The adhesive organs of Anura: a histological and molecular study

The cement gland is a secreting organ located at the anterior end of the la rva of anuran Amphibia. It is a highly conserved structure even if it has d ifferent shapes in the different species. The morphology and the histology of the cement glands of seven species are analysed: Xenopus laevis, Discogl ossus sardus, Bufo bufo, Bufo viridis, Rana esculenta, Rana latastei and Hy la intermedia. XCG and XAG are genes specifically expressed in the ce ment gland of Xenopus laevis and can be used as markers to identify cement gland territory. By Northern analysis and whole mount 'in situ' hybridization, t he expressions of these genes are tested in the studied species, the presen ce of homolog transcripts is detected in all the species, except Discogloss us sardus. Histological and molecular analysis show a substantial uniformit y among the different types of adhesive organs. On the basis of the prelimi nary results obtained, some phylogenetic relations are inferred according t o a recent phylogenetic tree based on molecular characters. The results see m to agree with the hypothesis that Pipidae, to which Xenopus laevis belong s, are nearer to Neobatrachia than to Archeobatrachia.