Chemical properties and biological activities of three highly purified major tetrodotoxin analogues.

Tetrodotoxin (TTX), the pufferfish toxin, has the potential to cause fatal food poisoning because of its potent voltage-gated sodium channel (Na) blocking activity. 4-epiTTX, 11-norTTX-6(S)-ol, and 11-oxoTTX are the major TTX analogues found in marine animals; thus, their chemical properties and biological activities should be determined. In this study, these three TTX analogues were purified to a high level (purity >97%) from pufferfish and newts.

The smell of Panulirus argus virus 1 (PaV1) infection: Disease-induced changes in metabolites in urine and hemolymph of Caribbean spiny lobsters Panulirus argus.

The Caribbean spiny lobster Panulirus argus is a social species in which individuals aggregate for protection during the day using chemicals in their urine as guiding cues. This behavior changes when animals are infected by Panulirus argus virus 1 (PaV1), such that healthy animals avoid the urine of diseased conspecifics. The aim of this study was to identify the molecules responsible for this switch in aggregation behavior.

Characterization and purification of lipovitellin-like egg yolk protein in a stony coral, Acropora aff. tenuis.

Three egg proteins (EP1, EP2, and EP3) were detected in ovulated eggs of Acropora aff. tenuis, a reef-building stony coral found in tropical and subtropical areas. The proteins were separated into different fractions by gel filtration chromatography, and different patterns were observed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting with antiserum against A.

Influences of seawater adaptation on the endocrine, osmoregulatory and immune systems in gill, peripheral blood leucocyte, skin and intestine of steelhead trout Oncorhynchus mykiss.

Endocrine, osmoregulatory and immune responses have been examined in blood plasma, gill, peripheral blood leucocyte (PBL), skin and intestine of steelhead trout Oncorhynchus mykiss reared for 4 weeks in seawater. Plasma lysozyme activity and pituitary growth hormone messenger ribonuculeic acid (mRNA) levels were higher and prolactin levels were lower in seawater than in freshwater. mRNA levels of hormone receptor and immune-related genes in gills, PBL and skin were influenced by seawater.

Cardimyxobolus iriomotensis n. sp. (Cnidaria: Myxosporea: Ortholineidae) parasitic in gill filaments of Rhinogobius species (Gobiiformes: Gobiidae) in Japan.

Cardimyxobolus iriomotensis n. sp. (Cnidaria: Myxosporea: Ortholineidae) is described from the gill filaments of Rhinogobius brunneus (type-host) and R.

Microbiome of the Boring Giant Clam Provides Insights Into Holobiont Resilience Under Coral Reef Environmental Stress.

Giant clams are key denizens of coral reef ecosystems, forming holobionts through symbiotic relationships with algae of the family Symbiodiniaceae, as in reef-building corals. In this study, we performed a tissue-specific microbiome analysis of the boring giant clam, Tridacna crocea and evaluated the impact of dark-induced bleaching on its outer mantle bacterial community. Using 16S rRNA metabarcoding, Endozoicomonas was identified as the dominant bacterial genus in most tissues, particularly in gills, implying an important contribution to the giant clam holobiont.

Time-Series RNA-Seq of Acropora tenuis Reveals Molecular Waves Leading to Synchronous Mass Spawning of Scleractinian Corals.

Although mass, synchronised spawning of scleractinian corals is a well-known phenomenon, its underlying molecular mechanisms, especially those that achieve synchronous release of gametes, are still unknown. In the genus Acropora, the dominant scleractinian coral in shallow reefs, spawning timing is synchronised in any given location, but often varies among locations. Here, we report gene expression cascades potentially driving synchronous mass spawning, revealed through transcriptome monitoring of Acropora tenuis, tracking both daily and monthly dynamics during a year-long experiment that included two spawning events.

Exploration of selection methods for optimal juveniles in hatchery-reared masu salmon (Oncorhynchus masou).

To explore selection methods for juveniles with favourable characteristics in masu salmon (Oncorhynchus masou), we tested two approaches: selection based on position in a waterway and selection based on swimming layer in a round tank. After selection, juveniles were reared in identical environments in two tanks until the smoltification season (spring of the following year), and their characteristics - including standard length, weight, condition factor, sex and smoltification rate - were observed. In the waterway selection experiment (Experiment 1), 284 juvenile broodstock fish from the Shiribetsu River strain were placed in an artificial waterway, with 67 individuals selected from both upstream and downstream groups.

