Chemical reactor models of optimal digestion efficiency with constant foraging costs

Logan, J. David; Joern, Anthony; Wolesensky, William

doi:10.1016/s0304-3800(03)00202-3

Cited by 17 publications

(10 citation statements)

References 33 publications

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“…Accordingly, the aim of some of the studies was to study the whole‐organism digestive and absorptive responses to different feeding conditions rather than to describe the detailed dynamics of individual prey in the fish stomach as in the present study. The chemical reactor theory (Penry & Jumars, 1987; Jumars, 2000 a , b ; Logan et al , 2003), which provides a compromise between mechanistic detail and whole‐organism responses (Logan et al , 2002), should prove useful for such studies. Presenting mechanistic details about the combined mechanical and chemical processes in the stomach of a predatory fish, the surface‐dependent cylinder model of gastric evacuation may, in return, provide an extension to the chemical reactor theory.…”

Section: Discussionmentioning

confidence: 99%

How are prey fishes of multiple meals evacuated from the stomach of a piscivorous fish?

Andersen

Beyer

2007

Journal of Fish Biology

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The observations that the gastric evacuation of a meal was accelerated after ingestion of an additional meal, whereas the evacuation of the latter meal was slowed down were compared to the predictions of mass-dependent models derived from experiments on evacuation of single meals. In contrast, the present study on cod Gadus morhua fed identical double meals of sandeel Ammodytes tobianus demonstrated that the evacuation of each meal was slowed down relative to the evacuation of a single meal. This fact could be explained by the exposed meal surface area being reduced while the meals were together in the stomach as it was expected by a surfacedependent cylinder interpretation of the square-root model. The cylinder model forecasted accurately the observed evacuation of each meal in the double-meal situation. The simple surface considerations of the model further explained the discrepancies between observed and expected evacuation rates using mass-dependent models, which suggested that the above finding of the previous studies was an artefact. The ability of the cylinder model to predict properly also the evacuation of multiple meals in juvenile coho salmon Oncorhynchus kisutch indicated that the model would apply to gastric evacuation in small-sized predatory fishes as well. This should increase considerably its value as a generic tool for studies on the feeding biology of fishes in the wild.

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Section: Discussionmentioning

confidence: 99%

How are prey fishes of multiple meals evacuated from the stomach of a piscivorous fish?

Andersen

Beyer

2007

Journal of Fish Biology

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“…Modeling has facilitated research that links digestive physiology with whole animal nutrition in production agriculture with vertebrates (380, 384) and aquaculture with invertebrates (376), and with ecological phenomena such as foraging ecology (298, 468) and community structure (353, 469). Modeling has also contributed to understanding impacts of temperature change (297, 474) that could improve predictions of animal responses to climate change (13).…”

Section: Digestive Designs That Match Gi Architecture To Food Composimentioning

confidence: 99%

Comparative Digestive Physiology

Karasov

Douglas

2013

Comprehensive Physiology

261

221

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In vertebrates and invertebrates, morphological and functional features of gastrointestinal (GI) tracts generally reflect food chemistry, such as content of carbohydrates, proteins, fats, and material(s) refractory to rapid digestion (e.g., cellulose). The expression of digestive enzymes and nutrient transporters approximately matches the dietary load of their respective substrates, with relatively modest excess capacity. Mechanisms explaining differences in hydrolase activity between populations and species include gene copy number variations and single-nucleotide polymorphisms. Transcriptional and posttranscriptional adjustments mediate phenotypic changes in the expression of hydrolases and transporters in response to dietary signals. Many species respond to higher food intake by flexibly increasing digestive compartment size. Fermentative processes by symbiotic microorganisms are important for cellulose degradation but are relatively slow, so animals that rely on those processes typically possess special enlarged compartment(s) to maintain a microbiota and other GI structures that slow digesta flow. The taxon richness of the gut microbiota, usually identified by 16S rRNA gene sequencing, is typically an order of magnitude greater in vertebrates than invertebrates, and the interspecific variation in microbial composition is strongly influenced by diet. Many of the nutrient transporters are orthologous across different animal phyla, though functional details may vary (e.g., glucose and amino acid transport with K+ rather than Na+ as a counter ion). Paracellular absorption is important in many birds. Natural toxins are ubiquitous in foods and may influence key features such as digesta transit, enzymatic breakdown, microbial fermentation, and absorption

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“…2003), digestion can become rate limiting (‘digestive bottleneck’; Kersten & Visser 1996), in which case only maximization of digestion rate maximizes the total amount of food absorbed (Jeschke 2007). Rate maximization over digestive processes has received relatively little attention (McWilliams & Karasov 1998; Raubenheimer & Simpson 1998; Jumars 2000; Logan, Joern & Wolesensky 2002, 2003) and will be the main focus of this study.…”

Section: Introductionmentioning

confidence: 99%

Longer guts and higher food quality increase energy intake in migratory swans

Gils

Beekman

Coehoorn

et al. 2008

Journal of Animal Ecology

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1. Within the broad field of optimal foraging, it is increasingly acknowledged that animals often face digestive constraints rather than constraints on rates of food collection. This therefore calls for a formalization of how animals could optimize food absorption rates. 2. Here we generate predictions from a simple graphical optimal digestion model for foragers that aim to maximize their (true) metabolizable food intake over total time (i.e. including nonforaging bouts) under a digestive constraint. 3. The model predicts that such foragers should maintain a constant food retention time, even if gut length or food quality changes. For phenotypically flexible foragers, which are able to change the size of their digestive machinery, this means that an increase in gut length should go hand in hand with an increase in gross intake rate. It also means that better quality food should be digested more efficiently. 4. These latter two predictions are tested in a large avian long-distance migrant, the Bewick's swan (Cygnus columbianus bewickii), feeding on grasslands in its Dutch wintering quarters. 5. Throughout winter, free-ranging Bewick's swans, growing a longer gut and experiencing improved food quality, increased their gross intake rate (i.e. bite rate) and showed a higher digestive efficiency. These responses were in accordance with the model and suggest maintenance of a constant food retention time. 6. These changes doubled the birds' absorption rate. Had only food quality changed (and not gut length), then absorption rate would have increased by only 67%; absorption rate would have increased by only 17% had only gut length changed (and not food quality). 7. The prediction that gross intake rate should go up with gut length parallels the mechanism included in some proximate models of foraging that feeding motivation scales inversely to gut fullness. We plea for a tighter integration between ultimate and proximate foraging models.

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Chemical reactor models of optimal digestion efficiency with constant foraging costs

Cited by 17 publications

References 33 publications

How are prey fishes of multiple meals evacuated from the stomach of a piscivorous fish?

How are prey fishes of multiple meals evacuated from the stomach of a piscivorous fish?

Comparative Digestive Physiology

Longer guts and higher food quality increase energy intake in migratory swans

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