Why can't young fish eat plants? Neither digestive enzymes nor gut development preclude herbivory in the young of a stomachless marine herbivorous fish

Day, Ryan D., German, Donovan P. and Tibbetts, Ian R. (2011) Why can't young fish eat plants? Neither digestive enzymes nor gut development preclude herbivory in the young of a stomachless marine herbivorous fish. Comparative Biochemistry and Physiology B-Biochemistry and Molecular Biology, 158 1: 23-29. doi:10.1016/j.cbpb.2010.09.010


Author Day, Ryan D.
German, Donovan P.
Tibbetts, Ian R.
Title Why can't young fish eat plants? Neither digestive enzymes nor gut development preclude herbivory in the young of a stomachless marine herbivorous fish
Journal name Comparative Biochemistry and Physiology B-Biochemistry and Molecular Biology   Check publisher's open access policy
ISSN 1096-4959
1879-1107
Publication date 2011-01-01
Year available 2010
Sub-type Article (original research)
DOI 10.1016/j.cbpb.2010.09.010
Volume 158
Issue 1
Start page 23
End page 29
Total pages 7
Editor Patrick J. Walsh
Thomas P. Mommsen
Leslie Lightheart
Place of publication Philadelphia, PA, U.S.A.
Publisher Elsevier
Collection year 2011
Language eng
Formatted abstract
Most young fishes lack the ability to function as herbivores, which has been attributed to two aspects of the digestive system: elevated nitrogen demand and a critical gut capacity. We compared the digestive morphology and biochemistry of two size classes of the marine herbivore Hyporhamphus regularis ardelio, pre-ontogenetic trophic shift (pre-OTS, < 100 mm) and post-ontogenetic trophic shift (post-OTS, > 100 mm), to determine what limits the onset of herbivory and how their digestive processes fit with current models of digestion. Two gut-somatic indices comparing gut length to body length (relative gut length) and body mass (Zihler's Index) demonstrated a significant decrease (RGL 0.59 → 0.49, P < 0.01; ZI 3.24 → 2.44, P < 0.01) in gut length relative to body size. There was little difference in enzyme activity between the two classes, with juveniles showing similar levels of carbohydrase and lipase and less protease compared with adults, indicating that juveniles did not preferentially target nitrogen and were as capable of digesting an herbivorous diet. These findings suggest that herbivory in this fish is not limited by the function of the post-oesophageal digestive tract, but rather the ability of the pharyngeal mill to mechanically process plants. Our findings offer partial support for the current model of stomachless digestion, indicating that further refinement may be necessary.
© 2010 Elsevier Inc. All rights reserved.
Keyword α-Amylase
alpha-Amylase
Trypsin
Lipase
Hemiramphidae
Halfbeak
RGL
Relative gut length
Zihler index
Plug-flow reactor
Adaptive modulation hypothesis
Pharyngeal mill
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ
Additional Notes Available online 25 September 2010.

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2011 Collection
School of Biological Sciences Publications
 
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Created: Thu, 24 Mar 2011, 21:58:09 EST by Gail Walter on behalf of School of Biological Sciences