Amniote vertebrates possess various mechanisms of sex determination, but their variability is not equally distributed. The large evolutionary stability of sex chromosomes in viviparous mammals and birds was believed to be connected with their endothermy. However, some ectotherm lineages seem to be comparably conserved in sex determination, but previously there was a lack of molecular evidence to confirm this. Here, we document a stability of sex chromosomes in advanced snakes based on the testing of Z-specificity of genes using quantitative PCR (qPCR) across 37 snake species (our qPCR technique is suitable for molecular sexing in potentially all advanced snakes). We discovered that at least part of sex chromosomes is homologous across all families of caenophidian snakes (Acrochordidae, Xenodermatidae, Pareatidae, Viperidae, Homalopsidae, Colubridae, Elapidae and Lamprophiidae). The emergence of differentiated sex chromosomes can be dated back to about 60 Ma and preceded the extensive diversification of advanced snakes, the group with more than 3000 species. The Z-specific genes of caenophidian snakes are (pseudo)autosomal in the members of the snake families Pythonidae, Xenopeltidae, Boidae, Erycidae and Sanziniidae, as well as in outgroups with differentiated sex chromosomes such as monitor lizards, iguanas and chameleons. Along with iguanas, advanced snakes are therefore another example of ectothermic amniotes with a long-term stability of sex chromosomes comparable with endotherms.

Faculty of Science Department of Ecology Charles University Prague Viničná 7 12844 Praha 2 Czech Republic

Natural History Museum of Crete University of Crete Knossou Avenue 71409 Irakleio Crete Greece

Zobrazit více v PubMed

Johnson Pokorná M, Kratochvíl L. In press. What was the ancestral sex-determining mechanism in amniote vertebrates? Biol. Rev. (10.1111/brv.12156) PubMed DOI

Pokorná M, Kratochvíl L. 2009. Phylogeny of sex-determining mechanisms in squamate reptiles: are sex chromosomes an evolutionary trap? Zool. J. Linn. Soc. 156, 168–183. (10.1111/j.1096-3642.2008.00481.x) DOI

Gamble T, Coryell J, Ezaz T, Lynch J, Scantlebury DP, Zarkower D. 2015. Restriction site-associated DNA sequencing (RAD-seq) reveals an extraordinary number of transitions among gecko sex-determining systems. Mol. Biol. Evol. 32, 1296–1309. (10.1093/molbev/msv023) PubMed DOI

Perrin N. 2009. Sex reversal: a fountain of youth for sex chromosomes? Evolution 63, 3043–3049. (10.1111/j.1558-5646.2009.00837.x) PubMed DOI

Rovatsos M, Altmanová M, Pokorná M, Kratochvíl L. 2014. Conserved sex chromosomes across adaptively radiated Anolis lizards. Evolution 68, 2079–2085. (10.1111/evo.12357) PubMed DOI

Mulcahy DG, Noonan BP, Moss T, Townsend TM, Reeder TW, Sites JW, Wiens JJ. 2012. Estimating divergence dates and evaluating dating methods using phylogenomic and mitochondrial data in squamate reptiles. Mol. Phylogenet. Evol. 65, 974–991. (10.1016/j.ympev.2012.08.018) PubMed DOI

Uetz P, Hošek J (eds). 2014. The reptile database. See http://www.reptile-database.org (accessed 21 March 2015).

Olmo E, Signorino GG. 2005 Chromorep: a reptile chromosomes database. See http://chromorep.univpm.it. (accessed 21 March 2015).

Oguiura N, Ferrarezzi H, Batistic RF. 2009. Cytogenetics and molecular data in snakes: a phylogenetic approach. Cytogenet. Genome Res. 127, 128–142. (10.1159/000295789) PubMed DOI

O'Meally D, Patel HR, Stiglec R, Sarre SD, Georges A, Marshall Graves JA, Ezaz T. 2010. Non-homologous sex chromosomes of birds and snakes share repetitive sequences. Chromosom. Res. 18, 787–800. (10.1007/s10577-010-9152-9) PubMed DOI

Vicoso B, Emerson JJ, Zektser Y, Mahajan S, Bachtrog D. 2013. Comparative sex chromosome genomics in snakes: differentiation, evolutionary strata, and lack of global dosage compensation. PLoS Biol. 11, e1001643 (10.1371/journal.pbio.1001643) PubMed DOI PMC

