To elucidate the immune response of the Manila clam Ruditapes philippinarum in a habitat, 20 clams were collected from the west coast of Korea; and immune parameters, including total hemocyte counts (THC), reactive oxygen species (ROS), cell necrosis, apoptosis, and DNA damage within hemocytes were investigated using a portable flow cytometer. The measurements were conducted immediately after sample collection in the field. The analyzed immune parameters were also compared with those measured in the clams kept at 4 °C for 12 h. The immune parameters of the field-collected clams were 737,568/ml of THC, 0.553% of DNA damage, 41.962 A.U. of ROS, 0.121% of necrosis rate, and 0.055% of apoptosis rate, respectively. These values significantly increased when the clams kept at 4 °C for 12 h in the present study, suggesting that a significant modulation of immune responses might have occurred during transformation from sampling site to laboratory. Therefore, in order to investigate the immunity of clam in habitat, it is necessary to consider measures to reduce the change of immunity that may occur during transportation to laboratory after sampling.
The developmental stage of germ cells during oogenesis in the giant abalone Haliotis gigantea can be categorized into six stages with histological features: (1) oogonium, (2) previtellogenic oocyte, (3) initial vitellogenic oocyte, (4) early active vitellogenic oocyte, (5) late active vitellogenic oocyte and (6) ripe oocyte. The size of oocyte, nucleus and nucleolus illustrated the increase tendency but size ratio of nucleolus to nucleus was decreased during oogenesis. During oogenesis the stainability in the cytoplasm of oocyte changes from basophilic to eosinophilic in H-E stain. And egg stalk and outer jelly membrane was developed in the oocyte. These histological changes are seemed to be preparation process for the yolk accumulation in the oocyte and the spawning.
Increase in seawater temperature during summer is one of the most important and serious issues confronted by abalone aquaculture farms, and can become the cause of the manifestation of diseases and ensuing mass mortality. The study was conducted to assess the survival rate, metabolism, changes of hemolymph and histological responses in abalone Haliotis discus hannai juvenile with increase of water temperature. This study will be used to manage abalone farm to cope with frequently the mass mortality occurring during summer season. Survival rate was 100% and falling rate was 0% at 20℃ (control group). But when temperature was elevated to 2 8℃, survival and falling rate was 30% and 70% for 5 exposure period, respectively. And all died after 3 time of exposure at 30℃. Lethal temperature for 5 days of abalone Haliotis discus hannai juvenile (5day-LT50) was 27.9 3℃ (confidence limit: 27.6-28.3℃). Oxygen consumption rate was sharply increased at upper temperature more than median lethal temperature for 5days (5day-LT50). Ammonia nitrogen excretion rate showed the similar tendency with oxygen consumption rate. The change of Glucose, ammonia, total protein in hemolymph was different. Ammonia was increased at median lethal temperature above, but total protein level was significantly reduced more than median lethal temperature. SOD activity was not showed significantly change compared to control group. Pathohistological response was not observed in 23℃ and 26℃ in comparison to control group. However break of hemolymph membrane, segment of fiber aggregate and degeneration were observed at above 28℃.
Clithon retropictum (family Neritidae) is an aquatic gastropod mollusk that mainly inhabits freshwater. Owing to considerable decreases in its occurrence and natural habitat, and unique ecological characteristics, it has been legally protected as an endangered species in South Korea. In this study, we analyzed the complete mitochondrial genome sequence of C. retropictum and reconstructed phylogenetic trees inferred from the sequences of protein-coding and cytochrome c oxidase 1 (cox1) genes. The phylogenetic tree accurately reflected its morphological taxonomy at the generic level. Inferred from the trees, the occurrence of Clithon species in freshwater has been interpreted as an independent evolutionary event derived from its marine snail ancestor.
Based on the results from the Amphioctopus fangsiao fishing trend survey conducted on November 27, 2015, the average fishing amount per person per day was estimated as 5 kg with the average catch of 50-70 and the maximum catch of 100-200. Two scenarios were applied for the catch estimation of Amphioctopus fangsiao by leisure fishing based on the data of MOF (2005) and the model of Lee (2010). First scenario is that 64,000 persons three times a year, and the estimated catch was 1,050 tons per year.
