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Assessment of the clock genes, Period (Per) 1, Per2, Per3, and Cryptochrome (Cry) 2, Cry3, and Cry4, can help better understand eel spawning ecology. In this study, the circadian rhythm and moonlight effects of these clock genes in the eel retina and hypothalamus were analyzed. We examined clock gene expression patterns under 12 h light:12 h darkness (12L12D), constant darkness (DD), and constant light (LL) conditions; under short photoperiod (SP; 9L15D) and long photoperiod (LP; 15L9D), and during the new moon (NM) and full moon in male eels. Per2 expression increased after sunrise, Cry2, and Cry4 expression increased around sunset, and Per1, Per3, and Cry3 expression increased before sunrise. Under SP conditions, oscillations of retinal Per3 and Cry4, which did not occur under LP conditions, were generated. In addition, retinal Cry4 oscillation was generated under NM conditions. These results suggest that the retina of the eel may play an important role in regulating circadian rhythm, and migration is initiated by the synchronization of clock genes by moonlight, suggesting that photic signals are closely related to the migratory activity of the eel. Research Highlights: Clock gene expression was analyzed under various conditions in the retina and hypothalamus of eel.Per2 mRNA expression peaked during the photophase, Cry2 mRNA expression peaked before the onset of the scotophase, and Cry4 mRNA expression peaked after the onset of the scotophase.Per1, Per3, and Cry3 mRNA expression peaked before the onset of the photophase, inducing oscillations.Under short photoperiod condition, oscillations of Cry4 and Per3 were induced, whereas under the new moon condition, oscillations of Cry4 were induced. [ABSTRACT FROM AUTHOR]

In this study, using Illumina sequencing, we sequenced first the complete mitochondrial genome (mitogenome) of two deep-sea eels, Histiobranchus bathybius and Simenchelys parasitica, collected from the East Mariana Basin in the Western Pacific Ocean. The complete length of the H. bathybius and S. parasitica mitogenomes were 16,696 and 16,687 bp, respectively, each containing 37 genes (13 protein-coding genes, 22 tRNA genes, and 2 ribosomal RNA genes). To enhance the accuracy of the identification of H. bathybius and S. parasitica, we performed a phylogenetic analysis of multiple deep-sea eels based on the mitochondrial DNA gene (cytochrome c oxidase subunit I [COI]) using the maximum likelihood method. Our phylogenetic tree analysis confirmed that the specimens collected in this study are congeneric species of H. bathybius and S. parasitica reported in previous studies. Based on these results, we report the first complete mitogenomes of H. bathybius and S. parasitica and a new record for the two species in the East Mariana Basin. [ABSTRACT FROM AUTHOR]

The geoduck clam is a high-value species in South Korea. However, the molecular and morphological characteristics of geoduck clams from the southern coast of South Korea remain unexamined. The accurate identification of native geoduck clams is crucial for their conservation and management. Therefore, this study used a combination of molecular and morphological analyses to characterize native geoduck clams from the southern coast of South Korea. Based on complete mitochondrial genome and morphological analyses, the native species of geoduck clam from this study area was identified as Panopea sp. 1. The complete mitochondrial genome sequencing of Panopea sp. 1 revealed a total of 16,225 bp in length with 37 genes (13 protein-coding genes, 22 tRNA genes, and 2 rRNA genes). It was also shown that Panopea sp. 1 belongs to the family Hiatellidae based on a phylogenetic analysis tree with 11 bivalve species. In particular, Panopea sp. 1 is closely related to three other Panopea species (Panopea sp., Panopea abrupta, and Panopea japonica). The phylogenetic analysis correlated with the morphological analysis. Overall, this is the first reliable record of Panopea sp. 1 in South Korea. These findings provide a basis for accurate species identification based on morphological characteristics and complete mitochondrial genome sequencing. [ABSTRACT FROM AUTHOR]

Research has been conducted on the validamycin A biosynthesis. The reduction of the bis(methylthio) moiety of C-5 stereoisomers and introduction of deuterium into the C-6 methylene group of 5-epi-valiolone are described.

The cleaner shrimp, Lysmata amboinensis, is an ornamental crustacean that is important both commercially, in the aquarium industry, and ecologically, owing to its symbiotic relationship with host fishes. Cleaner shrimp display high daytime activity, unlike other crustaceans, and are highly sensitive to light, particularly, in the 480–540 nm range. However, there have been few studies on the physiological characteristics of this species. In this study, we investigated effect of photoperiod and specific wavelength on the circadian rhythm of cleaner shrimp. Circadian rhythm was evaluated by quantifying the mRNA expression of clock genes such as lysmata amboinensis cryptochrome1 (laCry1) and lysmata amboinensis period 2 (laPer2) and melatonin concentration. The mRNA levels of clock genes were significantly higher at daytime than at night-time. Furthermore, at the red and green wavelengths, the difference in clock gene mRNA levels between day and night was significantly higher than that observed under white fluorescent light. Melatonin levels showed the opposite trend. Collectively, our findings demonstrate that the photoperiod regulates the biological rhythm of the cleaner shrimp and that the irradiation wavelength affects the biological rhythm. In particular, the red and green wavelengths appeared to be linked to the clock gene rhythm and melatonin levels. [ABSTRACT FROM AUTHOR]