Aquatic environments on the Tibetan Plateau host mostly endemic ostracode species. Previous work has identified nine species and provided valuable ecological information about the most prominent modern species in Lake Nam Co (Leucocytherella sinensis, Leucocythere dorsotuberosa, Fabaeformiscandona gyirongensis) and aquatic environments (rivers and ephemeral lacustrine water bodies) in the region. Fossil species from Nam Co sediments have underlined the potential of ostracodes as indicators of hydrological changes in the past. We still lack, however, information on population dynamics and a robust taxonomy. A first attempt to clarify the taxonomy of Tonnacypris gyirongensis has been made based on soft parts dissections and genetic sequences. Genome analysis requires enough and good quality of DNA which is limited in single ostracods due to their small size, thus, a parthenogenetic species was selected and cultivated in the laboratory to analyze at once two or three generations containing multiple clonal individuals from one mother, and thus all with almost identical DNA sequences throughout the genome. Culturing of the parthenogenetic ostracod species Bradleystrandesia sp. from an ephemeral pond next to Lake Nam Co produced 30 matrilines after 3 months and opens the opportunity to attempt sequencing for the first time a full genome of an ostracode.
This topic will focus on studying the (1) population structure, (2) life cycles, and (3) genetics of Ostracoda of Nam Co and its catchment. The goals are to generate spatio-temporal information on ontogeny, reproductive strategies and environmental sensitivities and tolerances. Population structure of the most dominant ostracod species using already extracted shells from surface sediments and sediment cores from lake Nam Co and its catchment (rivers, and ephemeral lacustrine environments) will be analyzed to document sizes and shapes of all different ostracod larval stages (A-8 to A), and differences between males and females, and sexual and asexual species. This will reveal reproduction and survival strategies to abrupt climate and environmental change and moreover it will facilitate identification down to species level even of ostracod instars. Data will be related to modern limnological variables for a better understanding of the variability of ostracod shell dimensions, sex ratios and endemicity. Life cycles for the dominant species will be identified and described for each type of environment. Ostracod culturing in the laboratory will be attempted using 10x genomics technology to establish a complete genome of an ostracod species, first to be known for this model group. Parallel RNA-single-cell transcriptomic analyses will be conducted to compare gene activity at different larval stages. Additionally, culturing experiments should be conducted to gather ecological information that will complement the one derived from previous field campaigns by designing different experiments to test preferences such as types of sediment, ionic composition of water and interaction among individuals. This research topic will (1) improve the use of ostracods as paleolimnological and paleoclimatic bioindicators and (2) provide key and biological, ecological and molecular pre-requisite information because Nam Co has been targeted as an International Continental Drilling Program (ICDP) site for the recovery of a long sedimentary record.
Cooperation within TransTiP
Chinese partners will focus on changes in water quality and water volume of Nam Co and other representative lakes during the past 40 years. The goal is to reveal the response and feedback of lake water cycle and watershed ecosystem changes to climate change on the Tibetan Plateau. Research includes collection of ecological and water quality parameters, analysis of the dynamics of lake area and lake water volume changes. Special emphasis will be given to a three-dimensional investigation of lake zooplankton, phytoplankton and nutritional environmental elements. Therefore, this data will complement and reinforced the German research topic by providing important recent environmental information, that will allow a better knowledge of ostracod ecological sensitivities, adaptation and reproduction strategies, and resilience during the past decades. Together we will be able to understand the resilience and adaptions of zooplankton, especially under the ongoing and future climate change.
Prof. Dr. Antje Schwalb, TU Braunschweig
Prof. Dr. Michael Pester, Leibniz Institute DSMZ & TU Braunschweig
Prof. Dr. Liping Zhu, ITP-CAS