The Pacific oyster Crassostrea gigas larvae were exposed to 4 cryoprotectants, dimethyl sulfoxide (DMSO), ethylene glycol (EG), glycerol and methanol, each with 4 four concentrations (10, 20, 30, and 40%) for permeation. Detail concentration of experiment on larvae were exposed to 2 two cryoprotectants, DMSO and EG, each with 4 four concentrations 22, 24, 26 and 28%) for permeation. 26% dimethyl surfoxide (DMSO) for 30 min and 28% EG for 120 min were determined as appropriate CPA and equilibration time by CPA permeation experiments of trochophore larvae. 22% DMSO for 60 min and 26% EG for 60 min were determined as appropriate CPA and equilibration time by CPA permeation experiments of D-shaped larvae. Larval abnormalities, a sign of the chemical damage, were a representative phenotype which was higher at a higher concentration and longer duration of the chemicals.
To investigate the tolerance of Sunray surf clam, Mactra chinensis in low salinities, survival and physiological responses related to osmoregulation of clams (60.2 ± 3.5 mm) were examined in 10, 20 and 30 psu at 15℃. The survival rate was 65.0% in 20 psu up to 216 h, while in 10 psu, severe mortality was recorded after 48 h and all died up to 96 h. Total hemocyte count (THC) was maintained a consistent level in 30 psu. While in 20 psu, it tended to decrease up to 24 h and afterwards, recovered gradually. In 10 psu, it was increased up to 6 h and tended to decrease later on. Osmolality of hemolymph followed the level of experimental water after 3 h 30 and 20 psu respectively, while in 10 psu, it did not completely follow the level of experimental water up to 48 h. Na+, Cl-, K+ and Ca of hemolymph showed the same as the result of osmolality. Glucose of hemolymph was significantly increased at 72 h in 20 psu. In 10 psu, it was significantly increased at 12 h first and sharply increased at 48 h. Aspartate aminotransferase (AST), alanine aminotransferase (ALT) and lactate dehydrogenase (LDH) of hemolymph were significantly increased at 48 h in 10 psu simultaneously. Oxygen consumption and ammonia excretion were significantly decreased below 20 psu. Therefore, it is judged to be harmful on physiological activity of Mactra chinensis when be exposed to 20 psu over 72 h or to 10 psu over 12 h, respectively.
A study was conducted to evaluate the effects of elevated water temperature on antioxidant and immunological response in the abalones, Haliotis discus discus and Haliotis gigantea. The abalones were exposed to various water temperature; 20, 21, 22, 24, 26 and 28℃ for 96 hours. After thermal stress for 96 hours, in the control, superoxide dismutase (SOD) activities in hepatopancreas of H. gigantea were higher (1.3 times) than the values in H. discus discus. Although SOD activities showed no significant differences in H. discus discus, the values in H. gigantea were significantly increased in 24℃ or higher compared to the control after 24 hours exposure. Catalase (CAT) activities in hepatopancreas of H. discus discus were higher (1.4 times) than the values of H. gigantea in the control. After thermal stress (≥ 26℃), CAT activities significantly increased in both species compared to the control. The phenoloxidase (PO) activity of hemolymph was decreased in both species exposed to high temperature (≥ 26℃) compared to the control (P < 0.05). The values of lysozyme were significantly decreased in H. discus discus exposed to 28℃, and in H. gigantea to 26℃. In conclusion, in both species, there was a significant increase on antioxidant abilities (CAT) and a decrease on immunological parameters (PO and lysozyme) after thermal stress of 26℃ or higher. Also, antioxidant enzymes, SOD activities significantly increased in H. gigantea, but there was no significance in H. discus discus after thermal stress. These results suggested that H. gigantea is considered to be more sensitive than H. discus discus on thermal stress even though the similar warm current type.
Temperature is the major environmental factor to determine the geographical distribution, species diversity and community structure of most living organisms. We hypothesized that temperature is being one of the environmental factors to determine community structure of the mollusks living in the intertidal zone of the rocky shore in the Jeju Island. For examination of our hypothesis, we sampled and analyzed mollusks quantitatively and seasonally at the 12 stations along the coast of Jeju Island from June 2011 to February 2012. Surface sea water and atmospheric temperature were used as temperature variables to analyze the correlation between community structure and temperature. The Jeju coast was divided into two areas (North-West area: lower temperature, South-East area: higher temperature) based on the surface sea water which was significantly different between the two areas (p < 0.05). There was no significant correlations, however, between community structure and temperature, and no significant difference (North-West and South-East areas) in the three variables (number of species, density and biomass) of the community structure between the two areas (p > 0.05). The foregoing hypothesis, therefore, was rejected based on the present results in the Jeju Island. Species diversity, which is based on the number of species, was higher in the South-East area than in the North-West area. Although temperature is not likely to be a provable factor to increase the species diversity in the intertidal malacofauna in the coast of Jeju Island, it could be affecting the community structure via interaction which the other factors such as grazing, salinity, dessication and tidal action.