Cell density-dependent mutual growth inhibition in harmful dinoflagellate Karenia selliformis and diatom Thalassiosira hendeyi.

The genus Karenia is widely distributed in coastal and oceanic waters worldwide, and several species of Karenia have been responsible for toxic and harmful algal blooms in global nearshore waters, leading to severe economic losses. In 2021, a significant algal bloom, dominated by Karenia selliformis, occurred in the eastern sea area of Hokkaido, Japan. To explore how K.

Life cycles of trematodes infecting six species of intertidal gastropods in Japan.

A variety of larvae and parthenitae of trematodes have been detected in gastropods in the intertidal zone in Japan. However, because of the difficulty associated with the morphological identification of these stages, they have rarely been identified to the species or higher taxonomic levels. In this study, trematodes of these stages were sampled from intertidal gastropods in the Japanese coastal regions and were identified to the species, genus, or family levels morphologically and molecularly to elucidate or predict their life cycles.

Transcriptomic insights into host transcriptional manipulation by ssDNA and ssRNA viruses in the marine planktonic diatom Chaetoceros tenuissimus.

The marine diatom Chaetoceros tenuissimus coexists in the coastal ocean with two distinct viruses: a circular single-stranded DNA virus and a single-stranded RNA virus. Both viruses are capable of killing the host in vitro experiments; however, the molecular mechanisms by which host genes respond and are utilized by these viruses for replication and proliferation remain unclear. In this study, RNA-seq analyses were conducted to investigate these mechanisms, and the host transcripts specific to each virus were validated by RT-qPCR.

Alteration of Molting-Related Metabolites in the Carapace of Kuruma Prawn (Penaeus japonicus) Juveniles After Fipronil Exposure.

In aquatic arthropods, molting is essential for normal development. An earlier study showed that 3-phosphoglycerate (3PG) and phosphoenolpyruvate (PEP), which are present in the exoskeleton, play important roles in its calcification. Under normal culture conditions, we found higher levels of 3PG and PEP at the pre-molt stage than that at the post-molt stage in the carapace of kuruma prawn juveniles (Penaeus japonicus).

Determination of Selenoneine in Seafood and Seafood-Derived Products.

Background: Selenoneine exhibits antioxidant properties and is thus expected to become a new functional ingredient. Accurately determining selenoneine levels in foods is therefore critical.

Objective: This study investigated and validated extraction methods for selenoneine in seafood and seafood-derived products.

Characterization of the fatty acid composition of Pacific bluefin tuna Thunnus orientalis larvae by body part and depending on growth rate.

In this study, we aimed to elucidate the characteristics of faster-growing Pacific bluefin tuna (Thunnus orientalis) larvae by focusing on the localization of long-chain polyunsaturated fatty acids in different body parts and at various days post-hatch (dph). To accomplish this, we compared low- and high-growth-rate groups of larvae under mass-rearing conditions. Multivariate analysis revealed that the first axis separated the dph and growth groups, and the high-growth-rate group tended to be distributed on the same side at 20 dph.

Expression of corticoid-regulatory genes in the gills of Atlantic salmon (Salmo salar) parr and smolt and during salinity acclimation.

In teleost fishes, cortisol is the major corticoid and has both glucocorticoid and mineralocorticoid actions. However, how fish tissues discriminate between these distinct corticosteroid actions is unclear. In mammals, the major factors responsible for intracellular corticosteroid regulation are glucocorticoid receptors (grs) and the mineralocorticoid receptor (mr), but their role in osmoregulation of fish is unclear.

Validation of a K Value Method for Freshness Evaluation of Bony Fish Using High-Performance Liquid Chromatography: An Interlaboratory Study.

Background: Freshness is one of the most important qualities of fish and has a significant impact on the utilization and commercial value. As global production and trade volumes of fishery products increase, standardization of scientific methods for evaluating fish freshness is required.

Objective: K value based on the ratio of ATP derivative contents is widely recognized as a scientific freshness index of fish.