The purpose of the present study is to get information on the reproductive characteristics of Octopus minor, especially focusing on monthly variations in mantle length and gonadosomatic index, sex ratio, fecundity, group maturity for the effective management of this biological resource. Gonadosomatic index showed a peak between July and September in females. The fecundity ranged from 97 to 213 eggs with the total weight of 96.8 g and 270.7 g, respectively. There was a good relationship between total weight (TW) and fecundity (F): F = 2.937TW0.752 (r2 = 0.80). The mantle length (ML) and total weight (TW) showed also a relationship: TW = 0.702ML2.417 (r2 = 0.72) in female, and TW = 0.605ML2.539 (r2 = 0.74) in male. The sex ratio (female/male) of O. minor was 1/0.85 (female 54.0%) showing predomination of female.
For the investigation on the distribution of a brackish water clam, Corbicula japonica inhabiting on the Eulsuk tidal flat in the Nakdong river estuary, faunal samples were collected at 20 sites in March, 2017. Sediments consisted of more than 80% of sand at all sampling sites, salinity was ranged from 25 to 30 psu. Sediment temperature and salinity did not show any difference between the sites in March, 2017. However, due to the influence of rainfall, salinity ranged from 0-30 psu depending on the season. The Corbicula japonica popualtion showed a patchy distribution with its density range of 0 to 52 ind.m-2, and their high density occurred at the southwest part of the tidal flat. The Corbicula population consisted of mainly large adults with their shell length of 25.2-28.6 mm (overall average: 26.72 mm). In July and August, spats with their shell length of 3 to 5 mm were observed, and this suggests that the recruitment of C. japonica should exist before May or June.
This paper was aimed to determine the population density of Saxidomus purpuratus according to the habitat environmental conditions of the southern coastal waters in Korea. The sediment type in Yeosu coast was dominated by silt (79.6 ± 0.5%), and followed by clay (19.7 ± 0.5%) and sand (0.7 ± 0.3%), and that in Geoje coast was similar to that of Yeosu coast (Silt 77.6 ± 0.4%, Clay 21.7 ± 0.7% and Sand 0.67 ± 0.4%). Thus the Saxidomus purpuratus habitat was mainly composed of silt. The population density of S. purpuratus in Yeosu coast was in the range of 0.5-2.0 ind./m2 and that in Geoje coast was 0.25-7.25 ind./m2. Among the caught individuals, the`proportion of immature individuals was 7.6% and 13.4% in Yeosu and Geoje coast, respectively.
Six species of cypraeid mollusks collected from the Korean waters were identified as Erronea onyx (Linnaeous, 1758), Maurita arabica (Linnaeous, 1758), Melicerona felina (Gmelin, 1791), Monetaria moneta (Linnaeous, 1758), Purpuradusta fimbriata (Gmelin,1791), and Talostolida teres (Gmelin, 1791). This is the first record from the Korea, providing a description of the species with illustration for the shell morphology. Including the present new records, the family Cypraeidae contained 11 genera and 20 species in the Korean waters.
To investigate the fauna and larval infection status of freshwater snails living in water stream and rice paddy, we collected 925 freshwater snails at 7 regions in Sejong and Daejeon at 2016 and 2017. From the survey, a total of 925 freshwater snails were identified as 6 families, 9 genus and 9 species. The collected ten species of freshwater mollusks were identified as Lymnaea pervia, Radix (Lymnaea) auricularia, Physa acuta, Cipangopaludina chinensis, Gyraulus convexiusculus, Hippeutis cantori, Segmentina hemisphaerula, Semisulcospira libertina, and Parafoussarulus manchuricus. The most populated snails was L. pervia and the second one was P. acuta. The cercariae of Paragonimus, Metagonimus and Echinostoma species were isolated from Semisulcospira, Gyraulus, Hippeutus, Parafoussarulus, Segmentina, Lymnaea and Radix collected at 3 regions among 7 surveyed regions. Collectively, this study presented that various species of freshwater snails and cercaria-infected snails are distributed at water stream and rice paddy at Sejong and Daejeon, and further investigation needs to be carried out to identify the fauna of freshwater snails in detail.
