Lui Roberto Laridondo, Blanco Daniel Rodrigues, Margarido Vladimir Pavan, Filho Orlando Moreira
Departamento de Genética e Evolução, Universidade Federal de São Carlos, Rodovia Washington Luís (SP 310) Km 235, CEP: 13565-905, São Carlos, SP, Brazil.
Micron. 2009 Jul-Aug;40(5-6):552-9. doi: 10.1016/j.micron.2009.03.004. Epub 2009 Apr 5.
B chromosomes are considered additional and non-essential; they likely originate from A chromosomes and follow a distinct evolution. In fish, approximately half of the Neotropical species with B chromosomes are Characiformes and 35% are Siluriformes. There has been no report of B chromosomes in Auchenipteridae until this moment. B chromosomes found in a population of Parauchenipterus galeatus from the São Francisco River basin in the state of Minas Gerais (Brazil) were small, metacentric, totally heterochromatic and exhibited intra-individual and inter-individual variation. The diploid number was 58 chromosomes (22 metacentric, 16 submetacentric, 12 subtelocentric and 8 acrocentric). The nucleolar organizing regions were simple and the heterochromatin intercalated in the ribosomal sites, characterized by CMA(3) and DAPI fluorochromes, was of a GC-rich constitution. The 5S rDNA genes were located in an intercalary position in only one chromosome pair. An hypothesis about the origin of the B chromosomes in P. galeatus and a review on B chromosomes in catfish are also presented in this study.
B染色体被认为是额外的且非必需的；它们可能起源于A染色体并遵循独特的进化过程。在鱼类中，拥有B染色体的新热带物种大约一半是脂鲤目，35%是鲶形目。直到目前，在项鳍鲶科中尚未有B染色体的报道。在巴西米纳斯吉拉斯州圣弗朗西斯科河流域的盖氏副项鳍鲶种群中发现的B染色体较小，为中着丝粒染色体，完全异染色质化，并且表现出个体内和个体间的变异。二倍体数目为58条染色体（22条中着丝粒染色体、16条亚中着丝粒染色体、12条近端着丝粒染色体和8条端着丝粒染色体）。核仁组织区简单，通过CMA(3)和DAPI荧光染料表征的插入核糖体位点的异染色质具有富含GC的组成。5S rDNA基因仅位于一对染色体的居间位置。本研究还提出了关于盖氏副项鳍鲶B染色体起源的假说以及对鲶鱼B染色体的综述。
