This study was conducted to investigate the effects of multiple stresses on physiological parameters in the hepatopancreas and hemolymph of a Pacific abalone, Haliotis discus hannai. The alteration of antioxidant enzymes including catalase (CAT), superoxide dismuatase (SOD) and immunological indicators such as phenoloxidase (PO), lysozyme activity and total hemocyte count (THC) were measured in a Pacific abalone exposed to nickel chloride solution of sublethal concentrations (200 and 400 μg/L) under higher thermal conditions (22 and 26℃) for 2 weeks. In this study, the hepatopancreas enzymes, CAT and SOD activity were significantly increased in the Pacific abalone exposed to NiCl2 compared to those of the control condition(18℃) at both 22 and 26℃. PO activity in the Pacific abalone exposed to NiCl2 also significantly increased at 26℃ thermal stress. But, THC decreased in the Pacific abalone exposed to NiCl2 at 26℃ (P < 0.05). Lysozyme activity was markedly elevated at 22℃ for 1 weeks and at 18℃ for 2 weeks after NiCl2 exposure. Our results showed that NiCl2 concentrations upper 200 μg/L were able to stimulate immune responses in Pacific abalones. Furthermore, complex stress, thermal stress, or NiCl2 can modify the immunological response and can lead to changes in the physiology of host-pollutant interactions in H. discus hannai. From these results, these biochemical parameters may represent a convenient indicator of monitoring heavy metal pollution in coastal areas.
This study investigated morphological and immunological functions of hemocytes from hard clam, Meretrix petechialis for determination of proper sediment composition and rearing density. The hard clams were cultured with various ratio of sand:mud (100:0, 70:30, 50:50, 30:70, 0:100) and rearing density (50, 100, 150 individuals/m2). After 4 weeks, viability, phagocytosis, reactive oxygen species (ROS)-release and apoptosis were analyzed by flow cytometry in the hemocyte of hard clam. Main types of hemocyte from hard clam were identified as hemoblast-like cell, agranulocyte, granulocyte and degranulated cell. In the sediment composition test, ROS-release was significant low at 70:30 and 50:50 although there were no significant differences in viability, phagocytosis and apoptosis under various conditions. In rearing density test, phagocytosis showed the highest value at density of 100 individuals/m2 and decreased at 150 individuals/m2. Also ROS-release increased rearing density-dependently. These results suggest that 50-70% of sand composition and rearing density less than 100 individuals/m2 would be a proper condition for hard clam culture. Moreover, Phagocytosis and ROS release would be useful indicators for physiological condition in artificial culture.
A radiotracer study was conducted to investigate bioaccumulation and subcellular partitioning of Cd and Zn in the different organs (gills, digestive glands and residue tissues) of the oyster (Crassostrea gigas) during 3-week exposure to water-borne source (with and without 20 μg Cd L-1 and 100 μg Zn L-1) and 3-week depuration in uncontaminated seawater. Cd and Zn in the whole soft tissue and individual organs continuously increased during 3-week exposure. Following 3-week exposure, metal concentrations in the gill tissue was 3.3-6 X Cd and 1.5-2.5 X Zn in two other organs while Cd and Zn in digestive glands was about twice the concentrations in residue tissues. The release rate of Zn (1.9% d-1) was a little faster than Cd (1.6% d-1) during 3-week depuration. Cd and Zn in the three organs was mostly in the detoxified form as metal rich granule, where > 60% in gills and residue tissues while > 30% in digestive glands. The Cd and Zn associated with metallothionein-like proteins was < 10% in the all organs. The potentially toxic and metabolically sensitive fractions (organelles and heat-sensitive protein) of Cd and Zn in the gill and residue tissues ranged 18-31%, while that in digestive glands was 47% for Cd and 36% for Zn. The trophically transferable fractions ranged 29-52% for Cd and 22-39% for Zn in the all organs. The results provide some clue to understand why oyster could accumulate unusually high concentrations of heavy metals and could habitat in metal contaminated environment.
