The adhesive organs of Anura: A histological and molecular study

Abstract

The cement gland is a secreting organ located at the anterior end of the larva of anuran Amphibia. It is a highly conserved structure even if it has different shapes in the different species. The morphology and the histology of the cement glands of seven species are analysed: Xenopus laevis, Discoglossus sardus, Bufo bufo, Bufo viridis, Rana esculenta, Rana latastei and Hyla intermedia. XCG and XAG are genes specifically expressed in the cement gland of Xenopus laevis and can be used as markers to identify cement gland territory. By Northern analysis and whole mount ’in situ’ hybridization, the expressions of these genes are tested in the studied species, the presence of homolog transcripts is detected in all the species, except Discoglossus sardus. Histological and molecular analysis show a substantial uniformity among the different types of adhesive organs. On the basis of the preliminary results obtained, some phylogenetic relations are inferred according to a recent phylogenetic tree based on molecular characters. The results seem to agree with the hypothesis that Pipi‐dae, to which Xenopus laevis belongs, are nearer to Neobatrachia than to Archeobatrachia.

Keywords:

• Anura
• Adhesive organ
• Gene expression
• XAG ‐XCG.