An anatomical and ultrastructural study on the dart sac and the dart of a Korean snail Nesiohelix samarangae was conducted to understand their morphological characteristics with the help of the light microscope and electron microscopes, TEM and SEM. Nesiolelix samarangae had two darts which are pure white structures 6-8 mm in length, tapering from 0.6-0.8 mm to 0.15-0.3 mm. The dart sac had a long conic lumen subdivided into two by a septal wall, and the darts were centrally embedded in the thick muscular layers of the sac. The darts occupied each of the two luminal spaces one per each. The convexed surfaces of the darts had many crystal buds in the shape of the petals. Otherwise, the convexed surfaces of the darts had numerous crystal buds in the shape of candle or topaz. The luminal surface of the dart sac was covered with a single columnar epithelium. The epithelial cells possessed microvilli on their free surface.
동양달팽이 (Nesiohelix samarangae) 의 타액선 (salivary gland) 과 타액관 (salivary duct) 의 구조적 특징과 기능을 이해하기 위하여 조직화학적 및 미세구조적 연구를 수행하였다. 타액선에서는 미세구조 관찰에서 1유형의 상피세포 (epithelial cell) 와 1유형의 지지세포 (supporting cell), 그리고 6유형 (T1-T6) 의 선세포들이 관찰되었다. 6유형의 선세포들 중 4유형의 선세포들이 조직화학적 실험에서 관찰되었다. 그 중 T1 선세포의 분비과립들은 산성점액다당류로 확인되었고, T2, T3, T4 선세포들의 분비과립들은 중성점액다당류로 확인되었다. 타액관에서는 1 개 유형의 T9의 상피세포가 관찰되었다. T9 세포는 타액관을 구성하는 유일한 상피세포로서, 형태는 원주형이었으며 유리표면에는 microvilli가 존재하였다. 기저막 쪽의 원형질막은 심하게 주름져 있어 전반적으로 수지상 형태를 보여 주었다. 핵은 세포질 상부에 존재하였고 하부의 세장한 수지상 세포질 내에는 다수의 mitochondria를 내재하고 있었다.
Histochemical and ultrastructural studies on the salivary gland and salivary duct of a land snail Nesiohelix samarangae were conducted to observe structural characteristics and function.The salivary gland consisted of one type of epithelial cell, one type of supporting cell, and six types of gland cells.Four out of six gland cell types were histochemically identified on these secretions. The one secreted acid mucopolysaccharide and the other three secreted neutral mucopolysaccharide.The salivary duct epithelium had only one type of columnar cell with microvilli on its luminal surface. The basal protoplasmic membranes of the epithelial cells were deeply infolded so many times all along the cell bases.
In present study, attempts were made to preserve abalone (Haliotis discus hannai) sperm in liquid form at low temperature, to evaluate the effect of various diluents in short-term storage on sperm, and cryopreservation procedures were optimized for the cryoprotectants and freezing rates, as well as the motility, survival rate, and the ultrastructural changes of sperm after short-term storage and cryopreservation were observed. The abalone sperm reached maximum motility until about 4 min after activation. The motility was constant for about 16 min, after which it dropped gradually, and about 50 min later all motility ceased. In Hanks' balanced salt solution (HBSS, 300 and 400 mOsmol/kg) and 150, 250 and 350 mOsmol/k artificial seawater (ASW), the sperm was immotile. After 100% ASW was added, motility of those sperm, which are in 300, 400 mOsmol/kg HBSS, 250, 350 mOsmol/kg ASW, could be again restored incompletely. Sperm motility can be maintained for 20 days of cold storage only in ASW of 850 and 1200 mOsmol/kg. A high motility index of 3.5-4.5 was observed for the first 8 days in 850 and 950 mOsmol/kg ASW. In other diluents sperm motility was constant less than 10 days, and the motility index was obviously lower than that of sperm in 850 and 1200 mOsmol/kg ASW. After 20 days of cold storage, survival rates of 10.2%-20.7% were obtained in ASW and 300 mOsmol/kg HBSS, and that in 400 HBSS (65.3%) was significantly higher than others. The constant period of sperm motility stored in 850 mOsmol/kg ASW was obviously longer than that in 1200 mOsmol/kg ASW after 6 days of storage. The sperm plunged into liquid nitrogen all died except that sperm using 15% glycerol as cryoprotectant restored 10.4% of motility. The highest motility index (3.4) was obtained with 5% glycerol and freezing procedure: <TEX>$-50^{\circ}C$</TEX>/min from <TEX>$20^{\circ}C$</TEX> to <TEX>$-80^{\circ}C$</TEX>.
