Small Body, Large Chromosomes: Centric Fusions Shaped the Karyotype of the Amazonian Miniature Fish Nannostomus anduzei (Characiformes, Lebiasinidae)

Author(s)

Rosa de Moraes, Renata Luiza ; Cavalcante Sassi, Francisco de Menezes ; Ferreira Marinho, Manoela Maria ; Rab, Petr ; Rebelo Porto, Jorge Ivan ; Feldberg, Eliana ; Cioffi, Marcelo de Bello

• Document type: Journal article
• Source: GENES; v. 14, n. 1, p. 12-pg., 2023-01-01.

Abstract

Miniature refers to species with extraordinarily small adult body size when adult and can be found within all major metazoan groups. It is considered that miniature species have experienced severe alteration of numerous morphological traits during evolution. For a variety of reasons, including severe labor concerns during collecting, chromosomal acquisition, and taxonomic issues, miniature fishes are neglected and understudied. Since some available studies indicate possible relationship between diploid chromosome number (2n) and body size in fishes, we aimed to study one of the smallest Neotropical fish Nannostomus anduzei (Teleostei, Characiformes, Lebiasinidae), using both conventional (Giemsa staining, C-banding) and molecular cytogenetic methods (FISH mapping of rDNAs, microsatellites, and telomeric sequences). Our research revealed that N. anduzei possesses one of the lowest diploid chromosome numbers (2n = 22) among teleost fishes, and its karyotype is entirely composed of large metacentric chromosomes. All chromosomes, except for pair number 11, showed an 18S rDNA signal in the pericentromeric region. 5S rDNA signals were detected in the pericentromeric regions of chromosome pair number 1 and 6, displaying synteny to 18S rDNA signals. Interstitial telomeric sites (ITS) were identified in the centromeric region of pairs 6 and 8, indicating that centric fusions played a significant role in karyotype evolution of studied species. Our study provides further evidence supporting the trend of diploid chromosome number reduction along with miniaturization of adult body size in fishes. (AU)

• FAPESP's process: 20/11772-8 - An integrative approach for the analysis of dispersal, adaptive and evolutionary processes between realted species with intercontinental distribution: the Osteoglossidae family (Teleostei, Osteoglossiformes) as an investigative model: part IV
• Grantee: Marcelo de Bello Cioffi
• Support Opportunities: Regular Research Grants
• FAPESP's process: 20/02681-9 - Evolutionary relationships and demographic history in Loricariidae (Siluriformes) species, with emphasis on Harttia genus
• Grantee: Francisco de Menezes Cavalcante Sassi
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 19/25045-3 - Chromosomal evolution, genetic diversity and demographic history in species of the genus Pyrrhulina (Characiformes, Lebiasinidae)
• Grantee: Renata Luiza Rosa de Moraes
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)