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ISSN : 1225-3480
우리나라 고성군 송지호의 기수역에서 채집된 2배체 일본재첩 (Corbicula japonica) 과 춘천 의암호 담수에서 채집된 3배체 재첩 (C. fluminea) 을 대상으로 핵형 및 번식특성의 차이점을 확인하기 위해 조사하였다. 2배체인 일본재첩은 25개 세포들에서 세포당 38 개의 염색체가 관찰되었다. 이들의 핵형은 상동염색체 2 개가 19 쌍을 이루고 있다. 염색체는 11 쌍의 telocentric과 3 set의 subtelocentric 그리고 3 쌍의 submetacentric 그리고 1 쌍의 metacentric 염색체로 구성되어 있었다. 일본재첩은 난생이며 자웅이체로 내반새와 외반새를 갖는 두 쌍의 아가미를 가지나, 이들은 보육낭으로 기능을 하지는 않는다. 난들과 정자들은 기수역에서 체외수정을 한다. 3배체인 재첩은 세포당 54 개의 염색체가 관찰되었다. 이들의 핵형은 상동염색체 3 개가 18 set를 이루고 있었다. 이들 염색체 18 set는 1 개의 metacentric group과 5 개의 submetacentric group, 그리고 12 개의 subtelo 또는 telocentric group으로 이루어져 있었다. 재첩은 난태생이며 기능적 자웅동체이다. 3배체 조건은 자웅동체성과 밀접한 관련을 가진다. 재첩의 경우는 주로 보육낭으로 기능을 하는 내반새 (inner-demibranch)를 갖는 2 쌍의 아가미를 가진다. 아가미의 내반새 구조에서는 임란기 중에는 완숙란들이 소모되고, 비임란기 중에는 완숙난들이 생식소의 자웅동체 소낭 내에서 생산되어 주기적 변화가 나타났다. 일본재첩과 재첩의 생식소발달 단계들은 조직학적 관찰에 의해 초기활성기, 후기활성기, 완숙기, 부분산란기, 퇴화 및 비활성기의 5 단계로 나눌 수 있었다.
We investigated to understand differences in the karyotypes and reproductive characteristics between the diploid clam, Corbicula japonica in the brackish water and the triploid clam, C. fluminea in the freshwater. The number of chromosomes of the diploid C. japonica were 38 chromosomes, which can be grouped into 19 pairs of two homologues. These can be divided into 11 pairs of telocentric, 4 pairs of subtelocentric, 3 pairs of submetacentric and 1 pair of metacentric chromosomes. C. japonica is oviparous and dioecious. The clam has two pairs of gills, with the inner and outer-demibranchs, however, they do not act mainly as marsupia. External fertilization occurs in the brackish water. The triploid marsh clam, C. fluminea has 54 chromosomes, which can be grouped into 18 sets of three homologues. These 18 sets can be divided into one metacentric group, five submetacentric groups and 12 subtelo- or telocentric groups. C. fluminea is ovoviviparous and functional hermaphrodites. The triploid condition may be closely related to hermaphroditism. This species has the inner-demibranchs acting mainly as marsupia. The depletion of ripe eggs occurred in the inner-demibranchs of the gill during the incubatory periods, and ripe eggs produced in the hermaphroditic follicles in the gonad during the non-incubatory periods. The gonad developmental stages of two marsh clams (C. japonica and C. fluminea) can be divided into five stages: early active stage, late active stage, ripe stage, partially spawned stages, and spent/inactive stage.
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