Institute of Parasitology, Biology Centre of the Academy of Sciences of the Czech Republic, Branisovská 31, 370 05 Ceské Budejovice, Czech Republic.
Parasitol Res. 2010 Feb;106(3):587-93. doi: 10.1007/s00436-009-1702-8. Epub 2009 Dec 24.
This paper reports results of the first cytogenetic study carried out on a recently described monozoic tapeworm, Khawia saurogobii Xi et al., 2009, from the Chinese lizard gudgeon (Saurogobio dabryi). The karyotype of this species is composed of eight pairs of metacentric and telocentric chromosomes (2n = 16; n = 3m + 5t), metacentric chromosomes representing the first, sixth, and eight pairs. All chromosomes except the largest pair displayed 4',6-diamidino-2-phenylidole (DAPI) positive heterochromatin in centromeric regions. In mitotic preparations stained with Giemsa, one of the homologues of a smaller metacentric chromosome pair (No. 7) showed a distinct secondary constriction, whereas the other did not. Fluorescent in situ hybridization (FISH) with 18S ribosomal DNA (rDNA) probe revealed that the chromosomes No. 7 carry each a cluster of ribosomal genes associated with the centromeric heterochromatin and confirmed that this chromosome pair contains a nucleolar organizer region (NOR). The rDNA-FISH also confirmed heteromorphism in the size of NOR (i.e., secondary constriction) observed after Giemsa staining. The present cytogenetic analysis revealed species-specific characters of K. saurogobii and showed that FISH may represent a new valuable cytogenetic tool suitable for comparative taxonomic or phylogenetic studies within the order Caryophyllidea in the future.
本文报道了对一种新描述的单殖吸虫 Khawia saurogobii Xi 等人的首次细胞遗传学研究结果。2009 年，从中国石龙子（Saurogobio dabryi）中分离出来。该物种的核型由 8 对中部和端着丝粒染色体组成（2n = 16；n = 3m + 5t），中部染色体代表第一、第六和第八对。除最大的一对外，所有染色体在着丝粒区域均显示 4'，6-二脒基-2-苯基吲哚（DAPI）阳性异染色质。在吉姆萨染色的有丝分裂制剂中，较小的一对中部染色体（第 7 对）的一个同源染色体显示出明显的次缢痕，而另一个则没有。18S 核糖体 DNA（rDNA）探针的荧光原位杂交（FISH）显示，第 7 号染色体携带与着丝粒异染色质相关的核糖体基因簇，并证实该染色体对包含核仁组织者区域（NOR）。rDNA-FISH 还证实了吉姆萨染色后观察到的 NOR（即次缢痕）大小的异态性。目前的细胞遗传学分析揭示了 K. saurogobii 的种特异性特征，并表明 FISH 可能代表一种新的有价值的细胞遗传学工具，适用于未来 Caryophyllidea 目中的比较分类学或系统发育研究。
