On some modern Ostracoda (Crustacea) from the Tibetan Plateau in SW China, with descriptions of three new species

Abstract

Studies of Holocene ostracods of the Tibetan Plateau have mostly centred around valves and carapaces collected from lake sediments, some at or near the substrate surface and others from short cores. Reports from habitats other than lakes are scarce, and few living species found in this region have appendages described, hindering further taxonomic and phylogenetic work. For this study collections of living ostracods were made in mostly ponds, as well as two rivers and one lake. Six species, including three previously undescribed, were recovered: Tonnacypris estonica (Järvekülg, 1960), Arctocypris edita n. sp., Cypris pubera O.F. Müller, 1776, Potamocypris variegata (Brady & Norman, 1889), Ilyocypris tibeta n. sp., and Fabaeformiscandona monticulus n. sp. Specimens of Tonnacypris estonica include males, previously unknown for this species, and suggesting it is a geographical parthenogen. A revision of the fifth limb morphology of the genus Arctocypris, and a subsequent amended diagnosis of the genus are given. Based on carapace and appendage features, Eucypris mareotica (Fischer, 1855) is transferred to this genus: Arctocypris mareotica (Fischer, 1855) com. nov. There are now ca. 100 ostracod species reported from modern or subsurface sediments on the Tibetan Plateau, but only 19 of those can be confirmed as alive when collected (i.e. had appendages intact). The families Limnocytheridae and Ilyocyprididae are both relatively diverse on the plateau compared with the Palaearctic zoogeographical region generally. About one third of ostracod species reported from the Tibetan Plateau are only known from there, suggesting a potentially very high rate of endemism.

Three new species of non-marine ostracods (Crustacea, Ostracoda) from small water bodies of northern China

“…Yu et al (2009) suggested that the number of Chinese endemic species should represent ~ 40% of the entire ostracods (including subfossil species) of this country. However, with the increasing knowledge on the extant non-marine ostracods of China (Kong et al 2014;Zhai and Zhao 2014;Yu 2018, 2020;Peng et al 2021), the ratio of endemic species seems to be declining. Among all the ostracods listed in The three new species also add to our knowledge on the geographical distribution of extant ostracods in general.…”

“… Yu et al (2009) suggested that the number of Chinese endemic species should represent ~ 40% of the entire ostracods (including subfossil species) of this country. However, with the increasing knowledge on the extant non-marine ostracods of China ( Kong et al 2014 ; Zhai and Zhao 2014 ; Ma and Yu 2018 , 2020 ; Peng et al 2021 ), the ratio of endemic species seems to be declining. Among all the ostracods listed in Table 2 , 12 species are endemic to the PA region: Candona quasiakaina Karanovic & Lee, 2012, Eucypris pigra (Fischer, 1851), Fabaeformiscandona alexandri (Sywula, 1981), F. myllaina Smith & Kamiya, 2007, Heterocypris auricularis Zhai & Zhao, 2014, H. vandouwei (Brehm, 1923), Ilyocypris innermongolica Zhai & Xiao, 2013, I.…”

“…The genus Tonnacypris has been rarely reported from China. The only named species of the genus reported from this country, T. estonica (Järvekülg, 1960), has been found from the Qinghai‒Tibet Plateau ( Li et al 2021 ; Peng et al 2021 ). Mischke et al (2003) found a fragment of the anterior part of RV of Tonnacypris (?)…”

“… T. rectangularis sp. nov. can be identified as belonging to this genus by the presence of peg on the LV [although not all specimens of this genus have pegs, see e.g., Peng et al (2021) ], presence of the c -seta on the L5 , a short d1 - and long d2 - setae on the L6 . There are nine extant species in this genus ( Meisch et al 2019 ).…”

“…The number of species presented by Yu (2014) is in accordance with the Martens and Savatenalinton (2011) estimate. Recently, a number of publications added taxa to the catalogue of the living non-marine ostracods of China (e.g., Zhai and Xiao 2013 ; Kong et al 2014 ; Zhai and Zhao 2014 ; Ma and Yu 2018 , 2020 ; Peng et al 2021 ), and the total number may be slightly more than 100. Probably many more species await discovery and description, considering the comparatively small number of taxonomic works done in China since Sars (1903) and Chen (1957) , and disparity of geographical settings with diverse aquatic ecosystems found across the vast land area of this country.…”