PDF(Pubmed)
Abstract：
Caryophyllideans are intestinal parasites of freshwater fishes, occupying a basal position among the ‘true’ tapeworms. We performed detailed cytogenetic analyses of the well-known caryophyllidean species Caryophyllaeus laticeps. For comparison, we also examined for the first time the chromosomes of Paracaryophyllaeus gotoi, a specific parasite of loaches in China. Both species showed a diploid chromosome number of 2n = 20, n = 10m. Chromomycin A3 (CMA3)/diamidino-2-phenylindole (DAPI) staining performed for the first time in the class Cestoda revealed CMA3+/DAPI− bands in the pericentromeric regions of the short arms of chromosome pair no. 7 in the karyotype of C. laticeps. Fluorescence in situ hybridization with the 18S rDNA probe confirmed the presence of a single cluster of major rDNA near the centromere on a pair of small chromosomes in both species. These findings support the hypothesis that the ancestral state in the family Caryophyllaeidae is a single interstitial cluster of major rDNA genes and thus one nucleolar organizer region per haploid genome. Our results, which we presented together with literature data plotted on a phylogenetic tree, show stability of caryophyllidean karyotypes at the genus level, but showed differences between genera without a clear phylogenetic signal. The data allowed us to at least formulate a hypothesis about the ancestral haploid chromosome number of n = 10 for the family Caryophyllaeidae and possibly for the sister family Capingentidae. In addition, we compared two populations of C. laticeps from water bodies with different levels of polychlorinated biphenyl contamination, showing a slightly increased incidence of chromosomal abnormalities at the contaminated site.
摘要：
石竹是淡水鱼的肠道寄生虫，在“真正的”tape虫中占据基础位置。我们对著名的石竹物种石竹进行了详细的细胞遗传学分析。为了比较，我们还首次检查了果肉旁的染色体，中国的一种特殊寄生虫。两个物种均显示出2n=20，n=10m的二倍体染色体数。在Cestoda类中首次进行的色霉素A3（CMA3）/二氨基-2-苯基吲哚（DAPI）染色揭示了染色体对第2号短臂的着丝粒区域中的CMA3/DAPI-带。7在C.laticeps的核型中。与18SrDNA探针的荧光原位杂交证实，在两个物种的一对小染色体上，着丝粒附近都存在单个主要rDNA簇。这些发现支持以下假设：石竹科的祖先状态是主要rDNA基因的单个间质簇，因此每个单倍体基因组有一个核仁组织者区域。我们的结果,我们将其与在系统发育树中绘制的文献数据一起呈现，在属水平上显示石竹核型的稳定性，但显示属之间的差异，没有明确的系统发育信号。数据使我们至少可以提出一个假设，即对于Caryophyllaeidae家族和姐妹家族Capingentidae来说，祖先单倍体染色体数n=10。此外,我们比较了来自不同程度的多氯联苯污染水体的两个种群。显示受污染部位染色体异常的发生率略有增加。
