B microchromosomes in the family Curimatidae (Characiformes): mitotic and meiotic behavior

A L Dias,Juceli Gonzales Gouveia,L Giuliano-Caetano,Waleska Gravena,Tatiane Ramos Sampaio

doi:10.3897/compcytogen.v5i4.1650

Abstract

In the present work, six curimatid species were analyzed: Cyphocharax voga (Hensel, 1870), Cyphocharax spilotus (Vari, 1987), Cyphocharax saladensis (Meinken, 1933), Cyphocharax modestus (Fernández-Yépez, 1948), Steindachnerina biornata (Braga & Azpelicueta, 1987) and Steindachnerina insculpta (Fernández-Yépez, 1948) collected from two hydrographic basins. All samples presented 2n=54 meta-submetacentric (m-sm) chromosomes and FN equal to 108, and 1 or 2 B microchromosomes in the mitotic and meiotic cells of the six sampled populations showing inter-and intraindividual variation. The analysis of the meiotic cells in Cyphocharax saladensis, Cyphocharax spilotus, and Cyphocharax voga showed a modal number of 54 chromosomes in the spermatogonial metaphases and 27 bivalents in the pachytene, diplotene, diakinesis and in metaphase I stages, and 27 chromosomes in metaphase II; in Cyphocharax modestus, Steindachnerina biornata, and Steindachnerina insculpta, spermatogonial metaphases with 54 chromosomes and pachytene and metaphase I with 27 bivalents were observed. The B microchromosome was observed as univalent in the spermatogonial metaphase of Cyphocharax spilotus, in the pachytene stage in the other species, with the exception of Cyphocharax saladensis, and Steindachnerina biornata in metaphase I. New occurrences of the B microchromosome in Cyphocharax voga, Cyphocharax saladensis and Steindachnerina biornata were observed, confirming that the presence of this type of chromosome is a striking characteristic of this group of fish.

Highlights

B chromosomes, known as supernumerary or accessory chromosomes, are additional dispensable chromosomes present in some individuals of some populations in some species
The analysis of the meiotic cells in C. saladensis, C. spilotus, and C. voga showed a modal number of 54 chromosomes in the spermatogonial metaphases and 27 bivalents in the pachytene, diplotene, diakinesis and in metaphase I stages, and 27 chromosomes in metaphase II; in C. modestus, S. biornata, and S. insculpta, spermatogonial metaphases with 54 chromosomes and pachytene and metaphase I with 27 bivalents were observed
The current study examines the frequency, behavior and distribution of B microchromosomes in mitotic and meiotic cells in six fish species of the family Curimatidae from two hydrographic basins

Summary

Introduction

B chromosomes, known as supernumerary or accessory chromosomes, are additional dispensable chromosomes present in some individuals of some populations in some species. Six species of the family Curimatidae were analysed: Cyphocharax voga (Hensel, 1870), C. spilotus (Vari, 1987), C. saladensis (Meinken, 1933), C. modestus (Fernández-Yépez, 1948), Steindachnerina biornata (Braga & Azpelicueta, 1987) and S. insculpta (Fernández-Yépez, 1948), collected from the Laguna dos Patos Hydrographic System/RS and Paranapanema River basin/SP/PR (Fig. 1, Table 1).

Results

Conclusion