Abstract
Oplegnathus fasciatus and O. punctatus (Teleostei: Centrarchiformes: Oplegnathidae), are commercially important rocky reef fishes, endemic to East Asia. Both species present an X1X2Y sex chromosome system. Here, we investigated the evolutionary forces behind the origin and differentiation of these sex chromosomes, with the aim to elucidate whether they had a single or convergent origin. To achieve this, conventional and molecular cytogenetic protocols, involving the mapping of repetitive DNA markers, comparative genomic hybridization (CGH), and whole chromosome painting (WCP) were applied. Both species presented similar 2n, karyotype structure and hybridization patterns of repetitive DNA classes. 5S rDNA loci, besides being placed on the autosomal pair 22, resided in the terminal region of the long arms of both X1 chromosomes in females, and on the X1 and Y chromosomes in males. Furthermore, WCP experiments with a probe derived from the Y chromosome of O. fasciatus (OFAS-Y) entirely painted the X1 and X2 chromosomes in females and the X1, X2, and Y chromosomes in males of both species. CGH failed to reveal any sign of sequence differentiation on the Y chromosome in both species, thereby suggesting the shared early stage of neo-Y chromosome differentiation. Altogether, the present findings confirmed the origin of the X1X2Y sex chromosomes via Y-autosome centric fusion and strongly suggested their common origin.
Highlights
The marine fish family Oplegnathidae includes only one genus Oplegnathus, which is currently composed of seven extant species [1]
A. farsecmiataursk(aFbigleurseiz1ee–hfe; tSeurpopmleomrpehnti,smFigoufrtehSi1s)s. ingle NOR site was observed in males and females of O. punctatus, but not in O. fasciatus (Figure 1e,f; Supplement, Figure S1)
The genus Oplegnathus proved to be a vital fish taxon which may provide a useful opportunity to study the evolution of sex chromosomes and sex determination
Summary
The marine fish family Oplegnathidae (order Centrarchiformes) includes only one genus Oplegnathus, which is currently composed of seven extant species [1]. O. fasciatus and O. punctatus, are commercially valuable taxa in East Asia, representing important fishery resources. 2 2ofof1616 for offshore cage aquaculture [2]. Extensive efforts have been undertaken to exploit their ggeenneetitcicssaannddggeennoommicisc,s,ininccluluddininggininsisgighhtstsinintotoththeeirirppooppuulalatitoionnaal lggeenneetitcicstsrtuructcuturere, ,wwitihthaannaaimimtoto fofossteterrththeetetecchhnnoolologgicicaal laaddvvaanncceemmeenntstsininththeeiriraaqquuaaccuultluturreee[[3[33–––666]].]