Earticle

The fish fauna of Hyodon-cheon and Soesokkak in Jeju-do, Korea, was investigated for a total of 15 days underwater from 20 Oct. to 5 Nov. 2008. Fish specimens were collected with a small net by SCUBA diving and fish specimens difficult to collect were photographed underwater using a underwater camera and camcorder. The fish specimens collected from the Hyodon-cheon were identified as 6 species, belonging to 3 families and 3 orders. and the fish specimens of Soesokkak were identified as 30 species, belonging to 22 families and 7 orders. The most dominant species were observed 3 species of Gobiidae in Hyodon-cheon and 7 species of Gobiidae in Seosokkak. Further studies are need to consistently monitoring on a varieties of environmental conditions in Hyodon-cheon and Soesokkak area.

Miamiensis avidus causes scuticociliatosis in cultured olive flounders (Paralichthys olivaceus), leading to economic losses in aquaculture in Korea. Quantitative evaluation of the viability of M. avidus is important to develop an effective vaccine or chemotherapeutic agent against it. We used a colorimetric assay based on the reduction of 2- (4-Iodophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium (WST-1) to quantify the viability of M. avidus. Using this method, we investigated the effect of protease inhibitors on the viability of M. avidus. The assay showed a clear difference in the optical density (OD) of over 104 ciliates, and the metalloprotease inhibitors 1, 10-phenanthroline and ethylenediaminetetraacetic acid (EDTA) reduced the viability of M. avidus by more than 90% when used at concentration of 5 mM and 100 μM, respectively. However, different morphological changes in the parasite were observed when exposed to these two inhibitors. These results indicate that the WST-1 assay is a simple and reliable method to quantify the viability of M. avidus, and metalloproteases are excellent targets for the development of agents and vaccines to control M. avidus infection.

This study investigated gametogenesis, gonadal development, reproductive cycle in cultured Takifugu rubripes. Fish at SAJO CS Co., Ltd. 1-3 year old were sampled from July 2003 to June 2004. The gonadosomatic index (GSI) of male and female reached maximum values of 11.91±3.01 and 3.23±2.61 in April, respectively. The hepatosomatic index (HSI) of male reached a maximum of 13.80±1.32 in May and that of female reached a maximum of 14.60±1.08 in June. The reproductive cycle could be divided into following successive stages in the ovary: growing stage (July to June), mature stage (November to April), and degenerative stage (April to July). Likewise, in the testis, the following stages were observed: growing stage (July to March), mature stage (November to June), spent stage (February to July), and degenerative and recovery stage (May to August).

In teleosts fish, a number of species perform spectacular migrations between seawater and freshwater environmental conditions. Japanese eel, Anguilla japonica is a commercially important species and catadromous fish that grows in fresh water, and moves to the sea to spawn. This study investigated the histological changes of organs of A. japonica based on acclimated to the aquatic environment of the seawater. To understand histological changes of organs tissue of A. japonica based on fresh water condition and seawater condition, 6 specimens (mean TL 62±2 cm, mean BW 578±43 g) were used for comparative observation using gills and skin. A large amount of mucous cells were found and chloride cells were rarely observed in the gills in fresh water condition. However, mucous cells were not observed and chloride cells were increased in seawater condition. In the skin, mucous cells were observed in each layer of epidermis from fresh water condition. On the other hand, mucous cells of seawater condition were decreased in each layer of epidermis. In the future, additional comparative studies on environmental characteristics related to the aspect of artificial sex maturation by hormone treatment, another organ tissue changes and osmotic pressure will be necessary.