DNA DIMINUTION (CHROMOSOME ELIMINATION) DURING DIFFERENTIATION INTO SOMATIC CELLS IN BALTIC, SOUTH PACIFIC AND NORTHEAST PACIFIC HAGFISH SPECIES.

分别在瑞典Kristineberg海洋生物站、新西兰Kaikoura海洋站和加拿大Bamfield海洋站采集到波罗的海鳗、粘液鳗、南太平洋鳗、环斑鳗和东北太平洋鳗。粘虫、刺参和刺参的生殖细胞(精原细胞)和体细胞(肝、血、鳃、肾)具有不同的染色体数目。精原细胞(44、72或80、48)与体细胞(28、34、34)的染色体数之差分别为16、38、46和14。在圆尾鱼中，观察到两种类型的标本，一种是生殖细胞染色体数较少的标本(72条)，另一种是染色体较大的标本(80条)。生殖细胞DNA相对清除量分别为43.5%、49.2%、52.8%。这些结果清除了…进一步研究表明，生活在波罗的海、南太平洋和东北太平洋的粘鳗3种，除祖先生殖细胞外，其余均在卵裂的早期阶段发生染色体去除。其中一种酶(Dra I)通过琼脂糖凝胶电泳法在两种类型的圆尾轮虫中都产生了仅限于种系DNA的条带。DNA过滤杂交实验证明，DNA片段大小约为100个碱基，仅存在于马尾松毛虫消除后的DNA中。这些片段几乎不包含在其他三个物种的种系基因组和体细胞基因组中。DNA滤膜杂交的结果表明，在这四个种中均未检测到EEEo1，而在华山松中检测到了EEEo2。较少

Baltic hagfish, Myxine glutinosa, south Pacific hagfish, Eptatretus cirrhatus, and northeast Pacific hagfish, Eptatretus stoutii, in the order Myxinida were collected in Kristineberg Marine Biological Station in Sweden, Kaikoura Marine Station in New Zealand, and Bamfield Marine Station in Canada, respectively. M.glutinosa, E.cirrhatus, and E.stoutii have been possess different chromosome numbers in their germ cells (spermatogonia) and somatic cells (liver, blood, gill and kidney). The difference of the chromosome numbers between spermatogonia (44, 72 or 80, and 48) and somatic cells (28, 34, and 34) was 16, 38 or 46, and 14, in M.glutinosa, E.cirrhatus, and E.stoutii, respectively. In E.cirrhatus, two types of specimens, those having the smaller number of chromosomes (72) in their germ cells and those having the larger one (80) were observed. The relative amount of DNA eliminated from germ cells averaged 43.5%, (M.g.), 49.2% (E.c.type A), 52.8% (E.s.), respectively. These results clea … More rly indicate that, in the 3 hagfish species in Myxinida which live in the Baltic Sea and south Pacific Ocean and northeast Pacific Ocian, chromosome elimination takes place during the early stages of cleavage except for the ancestral germ cells.DNA from germ line cells and somatic cells in M.glutinosa, E.cirrhatus (type A, type B), E.stoutii and Paramyxine atami (Japanese hagfish) had been isolated and digested with 4 kinds of restriction enzymes. One enzyme (Dra I) generated bands limited to germ line DNA in both types of E.cirrhatus by agarose gel electrophoresis. DNA filter hybridization experiments proved that the DNA fragments, about 100 bp long, are contained only in the eliminated DNA of E.cirrhatus. These fragments are hardly contained in the germ line genomes and somatic genomes of the other three species. As a result of DNA filter hybridization by using DNA fragments (germ line-restricted EEEo1 and EEEo2 from E.okinoseanus) as probes, it was appeared that EEEo1 was detected in none of the four species and EEEo2 was done in P.atami. Less