Karyotypic analysis of the multiple tetraploid allogynogenetic pengze crucian carp and its parents

Abstract

Pengze crucian carp ( Carassius auratus of pengze), just like silver crucian carp, is known to be a gynogenetic crucian carp. It is one of the most popular cultured fishes in China. The offspring developed from pengze crucian carp eggs activated by heterologous sperm shows obvious allogynogenetic biological effects in growth and fertilization rate, although the offspring is almost the same in morphology as the maternal pengze crucian carp. Recently, a multiple tetraploid form, which showed obvious morphological changes compared with the normal allogynogenetic offspring, was found in the offspring developed from pengze crucian carp eggs stimulated by sea carp ( Cyprinus acutidorsalis Wang) sperm. In this paper, the chromosome number and karyotype of the multiple tetraploid form and its parents were analyzed, using chromosomes of kidney cell-PHA culture in vivo prepared by flame-drying technique. The paternal sea carp had 2 n=100 diploid chromosomes and the karyotype of 28 metacentric, 24 submetacentric, 26 subtelocentric and 22 telocentric, NF=152. The maternal pengze crucian carp had 156 chromosomes in its karyotype, with 42 metacentric, 36 submetacentric, 39 subtelocentric, 33 telocentric, and 6 supernumerary microchromosomes. The karyotype of the multiple tetraploid allogynogenetic pengze crucian carp contained 206 chromosomes, with 56 metacentric, 48 submetacentric, 44 subtelocentric, 52 telocentric, and 6 supernumerary microchromosomes. Both the multiple tetraploid form and its maternal parent had six supernumerary microchromosomes. The results indicated that the chromosomes of the multiple tetraploid allogynogenetic pengze crucian carp consist of the whole maternal chromosome set and a haploid paternal chromosome set, which suggests that a few of the gynogenetic pengze crucian carp eggs have the gonochoristic reproductive ability to integrate with heterologous sperm nuclei.