In the Republic of Korea, Enterocytozoon hepatopenaei (EHP) was first isolated from Pacific whiteleg shrimp in April 2020; however, there are no existing reports of EHP infection in other shrimp or prawns. Here, we aimed to investigate EHP infection and its prevalence in giant freshwater prawn farms in the Republic of Korea. We tested prawns from 22 farms for EHP infection, and samples from eight farms showed positive EHP infection results in 2021. In EHP-infected prawn farms, the prevalence ranged from 4.9% to 18.2%. The prevalence of EHP infection in the Republic of Korea, derived from the prevalence in prawn farms, was estimated to be 0.8% in 2021. The proliferation of EHP was observed within the hepatopancreatic epithelial cells of prawns using H&E and Giemsa staining. Mature EHP was observed in the sinus between epithelial cells of the digestive tubules. Phylogenetic analysis revealed a clade distinct from the previously reported EHP in Pacific whiteleg shrimps. This is the first report of EHP infection in a giant freshwater prawn in the Republic of Korea, where the prevalence of EHP infection is not high, but it is recognized as an emerging disease that requires periodic monitoring and quarantine management in giant freshwater prawns.

Zostera marina L. plants have been seriously impacted by wasting disease along the Atlantic coasts of North America and Europe since the 1930s (Muehlstein 1989). Sudden declines in the population s...

Polydora hoplura Claparede 1868 (Polychaeta, Spionidae) is a mollusk shell-boring species which has been reported as a harmful species. In the present study, we sequenced and reported the mitochondrial genome (mitogenome) of P. hoplura from Korea. Its mitogenome was determined by long range PCR and primer walking. The mitogenome was found to be 17,707 bp in length and contained two ribosomal RNAs (rRNAs), 23 transfer RNAs (tRNAs), and 12 protein-coding genes which showed different gene arrangement with that in related mitogenomes of species of Sedentaria (Annelida). Interestingly, the atp8 gene was not found in the mitogenome of P. hoplura, whereas it is present in the mitogenomes of related species P. brevipalpa and P. websteri. Moreover, nad2 (3’ end) and cox1 (5’ end) genes overlapped in 23 bases. The mitogenome structure and gene contents of P. hoplura provide useful information on the evolution and phylogenetic relationship among polychaete species.

White tail disease (WTD) is caused by the Macrobrachium rosenbergii nodavirus (MrNV) and an extra-small virus (XSV). MrNV belongs to the Nodaviridae family. While the role of XSV in the pathogenicity of WTD remains unclear, MrNV is considered to be a significant factor in the disease. To study WTD infection in giant freshwater prawns (Macrobrachium rosenbergii), adult and post-larval (PL) prawns were collected from three giant freshwater prawn farms in Gyeongsangnam-do, Korea in 2021. Although the adult and PL prawns did not display any gross signs of WTD, MrNV was detected in both adult and PL in this study. However, XSV was not detected in both prawns. Phylogenetic analysis revealed that the capsid protein gene sequences of MrNV obtained in this study were robustly clustered with the MrNV group, and were clearly distinguished from Alphanodavirus and Betanodavirus groups of the family Nodaviridae. Although Zenker’s necrosis and myolysis were observed histopathologically in the abdominal striated muscle of adult and PL prawns, no gross signs associated with white tail were observed because of local lesions.

Three species of the genus Ishige (Phaeophyceae, Ishigeaceae) are known from Korea, Japan and Mexico; they include Ishige foliacea Okamura, I. okamurae Yendo and I. sinicola (Setchell and N.L. Gardner) Chihara. Two species, I. foliacea and I. okamurae, are present in the algal flora of Korea and Japan. The original description of I. okamurae defined two forms of branches, filiform and foliose, but later the foliose branch was recognized as a new species I. foliacea, which is epiphytic on I. okamurae but can also be free-living. The currently proposed lectotype for I. foliacea is based on a free-living form and does not reflect the intent of the original description of the species. In this study, we conducted the DNA barcoding for herbarium specimens to identify Ishige species. Additionally, the variation in cox3 sequences obtained from I. okamurae specimens with two morphological forms collected from waters around the Korean Peninsula was sufficient to separate two species, I. okamurae and its epiphyte I. foliacea. The epiphytic I. foliacea on the lectotype specimen of I. okamurae is designated as lectotype I. foliacea.

Background: The study evaluated the effects of a butaphosphan and cyanocobalamin mixture on the immune system and stress in olive flounders, Paralichthys olivaceus. Methods: The mixture was intramuscularly injected into olive flounders at the current recommended dose. Furthermore, to determine the toxicity of overdose, a histological examination was performed after injection of 1-, 2-, and 4-fold higher than the recommended dose. Results: Immunity parameters were altered during the first 2 weeks after a single intramuscular injection of the mixture in olive flounders (average weight 20.5 ± 1.1 g). The levels of all tested items, except glutathione and anti-protease, were higher in the treated group than in the control group in the first week; the levels of all tested items were even higher in the second week in the treated group than in the control group. The level of nitro-blue tetrazolium, myeloperoxidase, and superoxide dismutase between the two groups differed significantly. Changes in the stress response to different seawater temperatures (increase or decrease in seawater temperature by 3–5 °C using 50 L heated or cooled seawater tanks) were studied by determining the changes in cortisol and glucose levels on days 1 and 7. Both cortisol and glucose levels were significantly lower in the treated group than in the control group. Histological analysis did not reveal any abnormalities after intramuscular injection of the mixture at doses that were 1-, 2-, and 4-fold higher than the recommended dose. Conclusions: Intramuscular injection of a butaphosphan and cyanocobalamin mixture is safe and effective in reducing stress and improving immunity in olive flounders.