..OOnneeoof fththeemmaarkrkeeddfefeaatutureressoof fbboothth ssppeeccieies’s’ggeennoommeessisiisstththheeeppprrereesseseennncceceeooofffaaammuuullttliitppiplleele♀♀XX11XX1X11X1XX2X22X2/22♂ //♂XX1X11X2Y22YYsessexexxchchrorrommmoosoossomommeeesysystssettememm[7[7,8,8],], wwwhhicichhmmigighhtthhaavveeppootetenntitaialllylyssoommeebbeeaarirninggtotoththeeooobbbsseerrvveeddsseexxuuaal lddimimoorprphhisimsmininggrorowwththaanndd/o/orr ppoossssisbiibblylyytottooooothtthheeerrrtrttraraaitiisttsstththhaaatttaaarrereeiimimmpppooorrtrtataannntttffofoorrrtththheeeffiifsishshhbbbrrereeeedddiininngggiininnddduuusststrtryryy. 2(2m1mm/s/ms+m+2+m44/4asa)m,),w+whhi4lie4leaf)ef,emmwahalelieslesppfoeosmsesaeslsess22npno=s=s4e48s8schc2hrnorom=moos4os8ommcehesrso(m2(2mom/ss/omsmme+s+4(4626ama) )/[s7[m7––99]+.].T4Th6heae)mm[a7ap–p9p]pi.ninggTohofef dmdisiatsitpnipnctcintmgmiocircfordosasisattetielnllicltitetemDDiNcNrAoAsmamteooltlitifitsfestDhthrNorouAugghmhoflftuliufosorerthescsrecoenuncgecheinflinusiostiruteushchyeybnbrciredidiizinzaatsitioitounnh(F(yFIbSIrSHiHd)i)zuuantncioconvve(erFerIedSdHaa) supspneeccicofiivfciecareacdcucuammsupulaelatcitioifioncnoaofcfcsousommmeueloaoftfitohtnheemomfosononmthteheeolalfargrthgeemmmeetoatnacectenhntertircliacYrYgcehchmroreomtmaocoseosnomtmreiecooYf fOcO.h.fraofsamcsicaoitasutousms[1[e100]o,]f, wOwh.hifliaelsecLiLaitiueest t[a1al0.l].,[9w[9] ]hrierleppoLoritretedt daln.no[o9a] asrseospocoicaritaeitodionnobbeaetswtswoeeceinanttihothneebloeloctwacateitoeionnntohofef5lo5SScatanindodn1o18f8S5SSrDraDNnNdAA18aSanndrdDsNesexAx cahcnhrodromsmeoxososcomhmreoesmsooofsfoOOm. 2(2m1mm/s/ms+m+2+m44/4asa)m,),w+whhi4lie4leaf)ef,emmwahalelieslesppfoeosmsesaeslsess22npno=s=s4e48s8schc2hrnorom=moos4os8ommcehesrso(m2(2mom/ss/omsmme+s+4(4626ama) )/[s7[m7––99]+.].T4Th6heae)mm[a7ap–p9p]pi.ninggTohofef dmdisiatsitpnipnctcintmgmiocircfordosasisattetielnllicltitetemDDiNcNrAoAsmamteooltlitifitsfestDhthrNorouAugghmhoflftuliufosorerthescsrecoenuncgecheinflinusiostiruteushchyeybnbrciredidiizinzaatsitioitounnh(F(yFIbSIrSHiHd)i)zuuantncioconvve(erFerIedSdHaa) supspneeccicofiivfciecareacdcucuammsupulaelatcitioifioncnoaofcfcsousommmeueloaoftfitohtnheemomfosononmthteheeolalfargrthgeemmmeetoatnacectenhntertircliacYrYgcehchmroreomtmaocoseosnomtmreiecooYf fOcO.h.fraofsamcsicaoitasutousms[1[e100]o,]f, wOwh.hifliaelsecLiLaitiueest t[a1al0.l].,[9w[9] ]hrierleppoLoritretedt daln.no[o9a] asrseospocoicaritaeitodionnobbeaetswtswoeeceinanttihothneebloeloctwacateitoeionnntohofef5lo5SScatanindodn1o18f8S5SSrDraDNnNdAA18aSanndrdDsNesexAx cahcnhrodromsmeoxososcomhmreoesmsooofsfoOOm. .epspuunoncftcOatta.utpusu.s.nAcAlttalhthuoosu.ugAghhltthhtoheuesesgehrertephpoeosretrstrsepprororvtvisdidpeedrodvaaidpperderelialmimpirnienalarimyryidndeaesrcsyrcidrpieptsitociorninpotofioftnhtheoef mtmhueultlmitpipulelletispesexlexcshcehrxorcomhmroosmosomomseoesmysyestssetyemmsteinminOiOnpplOelgepgnlnaegtahtnhuaust,hs,umsm,omoreroedredeetdateailtiealedildesdtsutsudtduieidesiseasarearerneneneeedededededdtottooclcalarirfiyfyitists oorrigigininaannddmmooleleccuulalarrccoommmpppooossistiiittoiioonnn. ..
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