Most pleurodont lizard families (anoles, iguanas and their relatives), with the exception of the basilisks and casquehead lizards (family Corytophanidae), share homologous XX/XY sex chromosomes, syntenic with chicken chromosome 15. Here, we used a suite of methods (i.e. RADseq, RNAseq and qPCR) to identify corytophanid sex chromosomes for the first time. We reveal that all examined corytophanid species have partially degenerated XX/XY sex chromosomes, syntenic with chicken chromosome 17. Transcriptomic analyses showed that the expression of X-linked genes in the corytophanid, Basiliscus vittatus, is not balanced between the sexes, which is rather exceptional under male heterogamety, and unlike the dosage-balanced sex chromosomes in other well-studied XX/XY systems, including the green anole, Anolis carolinensis . Corytophanid sex chromosomes may represent a rare example of a turnover away from stable, differentiated sex chromosomes. However, because of poor phylogenetic resolution among pleurodont families, we cannot reject the alternative hypothesis that corytophanid sex chromosomes evolved independently from an unknown ancestral system.

Squamate reptiles (lizards, snakes, and amphibians) are an outstanding group for studying sex chromosome evolution—they are old, speciose, geographically widespread, and exhibit myriad sex-determining modes. Yet, the vast majority of squamate species lack heteromorphic sex chromosomes. Cataloging the sex chromosome systems of species lacking easily identifiable, heteromorphic sex chromosomes, therefore, is essential before we are to fully understand the evolution of vertebrate sex chromosomes. Here, we use restriction site-associated DNA sequencing (RADseq) to classify the sex chromosome system of the granite night lizard, Xantusia henshawi. RADseq is an effective alternative to traditional cytogenetic methods for determining a species’ sex chromosome system (i.e., XX/XY or ZZ/ZW), particularly in taxa with non-differentiated sex chromosomes. Although many xantusiid lineages have been karyotyped, none possess heteromorphic sex chromosomes. We identified a ZZ/ZW sex chromosome system in X. henshawi—the first such data for this family. Furthermore, we report that the X. henshawi sex chromosome contains fragments of genes found on Gallus gallus chromosomes 7, 12, and 18 (which are homologous to Anolis carolinensis chromosome 2), the first vertebrate sex chromosomes to utilize this linkage group.

Lionfishes are conspicuous and disruptive predators once introduced outside of their native range. Here we provide a revision of the occurrences of the common lionfish Pterois miles (Bennett, 1828) in the Mediterranean Sea, showing its rapid geographical expansion since 2012. A single lionfish was photographed in September 2016 during a scientific survey off the Vendicari coast, Southern Sicily, Italy. This is the first record of this notorious invasive species from Italian waters. Given its large size, conspicuous appearance, and venomous spines, it is critical to involve informed citizen scientists in tracking the spread of this species and to develop means to manage or adapt to its presence in the Mediterranean Basin.

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