Seawater monitoring, geochemical and benthic foraminiferal analysis of sediments were conducted to understand the occurrence of hypoxia and effect of mussel farming on benthic ecology in spring season of Gamak Bay. Bottom dissolved oxygen (DO) of surface sediment ranged 1.42-7.05 mg/l with average 4.90 mg/l and increased from northwest to south area. Hypoxia occurred at northwest area of station 1 and 3 with 1.8 mg/l, 1.4 mg/l, respectively. Contents of total organic carbon with 1.20% of average was decreased from northwest toward south area. Ratio of total organic carbon to total sulfur with 4.82 ranged 2.40-8.26 and increased from northwest toward southern part of bay. Polluted reductive conditions were gradually diffused from northwest toward south. These diffusion patterns were observed in species diversity, abundance frequency, and benthic foraminiferal assemblages composed of E. subarcticum-T. hadai (northwest and Daegyeongdo area), E. subarcticum-A. beccarii (central area) and E. subarcticum-E. clavatum (central and south area). It was thought that these organic pollution caused by the mussel farm distributed northwest area.
Samples of Corbicula japonica in the Seomjin River were collected from March 2016 to November 2016. Age of C. japonica was determined from the rings on the shell. The relationship between shell length (SL; mm) and shell height (SH; mm) was expressed by the following equation : SH = 0.8981SL - 0.4166 (R2 = 0.97), and between shell length (SL) and shell width (SW; mm) by the equation SW = 0.5715SL + 0.1583 (R2 = 0.95). Shell length (SL; mm) and total weight (TW; g) relation was also expressed by the following equation : TW = 0.0003SL3.0078 (R2 = 0.97). Based on the monthly variations in the marginal index (MI) of the shell, it is assumed that the ring of this species was formed once a year during the period of March. The time it takes to form the ring is estimated to be about 7 months (0.58 years). von Bertalanffy's growth parameters were estimated using the regression wizard of Sigmaplot (Systat Software, Inc., v. 10.0), a computer program. Maximum shell length (SL∞) was 40.1455 mm, growth rate was 0.3564/year, theoretical age at 0 shell length (t0) was 0.0644 year, and asymptotic total weight (TW∞) was 19.98 g. Growth curves for shell height (SH) and total weight (TW) fitted to the von Bertalanffy's equation were expressed as follows : SLt = 40.1455(1―e―0.3564(t―0.0644)) TWt = 19.98(1―e―0.3564(t―0.0644))3.0078
The purpose of this study is to suggest the age determination method of Saxidomus purpuratus. Samples of S. purpuratus were collected in Jinhae Bay in 2017. The method of observing with a lighting device is efficient in terms of time and economy since no additional procedure is required. However, shells thick larger than 2.4 mm were hard to observe. In this case, there is a method of cutting and dyeing the shell or dissolving with hydrochloric acid. These two methods can confirm the ring relatively clearly, but when using hydrochloric acid, the risk of damaging the shell is high. Therefore, it seems effective to observe the ring of S. purpuratus using a light device.
By the species composition of macrobenthic community on the tidal flat of Garolim Bay, study area was divided into two regions, located near mouth and inner part of bay. Two regions were named as TFMB (tidal flat in the vicinity of the mouth of bay) composed of Ojiri (OGA, OGB), Mandae (MD) and Gopa (GP), and TFIB (tidal flat of inner bay) composed of Youngtap (YT), Heuksuk (HS), Duksong (DS) and Changsun (CS). Species number, density and biomass of macrobenthos in TFMB were higher than in TFIB., Dominant species in TFMB were Heteromastus filiformis and Mediomastus sp. belonging to polychaetes, and besides that, Musculus senhousia and Ruditapes philippinarum as a member of bivalves were seasonally important species. However, dominant species in TFIB were Macrophthalmus japonicus, Ilyoplax pingi and some amphipod species belonging to crustaceans. Main species in TFMB were composed of species known to inhabit on mixed tidal flat, but those in TFIB were on mud flat. As a result of PCA, there were high correlations with occurring species and their specific environments. M. japonicus, I. pingi and C. sinense showed high positive relations with fine sedimentary environments (mean grain size, organic matter content, sorting and AVS etc.) being typically characteristics of mud flat of inner Garolim Bay. H. filiformis, Mediomastus sp., Nephtys polybranchia, Armandia lanceolata, M. senhousia and R. philippinarum were closely related with coarse sedimentary environments and ecological parameters of macrobenthic community (density, biomass, diversity index and richness index etc.) being typically characteristics of mixed flat of mouth of Garolim Bay.
The purpose of the present study is to know the reproductive characteristics of Korean Amphioctopus fangsiao focusing on the sex ratio, fecundity, group maturity and egg size for management of the species resource effectively. The sex ratio (female:male) of A. fangsiao was 1:0.7 (female 58.9%) showing predomination of female. The fecundity ranged from 195 eggs at 37.4 g to 1,295 eggs at 214.3 g of body weight. The relationship between total weight (TW) and fecundity (F) was F = 4.490TW1.023 (r2 = 0.80) and fecundity increased with body weight.
This study was investigated to statolith morphology, and examined applicability of the morphology to taxonomy the six Korean cephalopod species. The cephalopods used in the study were caught on the southern coast of Korea, and after transfer to the laboratory, statolith was extracted and observed. Observation results showed that the component parts of statolith were different between Octopoda and Decapoda consequently, it was possible to distinguish between Octopoda and Decapoda based on the statolith morphology. In Octopoda, the shape and location of the tip of the wing could be used as the taxonomic character. In Decapoda, Lateral dome and dorsal dome could be used for the taxonomic character. These morphological differences of statoliths are thought to be related to the ecology of each species.
