Checklist and Distribution of Calanoida (Crustacea: Copepoda) in Kazakhstan (Central Asia)

This work aims to analyze the zoogeographic distribution of Calanoida in Kazakhstan. Kazakhstan belongs to the Palaearctic region, and its territory is ascribed to the European–Siberian and Nagorno–Asian biogeographical subregions. The European–Siberian subregion includes the Volga–Ural, Irtysh, and Turkestan–Aral provinces. The Balkhash province belongs to the Nagorno–Asian subregion. Studies of the Calanoida fauna were carried out between 1997 and 2019. For this purpose, 7250 zooplankton samples were taken in 130 different water bodies. Findings of 26 species of Calanoida have been documented. The richest in species composition (20) is the Calanoida fauna of the Irtysh province. Ten Calanoida species have been recorded in the Volga–Ural province, 8 in the Turkestan–Aral province, 7 in the Balkhash province, and 5 in the Ponto–Caspian region. The distribution of the species richness of the order is determined by a complex of climatic factors, including the density of the hydrographic network, a variety of hydrochemical conditions, and accidental acclimatization of species. Far Eastern species (Sinodiaptomus sarsi, Neutrodiaptomus incongruens, Neodiaptomus schmackeri) entered the inland water bodies of Kazakhstan, most likely through the introduction of non-native fish species. The Black Sea species Acartia tonsa and Calanipeda aquaedulcis were introduced into the Caspian Sea with ballast waters. Three autochthonous species (Limnocalanus macrurus, Eurytemora grimmi, Eurytemora minor), formerly inhabiting the Caspian Sea, can now be considered extinct. Acanthodiaptomus denticornis, Arctodiaptomus (R.) salinus, Phyllodiaptomus blanci, and Eudiaptomus graciloides are widespread in the region. Endemic species (Gigantodiaptomus irtyshensis, Arctodiaptomus naurzumensis) and species are new for Kazakhstan (Diaptomus (Chaetodiaptomus) mirus, Eudiaptomus transylvanicus, Arctodiaptomus dentifer, A. (Rh.) ulomskyi were found in small waterbodies; they are known only from single occurrence sites as well as Eurytemora caspica. The last one was described from the northern part of the Caspian Sea, in the coastal zone. Further research into small water bodies that are poorly studied may expand our knowledge of the diversity of Calanoida in Kazakhstan. Calanoida fauna of Kazakhstan was closest to the fauna of countries with a continental climate and most strongly differed from countries with subtropical and Mediterranean types of climates.

Predation on Ciliates by the Suspension-Feeding Calanoid Copepod Acanthodiaptomus denticornis

The effects of prey size, hunger, and algal presence on the predation of the suspension-feeding calanoid copepod Acanthodiaptomus denticornis on the ciliates Tetrahymena corlisii (32 μm mean length), Paramecium aurelia (114 μm), P. caudatum (124 μm), Loxodes sp. [Formula: see text], and Stentor coeruleus[Formula: see text] and the flagellate Astasia longa (14 μm) were evaluated in laboratory experiments. Adult Acanthodiaptomus consumed all species, but not in proportion to their size. At low concentrations (prey < 200 μg C∙L−1), mean clearance rates ranged from 80 mL∙copepod−1∙d−1 (for Paramecium) to 13 mL∙copepod−1∙d−1 (for Loxodes). Clearance rates declined with increasing concentration of the same prey, as expected. Prey capture and ingestion was determined by cell width and prey escape reactivity. Hunger significantly increased predation rates at high prey levels. The presence of algae enhanced ciliate predation by hungry copepods at low prey levels, but had no other significant effects. Protozoan predation by Acanthodiaptomus generally exceeds its feeding on algae and nanoplankton. Results suggest that ciliates can be a significant part of the diet of some suspension-feeding freshwater copepods in situ, confirming the importance of ciliates as mediators of energy transfer from the microbial loop to higher trophic levels.