한국 서해안에 서식하는 살조개의 먹이를 조사하기 위해 계절별 현장조사와 실험실 먹이 실험을 병행하였다. 소화관내 식물플랑크톤은 분류군별로는 규조류, 와편모조류, 황색편모조류, 녹조류 등이었으며, 개체 수로는 규조류가 96.0％로 가장 높았고, 그 외 와편모조류 1.46%, 황색편모조류 1.42%, 녹조류 0.05%, 기타 0.07%였다. 춘계에 해당하는 3월에 가장 다양한 종 수와 함께 많은 개체 수의 식물플랑크톤이 해수와 소화관에서 관찰되었다. 살조개의 소화관 내용물의 식물플랑크톤의 월별 출현 종과 출현 개체 수는 주변 해수에 분포하는 식물플랑크톤의 월별 종 수와 출현 개체 수에 비해 낮은 수치였으나 그 경향은 서로 유사하였다. 소화관에서 3월에 나타난 우점종은 Thalassiosira leptopus, Paralia sulcata, Coscinodiscus marginatus였으며, 6월과 9월에는 Coscinodiscus marginatus, Thalassiosira leptopus, Paralia sulcata, 12월에는 Thalassiosira leptopus, Coscinodiscus marginatus, Paralia sulcata가 양적으로 우점하여 나타났다. 해수 중의 우점종과 소화관 내의 우점종과는 일치하지 않았으나, Thalassiosira leptopus는 비교적 높은 선택성 지수를 나타냈고, Coscinodiscus marginatus와 Paralia sulcata는 주로 양의 선택성 지수를 나타내었다.
Based on both field and laboratory experiments, seasonal changes in the species composition and abundance of phytoplankton in the gut contents of the jedo venus clam, Protothaca jedoensis, and its feeding selectivity were investigated. The phytoplankton in the gut contents comprised Bacillariophyceae (diatom), Chlorophyceae, Chrysophyceae, and Dinophyceae, of which the diatoms being the most predominant throughout the year. Although the number of species and the abundance of phytoplankton in the sea water were always more diverse and more abundant than in the gut contents, the relative number and abundance were generally similar in the seawater and in the gut contents. In the laboratory experiments, the relative abundances of Coscinodiscus marginatus and Thalassirosira eccentrica were much more higher in the gut contents than any other algal species, while Paralia sulcata, Skeletonema costatum, and Eucampia zodiacus were abundant in order of cell density in the ambient water. These results suggest that P. jedoensis may feed preferably on single algal cell or smaller chains of algal cells.
To know the effects on temperature and body size on the clearance rate (CR) of a small tidal flat bivalve, Coecella chinensis, laboratory experiments were performed with 20 individuals of different sizes (ranging from 7 to 25 mm) at 3 different temperatures (10, 15, <TEX>$20^{\circ}C$</TEX>). The relationship between body size and CR was determined by an allometric equation. The CR of C. chinensis varied greatly ranging from 0.003 to 0.103 L/individual/hr. Both temperature and body size affected significantly on the CR of C. chinensis. The CR at <TEX>$20^{\circ}C$</TEX>was 1.5 times higher than that at <TEX>$15^{\circ}C$</TEX> and 2.8 times than <TEX>$10^{\circ}C$</TEX>. The temperature coefficient (<TEX>$Q_10$</TEX>) between 10 and <TEX>$15^{\circ}C$</TEX> was higher than that between 15 and <TEX>$20^{\circ}C$</TEX>, which indicates that C. chinensis changes its CR more rapidly in lower temperature range. As body size increased, the CR increased more than 10-fold at all temperatures. The CR relative to flesh dry weight (FDW) were fitted well to the power function: CR = a <TEX>${\times}$</TEX> <TEX>$(FDW)^b$</TEX>. The exponent value (b) of the fitted equation ranged from 0.64 to 0.70, which are similar to those of other bivalves. The weight-specific CR (<TEX>$CR_w$</TEX>) was still affected by body size (p < 0.05). This implies that smaller individuals require more energy per unit biomass for growth, and the energy requirement for growth decreases as body size increases.
