planktonic, a unique way of life among freshwater stygobionts.