Tongue and taste organ development in the ontogeny of direct‐developing salamander Plethodon cinereus (Lissamphibia: Plethodontidae)

Abstract

The latest research on direct developing caecilian and anuran species indicate presence of only one generation of taste organs during their ontogeny. This is distinct from indirect developing batrachians studied thus far, which possess taste buds in larvae and anatomically distinct taste discs in metamorphs. This study is a description of the tongue and taste organ morphology and development in direct developing salamander Plethodon cinereus (Plethodontidae) using histology and electron microscopy techniques. The results reveal two distinct stages tongue morphology (primary and secondary), similar to metamorphic urodeles, although only one stage of taste organ morphology. Taste disc sensory zones emerge on the surface of the oropharyngeal epithelium by the end of embryonic development, which coincides with maturation of the soft tongue. Taste organs occur in the epithelium of the tongue pad (where they are situated on the dermal papillae), the palate and the inner surface of the mandible and the maxilla. Plethodon cinereus embryos only possess taste disc type taste organs. Similar to the direct developing anuran Eleutherodactylus coqui (Eleutherodactylidae), these salamanders do not recapitulate larval taste bud morphology as an embryo. The lack of taste bud formation is probably a broadly distributed feature characteristic to direct developing batrachians. J. Morphol. 277:906-915, 2016. © 2016 Wiley Periodicals, Inc.

Macro‐ and micromorphological remodeling of olfactory organs throughout the ontogeny of the fire salamander Salamandra salamandra (Linnaeus, 1758)

“…During metamorphosis, morphological remodeling also occurs in organs connected with chemoreception (taste and smell). It was determined that there are two generations of taste organs (taste buds in larvae and taste discs in adults) in metamorphosing species of amphibians (Żuwała & Jakubowski, 1991, 2001, 2007) and only one generation (taste discs) in direct developers like Eleutherodactylus coqui (Budzik, Żuwała, & Buchholz, 2015) and Plethodon cinereus (Budzik, Żuwała, & Kerney, 2016). Determining the remodeling that occurs in amphibians' olfactory organs during the process of metamorphosis would also be useful.…”

“…Plethodon cinereus (Budzik, _ Zuwała, & Kerney, 2016). Determining the remodeling that occurs in amphibians' olfactory organs during the process of metamorphosis would also be useful.…”

Developmental basis of evolutionary lung loss in plethodontid salamanders

“…1, A and B, and 2A in Budzik et al . ( 58 )]. Mekeel ( 18 ), relying solely on developmental morphology, was the first person to report a transient lung rudiment in plethodontids.…”

“…On the basis of our ontogenetic data and examination of adult animals, we believe that both Wilder and Lüdike misidentified as the glottis an unrelated transverse fold in the floor of the pharynx that forms embryonically as the initial primary tongue is replaced by the secondary (soft) tongue [Figs. 1, A and B, and 2A in Budzik et al (58)]. Mekeel (18), relying solely on developmental morphology, was the first person to report a transient lung rudiment in plethodontids.…”