We examined physiological responses related to the survival, oxygen consumption and filtration rate of the blood cockle, Tegillaarca granosa as a result of salinity changes. The 44-day LS50 (median lethal salinity) at 10ºC for adult and juvenile was 15.8 (confidence limits 13.5-18.2 psu) and 16.2 (confidence limits 14.1-18.4 psu) psu respectively, whereas the 11-day LS50 at 25ºC for adult and juvenile was 16.8 psu (confidence limits 12.9-21.2 psu) and 22.4 (confidence limits 20.5-24.7 psu) psu respictively. In conditions of decreasing salinity, Oxygen consumption and filtration rates decreased or varied irregularly as salinity decreased. The results of this study could prove important in investigating causes of mass mortality and managing shellfish aquaculture farms.
In other to understand the effect of yellow soil to mortality of Korean scallops, P. yessoensis, We investigated its mortality at indoor tanks. The environmental conditions such as water temperature, Salinity, Do and pH were continued constantly during the experimental periods. The 100% of survival rate showed in two experiments groups such as 0.1% and 0.4% of concentration of yellow soil and the other groups as 0.05% and 0.2% of concentration of yellow soil was appeared one dead scallop at each group for 8 days of the experiment periods. the gills of scallop in high concentration of yellow soil (0.2% and 0.4% groups) were covered by yellow soil particles so that this group's scallop should be got a high stress from yellow soil. I think this situation will be more continued for long time the scallop will become to dead. The results of bacteriological analysis did not isolated from haemolymph of scallops and no Perkinsus infectious disease in scallops and the scallops showed necrosis and degeneration on digestive grand and gills of scallop.
Correlation between community structure of herbivore and succession of macro-algal flora was examined in subtidal area of Dang-Sa Province, eastern coast of Korea from April 2008 to December 2009. For examination, the authors hypothesized that there are significant correlation between the foregoing two variables. Samplings were conducted every two months quantitatively with SCUBA diving at -3, -6 and -10 depth in the two line transects (barren and forest grounds). As results, rhodophyts was predominated in the algal flora based on the number of species and biomass; molluscs was predominated in the herbivores based on the number of species and echinoderms was predominated in that based on the biomass. There was no significant correlation between the foregoing two variables in the whole survey area and barren/forest grounds. Consequently, the hypothesis was rejected. The authors proposed that examination of correlation between the foregoing two variables should focus on the specific herbivore group(s) (e.g., amphipods) afterward.
인위적인 가온만으로도 새꼬막의 성숙 및 정상적인 난 발생이 이루어지는지 알아보기 위해 생존율, 성비, 비만도, 생식소발달빈도, 생식소지수, 수정률, 부화율 및 D형 유생까지의 발생소요시간을 조사하였다. 생존율은 대조구에 비해 가온구에서 낮았으며, 성비는 암컷의 비율이 높았다. 비만도는 대조구와 가온구가 유의한 차이를 보이는 가운데 수온 17℃ 이상부터 증가폭이 높게 나타났다. 생식소발달빈도는 암․수 모두 대조구의 경우 발달이 느렸으며, 가온구는 수온 20℃인 사육 21일부터 28일 사이에 성숙기에 도달한 개체들이 80%이상 관찰되었다. 생식소지수는 대조구에 비해 수온이 높을수록 증가하는 경향을 보였다. 새꼬막의 수정률은 82.17 ± 3.55% 였으며, 부화율은 63.57 ± 2.36%로 나타났다. D형 유생의 발생소요시간은 약 15시간으로 나타났다.
The investigated of survival rate, sex ratio, condition index, gonad development frequency, gonad index, fertilization rate, hatching rate and time required development of D shape larvae of the ark shell, Scapharca subcrenata. Survival rate was lower in heating group compared with control group(P < 0.05). Sex ratio(female:male) observed 1:0.97 in control group, 1:0.62 in heating group. Condition index was significantly higher in heating group than control group(P < 0.05) and higher increased more than water temperature 17℃ of heating group. Gonad development observed slow in control group but more than ripe stage 80% in heating group(21-28 day, 20℃). Gonad index was higher in heating group compared with control group(P < 0.05). Fertilization rate and hatching rate of the ark shell was observed 82.17 ± 3.55% and 63.57 ± 2.36%, respectively. The time required development of D shape larvae of the ark shell was observed 15 hour after fertilization. The suggested that results of the ark shell by heating were effective sex maturation and normal egg development.
