Function, form and evolution of food processing in salamanders

• Applicant: Professor Dr. Martin S. Fischer, since 12/2019
• Subject Area: Systematics and Morphology (Zoology) ; Sensory and Behavioural Biology ; Biophysics ; Nuclear Medicine, Radiotherapy, Radiobiology ; Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions
• Term: from 2016 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 318358183

• Final Report Year: 2021

Final Report Abstract

It used to be common textbook knowledge that lissamphibians do not manipulate prey and–contrary to most other vertebrates–swallow prey whole and unreduced. In this project, it was shown that salamanders do process prey intraorally and that their processing mechanisms might be more divers than in most other vertebrate groups. Most salamanders with metamorphic morphology use an intraoral processing mechanism that we described as “tongue-palate rasping”, where food objects are translated and pressed against and along the palatal dentition by cyclic loop-movements of the tongue. Salamanders with larval cranial morphology (i.e. larvae and paedomorphic salamanders) by contrast use a chewing mechanism where the lower jaw acts against the anterior palatal dentition and/or the upper jaw. Accordingly, salamanders show a developmental shift of the processing mechanism that is in accordance with the morphological changes they undergo across metamorphosis. Contrary to prey capture, intraoral prey processing is only slightly influenced by the medium (i.e. water or air) where feeding occurs: salamanders use basically the same processing mechanisms for aquatic and terrestrial feeding events, but the processing cycle number can be altered significantly across media. Similarly, prey types that differ in their mechanical properties are processed with significantly diverging processing cycles. Still, mechanical properties might not be the only factor that trigger diverging processing behaviour, but other factors, such as chemical cues seem to play an important role too. The results of this project have provided new insights into the feeding biology of salamanders. These insights might open new questions that should motivate further studies on the evolution of feeding systems in tetrapods or on behavioural and neuro-physiological aspects of food discrimination in salamanders.

Publications

• 2018. Aquatic-terrestrial transitions of feeding systems in vertebrates: a mechanical perspective. J. Exp. Biol. 221, jeb154427
  Heiss, E., Aerts, P., Van Wassenbergh, S.
  
• 2019. Chewing or not? Intraoral food processing in a salamandrid newt. J. Exp. Biol. 222, 12
  Heiss, E., Schwarz, D., Konow, N.
  
• 2019. Same but different: aquatic prey capture in paedomorphic and metamorphic Alpine newts. Zool. Lett. 5, 1–12
  Heiss, E., Grell, J.
  
• 2020. A salamander that chews using complex, three-dimensional mandible movements. J. Exp. Biol. 223, 12
  Schwarz, D., Konow, N., Roba, Y.T., Heiss, E.
  
• 2020. Flexibility of intraoral food processing in the salamandrid newt Triturus carnifex: effects of environment and prey type. J. Exp. Biol. 11
  Schwarz, D., Gorb, S.N., Kovalev, A., Konow, N., Heiss, E.
  
• 2020. Ontogenetic plasticity in cranial morphology is associated with a change in the food processing behavior in Alpine newts. Front. Zool. 17
  Schwarz, D., Konow, N., Porro, L.B., Heiss, E.
  
• Form, function, development and evolution of intraoral food processing in salamanders (PhD thesis, 2021)
  Daniel Schwarz