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Distinction between Gastric Digestion and Evacuation in Black Bass Fed Piscine Prey
Author(s) -
Wetzel James Edwin,
Kohler Christopher C.
Publication year - 2005
Publication title -
transactions of the american fisheries society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.696
H-Index - 86
eISSN - 1548-8659
pISSN - 0002-8487
DOI - 10.1577/t03-169.1
Subject(s) - micropterus , bass (fish) , dry matter , postprandial , bolus (digestion) , zoology , ingestion , chemistry , digestion (alchemy) , biology , food science , anatomy , fishery , biochemistry , chromatography , endocrinology , insulin
The terms “digestion” and “evacuation” are used interchangeably in studies of gastric processing in black basses Micropterus spp. We demonstrate that these processes are distinct and suggest that the differences may influence models involving the kinetics of gastric evacuation. Bolus (particulate matter) and residuum (bolus plus chyme (fluidized gastric contents)) sizes were used to examine gastric digestion (physical and chemical breakdown) and evacuation (passage of material from the stomach) in juvenile F 1 backcross hybrid backcross black bass (largemouth bass M. salmoides × (spotted bass M. punctulatus × largemouth bass)). Thirty‐five black bass (2.477–6.398 g), each fed a single female zebra danio Brachydanio rerio (wet weight = 139–619 mg), were sampled at 4.5 h postprandially. Dry‐matter contents of the bolus, chyme, and residuum were related to relative prandium (meal) size and black bass wet weight. The presence of detectable chyme dry matter at all prandium sizes demonstrated that gastric digestion and evacuation were distinguishable during at least a portion of postprandial gastric processing. At 4.5 h, postprandial digestion clearly exceeded evacuation, which indicated the potential for differences in kinetics between the two processes. When the disparity between gastric residuum and bolus weights (i.e., the chyme contribution) was ignored, gastric dry‐matter content was underestimated by approximately 30% (4.5 h postprandially). As relative prandium size increased, the disparity between estimated prandium, residuum, and bolus dry weights increased; bolus and prandium dry weights showed the greatest disparity. Increases in black bass size and relative prandium size increased the amount of evacuated dry matter (prandium minus residuum), suggesting that models relating consumption and evacuation rates must consider relative prandium size and predator size.