ISSN : 1225-3480
The Korean Acusta specimens were collected from six sites: Seo-gu, Incheon; Yeongyang, Gyeongsangbuk-do; Hongdo Island, Jeollanam-do; Jodo Island, Jeollanam-do; Chuncheon, Gangwon-do; and Seogwipo, Jeju-do. It was observed that the morphological characteristics follow the typical genus Acusta. In order to confirm their phylogenetic position, DNA analyses were conducted targeting three regions, cytochrome c oxidase subunit 1 (CO1), 16S ribosomal RNA (16S), and internal transcribed spacer 2 (ITS2). As a result, the Korean population of Acusta specimens were confirmed to be of the same species. In the phylogenetic trees, it was grouped in the same clade as Acusta redfieldi (Reeve, 1852) and showed the lowest variation of Acusta group. It was also the second most closely related to A. siebolditina (L. Pfeiffer, 1850). Therefore, the Korean Acusta is regarded as A. redfieldi and showed closer genetic similarity to the Chinese population than to the Japanese population. In addition, in this study, the nucleotide sequences of the Korean group Acusta are recorded in a public database for the first time, and then a photograph of the individual and a brief morphological description are provided.
Arcuatula senhousia, a bivalve mollusk, exerts a significant negative impact on ecological aspects within the realm of bivalve aquaculture. This study delved into the reproductive cycle and distribution of A. senhousia in Jinju Bay, Korea, spanning from February to December 2020. The species inhabiting Jinju Bay displayed a dense concentration in the central part of the bay, where shellfish aquaculture facilities are prevalent. However, they experienced a complete die-off in August, and no specimens were collected thereafter until the conclusion of the experiment. The reproductive cycle of A. senhousia, collected from February to July 2020, revealed that 13.6% were females, while 56% were males in the early developmental stage among the specimens collected in February. Males exhibited a more rapid maturation of reproductive organs. Gonadal maturation was observed in both male and female specimens starting in May, with spawning occurring from May to July. The mortality of A. senhousia observed in August was attributed to underwater hypoxia or anoxic conditions. The insights into the reproductive cycle of A. senhousia inhabiting the Jinju Bay area are anticipated to hold value for the development of techniques in shellfish aquaculture management.
In this study, we evaluated the effect of inland pollution sources on seawater and shellfish (Oyster and Scallop) in Goseong bay after rainfall events. We analyzed the sanitary indicator microorganism such as total coliform, fecal coliform and Escherichia coli (E. coli) in the discharge water of major inland pollutants, seawater and shellfish for 3 days after 25.5, 56.0 and 101.5 mm rainfall events. According to these results, the range of total coliform and fecal coliform was < 1.8-2,400 and < 1.8-2,400 after 25.5 mm rainfall and was from < 1.8 to 110 and from < 1.8 to 13 MPN/100 mL after 56.0 mm rainfall and was from 79 to 11,000 and from 79 to 11,000 MPN/100 mL after 101.5 mm rainfall in the discharge water of 2 waste water treatment plants. Also the range of fecal coliform and radius of impacted area of 9 contaminants (stream) was from 13 to 35,000 MPN/100 mL and from 14 to 2,249 m, respectively. The fecal coliform of seawater at 34 stations ranged from < 1.8 to 540 MPN/100 mL, respectively. And The E. coli level of shellfish (Oyster and Scallop) at 6 station ranged from < 18 to 5,400 MPN/100 g.
The sanitary survey was evaluated for sanitary state of seawater and shellfish in Chilcheondo area from September 2020 to February 2023. The stations of sanitary survey in Chilcheondo area were composed of 28 seawater station, 3 oyster (Crassostrea gigas) and 1 mussel (Mytilus galloprovinciallis). The samples were collected monthly at each station. The range of Fecal coliform, geometric mean and 90th percentile for 840 seawater samples were < 1.8-35,000 MPN/100 mL, < 1.8-3.3 and 1.8-34 MPN/100 mL, respectively and in addition to seawater in the Chilcheondo area satisfied as level of designated area according to Korea criteria and approved area according to US criteria. Also the range of Fecal coliform and E. coli for 88 oyster samples and 30 mussel samples were <18-35,000 and <18-9,200 MPN/100 g, respectively. The bacteriological quallity of shellfish collected from Chilcheondo area meets the standard value based on shellfish hygiene of the Food Sanitation Act of Korea and the Grade B according to the classification of shellfish harvesting areas of European Union.
In order to assess the health level of tidal flat, we investigated heavy metals of surface sediments and the biomarker genes of Ruditapes philippinarum samples in the west coast of Korea. Manila clams were collected from 8 sites of western coast and analyzed the total RNA of these meat part with RT-qPCR method. We have examined the geochemical characteristics of surface sediments and the concentration of inorganic elements of manila clam with XRF. It is possible for the health level of inhabit organisms using analysis of expression of biomarker genes such as heat shock protein 70 (Hsp70), heat shock protein 90 (Hsp90), glutathione S-transferases (GST) and thioredoxin (TRX). That is related to stress, immune and antioxidant related genes. Results showed that the expression of biomarker genes were changed in the 8 sites and were relevant with the heavy metal concentration of sediments, respectively. We suggested that biomarker genes were played an important role for the health level assessment of tidal flats.
The alveolate protozoan parasite Perkinsus olseni has a unique life cycle, including a mobile zoospore in an aerobic water column, vegetative trophozoite in the host tissues, and dormant hypnospore in an anaerobic environment such as decomposing host tissues or subsurface of the sediment. In this study, P. olseni trophozoites were induced from the zoospores in vitro using a Dulbecco Modified Eagle’s:Ham’s F-12 (DME/Ham’s F-12, 1:2) fortified with antibiotics and supplemented with 5% fetal bovine serum, 50 mM HEPES buffer, 3.5 mM sodium bicarbonate, and 200 mM L-glutamine. In the growth media, P. olseni zoospores developed into trophozoites and reproduced within two weeks at 25 °C room temperature. During two weeks of culture, the trophozoites increased their cell size from a few microns to 34.4 ± 14.1 μm in diameter. Numerous small-sized daughter cells of the trophozoites could be observed 4 and 6 days after incubation, suggesting that the doubling time of the trophozoites in the media can be 4 to 6 days. The hypnospore stage and subsequent zoosporulation could also be induced from the trophozoite stage developed in the growth media, confirming that the trophozoites are vital, although they were produced in vitro. The Dulbecco’s modified Eagle’s:Ham’s F-12 (DME/Ham’s F-12, 1:2) growth medium was considered a method of choice in the mass production of P. olseni trophozoites in vitro, as previously applied in in-vitro culture of Perkinsus spp.