The climate change causes the mass mortality of farmed fish and shellfish. In order to find genes involved in physiological response to temperature stress, we have performed sequencing of transcriptome in the pacific abalone (Haliotis discus hannai) after thermal stimulation. In the present study, we present a focused analysis on the heat shock factor 1(HSF1) which is rapidly induced to activate heat shock response (HSR) in host cells under thermal stress as a major transcriptional regulator of heat shock proteins (HSPs). The H. discus hannai HSF1 (HdhHSF1) cDNA contains an open reading frame of 1473 bp, encoding a protein of 490 aa. The deduced amino acid sequence of HdhHSF1 shared the high identity with sequences of the H. asinina (ABR15461.1, 81.6% identity) and H. diversicolor (AGN53400.1, 81.2% identity). The phylogenetic tree of HSF1 revealed that these proteins were divided into two clusters, one comprising vertebrate and mollusc proteins, and the other one containing insecta proteins. The qRT-PCR detected HdhHSF1 mRNA expressions in hemocyte and gill tissues examined. The mRNA expression of HdhHSF1 showed a significant increase at 20°C in gill and 30°C in hemocyte. The expression of HdhHSF1 increased significantly after thermal stress of 6 h in gill, and also increased significantly in hemocyte at 30°C. The present study is the first to report on the molecular cloning, characterization and tissue expression analysis of HSF1 in H. discus hannai. The results might provide new insights into the regulation of HSR in mollusca.
Microplastics discharged from human daily activities are not decomposed by sewage treatment but are introduced into the oceans through land-water systems, and are accumulated in filter-feeding bivalves. This study aimed to investigate microplastic accumulation in Mytilus galloprovincialis artificially exposed to microplastics. The mussels were exposed to fluorescent microplastics made of polypropylene (diameter of 53-63 μm) for 21 days at concentrations of 50 mg/L, 0.5 μg/L, and 0 μg/L. Microplastic distribution and concentration in mussel tissues were analyzed by histology and image processing, respectively. In our study, the microplastics used were partially decomposed into nano-sized particles during the experiment. Thus, two types of micro-particles were investigated in the present study: microplastics (φ < 5 mm) and nanoplastics (φ < 20 μm). Micro/nano-sized plastics were found only in the mussels exposed to the 50 mg/L concentration; the gill, stomach, stylus sac, secondary duct, and intestine of the mussels were the organs of accumulation. Pathological symptomssuch as hemocyte infiltration and digestive tubule atrophy were found around micro/nano-sized plastics, suggesting that these particles cause physiological disorders in mussels.
Metallothionein (MT) family is a metal binding protein that is involved in maintaining homeostasis in the body and detoxifying against heavy metal poisoning. Recently, MT has been studied as a biomarker, same as a cytochrome oxidase I (COI) gene, that can identify species of various organisms. Incilaria fruhstorferi is a large slug that is distributed in Jeju Island, Chuncheon, Busan, and Deokjeokdo. The genetic information of I. fruhstorferi registered in the NCBI (53 nucleotides and 21 proteins) is indicative of the organism’s study should be needed. The researchers conducted a transcriptome study using the Illumina HiSeq 2500 Next Generation Sequencing Platform for the genetic analysis of I. fruhstorferi and obtained the MT gene of I. fruhstorferi. Molecular phylogenetic analysis was carried out using the MT gene of I. fruhstorferi, confirming the similarity with molluscs belonging to Stylommatophora such as Nesiohelix samarangae, Arianta arbustorum, Helix aspersa and H. pomatia.
This study describes the ovarian development and the first report on atretic follicle in net cage cultured abalone, Haliotis discus hannai in Nohwa, Soan, Cheongsan, Bukpyeong, Korea. Sex ratio analysed male lower than female (1:0.56-0.89) and especially, there were significant differences in the cases of Nohwae, Soan, and Bukpyeong. The spawning period was sparse. Atretic follicles were observed from March to December at all research sites, and the rate of occurrence was high at ripe stage (from April to September). It is suggested that spawning disruption is caused by the atretic follicle. The process of the atretic follicle initially showed vacuolization in the cytoplasm, and the concensation nucleus with the aggregation of Vtg granules, The aggregated Vtg granules were absorbed and then only the jelly layer remained. Finally, the jelly layer was also degenerating.
