Long-term effects of arrested metamorphosis on dental systems in Salamandra salamandra (Salamandridae: Urodela)

Abstract

We describe the dental systems of six larvae of Salamandra salamandra hypophysectomized in 1976 under an earlier project to arrest metamorphosis. Larvae cover roughly three developmental stages from early (intrauterine) larval stage to early metamorphosis. Animals survived surgery and lived up to 16 months until fixation. One specimen was studied by histological serial sections. In the period until fixation larvae grew from approximately 3 cm to 7 cm in length (dependent on the developmental stage before surgery) retaining their larval appearance. Changes in the dental systems depended on the stage the larvae had reached before surgery. Generally, after surgery some traits had started or continued development, such as appearance of maxillae as well as resorption of the palatinal tooth patches and the coronoids in the youngest larva examined, whereas other traits had been largely retained and even continued to grow (e. g. larval dentate vomers). In three larvae, the anterior part of the palatines was covered by the posterior margin of the vomer giving the impression of a ‘vomeropterygopalatinum’, known from some newts as temporary fusion of vomer and palatine in consequence of a delayed metamorphosis. However, in the Salamandra-larvae both elements appeared to be connected syndesmotically rather than to be fused by bone tissue The oldest larva (metamorphic stage IV, approximately at the onset of metamorphosis), had lost the palatinal portion of pterygopalatina and had reduced the tooth patches of the vomers to a single row, but outgrowth of the vomerine bar had not taken place.