See the published version of this preprint at Frontiers in Zoology.
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Daniel Schwarz
Friedrich-Schiller-Universität Jena
Corresponding Author
ORCiD: https://orcid.org/0000-0002-5845-4027
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This work is licensed under a CC BY 4.0 License. Read Full License
Background: The feeding apparatus of salamanders consists mainly of the cranium, mandible, teeth, hyobranchial apparatus and the muscles of the cranial region. The morphology of the feeding apparatus in turn determines the boundary conditions for possible food processing mechanisms. However, the morphology of the feeding apparatus changes substantially during metamorphosis, prompting the hypothesis that larvae might use a different food processing mechanism than post-metamorphic adults. Salamandrid newts with facultative metamorphosis are suitable for testing this hypothesis as adults with divergent feeding apparatus morphologies often coexist in the same population, share similar body sizes, and feed on overlapping prey spectra.
Methods: We use high-speed videography to quantify the in vivo movements of key anatomical elements during food processing in paedomorphic and metamorphic Alpine newts (Ichthyosaura alpestris). Additionally, we use micro-computed tomography (μCT) to analyze morphological differences in the feeding apparatus of paedomorphic and metamorphic Alpine newts and sort them into late-larval, mid-metamorphic and post-metamorphic morphotypes.
Results: Late-larval, mid-metamorphic and post-metamorphic individuals exhibited clear morphological differences in their feeding apparatus. Regardless of the paedomorphic state being externally evident, paedomorphic specimens can conceal different morphotypes (i.e., late-larval and mid-metamorphic morphotypes). Though feeding on the same prey under the same (aquatic) condition, food processing kinematics differed between late-larval, mid-metamorphic and post-metamorphic morphotypes.
Conclusions: The food processing mechanism in the Alpine newt changes along with morphology of the feeding apparatus during ontogeny, from a mandible-based to a tongue-based processing mechanism as the mandible’s changing morphology prevents chewing and the tongue allows enhanced protraction. These results could indicate that early tetrapods, in analogy to salamanders, may have developed new feeding mechanisms in their aquatic environment and that these functional innovations may have later paved the way for terrestrial feeding mechanisms.
Keywords
salamander, kinematics, micro-CT, functional morphology, feeding apparatus, ontogeny, chewing, intraoral food processing, feeding, flexibility
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
This is a list of supplementary files associated with this preprint. Click to download.
- Video1.avi
Video 1. High-speed movie from a lateral perspective, showing a post-metamorphic I. alpestris processing a lake fly larvae (Chironomidae) under water. Three consecutive processing cycles can be observed. Notice how the tongue cyclically rasps the prey along the palate. The movie was recorded at 500 Hz and is played back at 50 Hz, which corresponds to 10% of the actual speed.
- Video2.avi
Video 2. High-speed movie from a anterio-lateral perspective, showing a mid-metamorphic I. alpestris processing a lake fly larvae (Chironomidae) under water. Five full processing cycles can be observed, cycle 1, 4, and 5 are mixed, or immediately followed, by transport movements. Notice how the tongue cyclically rasps the prey along the palate. The movie was recorded at 500 Hz and is played back at 50 Hz, which corresponds to 10% of the actual speed.
- Video3.avi
Video 3. High-speed movie from a lateral perspective, showing a mid-metamorphic I. alpestris processing a lake fly larvae (Chironomidae) under water. Five full processing cycles can be observed, cycle 3 is immediately followed by a transport movement. Notice how in every except the third cycle the haemolymph of the prey leaves the mouth during processing (i.e., an indication of structural damage). The movie was recorded at 500 Hz and is played back at 100 Hz, which corresponds to 20% of the actual speed.
- Video4.avi
Video 4. High-speed movie from a lateral perspective, showing a late-larval I. alpestris processing a lake fly larvae (Chironomidae) under water. Five full processing cycles can be observed, cycle 5 is mixed with a transport movement. Notice how the lower jaw is used to bite the prey. The movie was recorded at 500 Hz and is played back at 100 Hz, which corresponds to 20% of the actual speed
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CURRENT STATUS: Published
View the published article at Frontiers in Zoology.
Version 2
Posted 10 Aug, 2020
No community comments so far
Editorial decision: Accept
On 15 Aug, 2020
Review #1 received
Received 14 Aug, 2020
Reviewer #1 agreed
On 10 Aug, 2020
Reviewers invited
Invitations sent on 04 Aug, 2020
Editor assigned
On 03 Aug, 2020
Submission checks complete
On 02 Aug, 2020
Editor invited
On 02 Aug, 2020
No comments provided
Editorial decision: Major revision
On 18 Jul, 2020
Review #2 received
Received 17 Jul, 2020
Review #1 received
Received 08 Jul, 2020
Reviewer #2 agreed
On 02 Jul, 2020
Reviewer #1 agreed
On 29 Jun, 2020
Reviewers invited
Invitations sent on 25 Jun, 2020
Editor assigned
On 19 Jun, 2020
Submission checks complete
On 18 Jun, 2020
Editor invited
On 18 Jun, 2020
First submitted
On 17 Jun, 2020
Metrics
Comments: 0
PDF Downloads: ...
HTML Views: ...
Subject Areas
Animal Physiology
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See the published version of this preprint at Frontiers in Zoology.