This study evaluated bacteriological and toxicological safety of three shellfishes produced in the Gangjin Bay from January 2015 to June 2017. Single sampling station was selected in the shellfish ground of oyster, short neck clam and small ark shell. The ranges of total coliform, fecal coliform and E. coli levels for 29 oyster samples were < 18-5,400, < 18-130, < 20-80 MPN/100 g and 30-6,900 CFU/ g, respectively. Those for 29 short neck samples were 20-3,500, < 18-330, < 20-230 MPN/100 g and 40-3,700 CFU/ g respectively and those for 30 small ark shell samples were < 18-< 16,000, < 18-460, < 20-80 MPN/100 g and 30-6,900 CFU/ g respectively. From all samples, any Salmonella sp. were not detected. Also paralytic shellfish toxins were not detected and diarrhetic shellfish toxins were detected below the limit of quantification. As the results of the bacteriological evaluation, it was confirmed that the shellfishes produced in Gangjin Bay meet the standard of shellfish hygiene of the Food Sanitation Act and were assessed to be the Grade A of EU criteria.
A bacteriological survey in cultured scallop Argopecten irradians was conducted in Jaran bay, Korea from April, 2016 to January, 2017. A total number of 32 Vibrionaceae isolates were collected, dominantly. All isolates were phenotypically characterized and then identified with sequencing of the 16S rDNA and rpoA gene. A fifth species of Vibrionaceae were identified as Vibrio harveyi (8 strains, 25.0%), Vibrio alginolyticus (4 strains, 12.5%), Vibrio mediterranei (3 strains, 9.4%), Vibrio shilonii (3 strains, 9.4%) and Vibrio chagasii (3 strains, 9.4%), Photobacterium jeanii (2 strains, 6.3%), Photobacterium swingsii (1 strains, 3.1%), Vibrio artabrorum (1 strains, 3.1%), Vibrio cyclitrophicus (1 strains, 3.1%), Vibrio fortis (1 strains, 3.1%), Vibrio owensii (1 strains, 3.1%), Vibrio parahaemolyticus (1 strains, 3.1%), Vibrio Pelagius (1 strains, 3.1%), Vibrio splendidus (1 strains, 3.1%), Vibrio zhanjiangensis (1 strains, 3.1%). In the aquacultured scallop Argopecten irradians, Harveyi clade is a major clade including by V. harveyi (3), V. alginolyticus (3) and V. parahaemolyticus (1). Most of detected all bacteria were vibrio species that are associated with bivalve molluscs in commensal or pathogenic relations.
As one of optimal condition for establishment of criteria of tidal flat oyster farm, we investigated food selectivity between phytoplankton composition in seawater and gut content of oyster reared at 4 × 3 different condition in exposure duration and rack height on the eastern coast of Wando island, Korea. The seawater temperature ranged from 8.9℃ to 28.0℃, which was characterized as lower ranged temperature difference because of strong tidal front around Jindo and indirect influence of off sea waters. Salinity was ordinarily maintained in the range of 30-33 psu, because a hydrodynamic feature prevents the magnitude land-driven freshwater input from Doam tidal gate in Gangjin-gun. A total of 58 phytoplankton species (37 genera) were identified with 58 species of Bacilariophyceae (35 genera) and 5 species of Dinophyceae (2 genera) in seawater but 50 species (50 genera) with 47 species of Bacilariophyceae (31 genera) and 3 species of Dinophyceae (2 genera). The gut content was highly correlated with the standing stock of phytoplankton in seawater. The common dominant species were Paralia sulcata, Navicula sp., Chaetoceros sp. and so on. A Bacillaria paxillifer showed a complementary selectivity to that of Cheatoceros genus with strong positive electivity in the blooming season. In exposure duration experiment, gut content of 1 hr level was significantly higher than that of 2-4 hr level, which can be a feasible criteria for a facility of oyster rack farm in tidal flat.
