Two new species of the Diacyclops languidoides-group (Copepoda, Cyclopoida) from groundwaters of Austria

Two new syntopic species of the Diacyclops languidoides-group (D. danielopoli n. sp. and D. felix n. sp.) are described from interstitial groundwaters of Lobau wetlands, Austria. Both species lack the exopodal seta on antenna basipod, but differ in several minute morphological details of antennules, antennae, maxillulary palp, coxal plates, P4 basipod and caudal rami. Some of these characters are present in D. danielopoli n. sp. in an apomorphic state (reduction of setation patterns, longer aesthetascs on male and female antennules, absence of exopodal seta on maxillulary palp, longer dorsal caudal seta) suggesting a higher degree of specialization to the subterranean environment than in D. felix n. sp. The relationship between the reduction of setation patterns on mouthparts and the degree of stygobitization in the Diacyclops languidoides-species group is critically discussed.