Porphyran from discolored nori prevents metabolic syndrome through microbiota-bile acid-ceramide pathway.

Nori is a component of the traditional Japanese diet. The Japanese have a low prevalence of obesity and cardiovascular disease worldwide, and components of nori may have disease-preventive effects. Here, we focused on porphyran, which is abundant in nori that is discarded due to discoloration, and investigated the effects of nori-derived porphyran on gut microbiota, bile acid composition, and ceramide synthesis.

Evaluating Type III Secretion System Genes (escE, esaE and eseJ) of Edwardsiella piscicida for Virulence in Japanese Flounder (Paralichthys olivaceus).

Edwardsiella piscicida, an etiological agent of edwardsiellosis in finfish, causes severe damage to the aquaculture industry in the world. The virulence of E. piscicida is known to be associated with the type III secretion system (T3SS) which is a protein transport nanomachine that injects effector proteins directly into host cells to be resistant to phagocyte killing.

Selenoneine scavenges hydroxyl radicals by self-oxidation in hydrogen peroxide and by forming seleninic acid, which is reduced back to selenoneine.

Selenoneine (SEN), a selenium analog of ergothioneine (EGT), is widely distributed in marine fish and is a strong radical scavenger. Electron spin resonance spectrometry showed that SEN monomer and dimer directly scavenged ·OH generated by irradiating hydrogen peroxide (H2O2) with ultraviolet light. The radical scavenging capacity was stronger for SEN monomer, dimer, and EGT in that order.

Brominated bitter compounds from the skin tubercle gland of the stonefish Synanceia verrucosa.

The skin tubercle gland of the stonefish Synanceia verrucosa secretes "ichthyocrinotoxin." Ichthyocrinotoxins have been suggested to act as antifeedants against predators and as anthelmintics against parasites. Three novel compounds, synanceins A (1), B (2), and C (3), were isolated from S.

A Lectin AtTL-2 Obtained from aff. Induced Stimualation of Phagocytosis of Symbiodiniaceae.

The coral aff. selectively acquired various zooxanthella (Symbiodiniaceae) strains, and one of the selective factors was lectins. The .

Transcriptome Analysis of Genes Responsive to Nutrient Level Changes in the Marine Red Alga Pyropia yezoensis (Nori).

The cultivation of the red alga Pyropia (nori) is among the most significant aquaculture industries in East Asia. Nutrient deficiency-induced "discoloration" poses a serious threat to the industry, substantially impacting both harvest quality and production levels. In this study, we conducted transcriptome analysis (RNA-Seq) of P.

Introduction of (Trematoda: Azygidae) to Japan with its life cycle information.

In Japan, three trematode species of the genus have been recorded: , , and Here, we report the first detection of in Japan, identified from the introduced snakehead This trematode was previously known only from the snakeheads in mainland China. Between 2015 and 2024, we sampled snakeheads and snails in Japan, collecting adult trematodes and rediae. Adult trematodes were identified morphologically as , a determination corroborated by molecular analyses of the COI and 28S rDNA regions.

Size-dependent resource allocation to reproduction in Japanese anchovies (Engraulis japonicus).

Size-related changes in reproductive potential are essential for understanding population dynamics and life history strategies; however, the mechanisms driving variation between individuals and sexes remain unclear. Using a diet-switch experiment and carbon and nitrogen stable isotope ratios (SIRs) as quantitative indicators, we investigated how large (parents) and small (offspring) spawning male and female Japanese anchovies (Engraulis japonicus) allocate energy to reproduction. Large individuals of both sexes exhibited higher energy investment in gamete production than small individuals, reflecting a trade-off between growth and reproduction.

Establishment of a New Endothelial Cell Line of Japanese Eel and Its Application to the Investigation of Temperature Preference of Japanese Eel Endothelial Cells-Infecting Virus.

Japanese eel endothelial cells-infecting virus (JEECV) is the causative agent of viral endothelial cell necrosis of eel (VECNE), which adversely affects eel aquaculture in East Asian countries. The virus primarily infects vascular endothelial cells and causes the enlargement of cell nuclei. Notably, high water temperatures (approximately 35°C) reduce the mortality from VECNE, but the temperature preference of this virus is not known.