Sodium hypochlorite (NaOCl) is a disinfectant, which is widely used in homes and industries, such as power plants, particularly as an antifouling chemical for cooling water. However, owing to the high toxicity of this chemical, it might have a negative effect on the ecosystem, if leaked into the ocean. In the present study, we investigated the immune response of oysters exposed to NaOCl for determining the possible effects on the marine ecosystem. The survival rate and immune responses of the trochophore larvae in NaOCl diluted to 0.01, 0.05, 0.1, 0.5, and 1, 5 ppm, and seawater (control), were investigated at different time intervals under in vitro and in vivo conditions. In the in vitro experiments, the changes in immune responses over time after exposure of hemocytes to NaOCl (in vitro-1) and immune responses of hemocytes over time after NaOCl is diluted with sea water (in vitro-2) were studied. We found that the mortality rate of the larvae was the highest at a concentration of more than 1 ppm after 5 h of exposure. Immune responses of the hemocytes exposed to NaOCl increased 12 h after exposure but reached the same level as that of the control after 24 h of exposure in both in vitro-1 and 2. For, in vivo experiment, the level of NO increased if the adult oysters were raised at NaOCl concentrations of 1 ppm or more, for more than 4 d. Overall, the findings of this study suggest that the concentration affecting the mortality of larvae or adult, and immune response of adult oysters might be more than 1 ppm.
For the comparative investigation on the ecological characters of the brackish water clam, Corbicula japonica populations inhabiting at the Seomjin River estuary (SRE) and the Eulsuk tidal flats (ETF) in Nakdong River estuary, the sampling was performed by monthly from Mar. to Nov., 2017. The habitats of Corbicula populations in the SRE and the ETF consisted of sand more than 80%. The mean salinity of the SRE and the ETF was 17 psu and 20 psu, respectively. The average shell length of C. japonica was about 10 mm in the SRE, but more than 20 mm in the ETF. However, the density of C. japonica was more than 30 times higher in the SRE. The optimal salinity for the filtration activity of C. japonica was observed from 5 to 15 psu in the SRE, but that in the ETF was observed up to 30 psu. The growth rate of C. japonica in SRE was relatively higher than that of ETF, especially it was higher from April to August. In SRE, spats with the shell length of 2 mm were observed from April, and the density of 2-4 mm individuals rapidly increased in May. In both the SRE and the ETF, the highest density of Corbicula spats was found in July, 2017. From the histological observations on gonadal organs, individuals with spent stage were observed in June, 2017. This suggests that the recruitment of C. japonica would be happened before June.
The purpose of this study is to investigate distribution pattern and variation of mollusca species in the rocky intertidal zone of the mid-western coast of Korea from July 2016 to May 2017. Five stations determined at Seocheon, Gunsan and Buan in the mid-western coast were divided into high, middle, and low sections, and sampling was conducted using a quadrate of 50 cm × 50 cm (0.25 m2). Each station was photographed with a camera and quantitative investigation was conducted based on the photographic data. A number of 16 mollusca species occurred during the investigation period. The mean density was 530 ind./m2 and the mean biomass was 141.42 gWWt/m2. The major density dominant species were a Reishia clavigera, Cellana toreuma, Nerita japonica, Littorina brevicula. Cluster analysis results by density data indicated 3 groups. The A group consisted of the St. 2, the B group consisted of the St. 1 and St. 3, and C group consisted of St. 4 and St. 5. Among the species that contributed to the similarity of each group, A group was Littorina brevicula and Crassostrea gigas, B group was Littorina brevicula and Reishia clavigera, C group was Reishia clavigera and Cellana toreuma.
Metallothionin (MT) is well-known as a biomarker gene induced by various stimuli including heavy metals in vertebrates and invertebrates. This leads many researchers to conduct molecular phylogenetic analysis on the basis of the MT gene and amino acids in the world. In the mollusks, however, it is hard to identify the classification and types of MT even with the MT sequences registered in NCBI. In this study, the mollusks MT genes from NCBI were reanalyzed to establish the taxonomic importance of MT. To this end, 180 complete MT amino acid sequences out of the analyzed 247 mollusks MT sequences obtained from NCBI were selected. Through the association analysis, 58 MT genes were categorized as 12 groups based on molecular phylogenetic analysis. We also analyzed the status of Mollusks MT-related studies through pubmed search. Based on this study, we constructed a website to increase the utilization of the analyzed data by sharing the related information through the following website (http://bioinfo.sch.ac.kr/metallothionein). Thus, it will be much easier and faster to annotate and conduct molecular phylogenetic analysis with any MT gene derived from RNA-seq and Genome-seq data of new mollusks in the future.
Benthic mollusk communities in the upper part of the Ba Lai River (the Mekong Delta), located upstream an irrigation dam, were investigated with respect to species composition, densities, biodiversity and some ecological aspects in 5 sampling stations. Densities of bivalve communities ranged from 21.5 ± 8.2 inds/10 cm2 to 28.5 ± 3.3 inds/10 cm2. In summary, 12 species from six Bivalvia families were recognised. Preliminary investigation on reproductivity of Corbicula blandiana showed the species is dioecious (specimens with separately female or male gonads were indicated), perhaps non-incubatory. Find of Meretrix lyrata, the most abundant commercial species in southern Vietnam, brings up a necessity on suitable policy and exploration in the Ba Lai to conserve valuable species for economic development and scientific purpose.
Seven unrecorded marine mollusks species, including 6 gastropods and 1 bivalve, were collected from Korean waters (Jeju-do and Gyeongsangnam-do). They were identified as Pectinodonta orientalis Schepman, 1908, Scutus unguis (Linnaeous, 1758), Gyrineum lacunatum (Mighels, 1845), Sinum planulatum (Recluz, 1843), Syrnola cinctella A. Adams, 1860, Hemilienardia subspurca (Hervier, 1896), and Laevicirce soyoae Habe, 1951. In this study, we provide descriptions and pictures of the shell morphology of 7 species as a new record in the Korean sea.
This study measured nitric oxide (NO) concentration using Griess assay in three shell length groups of spats aged 2.5 months that had been exposed to various concentrations of a pro-inflammatory drug (lipopolysaccharide, LPS). The shell lengths of small-, medium-, and large-size groups were 1.15 mm, 4.24 mm, and 6.40 mm, respectively, suggesting that there was significant variation in the shell length even though they were fertilized simultaneously. The NO concentration increased significantly as the LPS concentration increased specifically, NO was the highest in spats of small size followed by spats of medium and large sizes. Thus, our study showed that failure to thrive (FTT) spats are more susceptible to inflammation-inducing environments. We conclude that NO measurement using Griess assay is useful for evaluating the health of spats, and FTT spats are likely to have a low resistance to inflammatory conditions and poor health.