Hophophthys属的bighe鱼(H.melitrix和H.nobilis)是重要的水产养殖物种。他们接受了广泛的多学科研究,但是细胞遗传学仅限于常规方案。这里,我们采用Giemsa-/C-/CMA3-染色和多基因家族和端粒重复的染色体定位。两个物种共享(i)二倍体染色体编号2n=48和核型结构,(ii)低含量的组成型异染色质,(iii)不存在间质性端粒位点(ITS),(iv)与一个主要rDNA簇相邻的一对5SrDNA基因座,和(v)一对共定位的U1/U2的snDNA串联重复。这两个物种,另一方面,差异在于(i)在最大的顶心对11上存在/不存在组成性异染色质的明显间隙阻滞,以及(ii)主要(CMA3阳性)rDNA位点的数量。此外,我们在这里申请,第一次,H.harmandi的传统细胞遗传学,一种被认为在野外灭绝和/或与H.melitrix广泛杂交的物种。它的2n和核型描述与前两个物种中发现的相匹配,而银染显示主要rDNA的分布差异。因此,the鱼代表了另一种与总体核型分化无关的分类学多样性,其中2n和核型结构不能帮助区分密切相关物种的基因组。另一方面,我们证明了两个细胞遗传学特征(组成型异染色质和主要rDNA的分布)可能对纯物种的诊断有用。这些标记的普适性必须通过分析其他big鱼的纯种群来进一步验证。
The bighead carps of the genus Hypophthalmichthys (H. molitrix and H. nobilis) are important aquaculture species. They were subjected to extensive multidisciplinary research, but with cytogenetics confined to conventional protocols only. Here, we employed Giemsa-/C-/CMA3- stainings and chromosomal mapping of multigene families and telomeric repeats. Both species shared (i) a diploid chromosome number 2n = 48 and the karyotype structure, (ii) low amount of constitutive
heterochromatin, (iii) the absence of interstitial telomeric sites (ITSs), (iv) a single pair of 5S rDNA loci adjacent to one major rDNA cluster, and (v) a single pair of co-localized U1/U2 snDNA tandem repeats. Both species, on the other hand, differed in (i) the presence/absence of remarkable interstitial block of constitutive
heterochromatin on the largest acrocentric pair 11 and (ii) the number of major (CMA3-positive) rDNA sites. Additionally, we applied here, for the first time, the conventional cytogenetics in H. harmandi, a species considered extinct in the wild and/or extensively cross-hybridized with H. molitrix. Its 2n and karyotype description match those found in the previous two species, while silver staining showed differences in distribution of major rDNA. The bighead carps thus represent another
case of taxonomic diversity not associated with gross karyotype differentiation, where 2n and karyotype structure cannot help in distinguishing between genomes of closely related species. On the other hand, we demonstrated that two cytogenetic characters (distribution of constitutive
heterochromatin and major rDNA) may be useful for diagnosis of pure species. The universality of these markers must be further verified by analyzing other pure populations of bighead carps.