Cytogenetic Analysis of Sturisoma barbatum (Loricariidae): New Inferences about Karyotypic Diversification of Sturisoma

Abstract

Cytogenetic studies in Sturisoma are rare; this genus had 11 valid species distributed in basins in South America. In this article, we aimed to expand on the cytogenetic data available for Sturisoma, contributing to the record of the karyotype and other chromosomal characteristics of both minor and major ribosomal DNA of S. barbatum from the upper Paraguay River basin. This population had diploid chromosome number 66, a karyotype composed of 20 metacentric, 14 submetacentric, 14 subtelocentric, and 18 acrocentric chromosomes, and a fundamental number of 114 for both sexes. Heterochromatic regions were observed in the short arms of the nucleolus organizer regions (NOR)-bearing chromosome pair. Fluorescence in situ hybridization revealed a single 18S site and multiple 5S ribosomal DNA sites. Data from NORs confirmed the tendency of this family to present simple NORs sites, as well as multiple sites of 5S ribosomal DNA. Pericentric inversions (or other types of centromeric shift) and/or deletions appear essential in the karyotype evolution and differentiation among S. barbatum. The present data are valuable to help in understanding karyotypic evolution in Loricariidae.