본 조사는 진해만에서 지중해담치 양식의 연간 생산력을 추정하기 위해 실시하였다. 양식장내 연간 수온변화는 7.2-25.9 ℃, 염분도는 32.9-4.0 psu, 용존산소는 7.9-8.7 mg/l로 나타났다. 4월에 각장의 길이가 최소 3.3 mm인 치패가 가입되었으며, 조사기간 중 최대 82.5 mm까지 채집되었다. 각장의 경우 시간이 지남에 따라 연중 점진적으로 증가하는 양상을 보였으나, 습중량은 여름철에 급격히 증가하였다. 따라서 월별 생산량의 경우도 가입 이후에 완만한 증가를 나타내다가 여름철에 접어들면서 급격히 증가한 후에 수온이 하강하면서 감소하였다. 여름철 성장이 전체 생산량을 좌우하는 것으로 나타났다. 양식장내 지중해담치의 연간 생산량은 수심별로 차이를 나타냈다. 생산량자료를 근거로 생산력을 계산한 결과, 조사기간 동안 진해만의 지중해담치 생산력은 약 196 ton/ha/yr으로 추정되었다.
This study have conducted to calibrate the productivities on the mussel (Mytilus galloprovincialis) cultures in Jinhae Bay. Annual water temperature, salinity and dissolved oxygen have varied to 7.2-25.9℃, 32.9-34.0 psu, 7.9-8.7 mg/l, respectively. In April, the smallest size of spat, 3.3 mm in shell length, have recruited, and 82.5 mm have recorded to the maximum. In summer, variations of growing up between individuals showed both shell length and weights at same cohort. Annual production at 2 m, 5 m, 8 m depth calculated to 10.91, 10.85 and 9.19 gWWt/ind./yr, respectively. Mussel cultivated in the upper part of the water column (two meter depth) were significantly longer and heavier than those in lower part (eight meter depth). After the recruitment, monthly production showed gradual increment at all positions during summer. As results, annual production of mussel cultivated seemed to be controlled by conditions of growing up in summer. Based on the productivities calculated to this study, the total annual production of the mussel cultivated in Jinhae Bay have estimated about 196 ton/ha/yr.
Gonadosomatic index, condition index and reproductive cycle with the gonadal development of the female Octopus ocellatus were investigated by histological observations and morphometric data, from January to December, 2000. And changes in biochemical components of the ovary and the trunk tissues including the digestive organ associated with gonadal development were studied by biochemical analysis from January to October, 2001. The specimens were collected at the coastal waters of Buan, Jeollabuk-do, Korea, from January 2000 to October 2001. O. ocellatus is a dioecious organism. The gonad of O. ocellatus locates medially in posterior region of the body. Morphology of the ovary shows round and oval in shape, the average diameter and external colour of ripe ovary was 32 mm and semitransparent light brown in colour. As the ovary was getting mature, transparent elongated eggs covered with chorion were present in the ovarian cavity. Monthly changes in the gonadosomatic index (GSI) showed a similar pattern with those of the condition index. The GSI and condition index began to increase in March and reached the maximum in April. And then, their values decreased from May and reached the minimum in September. Reproductive cycle of O. ocellatus can be categorized into five successive stages: early developing stage (September to December), late developing stage (November to March), ripe stage (March to May), partially spawned stage (April to June), and degenerative/resting stage (June to October). Follicle cells attached to an oocyte were involved in vitellogenesis in the cytoplasm of the vitellogeneic oocyte and formation of chorion (secondary egg membrane) of the ovarian eggs. Spawning occurred between April and June. The spawning period was once a year and the peak took place between May and June. This species belongs to semelparity. According to changes in biochemical contents of the ovary and the digestive organ, monthly variations of moisture, total protein, total lipid and glycogen contents (%) in the ovary showed a negative correlationship with those of the trunk tissues including the digestive organ. Accordingly, it is assumed that the ovary only may be received nutrient supply (total lipid content) for gonadal development from the trunk tissues including the digestive organ (r = -0.55, p < 0.05).