퍼킨서스편모충 P. olseni는 우리나라 바지락의 대부분이감염되어 있으며 극심한 염증을 유발하는 우리나라 바지락의대표적 기생충이다. 본 연구에서는 퍼킨서스편모충의 생태학적 특성을 조사하고자 영양체에서 휴면포자로 전환되는 과정과 유주자를 형성하는 과정에서 수온과 염분이 미치는 영향을조사하였다. 조사결과 영양체에서 휴면포자로의 유도는 수온이 높을수록 유도율이 높고 휴면포자의 직경이 커지는 현상이관찰되었다. 또한 유주자 형성은 고수온, 고염분의 환경에서잘 형성됨으로써 10℃이하에서는 유주자 발생이 이루어지 않으며, 10 ppt에서는 유주자 형성이 급격히 감소하고 5 ppt에서는 유주자 발생이 이루어지지 않음이 확인되었다. 이러한 퍼킨서스편모충의 생태학적 정보는 이 질병의 구제 대책 수립에중요한 정보를 제공할 수 있을 것으로 기대된다.
The genus Perkinsus are parasitic protozoans that cause massive inflammatory responses in infected marine shellfish worldwide. This ultimately leads to great economic losses. This study examined the effects of water temperature and salinity on the formation of prezoosporangia and zoosporangia in order to understand the ecology of the pathogens. The induction of prezoosporangia from trophozoites occurred readily at higher water temperatures (20 and 30°C) and they had larger diameters than those incubated at lower temperatures (4 and 10°C). The formation of zoospores in prezoosporangia was also strongly influenced by water temperature and salinity; prezoosporangia exposed to water temperatures of 20 and 30°C and salinities of 20 and 30 ppt had high rates of zoosporulation, while no or very low rates of zoosporulation were observed at temperatures below 10°C or salinity below 10 ppt. Our data will be useful for the development of strategies to counter P. olseni proliferation in Korean waters.
성장기 해역별 해만가리비의 총지질 함량은 8월 통영해역에서 가장 높았으나, 9월과 10월에는 감소하였고 11월에는 가장낮은 수치로 현저히 감소하였다. 해역별 phytoplankton의 총지질함량은 통영해역에서 가장 높은 것으로 나타나 통영해역에서의 가장 성장이 좋은 결과와 잘 일치하여 먹이생물인phytoplankton의 총지질 함량이 해만가리비의 성장에 중요한 역할을 하는 것으로 보인다. 통영해역은 8월에 최고를, 11월에는 감소하는 경향을 나타냈다. 성장기에 있어서 해만가리비의 해역별 계절에 따른 지방산 조성중 포화지방산으로서는16:0, 18:0가 주성분을 이루었고, 불포화지방산인monoenoic acid는 16:1n-7, 18:1n-7, 20:1n-9, ARA (20:4n-6), EPA (20:5n-3), DHA (22:6n-3)가 주성분이었다. 해만가리비의 성장기 (8-11월) 에 있어서 해역별phytoplankton의 지방산 조성은 여름철인 8월에 오메가-3고도불포화지방산은 성장이 나쁜 남해 해역이 높은데 비하여통영과 남면해역은 낮았다.
The total oil proportion of bay scallop by areas during the growing period was the highest (2.8%) at Tongyong in August, then it decreased to 1.88% in September and 0.62% in October, and it was the lowest (0.22%) in November. The total oil proportion of phytoplankton by areas was the highest at Tongyong, where it was decreased from 5.02% in August and 3.29% in September to 2.48% in October and 1.66% in November. For the composition of fatty acid of bay scallop by areas and seasons during the growing period, the major composition was 16:0 and 18:0 as saturated fatty acid, and 16:1n-7, 18:1n-7, 20:1n-9, ARA(20:4n-6), EPA (20:5n-3), DHA(22:6n-3) as monoenic acid. TMTD (4,8,12- trimethyltridecanoic acid) was detected in a little amount as special fatty acid. For the composition of fatty acid of prey by areas during the growing period of bay scallop from August to November 1998, n-3HUFA, Omega-3 highly unsaturated fatty acid, in August was 47.11% at Namhae in slowest growth, while it was distinctively low with 34.26% at Tongyong and 14.06% at Nammeon.
