Artem Yu Sinev

Investigation of the morphology of the rare Australian cladoceran, Australochydorus aporus Smirnov & Timms, 1983 (Crustacea: Cladocera: Chydoridae) based on type material led to re-evaluation of the genus Australochydorus Smirnov & Timms, 1983, previously presumed to be monotypic. Three species of the genus Chydorus s.lato: East Asian Chydorus breviceps (Stingelin, 1905), Neotropical Chydorus nitidulus (Sars, 1901) and African Chydorus tilhoi Rey & Saint-Jean, 1969 are translocated to the genus Australochydorus, and emended diagnosis of the genus is provided. Translocation of these species into Australochydorus eliminates the last deviating species from Chydorus s.str. and makes it a fully monophyletic group. Australochydorus differs from Chydorus s. str. in strongly oval or ovoid body, in tip of rostrum located at the middle of body height, in posterior setae of valves attached close to the valve margin, in absence of posterior or both major head pores, in elongated narrow postabdomen, and in details of morphology of appendages.

Research into the morphology of the rare Western Australian cladoceran, Alona setuloides Smirnov and Timms, 1983, (Crustacea: Cladocera: Chydoridae), based on type material, led to its translocation to the genus Ovalona Van Damme and Dumont, 2008. O. setuloides is one of the most primitive members of the genus and is a sister species to the Mediterranean Ovalona nuragica (Alonso, 1996). The main synapomorphy between these two species lies in the lateral head pores (in the form of small, rounded cavities), unique to Alona s. lato. These two species also exhibit a morphology similar to that of the Andean Ovalona nigra (Smirnov, 1995). The species in this group are relict, rare, and confined to specific habitats. The current distribution of the nuragica-group can be explained by the “theory of ejected relicts”. The group likely originated in the Mesozoic; it was distributed throughout Mesozoic Gondwana, but is now replaced by the eurybiotic pulchella-clade, the terminal group of Ovalona.

Cladocera (Crustacea: Branchiopoda) of seven large lakes in Jiangsu province, East China were studied during November 2023, January 2024, and March of 2024. Our study reveals 46 species of Cladocera, two of them, Coronatella jejuana Sinev, Lee & Kotov, 2022 and Daphnia (Daphnia) sinevi Kotov, Ishida & Taylor, 2006, are new for China. Among them, in total, 22 species were predominantly Boreal, 15 species have core area of distribution in the south part of the temperate zone and subtropics, and 17 were tropical species. Concerning the seasons, 40 species were found in November, 17 in January, and 25 in March. Our study revealed two opposite overwintering strategies in local Cladocera composition. Species of subtropical and tropical origin, as well as some species of Boreal origin, produce resting eggs in November and disappear in winter. All 17 species present in January, in contrast, form parthenogenetically reproducing overwintering populations. Our data confirm the hypothesis on the East China Plain as a transitory zone between Boreal and Tropical faunistic complexes of Cladocera.

The distribution and ecological preferences of the rare water flea Ovalona karelica (Stenroos, 1897) (Crustacea, Branchiopoda, Cladocera) were analysed for the first time for European Russia. The species was found in different types of waterbodies, such as floodplain lakes of the Kerzhensky State Nature Biosphere Reserve, Nizhny Novgorod City and mouths of rivers inflowing into reservoirs. Ovalona karelica inhabits waters with wide ranges of pH, salinity, oxygen content and trophicity. Development of semi-submerged macrophytes (Stratiotes, Hydrocharis, Salvinia) is the main factor influencing occurrence of the species and its abundance.

Two species of the water fleas from subgenus Coronatella (Ephemeralona) Sinev, 2020 from the Southern Hemisphere are revised and redescribed based on type material. South African Coronatella (Ephemeralona) striolata (Sars, 1916) differs from all other species of the subgenus in extremely large eye and ocellus and unique morphology of male postabdomen. Coronatella (Ephemeralona) vermiculata (Smirnov & Timms 1983), initially described as a subspecies of Alona davidi Sars, 1903, differs from other species of the subgenus in a truncated rostrum and spine-like posterior setae of valves. Morphology and taxonomic position of the studied species is discussed. With all other species of the subgenus Coronatella (Ephemeralona) confined to Europe, North Africa and arid belt of Asia, the subgenus has a well-described previously bipolar (antitropical) distribution.

Cladoceran samples from Peninsular Malaysia were collected during four sampling trips: in October 2013, November–December 2014, January–February 2018, and September 2022. More than 50 localities were sampled on each trip, including ditches, canals, rivers, ponds, swamps, lakes, old mining pools, and reservoirs. In these samples, we revealed six species new to Malaysia: two of them are planktonic (Bosmina meridionalis and Bosmina fatalis) and four are substrate-associated (Simocephalus expinosus, Anthalona spinifera, Anthalona vandammei, Karualona serrulata). Both species of the genus Bosmina appear to be recent additions to the local fauna, as this genus was not recorded in Malaysia until the last decade. New records are obtained on three rare local species: Simocephalus mixtus, Streblocerus spinulatus, and Acroperus harpae. The morphology of two uncommon East Asian species, Coronatella acuticostata and Chydorus obscurirostris tasekberae was investigated in detail for the first time. With the new records, the list of valid cladoceran species of Malaysia now consists of 72 species as compared to 62 species reported by Idris (1983) in his monograph. However, more studies are needed to produce an exhaustive final species list of the Malaysian cladocerans.

