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ISSN : 1225-3480
The authors observed histochemical and ultrastructural characters on the osphradium of Rapana venosa Valenciennes using light microscope, scanning and transmission electron microscpes. The results were as follows:1)The basic structure of osphradium was bipectinated shape, which consisted of a septum situating in the center of osphradium and numerous osphradial leaflets. On the other hand, Epidermis of ospradial leaflets formed the structure of pseudostratified ciliated columnar epithelium which was composed of an epithelial cell layer, a basal cel layer and a neuropile. 2) Ciliated dpithelial cells:A large number of these cells were observed on the lateral and ventral regions but a small number of them were observed on the dorsal region. These cells had cylindrical microvilli, slender mitochondria and serve fibers.3) Supporting cells: These cells had cylindrical microvilli, spongy layer, electron dense granules, mitochondria and nerve fibers4) Four types secretory epothelial cells: Four distinct types of secretory epithelial cells were recognized and were arbitrily designated as Type I, Type II, Type III and Type IV.cell type I: These cells contained electron denwe granules(diameter, 0.94-1.56<TEX>${\mu}{\textrm}{m}$</TEX>), well developed Golgi apparatus and rough endoplasmic reticula, cell type II: These cills contained two types of granules of the different electron density. One was high electron density granules which were 0.4-1.0<TEX>${\mu}{\textrm}{m}$</TEX> in diameter, The other was low electron density granules which were 0.75-1.2<TEX>${\mu}{\textrm}{m}$</TEX> in diameter.cell type III:These cells had fibrous secretory materials and exhibited strongly positive reaction with Toluidine blue.cell type IV:A large number of this type of cells were observed on the ventral region of ospgradial leaflets and positively reacted with periodic acid Schiff reagent. 5)Dark cells contained several electron dense cillaty rootlets and unmerous granules but cellular organelles were not observed.6) Four types basal cells: Four distinci types of basal cells were recognized and arbitrarily designated as Type I, Type II, Type III and Type IV.Cell type I(light cell): These cells exhibited low electuon density and contained short smooth endoplasmic reticula, several vacuoles and granules.
The study had been carried out three times, from April 1987 for the purpose of analysis on the community structure and the distribution patterns of the Molluscan shells at the intertidal zone of Cheju Island. 1) The Molluscan shells collected and identified at all studied sites were composed of 3 classes, 10 orders, 23 families and 42 species.2) In all studied sites, individual numbers according to species were Nodilittorina exigua, Monodonta neritoides, Lunella coronata coreensis, Heminerita japonica in order. On the other hand, the dominant species of the rocky sits were N. exigua, M. neritoides and the rocky and silty-sand sites was Batillaris multiformis.3) In the vertical zonation, in the supralitorial zone, N. exigua was dominant species and the wpper-tidal zone, N. exigua, H. japonica and B. Multiformis were dominant species, but B. multiformis was dominant in the rocky and silty sand sites. In the middle tidal zone, M. neritodes, H. japonica, L. coronata coreensis were dominant and in the lower tidal zond, M. neritodes, L. coronata coreensis, Liolophura japonica were dominant.4)In the analysis on community of Molluscan shells, Chagwi, Pyoson an dAewol sites were more diverse than other sites in the species diversity and environmental inhibits were also favorable.5) Community similarities among the studied sites based on the similarities values were divided into two groups according to the difference of the ground: Hagwi, Chongdal and Sehwa sites group and the others sites group.
The gonadal development, the annual reproductive cycle and the first sexual maturity of surf clam, Mactra veneriformis Reeve were studied histologically. Speciemens were monthly collected at the intertidal zone of Naechodo, Chollabuk-do, Korea, for one year from March 1986 to February 1987. Sexuality of the clam is dioecious. The gonads were located between the subregion of mid-intestinal gland in the visceral cavity and the reticular connetive tissues of the foot, The ovary is composed of a number of ovarian sacs, and the testis comprise several testiculat lobules. The undifferentiated mesenchymal tissues and eosinophilic granular cells function as nutritive cells in the early stage. The ripe eggs were about 50-60<TEX>${\mu}{\textrm}{m}$</TEX> in diameter, and they were wurroundedby the gelatinous membranes. The spawing period was from early June to September the main spawning occurred beetween July and August when the water temperature reached above 24<TEX>$^{\circ}C$</TEX>. The annual reproductive cycle of this species could be classified into five successive stages: multiplicative(January to March), growing(March to May), mature(April to August), spent(June to September), degenerative and resting(September to February). The monthly changes of fatness coefficient closely correlated with the annual reproductive cycle. Percentages of the first sexual maturity of female and male clams were over 50% among those individals ranging from 2.1 To 2.5cm, and 100% in those over 2.6cm in shell length.
The chromosome of Cipangopaludina chinensis malleata Chunchon area in 1988 was analysed by using aceto-orcein squash techniques of spermatogonial tissues to obtain mitotic and meiotic chromosomes. The chromosome cycle did not differ, in general, from that found in other snails, C. chinensis malleata has 18 diploid chromosomes and they were identified and classified into 2 groups. The mitotic chromosome complement of this species consists of 2 pairs of metacentric and 7 pairs of submetacentric chromosomes, Spermatogonial metaphase chromosomes range in length from 4.10 <TEX>${\mu}{\textrm}{m}$</TEX> for the largest pair to 2.20 <TEX>${\mu}{\textrm}{m}$</TEX> for the smallest pair.
The chromosome of Anodota woodiana in the Lake Uiam was analysed as using air drying technique of spermatogonial tissue to obtain mitotic and meiotic chromosomes. The chromosome chcle did mot differ, in general, from that found in other bivalves. Chromosome of this species consisted of metacentrics and submetacentrics. The longest chromosome was 2.1 <TEX>${\mu}{\textrm}{m}$</TEX> and the shortest was about 1.4 <TEX>${\mu}{\textrm}{m}$</TEX> in length.