African swine fever virus variants with different numbers of a 10-bp tandem repeat were isolated in South Korea soon after being identified in wild boar. The short emergence periods and sympatric distributions within a narrow geographical region suggest that the variants were sporadically generated in the pre-existing viral population.

We designed an experiment to analyze the gut content of Rotifera based on DNA barcoding and tested it on Asplanchna sp. in order to ensure that the DNA extracted from the rotifer species is from the food sources within the gut. We selected ethanol fixation (60%) to minimize the inflow effects of treated chemicals, and commercial bleach (the final concentration of 2.5%, for 210 s) to eliminate the extracellular DNA without damage to the lorica. Rotifers have different lorica structures and thicknesses. Therefore, we chose a pretreatment method based on Asplanchna sp., which is known to have weak durability. When we used the determined method on a reservoir water sample, we confirmed that the DNA fragments of Chlorophyceae, Diatomea, Cyanobacteria, and Ciliophora were removed. Given this result, Diatomea and cyanobacteria, detected from Asplanchna, can be considered as gut contents. However, bacteria were not removed by bleach, thus there was still insufficient information. Since the results of applying commercial bleach to rotifer species confirmed that pretreatment worked effectively for some species of rotifers food sources, in further studies, it is believed to be applicable to the gut contents analysis of more diverse rotifers species and better DNA analysis techniques by supplementing more rigorous limitations.

The aim of this paper is to study the species composition, structure and seasonal dynamics of the cladoceran fauna and species associations in inland water bodies of Jeju Island (Republic of Korea). Only 47 taxa were found in 199 samples. Such faunal paucity could be explained by the existence of only a few types of aquatic environments on Jeju Island as compared to continental China and the Far East of Russia, with their great diversity of water types. We have demonstrated a high significance of the tropical species on Jeju. Our data confirm seasonal faunistic changes in the continental waters of Jeju Island. The rate of tropical taxa is highest in September, after the monsoon season, while the Far Eastern endemic taxa are more common in winter. At the same time, the contribution of Boreal taxa to the fauna of the island is low even in winter. Species associations have been revealed based on binominal distribution; they change significantly from summer to winter. However, a contribution of Boreal taxa to the species associations also is minimal (even in winter), whereas tropical taxa contribute to them greatly (including in winter). We can propose a rough scheme of faunal formation exploring the whole set of obtained information. Initially, at the earlier stages of the island formation, its fauna was consisted of some pre-Pleistocene taxa. Then, during the Pleistocene time, Jeju Island was secondarily interconnected with more southern territories, and tropical species have colonized it. Recent Boreal cladoceran invaders arrived at the island water bodies later when they were already inhabited by formed associations, and for this reason only few of them were able to settle down there. Such a scheme is a hypothesis which needs to be checked by the future phylogeographic studies.

Lee KL, et al. J Vet Sci. 2021 Mar;22(2):e28. https://doi.org/10.4142/jvs.2021.22.e28