Genetic differentiation among distinct karyomorphs of the wolf fish Hoplias malabaricus species complex (Characiformes, Erythrinidae) and report of unusual hybridization with natural triploidy

Abstract

In this study, genetic differentiation between karyomorphs A (2n = 42) and D (2n = 39/40) of the wolf fish Hoplias malabaricus, which is comprised of several cryptic species that present a wide variety of diploid chromosome numbers and sex chromosome systems, resulting in the identification of seven distinct karyomorphs (A-G), was investigated using a combination of molecular and cytogenetic tools. Deep sequence divergences for both karyomorphs were observed and indicate a long period of reproductive isolation between karyomorphs A and D. Additionally, one individual with 61 chromosomes was identified, which, as far as is known, is the first case of natural triploidy resulting from the hybridization between these highly differentiated karyomorphs of H. malabaricus. Molecular and cytogenetic analyses revealed that this allotriploid specimen carries two sets of maternal chromosomes from karyomorph D (2n = 40) and one set of chromosomes from karyomorph A (n = 21). Moreover, ribosomal sites and active nucleolus organizer regions from both parental contributors were found in the triploid hybrid. Considering the significant genetic distances between karyomorphs A and D, one of the primary reasons for the lack of recurrent reports of hybridization in the H. malabaricus species complex may be due to post-zygotic barriers, such as hybrid sterility or unviability.

Sex Chromosome Evolution and Genomic Divergence in the Fish Hoplias malabaricus (Characiformes, Erythrinidae)

“…An array of molecular and cytogenetic methods, including DNA barcoding and phylogeographic approaches, have already led to the hypothesis that H. malabaricus likely represents a “species complex,” with several undescribed species (Bertollo et al, 2000 ; Santos et al, 2009 ; Cioffi et al, 2012 ; Marques et al, 2013 ). Furthermore, different karyomorphs with a sympatric or syntopic occurrence were found to lack any hybrid forms, as proven by cytogenetic and RAPD (random amplified polymorphic DNA) analyses (Dergam et al, 1998 , 2002 ; Bertollo et al, 2000 ), yet a sporadic case of hybridization followed by an elevation of the ploidy level was already reported (Utsunomia et al, 2014 ).…”

DNA barcoding techniques used to identify the shared ichthyofauna between the Pantanal floodplain and Upper Parana River

“…Other studies have reported that Hoplias malabaricus (Utsunomia et al 2014a), Synbranchus marmoratus (Torres et al 2005;Utsunomia et al 2014b), Rhamdia quelen (Martinez et al 2011), Sternopygus macrurus (de Almeida-Toledo et al 1993), Eigenmannia virescens (Silva et al 2009), E. trilineata (Moys es et al 2010) and Brachyhypopomus pinnicaudatus (Giora 2009) are species complexes, but this is the first time that Leporinus striatus and Pimelodus maculatus are listed as putative species complexes.…”

Triploid Induction in the Yellowtail Tetra, Astyanax altiparanae, Using Temperature Shock: Tools for Conservation and Aquaculture

“…(Pansonato‐Alves et al ); Gymnotus carapo (Fernandes‐Matioli et al ); Eigenmannia sp. (Almeida Toledo et al ); Hoplias malabaricus (Utsunomia et al ); Hoplerythrinus unitaeniatus (Giulino‐Caetano and Bertollo ); Richomycterus davisi (Borin et al ); Rhamdia quelen (Tsuda et al ); Astyanax schubartii (Morelli et al ); Astyanax sp. (Fauaz et al ; Kantek et al ); and Astyanax scabripinnis (Maistro et al ; Machado et al ).…”