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
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