ZZ/ZW sex chromosome system in the endangered fish Lignobrycon myersi Miranda-Ribeiro, 1956 (Teleostei, Characiformes, Triportheidae)

Abstract

Lignobrycon myersi is an endemic fish species from a few coastal rivers in northeastern Brazil. Based on molecular evidence, Lignobrycon myersi and genera Triportheus Cope, 1872, Agoniates Müller & Troschel, 1845, Clupeacharax Pearson, 1924 and Engraulisoma Castro, 1981 were placed in the family Triportheidae. In the present work, we report the first cytogenetic data for Lignobrycon myersi to test the hypothesis that Lignobrycon and Triportheus are closely related. Studied specimens presented 2n=52 with 28 (m)metacentric , 18 (sm)submetacentric and six (st)subtelocentric chromosomes for males and 27 m, 19 sm and 6 st for females, characterizing a ZZ/ZW sex chromosome system. The Z chromosome corresponds to the largest chromosome in karyotype while the W is about 50% smaller than the Z and largely heterochromatic. Terminal nucleolus organizer regions, GC-rich sites and 18S rDNA signals were detected on pair 14. However, additional 18S rDNA sites were observed in the W chromosome. The 5S rDNA was mainly detected on long arms of pair 7. The apparent synapomorphic chromosomal traits of Triportheus and Lignobrycon myersi reinforce their close phylogenetic relationship, suggesting that the ZZ/ZW chromosome system in both genera has arisen before cladogenic events.

Chromosomal Evolution in Lower Vertebrates: Sex Chromosomes in Neotropical Fishes

“…In turn, the W chromosome of all species was strongly painted using the W-probe from the phylogenetically basal species T. auritus , demonstrating that the ZW system in Triportheus had a common origin within the genus [ 42 ]. Moreover, recent findings showing a morphologically similar ZZ/ZW sex system in Lignobrycon myersi (Triportheidae) [ 83 ], as well as the occurrence of female heterogamety in species from a sister family (Gasterpelecidae) [ 84 ], open new perspectives for investigations of the evolutionary history of the sex chromosomes among these groups. ( Figure 4 ).…”

Molecular Identification and Traceability of Illegal Trading inLignobrycon myersi(Teleostei: Characiformes), a Threatened Brazilian Fish Species, Using DNA Barcode

“…The highest differentiation between Astyanax and the other genera (22 to 24%) was expected because Lignobrycon and Triportheus have been recently removed from the family Characidae and placed into a distinct family (Triportheidae) according to phylogenetic analyses [ 16 ]. Indeed, L. myersi shares several synapomorphic traits with Triportheus , including an unusual sex chromosome system in Characiformes [ 17 ].…”

“…Voucher specimens were deposited in the fish collection of Instituto Nacional da Mata Atlântica (INMA) in Santa Teresa, State of Espírito Santo (#MBML6400). Because of their close phylogenetic relationship with Lignobrycon [ 16 , 17 ], COI sequences of Triportheus species obtained in the present study and available in GenBank were included. These additional sequences comprised Triportheus guentheri from São Francisco River (present paper; HM404957.1) [ 18 ], T. nematurus (GU701461.1; GU701945.1; GU701458.1; GU701457.1) [ 19 ], and T. angulatus (GU060427.1) [ 20 ].…”

Comparative cytogenetic analysis of fishes in the genus Trichopodus (Osphronemidae) in Thailand

“…In some cases, these heterochromatins can be revealed at interstitial regions in some Pomacentrid fishes to support that the chromosomal evolution in this family is related to chromosome fusion (Takai 2012). Moreover, constitutive heterochromatins are also highly accumulated on the W sex chromosome in Parodon hilarii (Parodontidae) (Moreira-Filho et al 1993,), Characidium fish (Crenuchidae) (Vicari et al 2008) and Lignobrycon myersi (Triportheidae) (Rodrigues et al 2016).…”