Matsubara K, Tarui H, Toriba M, Yamada K, Nishida-Umehara C, Agata K, Matsuda Y. 2006. Evidence for different origin of sex chromosomes in snakes, birds, and mammals and step-wise differentiation of snake sex chromosomes. Proc. Natl Acad. Sci. USA 103, 18 190–18 195. (10.1073/pnas.0605274103) PubMed DOI PMC

Alföldi J, et al. 2011. The genome of the green anole lizard and a comparative analysis with birds and mammals. Nature 477, 587–591. (10.1038/nature10390) PubMed DOI PMC

Vicoso B, Bachtrog D. 2013. Reversal of an ancient sex chromosome to an autosome in Drosophila. Nature 499, 332–335. (10.1038/nature12235) PubMed DOI PMC

Vicoso B, Bachtrog D. 2015. Numerous transitions of sex chromosomes in Diptera. PLoS Biol. 13, e1002078 (10.1371/journal.pbio.1002055.pmid:25575020) PubMed DOI PMC

Koubová M, Johnson Pokorná M, Rovatsos M, Farkačová K, Altmanová M, Kratochvíl L. 2014. Sex determination in Madagascar geckos of the genus Paroedura (Squamata: Gekkonidae): are differentiated sex chromosomes indeed so evolutionary stable? Chromosom. Res. 22, 441–452. (10.1007/s10577-014-9430-z) PubMed DOI

Rovatsos M, Pokorná M, Altmanová M, Kratochvíl L. 2014. Cretaceous park of sex determination: sex chromosomes are conserved across iguanas. Biol. Lett. 10, 20131093 (10.1098/rsbl.2013.1093) PubMed DOI PMC

Mengden GA, Stock AD. 1980. Chromosomal evolution in Serpentes; a comparison of G and C chromosome banding patterns of some colubrid and boid genera. Chromosoma 79, 53–64. (10.1007/BF00328472) DOI

Pyron RA, Burbrink FT, Wiens JJ. 2013. A phylogeny and revised classification of Squamata, including 4161 species of lizards and snakes. BMC Evol. Biol. 13, 93 (10.1186/1471-2148-13-93) PubMed DOI PMC

Pyron RA, Reynolds RG, Burbrink FT. 2014. A taxonomic revision of boas (Serpentes: Boidae). Zootaxa 3846, 249–260. (10.11646/zootaxa.3846.2.5) PubMed DOI

Hsiang AY, Field DJ, Webster TH, Behlke ADB, Davis MB, Racicot RA, Gauthier JA. 2015. The origin of snakes: revealing the ecology, behavior, and evolutionary history of early snakes using genomics, phenomics, and the fossil record. BMC Evol. Biol. 15, 87 (10.1186/s12862-015-0358-5) PubMed DOI PMC

Rovatsos M, Altmanová M, Johnson Pokorná M, Kratochvíl L. 2014. Novel X-linked genes revealed by quantitative polymerase chain reaction in the green anole, Anolis carolinensis. Genes Genomes Genet. 4, 2107–2113. (10.1534/g3.114.014084) PubMed DOI PMC

Nguyen P, Sýkorová M, Šíchová J, Kůta V, Dalíková M, Čapková Frydrychová R, Neven LG, Sahara K, Marec F. 2013. Neo-sex chromosomes and adaptive potential in tortricid pests. Proc. Natl Acad. Sci. USA 110, 6931–6936. (10.1073/pnas.1220372110) PubMed DOI PMC

Gamble T, Geneva AJ, Glor RE, Zarkower D. 2014. Anolis sex chromosomes are derived from a single ancestral pair. Evolution 68, 1027–1041. (10.1111/evo.12328) PubMed DOI PMC

Ye J, Coulouris G, Zaretskaya I, Cutcutache I, Rozen S, Madden TL. 2012. Primer-BLAST: a tool to design target-specific primers for polymerase chain reaction. BMC Bioinform. 13, 134 (10.1186/1471-2105-13-134) PubMed DOI PMC

Young MJ, O'Meally D, Sarre SD, Georges A, Ezaz T. 2013. Molecular cytogenetic map of the central bearded dragon, Pogona vitticeps (Squamata: Agamidae). Chromosom. Res. 21, 361–374. (10.1007/s10577-013-9362-z) PubMed DOI

