National Bureau of Fish Genetic Resources, Canal Ring Road, P.O. Dilkusha, Lucknow-226002, Uttar Pradesh, India.
J Fish Biol. 2009 Oct;75(5):1079-91. doi: 10.1111/j.1095-8649.2009.02379.x.
Mahseer is a group of fish species that are well known as food and game fishes. The taxonomy of the mahseer species is confusing owing to the morphological variations and habitat adaptation. Detailed karyomorphological investigations have been carried out in seven species of mahseer, using karyotyping, Ag-NOR and fluorescent staining techniques. The basic diploid chromosome number (2n), in all mahseer species, was observed to be 100; however, the karyotype formula varied among the species, which were recorded as: 20m + 14sm + 22st + 44t (fundamental arm number, FN = 134) in Tor khudree; 22m + 24sm + 24st + 30t (FN = 146) in Tor mussullah; 12m + 22sm + 14st + 52t (FN = 134) in Tor putitora; 20m + 24sm + 24st + 32t (FN = 144) in Tor tor; 20m + 30sm + 24st + 26t (FN = 150) in Tor chelynoides; 20m + 20sm + 20st + 40t (FN = 140) in Tor progeneius; and 20m + 18sm + 14st + 48t (FN = 138) in Neolissochilus hexagonolepis. Silver staining of the chromosomes revealed the presence of multiple nucleolar organizer regions (NOR) in these mahseer species. The highest number of NORs was observed in T. tor (four pairs of chromosomes), whereas the other six species possessed Ag-NOR signals on only two pairs of chromosomes. Although chromomycin A(3) (CMA(3)) staining induced bright fluorescence signals on same Ag-NORs sites, with CMA(3), one additional signal was observed on the p arm of subtelocentric chromosomes in T. tor, T. chelynoides, T. progeneius and N. hexagonolepis, which may indicate the presence of inactive NOR in these species. The information on cytogenetic profile of these mahseer species is discussed in the light of cytotaxonomic implications and understanding the karyoevolution of these fish species.
马哈鱼是一种以食用和游钓为主要用途的鱼类。由于形态变异和栖息地适应等因素，马哈鱼物种的分类一直存在混淆。本研究采用核型分析、Ag-NOR 银染和荧光原位杂交技术，对 7 种马哈鱼进行了详细的核型形态学研究。所有马哈鱼物种的基本二倍体染色体数（2n）均为 100 条，但种间的核型公式存在差异，分别为：Tor khudree 的 20m+14sm+22st+44t（臂数总数，FN=134）；Tor mussullah 的 22m+24sm+24st+30t（FN=146）；Tor putitora 的 12m+22sm+14st+52t（FN=134）；Tor tor 的 20m+24sm+24st+32t（FN=144）；Tor chelynoides 的 20m+30sm+24st+26t（FN=150）；Tor progeneius 的 20m+20sm+20st+40t（FN=140）；以及 Neolissochilus hexagonolepis 的 20m+18sm+14st+48t（FN=138）。染色体银染显示，这些马哈鱼物种存在多个核仁组织区（NOR）。在 T. tor 中观察到最多的 NOR 数（4 对染色体），而其他 6 种鱼类仅在 2 对染色体上具有 Ag-NOR 信号。虽然 Chromomycin A3（CMA3）染色在相同的 Ag-NOR 位点诱导出明亮的荧光信号，但在 T. tor、T. chelynoides、T. progeneius 和 N. hexagonolepis 的近端着丝粒染色体的 p 臂上观察到一个额外的 CMA3 信号，这可能表明这些物种存在非活性 NOR。本文根据细胞学分类学的意义和对这些鱼类核型进化的理解，讨论了这些马哈鱼物种的细胞遗传学特征。