Two rare East Asian cladocerans, Coronatella (Coronatella) trachystriata (Chen, Zhang et Liu, 1994) and Nedorhynchotalona chiangi Kotov & Sinev, 2011, were found in Qili Lake on the border of Anhui and Jiangsu Provinces of China. Morphology of the species was studied by scanning electron microscopy for the first time, revealing unique morphological features: valve sculpture as a system of ridges in C. (C.) trachystriata and head shield with only lateral head pores present in N. chiangi. Both species have numerous adaptations for a benthic mode of life. They were found in a pelagic plankton sample during strong wind action, but were absent in littoral samples. Our data suggest that both species inhabit bottom sediments in a deeper zone of lakes at some distance from the shore, usually not sampled during cladoceran faunistic surveys. Morphology and distribution of the species are discussed.

Here we attempt to clarify a faunistic composition of branchiopods from southern Tajikistan and the southern part of the Tajik Pamir Plateau (Central Asia) based on samples collected from June 24 to July 6, 2023. In total, 19 species of branchiopods were identified from plain West and South Tajikistan, and 27 species were recorded in Tajik Pamir. Five taxa were newly recorded for the territory of Tajikistan: Chirocephalus cf. bobrinskii (Alcock, 1898), Ceriodaphnia dubia Richard, 1894 s. lat., C. megops Sars, 1862, Ilyocryptus spinifer Herrick, 1882, and Anthalona harti harti Van Damme, Sinev & Dumont, 2011. The previous identifications were corrected for four more taxa. Morphological traits and taxonomic position of several species were discussed in detail, namely two abovementioned anostracan taxa, Eulimnadia behningi Smirnov, 1949 (Spinicaudata), Anthalona harti harti and Coronatella rectangula (Sars, 1861) (Anomopoda). To date, the faunistic list of Tajikistan includes 77 valid branchiopod taxa. Plain Tajikistan is inhabited by both boreal and tropical branchiopod species, what indicates its geographic position on the edge of the Palearctic. Tajik Pamir fauna includes a specific component of alpine species and regional endemics. Complex relief and geographic position of Tajikistan make it prospective for future faunistic, biogeographic and phylogeographic research.

A new species of Ovalona Van Damme & Dumont, 2008 (Cladocera: Anomopoda) related to the rare Australian species Ovalona archeri (Sars, 1888), is described from the Mekong Delta, South Vietnam. Ovalona garibiani sp. nov. differs from O. archeri in morphology of antenna, postabdomen, and proportions of setae on thoracic limbs II–III. Both species differ from other species of the genus Ovalona in the postabdomen with a narrow and sparsely spaced group of lateral setulae, the distance between the postanal groups being slightly greater than the width of the group. O. garibiani sp. nov. is a rare phytophilous species, known from a few localities in continental Malaysia, Southern Thailand and Vietnam.

A study was conducted to evaluate zooplankton species composition, abundance, and diversity in both natural and artificial lakes with varying trophic levels and to determine the relationship between zooplankton community structure and lake environmental conditions. This study hypothesized that correlations exist between zooplankton community structures and environmental parameters associated with eutrophication in natural and artificial lakes. Sampling was conducted across 16 distinct freshwater lentic ecosystems in Malaysia, including natural lakes/swamps, reservoirs, constructed lakes/ponds, and old mining lakes, spanning a range of trophic levels from mesotrophic to hypereutrophic conditions. Physicochemical parameters were measured in situ, while water and zooplankton samples were collected for nutrient analyses, as well as for zooplankton identification and enumeration. Throughout this study, a total of 58 zooplankton species, consisting of 36 species of rotifers, 12 species of cladocerans, and 10 species of copepods, were recorded. The highest zooplankton density (365.7 ± 13.7 ind L⁻¹) was recorded in constructed lakes/ponds while the lowest density was recorded in natural shallow lakes/swamps (200.5 ± 25.5 ind L⁻¹). On the other hand, significantly higher (p < 0.05) mean species diversity was observed in natural lakes/swamps (H’ = 2.2 ± 0.0); whereas, the lowest diversity was in old mining lakes (H’ = 1.5 ± 0.1). The canonical correspondence analysis (CCA) scores indicated that Polyarthra vulgaris and Chydorus ventricosus were the discriminating species in natural shallow lakes/swamps associated with high water transparency. Meanwhile, the small-sized cladocerans (Ceriodaphnia cornuta) and rotifers (Keratella spp., Brachionus spp., and Trichocerca spp.) were the most discriminating species in lakes with high turbidity, nutrients, and chlorophyll a concentrations, which are the main features of reservoirs and constructed lakes/ponds. Low density and diversity in old mining lakes were due to a low species number and the dominance of two species, Lophocharis curvata (38.8%) and Ptygura libera (39.7%). Overall, the high dominance of a specific zooplankton species resulted in lower biodiversity in artificial ecosystems compared to natural ecosystems. This study elucidated that zooplankton community structure in lakes was significantly influenced by the environmental conditions related to the lake trophic status.