Remarkably high ingestion ratio of acidic food in juvenile marble goby, Oxyeleotris marmorata

Abstract

Behavioral test was conducted to determine the level of food pH which was preferable by the juvenile marble goby, <em>Oxyeleotris marmorata</em> (50 individuals or replicates; total length 6.6–7.0 cm) using agar gel pellets. Eight pH levels of agar gel pellets were prepared (pH 2.4, 3.0, 3.2, 3.4, 4.1, 4.9, 5.1, and the pure agar gel pellet without pH modification—pH 5.9). The ingestion ratio for each pH treatment of agar gel pellet was calculated, and the binary data (ingested or rejected) was analyzed using binomial test. Negative relationship was found between the ingestion ratio and pH level of the agar gel pellets. The highest ingestion ratio was found in the agar gel pellet with pH 2.4 (ingestion ratio, 94%), following by pH 3 (85%), pH 3.2 (3% agar gel powder; 65%), pH 3.2 (2% agar gel powder; 58%), pH 3.4 (24%), pH 4.1 (6%), pH 4.9 (6%), pH 5.1 (6%), and pH 5.9 (2%). The ingestion ratio of pH 2.4 agar gel pellet was significantly higher (<em>P</em> < 0.05) than that in the other treatments except that of pH 3.0. These results confirmed the taste preference of <em>O. marmorata</em> for acidic foods, and the most preferred was the one with pH 2.4–3.0.