이 연구는 1999년 11월부터 2000년 9월까지 Micronesia Chuuk Island 연안에서 채집한 Trochus niloticus의 생식세포형성과정, gonad bulk index (GBI), 월별 난모세포 크기 변화 생식주기 그리고 산란리듬 탐색을 조직학적인 방법으로 조사하였다. T. niloticus는 자웅이체로 성비는 암수 1:1이었다 (p > 0.05). 난소는 난황구기 단계의 난모세포와 정소는 정세포와 정자가 연중 관찰되었다. 월별 GBI는 2월, 3월, 4월 그리고 6월에 다른 달보다 높았다. 주 산란은 4-5월 그리고 6-7월에 일어났지만, 부분 산란하는 개체가 연중 관찰되었다. 월령에 따른 GBI는 다른 월령보다 보름에 높아, 산란은 보름과 하현 사이에 일어나는 것으로 추정된다.
Gametogenesis, changes of gonad bulk index (GBI), monthly variation in oocyte diameter, reproductive cycle and spawning with lunar cycle of the top shell, Trochus niloticus were investigated by histological examination. The specimens were sampled in the coastal waters of Chuuk Island, Micronesia, form November 1999 to September 2000. T. niloticus is a gonochorism, and the female and male were present in an approximately 1:1 ratio (p > 0.05). The ovary contained with the oocyte of yolk stage, the testis composed of the spermatid and spermatozoa at around the year. Monthly GBI were higher at February, March, April and June than the other months. Major spawning occurred between April and May, and June and July but the individuals of partially spawning were presented throughout the year. GBI with lunar cycle were higher at the full moon than the other lunar phase. These results suggest that the spawning occurred between the full moon and last quarter moon.
Reproductive cycle, the condition index, sex ratio of the Pacific oysters, Crassostrea gigas were investigated by histological and morphometric data. The specimens were collected in the two oyster farms of Geoje and Namhae, Gyeongsangnam-do, Korea, from November 1995 to October 1996. Growth of shell length in two regions was similar, but growth of total weight of the oyster in Namhae was faster than that in Geoje oyster farm. The spawning periods in female and male clams were from July to October in Geoje and from June to October in Namhae oyster farm. Ripe oocytes were approximately 50 m in diameter. The reproductive cycle of in females and males in Geoje and Namhae oyster farms can be divided into five successive stages: early developing, late developing, ripe, partially spawned and spent/inactive. Monthly changes in gonad developmental phases showed somewhat different patterns between female and male clams except for the spawning period. On the whole, however, monthly changes in the gonad developmental phases showed a similar pattern in the same sex. The sex ratios of females to males in Geoje and Namhae oyster farms were not significantly different from a 1:1 sex ratio (<TEX>$x^2$</TEX> = 0.55 (p > 0.05) in Geoje and <TEX>$x^2$</TEX> = 0.27 ( p > 0.05) in Namhae). Artificial induction of maturation by heating of adult oysters (two-year-old) was investigated from 17 January to 18 March in 1996. Maturity at the fixed water temperature group of <TEX>$20^{\circ}C$</TEX> was 80%, it showed the highest maturity of experimental groups cultured for five weeks. The survival (%) of Crassostrea gigas in the raised water temperature experimental groups (15, 20, <TEX>$25^{\circ}C$</TEX>) were over 98.5%, as similar to the control group (100%). But, the survival of C. gigas in the fixed water temperature experimental groups (15, 20, 25, <TEX>$30^{\circ}C$</TEX>) were decreased with the increase of the water temperatures. In the fixed water temperature experimental group of <TEX>$30^{\circ}C$</TEX>, the survival was 51.1%. Base on these results, the fixed water temperature of <TEX>$20^{\circ}C$</TEX> was the best condition for artificial induction of sexual maturation.