This is a preprint, a preliminary version of a manuscript that has not completed peer review at a journal. Research Square does not conduct peer review prior to posting preprints. The posting of a preprint on this server should not be interpreted as an endorsement of its validity or suitability for dissemination as established information or for guiding clinical practice.
Learn more about In Review
Research
Daniel Schwarz
Friedrich-Schiller-Universität Jena
Corresponding Author
ORCiD: https://orcid.org/0000-0002-5845-4027
Badges
Prescreen
This manuscript passed our Prescreen assessment
Complete author information
Appropriate declaration statements
Potential risks to human health
Prescreen
Peer Review Timeline
CURRENT STATUS: Published
View the published article at Frontiers in Zoology.
Version 2
Posted 10 Aug, 2020
No community comments so far
Editorial decision: Accept
On 15 Aug, 2020
Review #1 received
Received 14 Aug, 2020
Reviewer #1 agreed
On 10 Aug, 2020
Reviewers invited
Invitations sent on 04 Aug, 2020
Editor assigned
On 03 Aug, 2020
Submission checks complete
On 02 Aug, 2020
Editor invited
On 02 Aug, 2020
No comments provided
Editorial decision: Major revision
On 18 Jul, 2020
Review #2 received
Received 17 Jul, 2020
Review #1 received
Received 08 Jul, 2020
Reviewer #2 agreed
On 02 Jul, 2020
Reviewer #1 agreed
On 29 Jun, 2020
Reviewers invited
Invitations sent on 25 Jun, 2020
Editor assigned
On 19 Jun, 2020
Submission checks complete
On 18 Jun, 2020
Editor invited
On 18 Jun, 2020
First submitted
On 17 Jun, 2020
Metrics
Comments: 0
PDF Downloads: ...
HTML Views: ...
Subject Areas
Animal Physiology
License:
This work is licensed under a CC BY 4.0 License. Read Full License
View the published article at Frontiers in Zoology.
Background: The feeding apparatus of salamanders consists mainly of the cranium, mandible, teeth, hyobranchial apparatus and the muscles of the cranial region. The morphology of the feeding apparatus in turn determines the boundary conditions for possible food processing mechanisms. However, the morphology of the feeding apparatus changes substantially during metamorphosis, prompting the hypothesis that larvae might use a different food processing mechanism than post-metamorphic adults. Salamandrid newts with facultative metamorphosis are suitable for testing this hypothesis as adults with divergent feeding apparatus morphologies often coexist in the same population, share similar body sizes, and feed on overlapping prey spectra.
Methods: We use high-speed videography to quantify the in vivo movements of key anatomical elements during food processing in paedomorphic and metamorphic Alpine newts (Ichthyosaura alpestris). Additionally, we use micro-computed tomography (μCT) to analyze morphological differences in the feeding apparatus of paedomorphic and metamorphic Alpine newts and sort them into late-larval, mid-metamorphic and post-metamorphic morphotypes.
Results: Late-larval, mid-metamorphic and post-metamorphic individuals exhibited clear morphological differences in their feeding apparatus. Regardless of the paedomorphic state being externally evident, paedomorphic specimens can conceal different morphotypes (i.e., late-larval and mid-metamorphic morphotypes). Though feeding on the same prey under the same (aquatic) condition, food processing kinematics differed between late-larval, mid-metamorphic and post-metamorphic morphotypes.
Conclusions: The food processing mechanism in the Alpine newt changes along with morphology of the feeding apparatus during ontogeny, from a mandible-based to a tongue-based processing mechanism as the mandible’s changing morphology prevents chewing and the tongue allows enhanced protraction. These results could indicate that early tetrapods, in analogy to salamanders, may have developed new feeding mechanisms in their aquatic environment and that these functional innovations may have later paved the way for terrestrial feeding mechanisms.
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
This is a list of supplementary files associated with this preprint. Click to download.
- Video1.avi
Video 1. High-speed movie from a lateral perspective, showing a post-metamorphic I. alpestris processing a lake fly larvae (Chironomidae) under water. Three consecutive processing cycles can be observed. Notice how the tongue cyclically rasps the prey along the palate. The movie was recorded at 500 Hz and is played back at 50 Hz, which corresponds to 10% of the actual speed.
- Video2.avi
Video 2. High-speed movie from a anterio-lateral perspective, showing a mid-metamorphic I. alpestris processing a lake fly larvae (Chironomidae) under water. Five full processing cycles can be observed, cycle 1, 4, and 5 are mixed, or immediately followed, by transport movements. Notice how the tongue cyclically rasps the prey along the palate. The movie was recorded at 500 Hz and is played back at 50 Hz, which corresponds to 10% of the actual speed.
- Video3.avi
Video 3. High-speed movie from a lateral perspective, showing a mid-metamorphic I. alpestris processing a lake fly larvae (Chironomidae) under water. Five full processing cycles can be observed, cycle 3 is immediately followed by a transport movement. Notice how in every except the third cycle the haemolymph of the prey leaves the mouth during processing (i.e., an indication of structural damage). The movie was recorded at 500 Hz and is played back at 100 Hz, which corresponds to 20% of the actual speed.
- Video4.avi
Video 4. High-speed movie from a lateral perspective, showing a late-larval I. alpestris processing a lake fly larvae (Chironomidae) under water. Five full processing cycles can be observed, cycle 5 is mixed with a transport movement. Notice how the lower jaw is used to bite the prey. The movie was recorded at 500 Hz and is played back at 100 Hz, which corresponds to 20% of the actual speed
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