Comparative Chromosome Studies in the Genus Carassius, Especially with a Finding of Polyploidy in the Ginbuna (C.auratus langsdorfii)

Abstract

The somatic chromosomes of the goldfish (Carassius auratus auratus), kinbuna (C.auratus subsp.), ginbuna (C.auratus langsdorfii) and crucian carp (C.carassius) were studied comparatively.For chromosome study, cells obtained from kidneys and gills were used after treatment with colchicine. The preparations were made according to the airdrying method and stained with Giemsa.
The results showed that the goldfish, kinbuna, and crucian carp examined had the same diploid chromosome number of 100.Their karyotypes consisted of 10 pairs of metacentrics, 20 pairs of submetacentrics, and 20 pairs of acrocentric elements, in which one or two members, presumably the fifth longest pair, had a satellite on the short arm. There was no morphological difference between the male and female karyotypes.
The chromosomes of the ginbuna were examined in two local varieties obtained from the Miyazaki and the Kanto districts, because in the latter region the ginbuna consisted almost entirely of females.In the ginbuna of the Miyazaki district3females and4males showed the chromosome number of 100 in 2n and had a similar karyotype with the other two subspecies of C. auratus, with the exception of a male having over 100 chromosomes.In contrast, of the30females collected from the Kanto district, 28 had the chromosome number of156, consisting of17pairs of metacentrics, 31pairs of submetacentrics and30pairs of acrocentrics and the remaining 2 females revealed to have206chromosomes showing22pairs of metacentrics, 41pairs of submetacentrics and40pairs of acrocentrics.These evidences may suggest that the ginbuna distributed in the Kanto district might represent the triploid and tetraploid states in their chromosome conditions.The mechanism of gynogenesis is discussed in respect to the persistence of the unisexual polyploid populations.