Rovatsos M, Johnson Pokorná M, Altmanová M, Kratochvíl L. 2015. Female heterogamety in Madagascar chameleons (Squamata: Chamaeleonidae: Furcifer): differentiation of sex and neo-sex chromosomes. Sci. Rep. 5, 13196. PubMed PMC

King M, Mengden GA, King D. 1982. A pericentric-inversion polymorphism and s ZZ/ZW sex-chromosome system in Varanus acanthurus Boulenger analyzed by G- and C-banding and Ag staining. Genetica 58, 39–45. (10.1007/BF00056001) DOI

Johnson Pokorná M, Rovatsos M, Kratochvíl L. 2014. Sex chromosomes and karyotype of the (nearly) mythical creature, the Gila monster, Heloderma suspectum (Squamata: Helodermatidae). PLoS ONE 9, e104716 (10.1371/journal.pone.0104716) PubMed DOI PMC

Pokorná M, Rábová M, Ráb P, Ferguson-Smith MA, Rens W, Kratochvíl L. 2010. Differentiation of sex chromosomes and karyotypic evolution in the eye-lid geckos (Squamata: Gekkota: Eublepharidae), a group with different modes of sex determination. Chromosome Res. 18, 809–820. (10.1007/s10577-010-9154-7) PubMed DOI

Zhou Q, Zhang J, Bachtrog D, An N, Huang Q, Jarvis ED, Gilbert MT, Zhang G. 2014. Complex evolutionary trajectories of sex chromosomes across bird taxa. Science 346, 1246338 (10.1126/science.1246338) PubMed DOI PMC

Waters PD, Wallis MC, Marshall Graves JA. 2007. Mammalian sex: origin and evolution of the Y chromosome and SRY. Semin. Cell Dev. Biol. 18, 389–400. (10.1016/j.semcdb.2007.02.007) PubMed DOI

Pyron RA, Burbrink FT. 2012. Extinction, ecological opportunity, and the origins of global snake diversity. Evolution 66, 163–178. (10.1111/j.1558-5646.2011.01437.x) PubMed DOI

Sex Chromosome Turnovers and Stability in Snakes

Cytogenetic Analysis of Satellitome of Madagascar Leaf-Tailed Geckos

Heteromorphic ZZ/ZW sex chromosomes sharing gene content with mammalian XX/XY are conserved in Madagascan chameleons of the genus Furcifer

Robertsonian fusion triggers recombination suppression on sex chromosomes in Coleonyx geckos

Madagascar Leaf-Tail Geckos (Uroplatus spp.) Share Independently Evolved Differentiated ZZ/ZW Sex Chromosomes

ZZ/ZW Sex Chromosomes in the Madagascar Girdled Lizard, Zonosaurus madagascariensis (Squamata: Gerrhosauridae)

Cytogenetic Analysis of the Members of the Snake Genera Cylindrophis, Eryx, Python, and Tropidophis

Expanding the classical paradigm: what we have learnt from vertebrates about sex chromosome evolution

Sex chromosome evolution among amniotes: is the origin of sex chromosomes non-random?

Are Geckos Special in Sex Determination? Independently Evolved Differentiated ZZ/ZW Sex Chromosomes in Carphodactylid Geckos

With or Without W? Molecular and Cytogenetic Markers are Not Sufficient for Identification of Environmentally-Induced Sex Reversal in the Bearded Dragon

Poorly differentiated XX/XY sex chromosomes are widely shared across skink radiation

Evolutionary Variability of W-Linked Repetitive Content in Lacertid Lizards

Sex is determined by XX/XY sex chromosomes in Australasian side-necked turtles (Testudines: Chelidae)

ZZ/ZW Sex Determination with Multiple Neo-Sex Chromosomes is Common in Madagascan Chameleons of the Genus Furcifer (Reptilia: Chamaeleonidae)

Cytogenetic Analysis Did Not Reveal Differentiated Sex Chromosomes in Ten Species of Boas and Pythons (Reptilia: Serpentes)

Conserved sex chromosomes and karyotype evolution in monitor lizards (Varanidae)

Turtles of the genera Geoemyda and Pangshura (Testudines: Geoemydidae) lack differentiated sex chromosomes: the end of a 40-year error cascade for Pangshura

Evolutionary Dynamics of the W Chromosome in Caenophidian Snakes

Stable Cretaceous sex chromosomes enable molecular sexing in softshell turtles (Testudines: Trionychidae)