We investigated the reproductive cycle with gonadal development of the female Cyclina sinensis by histological observations and seasonal changes in biochemical components of the adductor muscle and visceral mass tissues were studied by biochemical analysis, from January to December, 2001. The reproductive cycle of this species can be classified into five successive stages: early active stage (February to April), late active stage (March to June), ripe stage (May to August), partially spawned stage (July to October) and spent/inactive stage (September to February). Total protein contents in the adductor muscle tissues reached the maximum in February (early active stage) and appeared the minimum in June (ripe stage), while their contents in the visceral mass tissues reached the maximum in the late active and ripe stages (June) and gradually decreased from July (partially spawned stage) to November (spent/inactive stage). Changes in total protein contents showed a negative correlationship between the adductor muscle and visceral mass tissues (r = -0.499, p = 0.099). Total lipid contents in the adductor muscle tissues reached the maximum in January (the inactive stages) and their contents gradually decreased from February. Their contents in the visceral mass tissues, however, reached the maximum in June (late active and ripe stage) and gradually decreased from July (the partially spawned stage). On the whole, total lipid contents showed a negative correlationship between the adductor muscle and visceral mass tissues (r = -0.631, p < 0.05). Therefore, These results indicate that the nutrient contents of the adductor muscle and visceral muscle tissues change in response to gonadal energy needs. Glycogen contents in the adductor muscle tissue reached the maximum in March (early and late active stages) and decreased from July to September (partially spawned stage). while their contents in the visceral mass tissues reached the maximum in June (late active and ripe stages) and gradually decreased from July (partially spawned stage). Thereafter, their levels gradually increased in November (spent/inactive stage). On the whole, changes in glycogen contents appeared negative correlationship between the adductor muscle and visceral mass tissues. However, they showed no significant different (r = -0.307, p = 0.331).
Arkshell clams, Scapharca broughtonii, are economically important edible bivalves and widely cultivated in the Southern coast of Korea. Recently, the production of S. broughtonii has been dramatically decreased and various reasons including chemical pollution were suspected to be related to the production declines. However, it remains unknown whether the chemical pollution levels of the surrounding environments were high enough for the biological and ecological disturbance for the population of S. broughtonii, because no systematic toxicological study using S. broughtonii has been conducted previously. In the present study, we exposed arkshell clams, S. broughtonii to various waterborne pollutants including heavy metals (Cd, Cu and Hg), ammonia and organotins (tributyltin and triphenyltin) to determine the effect concentrations of these pollutants for the survival of S. broughtonii for 20 days. The median lethal concentrations (<TEX>$LC_50$</TEX>) of S. broughtonii were 2.1 mg/l for Cd, 0.065 mg/l for Cu, 0.40 mg/l for Hg, 79.4 mg/l for total ammonia (1.9 mg/l for unionized ammonia), 0.5 <TEX>${\mu}$</TEX>g/l for TBT, and 14<TEX>${\mu}$</TEX>g/l for TPhT. Lethal toxicity of the most pollutants increased with both exposure duration and concentration. The toxicity of TBT was greatest for S. broughtonii, followed by TPhT > Cu > Hg > Cd > ammonia. The sensitivities of S. broughtonii to heavy metals and TBT were comparable to those of other aquatic organisms, but they were relatively tolerable to ammonia. The environmental concentrations of the tested pollutants were compared with the effect concentrations of those for the survival of S. broughtonii to assess the potential risks of the pollutants in the field conditions.
