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

Altmanová Altmanová,Augstenová Augstenová,Mazzoleni Mazzoleni,Kostmann Kostmann,Kratochvíl Kratochvíl,Frynta Frynta,Rovatsos Rovatsos

doi:10.3390/genes10110934

Altmanová Altmanová, Augstenová Augstenová + Show 5 more

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https://doi.org/10.3390/genes10110934

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Abstract

Homologous and differentiated ZZ/ZW sex chromosomes (or derived multiple neo-sex chromosomes) were often described in caenophidian snakes, but sex chromosomes were unknown until recently in non-caenophidian snakes. Previous studies revealed that two species of boas (Boa imperator, B. constrictor) and one species of python (Python bivittatus) independently evolved XX/XY sex chromosomes. In addition, heteromorphic ZZ/ZW sex chromosomes were recently revealed in the Madagascar boa (Acrantophis sp. cf. dumerili) and putatively also in the blind snake Myriopholis macrorhyncha. Since the evolution of sex chromosomes in non-caenophidian snakes seems to be more complex than previously thought, we examined ten species of pythons and boas representing the families Boidae, Calabariidae, Candoiidae, Charinidae, Pythonidae, and Sanziniidae by conventional and molecular cytogenetic methods, aiming to reveal their sex chromosomes. Our results show that all examined species do not possess sex-specific differences in their genomes detectable by the applied cytogenetic methods, indicating the presence of poorly differentiated sex chromosomes or even the absence of sex chromosomes. Interestingly, fluorescence in situ hybridization with telomeric repeats revealed extensive distribution of interstitial telomeric repeats in eight species, which are likely a consequence of intra-chromosomal rearrangements.

Highlights

Snakes (Serpentes) are a clade of toxicoferan reptiles
We studied ten species belonging to six families of boas and pythons: Chilabotrus angulifer, Eunectes notaeus (Boidae), Calabaria reinhardtii (Calabariidae), Candoia paulsoni (Candoiidae), Lichanura trivirgata (Charinidae), Morelia bredli, Morelia spilota (Pythonidae), Acrantophis dumerili, Acrantophis madagascariensis, and Sanzinia madagascariensis (Sanziniidae) (Table 1)
The results are presented in the figures according to the technique used in the order: Giemsa-stained karyograms of previously cytogenetically unstudied species (Figure 1), C-banding (Figure 2), distribution of (TTAGGG)n motifs (Figure 3), rDNA accumulations (Figure 4) and (GATA)8 motifs, and comparative genomic hybridization (CGH) (Figure 6)

Summary

Introduction

Snakes (Serpentes) are a clade of toxicoferan reptiles. With almost 3800 extant species, snakes represent about one third of all reptilian species [1]. Traditional taxonomy classifies snakes into three major lineages: Caenophidia, and the likely paraphyletic Scolecophidia and Henophidia [2,3,4,5]. Caenophidia is the most specious and diverse group, including more than 3100 species [1]. Scolecophidia is a group of approximately 400 species of blindsnakes with worm-like body shape and fossorial lifestyle. Henophidian snakes include about 200 species [1], recently divided into 21 families [3,6]

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