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Why can't young fish eat plants? Neither digestive enzymes nor gut development preclude herbivory in the young of a stomachless marine herbivorous fish
Citation
Day, R and German, DP and Tibbetts, IR, 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. Part B, 158, (1) pp. 23-29. ISSN 1096-4959 (2011) [Refereed Article]
Copyright Statement
Copyright 2011 Elsevier
DOI: doi:10.1016/j.cbpb.2010.09.010
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, preontogenetic
trophic shift (pre-OTS, b100 mm) and post-ontogenetic trophic shift (post-OTS, N100 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, Pb0.01; ZI 3.24→2.44, Pb0.01) 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.
Item Details
Item Type: | Refereed Article |
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Keywords: | α-amylase, trypsin, lipase, Hemiramphidae, halfbeak, RGL, Zihler Index, plug-flow reactor, adaptive modulation hypothesis, pharyngeal mill |
Research Division: | Biological Sciences |
Research Group: | Zoology |
Research Field: | Animal structure and function |
Objective Division: | Environmental Management |
Objective Group: | Marine systems and management |
Objective Field: | Marine biodiversity |
UTAS Author: | Day, R (Dr Ryan Day) |
ID Code: | 95697 |
Year Published: | 2011 |
Web of Science® Times Cited: | 10 |
Deposited By: | Sustainable Marine Research Collaboration |
Deposited On: | 2014-10-07 |
Last Modified: | 2017-10-31 |
Downloads: | 0 |
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