A comparative analysis of size and age structures of coastal subfossil shell assemblages of the shortnecked clam Ruditapes philippinarum from open and protected bays of Cheju Island (Korea) was carried out. On the whole, taking into account the damage of small fragile shells, size and age structures of the shell assemblages corresponded to the classical curve of bivalve population distribution when its mortality diminishes with age increase up to a certain threshold. It was found that shell samples from open bays of the western, southern and eastern coasts included shells of smaller and younger individuals (L ≤ 40 mm, ≤ 4 years) than samples from the eastern protected bay (L ≤ 54.5 ㎜, ≤ 6 years). Evidently, strong wave activity was the reason for a short life-span of the clams from the open areas. Growth was investigated retrospectively by annual growth rings on the shells. Growth rates of the clams from the various coasts of Cheju Island differed. However, growth rates of the clams from different biotopes at the same (eastern) side of the Island were similar. Shell height/length and width/length ratios statistically significantly increased with the clam age increase. Most likely, the reason for such shell shape alteration is that more conglobated individuals more survive being more energy-optimal than oblong specimens.
Ultrastructural characteristics of the testis and spermatogenesis of Crassostrea gigas were investigated by Transmission and Scanning Electron microscope observations. The testis is a diffuse organ consisting of branching acini containing differentiating germ cells in a variety of stages. The acinus is surrounded by an intermitent layer of myoepithelial cells andis divided into subcompartments that are partially separated by pleomorphic accessory cells which remain in close contact with germ cells until late stages of development. these accessory cells contain a large quantity of glycogen particles and lipid droplets in the cytoplasm. Therefore, it is assumed that they are involved in the supplying of the nutrients for germ cell development, while any phenomena associated with phagocytosis of undischarged, residual sperms by lysosomes could be find in the cytoplasm of the accessory cells. The morphology of the spermatozoon has a primitive type and is similar to those of other bivalves. Mature spermatozoa consist of broad, cap-shaped acrosomal vesicle, subacrosomal material (containing axial rod embedded in a granular matrix), a oval nucleus showing deeply invaginated anteriorly, two triplet substructure centrioles surrounded by four spherical mitochondria, and satelite fibres appear to the distal centriole and plasma membrane. Spermatozoa of C. gigas resemble to those of other investigated ostreids. In particular, the anterior region of the acrosomal vesicle is transversely banded. It is assumed that differences in this acrosomal substructure are associated with the inability of fertilization between the genus Crassostrea and other genus species in Ostreidae. Therefore, we can use sperm morphology in the resolution of taxonomic relationships within the Ostreidea. The spermatozoon is approximately 42-47 μm in length including an oval sperm nucleus (about 0.91 μm in length), an acrosome (about 0.42 μm in length) and tail flagellum (40-45 μm). The axoneme of the sperm tail flagellum consists of nine pairs of microtubules at the periphery and a pair at the center. The axoneme of the sperm tail shows a 9 + 2 structure. These morphological charateristics of acrosomal vesicle belong to the family Ostreidae in the subclass Pteriomorphia.
For the studies of germ cell development and maturation in the ovary, the gametogenic cycle and the number of spawning seasons per year in female Ruditapes philippinarum were investigated by quantitative statistical analysis using an Image Analyzer System. Compared with the results by qualitative and quantitative analyses, monthly variations in female gonad indice by qualitative histological analysis showed a pattern similar to that of the female gametogenic cycle calculated by quantitative statistical analysis. The number of spawning seasons occurred once per year, from June to October. In quantitative statistical analysis using an image analyzer system, monthly changes in the portions (%) of the ovary area to total tissue areas in females increased in March and reached a maximum in May, and then showed a rapid decrease from June to October when spawning occurred. And also monthly changes in portions (%) of follicle areas to the ovary area and in portions of oocyte areas to ovarian tissue areas in females began to increase in March and reached a maximum in May, and then. rapidly dropped from June to October when spawnig occurred. From these data, it is apparent that the number of spawning seasons occurred once per year, from June to October. Monthly changes in the number of the oocyte per mm2 and in mean diameter of the oocyte in captured image which were calculated for each female slide showed a maximum in May and reached the minimum from December to February 2004. Therefore, female R. philippinarum showed a unimodal gametogenic cycle during the year.