The cladocerans of the order Ctenopoda are widely distributed and fairly well-known representatives of aquatic communities. Most of them inhabit continental waters of different types while two species of the subfamily Penilinae and family Pseudopenilidae occur in the pelagic zone of the world ocean and in the deep bottom sediments of the Black Sea, respectively (Korovchinsky, 2004a; Korovchinsky & Sergeeva, 2008). The group is most diverse and abundant in tropical, subtropical, and southern temperate latitudes but is represented in all climatic zones, and on all continents save Antarctica and New Zealand. Its representatives (e.g., Sida spp., Diaphanosoma spp., Holopedium spp., Penilia avirostris Dana) often dominate the pelagic and littoral zooplankton communities. In spite of their comparatively low species richness, ctenopods demonstrate high morphological diversity and have developed various life strategies with adaptations to different habitats and predator avoidance. The peculiar adaptations of their representatives place them in a unique position within Cladocera and Branchiopoda (Korovchinsky, 1990, 2004a)...weiterlesen