Tracking the Evolutionary Trends Among Small-Size Fishes of the Genus Pyrrhulina (Characiforme, Lebiasinidae): New Insights From a Molecular Cytogenetic Perspective.

Vanessa Cristina Sales Oliveira,Francisco De Menezes Cavalcante Sassi,Manoela Maria Ferreira Marinho,Geize Aparecida Deon,Marcelo De Bello Cioffi,Luiz Antonio Carlos Bertollo,Thomas Liehr,Ahmed B H Al-Rikabi,Renata Luiza Rosa De Moraes,Patrik Ferreira Viana,Eliana Feldberg

doi:10.3389/fgene.2021.769984

Abstract

Miniature fishes have always been a challenge for cytogenetic studies due to the difficulty in obtaining chromosomal preparations, making them virtually unexplored. An example of this scenario relies on members of the family Lebiasinidae which include miniature to medium-sized, poorly known species, until very recently. The present study is part of undergoing major cytogenetic advances seeking to elucidate the evolutionary history of lebiasinids. Aiming to examine the karyotype diversification more deeply in Pyrrhulina, here we combined classical and molecular cytogenetic analyses, including Giemsa staining, C-banding, repetitive DNA mapping, comparative genomic hybridization (CGH), and whole chromosome painting (WCP) to perform the first analyses in five Pyrrhulina species (Pyrrhulina aff. marilynae, Pyrrhulina sp., P. obermulleri, P. marilynae and Pyrrhulina cf. laeta). The diploid number (2n) ranged from 40 to 42 chromosomes among all analyzed species, but P. marilynae is strikingly differentiated by having 2n = 32 chromosomes and a karyotype composed of large meta/submetacentric chromosomes, whose plesiomorphic status is discussed. The distribution of microsatellites does not markedly differ among species, but the number and position of the rDNA sites underwent significant changes among them. Interspecific comparative genome hybridization (CGH) found a moderate divergence in the repetitive DNA content among the species’ genomes. Noteworthy, the WCP reinforced our previous hypothesis on the origin of the X1X2Y multiple sex chromosome system in P. semifasciata. In summary, our data suggest that the karyotype differentiation in Pyrrhulina has been driven by major structural rearrangements, accompanied by high dynamics of repetitive DNAs.

Highlights

Characiformes comprise a very diverse and abundant freshwater order (Nelson et al, 2016), in which the family Lebiasinidae is represented by 75 valid species (Fricke et al, 2021) widely distributed across South and Central America (Weitzman and Weitzman, 2003)
All species were properly identified by morphological criteria, and the specimens were deposited in the fish collection of the Museu de Zoologia da Universidade de São Paulo (MZUSP) under the voucher numbers (119077, 119079, 123073, 123080) and the Universidade Federal da Paraíba (UFPB) museum under the voucher number (12079, 12080, 12082 and 12083)
Pyrrhulina sp., P. obermulleri, and Pyrrhulina cf. laeta presented a remarkable series of interstitial and pericentromeric C-bands, in addition to telomeric ones (Figure 2)

Summary

Introduction

Characiformes comprise a very diverse and abundant freshwater order (Nelson et al, 2016), in which the family Lebiasinidae is represented by 75 valid species (Fricke et al, 2021) widely distributed across South and Central America (Weitzman and Weitzman, 2003). Most Lebiasinidae species reach about 60 mm of Standard Length (SL), but miniature species, not surpassing a maximum of 26 mm SL, is found within the Pyrrhulininae, whereas medium-sized species up to 150 mm SL can be found within Lebiasininae (Weitzman and Weitzman, 2003) Because of their small sizes and difficulties in obtaining good chromosomal preparations, species of Lebiasinidae were, for a long time, little analyzed in terms of cytogenetics, with scarce references mainly on the chromosomal number of few species (Scheel, 1973; Oliveira et al, 1991; Arai, 2011). Both P. australis and Pyrrhulina aff. australis showed similar data 2n

Methods

Results

Discussion

Conclusion