New records of two deep-sea eels collected from the Western Pacific Ocean based on COI and 16S rRNA genes

Background

Two deep-sea eels collected from the Western Pacific Ocean are described in this study. Based on their morphological characteristics, the two deep-sea eel specimens were assumed to belong to the cusk-eel family Ophidiidae and the cutthroat eel family Synaphobranchidae.

Methods and results

To accurately identify the species of the deep-sea eel specimens, we sequenced the mitochondrial genes (cytochrome c oxidase subunit I [COI] and 16S ribosomal RNA [16S rRNA]). Through molecular phylogenetic analysis based on mtDNA COI and 16S rRNA gene sequences, these species clustered with the genera Bassozetus and Synaphobranchus, suggesting that the deep-sea eel specimens collected are two species from the genera Bassozetus and Synaphobranchus in the Western Pacific Ocean, respectively.

Conclusions

This is the first study to report new records of the genera Bassozetus and Synaphobranchus from the Western Pacific Ocean based on COI and 16S rRNA genes

     

Changes of physiological rhythms of N-methyl-d-aspartate receptors in the chum salmon Oncorhynchus keta: effect of seawater acclimation during the parr-smolt transformation

We examined changes on N-methyl-d-aspartate receptors (NRs) in different growth stages (early parr, parr, and early smolt) of chum salmon, Oncorhynchus keta, during parr-smolt transformation from freshwater to seawater. Expression levels of NR genes mRNA and concentration of cortisol, T₃, T₄, dopamine and Na⁺/K⁺-ATPase activity significantly increased at salinity change condition. Moreover, in cultured brain cells, NRs were significantly lower in all groups treated with MK-801 (an antagonist of NRs) than in the early parr stage group in the FW treatment. We confirmed that the reduction in mRNA expression levels of NRs increased from the early parr to the early smolt stage. The information reported here should be taken into account in future studies on the relationship between memory factors of natal streams and homing mechanisms in Salmonidae.     

Population characteristics of two seahorses, Hippocampus coronatus and Hippocampus mohnikei, around seagrass beds in the southern coastal waters of Korea

Population characteristics of two seahorse species, Hippocampus coronatus and Hippocampus mohnikei, in seagrass beds in the southern coastal waters of Korea were determined based on field observations. In Zostera beds in the Yeosu area, there was a mean density of 2.9 seahorses per 1,000?m² for H. coronatus and 1.4 seahorses per 1,000?m² for H. mohnikei. The greatest numbers of young individuals of both species were observed in July, with numbers decreasing through November. The male:female sex ratio was 1:1.6 for H. mohnikei and 1:1.7 for H. coronatus. Breeding males of H. coronatus and H. mohnikei were observed from July to November and from July to September, respectively. Within the study site, the populations of the two seahorse species exhibited low density and patchy distributions, with variation in temporal abundance being significantly correlated with water temperature. The findings of this study provide the basis for future research on the population status of H. coronatus and H. mohnikei in seagrass beds.     

Effects of light-emitting diodes on thermally-induced oxidative stress in the bay scallop Argopecten irradians

ABSTRACT

Water temperature is an important stressor that affects the physiological and biochemical responses of scallops. In this study, we investigated the effect of different light-emitting diodes (LEDs; red, green and blue) on oxidative stress in Argopecten irradians. PCR revealed MnSOD mRNA expression in the digestive diverticula, gill, adductor muscle and eye. CAT and HSP70 mRNA were expressed in the digestive diverticula, gill and adductor muscle. Additionally, we measured the changes in the expression of HSP70, MnSOD and CAT as well as H₂O₂ levels during thermal/laboratory stress. In the digestive diverticula, gill and adductor muscle, the mRNA expressions and activities and H₂O₂ levels significantly increased in response to thermal changes. The gene expressions and activities and H₂O₂ levels were significantly lower in scallops that received green LED light than in those that received no mitigating treatment. A comet assay revealed that thermal change groups had increased rates of nuclear DNA damage; however, treatment with green LED reduced the frequency of damage. The results indicated that low or high water temperature conditions induced oxidative stress in A. irradians but that green LED significantly reduced this stress.     

Complete genome sequence of strain s85, a novel member of the family Flavobacteriaceae

An agar-degrading marine bacterium identified as a novel member of the family Flavobacteriaceae (strain S85) was isolated from seawater in Micronesia. The sequenced strain S85 genome is composed of 3,384,629 bp in a circular chromosome, which includes 2,883 complete open reading frames.     

Changes in circadian parameters of humbug damselfish,Dascyllus aruanus according to lunar phase shifts in Micronesia

The objectives of this study were to test the nighttime effects of the lunar phase on circadian rhythm in the humbug damselfish, Dascyllus aruanus. We measured moonlight intensities at eight different phases across the lunar cycle. At each lunar phase, the circadian rhythm was evaluated by measuring the clock genes cryptochrome 1 and period 2. In addition, we measured arylalkylamine N-acetyltransferase 2 (AANAT2), melatonin and melatonin receptor 1 (MT-R1). The moonlight intensity was highest at full moon and lowest during the waning crescent. Clock gene expression was highest during the full moon compared to the other phases. By contrast, the plasma concentrations of AANAT2 and melatonin and the MT-R1 mRNA expression were highest during the full moon phase. Our results suggest that moonlight affects circadian rhythm patterns in the humbug damselfish. There is a need to investigate potential other physiological effects of lunar phase shifts.     

Draft genome sequence of Marinobacterium stanieri S30, a strain isolated from a coastal lagoon in Chuuk state in Micronesia

In this study, we isolated xylan-degrading bacteria from a coastal lagoon of Micronesia and identified the bacteria as Marinobacterium stanieri S30. GSFLX 454 pyrosequencing and sequence analysis of the M. stanieri S30 genome generated 4,007 predicted open reading frames (ORFs) that could be candidate genes for producing enzymes with different catalytic functions.