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ISSN : 1225-3480
The authors carried out paralytic shellfish poison bioassay on the 9 kinds of shellfishes collected from Pusan and Kyungnam areas of Korea from April to July, 1986. The areas are the main producing district of fisheries in Korea and the samples were collected from their producing sites-natural, cultured and marketed. There were little or no PSP in the majority of the shellfishes, but 3 natural (Pusan Il-Kwang <TEX>$700{\mu}g$</TEX>, Koje Okpo <TEX>$648{\mu}g$</TEX>, Chungmoo Madong <TEX>$124{\mu}g/100gm$</TEX> meat) and 1 marketed (Pusan Chakalchi <TEX>$490{\mu}g/100gm$</TEX> meat) blue mussels contained relatively high PSP only in April. It is considered that there will be a possibility of paralytic shellfish poisoning, and control program for preventing the poisoning is necessary in Korea.
Pettancylus nipponicus (freshwater limpet) collected from the Lake Choon Cheon were cultrued in aquarium and studied in the respects of an egg deposition and the developmental characters of cleavage. The species were collected only in the Lake Uiam and Choon Cheon and easily sampled on the debris like vinyls and cans. Those smooth surfaces were suitalble substrata for attaching. P. nipponicus, about 4 mm in adult, deposited an egg in one calcareous egg-capsule on the aquarium walls, while many eggs are surrounded in a jelly-like egg-envelope in the most gastropods. And another special features was that an egg-capsule was consisted of two valves and the suture was opended as hatching. A diameter of its egg was <TEX>$55{{\mu}m}$</TEX> and the length of an egg capsule was <TEX>$620{{\mu}m}$</TEX> and <TEX>$510{{\mu}m}$</TEX> in long and short diameter, respectively. It took about 8 hours from beginning cleavage to 16-cell stage and about one year to become an adult.
One of the most medically important snail species of Korea is Semisulcospira spp., a member of the freshwater prosobranch family pleuroceridae. The parasites that these snails transmit to humans are mainly Paragonimus westermani and Metagonimus yokogawoi. On the other hand, Semisulcospira snails are edible as a foodstuff in Korea. The present study was first aimed to detect out residual pesticides in the snails collected at the endemic and non-endemic areas of paragonimiasis in Korea and to make relationship to the detectability of larval trematodes shed from the snails. In addition, water specimens from the habitats where the snails were collected were sampled and analysed to elucidate environmental conditions of the habitats. This malaco-ecological survey was done at 7 endemic and 3 non-endemic areas of paragonimiasis for about more than 2 years, May, 1984 through October, 1986. All the water smaples both from the endemic and non-endemic areas of paragonimiasis showed normal ranges of the criteria of upper freshwater streams, with lower B.O.D. (0.4~2.0 ppm) and higher D.O. values (9.5~11.0 ppm) than those in the large river systems Infection rate of digenetic trematodes in total snails collected was 6.7%, but no Paragonimus cercaria was detected out at all even in the endemic areas of paragonimiasis. The ecological factors affecting Paragonimus larvae in the snails were also discussed. A total of 9 chlorinated hydrocarbon pesticieds was targeted to detect out from the tissues of snails. Out of 9 pesticides, aldrin, beta-BHC, p, p-DDT, dieldrin, DDE, lindane, heptachlor and heptachlor epoxide were eluted from the snails. The highest levels of the pesticides were mostly detected out in the snails collected from the Donghae-Chun area of Haman and the Kangwha area of Kyongki-Do, where the lowest infection rates of trematode cercariae (0~0.5%) were revealed. The possibilities that the residual pesticides in the freshwater animals including Semisulcospira snails might be transferable to humans were also discussed.
Corbicula fluminea, one of the 2 species in the family Corbiculidae living in the Lake Uiam, was used as an experimental material and the embryonic development and the structure of glochidia of this species were investigated. This freshwater mussels was oviparous, but some ovoviviparous: incubated their youngs in the inner-demibranchs or outer-demibranchs, however, chiefly used the inner-demibranchs as brood-pouch. The average time required from a fertilized egg to two-cell stage, veliger stage, and glochidium was 76 minutes, 3 hours, and 17 hours, respectively, The mean size of glochidium was <TEX>$168{\mu}m$</TEX> in shell height, <TEX>$195{\mu}m$</TEX> in shell lengh, <TEX>$114{\mu}m$</TEX> in hinge legth and the form of glochidium was D-type and had no hooks or hooklets for attaching to fish like Unioidae.
Genetic variations of Semisulcospjra gottschei in Korea were investigated by means of starch gel-electrophoresis. The results are as follows; 1) Eight loci of <TEX>${\alpha}$</TEX>-Gpd, Mdh-2, Pept-1, Pgm-2, Gp-1, Gp-2, Gp-3 and Gp-4 were monomorphic, and 8 loci of Mpi, Mdh-1, Pgi, Got, Pept-2, Pept-3, Pgm-1 and Sdh showed genetic variations. 2) Means of allele per locus (<TEX>$\bar{A}$</TEX>) and polymorphism (P) were revealed 0.64 and 0.44, respectively. The value of heterozygosity (<TEX>$H_G$</TEX>) showed a little more than heterozygosity <TEX>$H_D$</TEX>. (<TEX>$H_D$</TEX>=0.09, <TEX>$H_G$</TEX>=0.13) 3) Genetic variation appears to be due to loci of Got, Pept, Pgi, and Sdh, all of which of the <TEX>$H_D$</TEX> values are high.