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First published online December 10, 2003
Journal of Experimental Biology 207, 225-232 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.00741

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Postprandial response of gastric pH in leopard sharks (Triakis semifasciata) and its use to study foraging ecology

Yannis P. Papastamatiou^* and Christopher G. Lowe

Department of Biological Sciences, California State University Long Beach, 1250 Bellflower Blvd, Long Beach, CA 90840 USA

View larger version (39K): [in a new window]   Fig. 1. Continuous gastric pH measurements from six adult female leopard sharks Triakis semifasciata (Leo 1-6) fitted with a pH/temperature probe. Temperature is depicted in grey, pH in black. Arrows point to feeding events; numbers above arrows represent meal size (percentage of the shark's body mass). `?' indicates the point where a meal of unknown mass was consumed. All meals were squid except for that marked with an asterisk, where a meal of capelin Mallotus villosus was consumed.

View larger version (15K): [in a new window]   Fig. 2. Regression correlations between titration time and meal size in six adult leopard sharks. Sharks were fitted with pH/temperature probes and fed meals of squid. Meal size is expressed as both a percentage of the shark's body mass (A) and in kg (B).

View larger version (19K): [in a new window]   Fig. 3. Change in gastric pH of juvenile leopard sharks following ingestion of squid at 1% body mass. Samples of gastric fluid were removed from the shark's stomach, and pH readings corrected to a standardized value at 18°C. Values are means ± 1 S.D.; numbers above bars are sample sizes. Bars with the same letter are statistically insignificant from each other (see text for details).

View larger version (18K): [in a new window]   Fig. 4. Gastric pH changes in juvenile leopard sharks fed a meal of squid at 1% body mass Mb. Six sharks were fed a second meal of squid (1%Mb) 24 h after the first. The pH of the gastric fluid was determined 1 h after the second meal. All pH readings were corrected to a standardized temperature of 18°C. Values are means ± 1 S.D.; numbers above bars represent sample sizes. Bars with the same letter are statistically insignificant from each other (see text for details).