The study investigated the growth and appearance characteristics of domestic Yesso scallops, Patinopecten yessoensis (Korea: Gangneung hanging culture, Pohang sowing culture) and imported Yesso scallops (Japan: Hokkaido sowing culture) which being sold in the eastern coast area of South Korea, and compared their commercial value. In domestic Yesso scallops reared by hanging method, the relative growth relationship for the shell height was shown as SL = 0.6658 SH + 35.388 (R2 = 0.7071), SW = 0.1896 SH + 7.52 (R2 = 0.2263), TW = 4.35 SH . 302.72 (R2 = 0.7007), MW = 1.9975 SH . 175.58 (R2 = 0.7523) in shell length, shell width, total weight, meat weight, respectively. Relative growth relationship of each regions in Yesso scallop was shown the straight on growth in all three different habitat. The percentage of shell height to shell length (SH/SL, %) was 103.95 ± 0.36% and the percentage of meat weight to total weight (MW/TW, %) was 41.91 ± 0.27%, they were shown significantly higher than others in domestic Yesso scallop reared by hanging method. In the sex ratio of Yesso scallops according to culture mode, the percentage of female was very low as 3.3% compared to 96.7% of male in one reared by hanging method in Korea. On the other hand, the percentage of female was similar with female as 41.1-44.4% in scallops reared by sowing method in Korea and Japan. The size of Yesso scallops was larger and the ratio of meat weight to total weight was higher in one reared by hanging method in Korea than others. Therefore, Yesso scallops reared by hanging method in Korea has a higher commercial value than Yesso scallops reared by sowing method in Japan.
This paper was aimed to sedimentary environment appropriate for survival and inhabit of Saxidomus purpuratus juvenile. The sediment type in Goheung coast was dominated by silt (78.1 ± 0.6%), and followed by clay (20.2 ± 0.7%) and sand (1.7 ± 0.8%), and that in Hwagye coast was similar to that of Goheung coast (Silt 78.5 ± 0.7%, Clay 20.7 ± 0.6% and Sand 0.8 ± 0.4%). Thus the Saxidomus purpuratus juvenile habitat was mainly composed of silt. In case of Saxidomus purpuratus adult habitat, silt (79.6 ± 0.5%), and followed by clay (19.7 ± 0.5%) and sand (0.7 ± 0.3%). But, the research results, sedimentation environment showed the highest response rate (50%) as the environmental factors for juvenile survival. Sandy silty showed the highest response rate (83%) for the most appropriate sedimentation environment.
Based on the results from the utilization of minimum octopus minor listening survey conducted on from Mar. to Aug. 2017, definition of the minimum octopus minor is less than 10g. Major fishing gear is longline and handicraft (shovel) in Muan, trap, longline, shovel in Mokpo and in Wando, Gangjin, Boseong is trap. It is trap and longline in Jangheung, only longline in Yeosu. All cities, it is not doing fisheries in closed season. The fishing gear of catch minimum octopus minor is handicraft in Muan (shovel) and in Mokpo (scoop net). The fishing season of minimum octopus minor is from August to early September. The ratio of catch is difficult to estimate because it is caught by reservation.
In August-September 2015, massive mortality occurred on net cage cultured abalone in Wando, Korea. We performed research for find mortality cause in 15 farms in Wando. There were no pathogen detection in abalone of research site. However, as a result of the red tide biomonitoring of the NIFS, the density of C. polykrikoides was detected to 4,500 cells/mL in the area of the damaged farm on September 7. At the research day, we detected average density of 26 cells/mL (inside a net cage) and 21 cells/mL (outside a net cage) also, C. polykrikoides were observed on the gill of abalone in three research site. We are considered on damaged abalone to be that the histopathological resesults in gill and hemolymph were effected by acute factors, and histopathological degeneration of hepatopancreas and low glocose concentration were effected by chronic factors. Therefore, it is thought that the mortality of net cage cultured abalone is casued by a combination factors of physiological weakness by the chronical affect and acute affect such as a red tide.
