Morphology and ecology of a group of small, pelagic, tropicalTropocyclops (Crustacea, Copepoda, Cyclopoida), with the descriptionof a new species from South China.

Abstract

Tropocyclops bopingi n.sp. is a 0.4 mm cyclopoid found in Liuxi He Reservoir, Guangdong, South China. It is probablywidespread in South China, and appears in the Fauna Sinica under the name T. parvus. True T. parvus is a Central Americanspecies that is here redescribed from its type locality, Lake Petén Itzá in Guatemala. T. bopingi is related to T. tenellus from thelimnetic zone of Lake Tanganyika and other lakes in Central Africa, and all of them live under climatic conditions that aretransitory between subtropical and tropical. T. tenellus is even smaller and more buoyant than T. bopingi and, at least in LakeTanganyika, it tends to occur closer to the water surface than other zooplankton during the daytime. It does not carry egg balls,but extrudes eggs one at a time. T. tenellus and T. bopingi appear morphologically closer to each other than to T. parvus, but allthree are ecologically similar: extremely small, pelagic species that presumably feed on small particles in the water. I hypothesizethat environmental conditions in subtropical-tropical transition zones combine with predation and competitive pressure to offer aselective advantage to such omnivorous species in the open water of large lakes or reservoirs.