Acute hepatopancreatic necrosis disease (AHPND) is a bacterial disease caused by Vibrioparahaemolyticus. Currently, various Vibrio strains, including V. campbellii, V. owensii, and V. harveyi, have been reported as causative pathogens. Thus, controlling AHPND to maintain high production in shrimp aquaculture is difficult. We evaluated the antimicrobial activity of five Bacillus strains (B1, B3, B5, B7, and B8)—isolated from seawater in Jeju, South Korea—against 12 Vibrio strains (10 AHPND strains and 2 non-AHPND strains). All tested Bacillus strains inhibited the growth of at least one of the tested Vibrio strains in the dot-spot method. Among them, B1 and B3, the most effective Bacillus strains against the Vibrio strains, particularly against AHPND-causing V. campbellii (Vc_AHPND), were further used in a challenge test. After 48–60 h of Vc_AHPND immersion, a significantly higher survival rate was observed in the B1-treated group (100%) than in the non-Bacillus-treated group (64.3%). Based on the qPCR analysis of AHPND, the cycle threshold values were 31.63 ± 0.2 (B1-treated group) and 38.04 ± 0.58 (B3-treated group), versus 28.70 ± 0.42 in the control group. Genome sequencing and phylogenetic analysis revealed that B1 and B3 were classified as B. velezensis. The 16S rRNA sequences and complete genome sequences of B1 and B3 were deposited in GenBank.

The big belly seahorse (Hippocampus abdominalis), a well-known ingredient of traditional medicine, possesses anti-inflammatory, anti-aging, anti-fatigue, and anti-thrombotic properties, and also increases male fertility. This study demonstrates that the ethanolic extract of dried H. abdominalis (EEHA) has anti-melanogenic effects in B16F10 melanoma cells and zebrafish larvae. EEHA significantly reduced the α-melanocyte-stimulating hormone (α-MSH)-induced melanogenesis in B16F10 melanoma cells without causing cytotoxicity. At a concentration of 200 µg/mL, EEHA had significant anti-melanogenic activity in zebrafish larvae, accompanied by a severe reduction in the heart rate (118 ± 17 heartbeats/min) compared to that of the untreated group (185 ± 8 heartbeats/min), indicating that EEHA induces cardiotoxicity at high concentrations. Below 100 µg/mL, EEHA significantly reduced melanogenesis in zebrafish larvae in the presence or absence of α-MSH, while the heart rate remained unaltered. Additionally, EEHA downregulated the release of cyclic adenosine monophosphate (cAMP) and the phosphorylation of cAMP response element-binding protein (CREB) in B16F10 melanoma cells, which inhibited microphthalmia-associated transcription factor (MITF), leading to the inhibition of tyrosinase activity. EEHA also increased the phosphorylation of extracellular-signal regulated kinase (ERK). The ERK inhibitor PD98059 interfered with the anti-melanogenic activity of EEHA in B16F10 melanoma cells and zebrafish larvae, indicating that the ERK signaling pathway might regulate the anti-melanogenic properties of EEHA. Altogether, we conclude that EEHA represses the cAMP–CREB–MITF axis, which consequently inhibits tyrosinase-mediated melanogenesis. We propose that at low concentrations, EEHA can serve as a promising anti-melanogenic agent that could be used to prepare whitening cosmetics and for treating melanogenic disorders.

Freshwater crayfish, which are cultivated in aquaculture, are economically important for food and ornamental purposes. However, relatively few studies have focused on potentially pathogenic viruses in crayfish compared to in penaeid shrimp. Commodity red claw crayfish (Cherax quadricarinatus; 400 crayfish in 10 batches) and red swamp crayfish (Procambarus clarkii; 40 crayfish in 2 batches) imported into South Korea from Indonesia and China were screened by PCR to detect infectious hypodermal and hematopoietic necrosis virus (IHHNV or Decapod penstylhamaparvovirus 1). IHHNV was detected in tissue samples pooled from nine out of ten batches of red claw crayfish imported from Indonesia. Phylogenetic analysis of PCR amplicons from representative pools clustered the IHHNV strain with infectious-type II sequences commonly detected in Southeast Asian countries rather than with type III strains detected previously in whiteleg shrimp (Penaeus vannamei) cultured in South Korea. IHHNV DNA was detected most frequently in the muscle (eight batches, 66.7% samples), followed by in the hepatopancreas (five batches, 41.7% samples) and gills tissue (three batches, 25.0% samples). These data suggest that red claw crayfish could be a potential carrier of the virus and that quarantine procedures must be strengthened in South Korea to avoid importing infectious types of IHHNV in commodity crustaceans such as red claw crayfish.

Fisheries and Aquatic Sciences

Acute hepatopancreatic necrosis disease (AHPND) caused by Vibrio parahaemolyticus (Vp_AHPND) has been reported in commodity shrimp, but the potential risk of its global spread via frozen shrimp in the shrimp trade is yet to be fully explored. We hypothesized that frozen shrimp with AHPND could be a source of Vp_AHPND transmission; thus, the infectivity of frozen shrimp with AHPND was evaluated using a shrimp bioassay. To prepare infected frozen shrimp, 12 Penaeus vannamei (average weight, 2 g) were exposed to Vp_AHPND by immersion in water with a Vp_AHPND concentration of 1.55 × 10⁷ CFU mL⁻¹; once dead, the shrimp were stored at −80 °C for further analysis. After two weeks, a PCR assay was used to confirm AHPND positivity in frozen shrimp (n = 2), and Vp_AHPND was reisolated from the hepatopancreases of these shrimp. For the infectivity test, 10 P. vannamei (average weight, 4 g) were fed with the hepatopancreases of Vp_AHPND -infected frozen shrimp (n = 10). After feeding, 70% of the shrimp died within 118 h, and the presence of Vp_AHPND was confirmed using a PCR assay and histopathology examination; moreover, Vp_AHPND was successfully reisolated from the hepatopancreases of the dead shrimp. We are the first to evaluate the potential transmissibility of Vp_AHPND in frozen shrimp, and our results suggest that frozen shrimp with AHPND are a potential source of disease spreading between countries during international trade.