Eurytemora gracilicauda (Copepoda: Calanoida) in the Russian Arctic

Abstract

As a result of studying the populations of Eurytemora genus crustaceans from the internal reservoirs of the drainage basin of the White, Pechora Seas, the Lena deltas, Island of Wrangel and Kamchatka peninsula was set that the species Eurytemora gracilicauda is common along the entire northern border of Russian Eurasia. It was shown that the species distribution for populations from the rockpools of the Kandalaksha Bay of the White Sea, from Lake on Kashin Island in the Pechora Sea and from the Lena River Delta was sequentially along the coast of the Arctic. Studies are based on genetic (parts of CO1 and ITS1 genes) and morphological analyzes of the studied populations. The synonymy of the Kamchatka species E. kurenkovi and E. gracilicauda was confirmed by the morphological analysis. Variation coefficients (CV), calculated for the populations of females from the White Sea, the Lena River delta and from the Kamchatka do not exceed 10%, which indicates a low morphological variability of the species. The most widely represented in the genetic analysis, the White Sea population has a low level of genetic variability, which, together with significant tolerance to the fluctuations of salinity in the rockpools in which it lives, may indicate its recent introduction to the region. A phylogenetic reconstruction was not revealed reliable topology for the species E. gracilicauda. It was shown that E. gracilicauda is not related to the affinis group species. Molecular Clocks with use part of CO1 gene and paleontological calibration revealed the speciation of E. gracilicauda species on the Paleocene – Late Cretaceous boundary. We also can hypothesize a Laurasian origin of the Eurytemora genus.