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Highlights
• A proteomic analysis of the mandibular glands of Shinisaurius crocodilurus and Corucia zebrata, was performed.
• Scanning electron microscopy of S. crocodilurus' teeth revealed a sharp ridge on the anterior surface, but no grooves.
• Scanning electron microscopy of C. zebrata teeth showed a flattened crown with a pointed cusp.
• Proteomic analysis of gland extracts of S. crocodilurus and C. zebrata showed absence of venom-derived peptides or proteins.
• Our results strongly support the non-venomous character of both S. crocodilurus and C. zebrata.
Abstract
Based on its phylogenetic relationship to monitor lizards (Varanidae), Gila monsters (Heloderma spp.), and the earless monitor Lanthanotus borneesis, the Chinese crocodile lizard, Shinisaurus crocodilurus, has been assigned to the Toxicofera clade, which comprises venomous reptiles. However, no data about composition and biological activities of its oral secretion have been reported. In the present study, a proteomic analysis of the mandibular gland of S. crocodilurus and, for comparison, of the herbivorous Solomon Island skink Corucia zebrata, was performed. Scanning electron microscopy (SEM) of the teeth from S. crocodilurus revealed a sharp ridge on the anterior surface, but no grooves, whereas those of C. zebrata possess a flattened crown with a pointed cusp. Proteomic analysis of their gland extracts provided no evidence of venom-derived peptides or proteins, strongly supporting the non-venomous character of these lizards. Data are available via ProteomeXchange with identifier PXD039424.
Highlights
• Proteomic analyses of submandibular gland extracts of two alligator lizards of the Anguidae family are reported.
• A conserved set of putative toxins was found in the submandibular gland extracts of Abronia lythrochila and A. graminea.
• Toxins evolved in oral secretions of paleo- and neoanguimorpha over more than 100 million years of Anguimorpha cladogenesis.
• Electron microscopy of pleurodont teeth of A. lythrochila showed no sign of groove, external opening or striations.
• Assessing the role toxins play in the ecology of extant anguimorph lizards deserves functional studies in natural prey.
Abstract
A useful approach to deepen our knowledge about the origin and evolution of venom systems in Reptilia has been exploring the vast biodiversity of this clade of vertebrates in search of orally produced proteins with toxic actions, as well as their corresponding delivery systems. The occurrence of toxins in anguimorph lizards has been demonstrated experimentally or inferred from reports of the toxic effects of the oral secretions of taxa within the Varanidae and Helodermatidae families. In the present study, we have focused on two alligator lizards of the Anguidae family, the Mexican alligator lizard, Abronia graminea, and the red-lipped arboreal alligator lizard, A. lythrochila. In addition, the fine morphology of teeth of the latter species is described. The presence of a conserved set of proteins, including B-type natriuretic peptides, cysteine-rich secretory proteins, group III phospholipase A2, and kallikrein, in submandibular gland extracts was demonstrated for both Abronia species. These proteins belong to toxin families found in oral gland secretions of venomous reptile species. This finding, along with previous demonstration of toxin-producing taxa in both paleo- and neoanguimorpha clades, provides further support for the existence of a handful of conserved toxin families in oral secretions across the 100+ million years of Anguimorpha cladogenesis.