Behavior and gustatory reception of air-breathing catfishes (Clariidae)

Abstract

Taste preferences to classical taste substances and L-isomers of free amino acids and feeding behavior are analyzed in clariids Clarias gariepinus, C. macrocephalus, and C. batrachus and the hybrid between C. macrocephalus (female) and C. gariepinus (male). It is found that citric acid (0.26 M) is palatable for all studied clariids, and the presence of this acid in agar-agar pellets considerably increases their consumption by fish. The stimulating effect of citric acid on C. gariepinus and C. macrocephalus is greater than the effect of water extracts of organisms consumed by these species or of artificial foods. Sucrose (0.29 M) is palatable for both species. The palatability of sodium chloride (1.73 M) and calcium chloride (0.9 M) is the same for C. gariepinus and the hybrid but different for C. macrocephalus (p < 0.05), indicating the patroclinous type of taste preference inheritance. Of the 21 free amino acids (0.1–0.001 M), 17 are palatable for C. gariepinus (methionine, alanine, glutamine, cysteine, histidine, etc.) and four are indifferent (arginine, leucine, isoleucine, and tryptophan). No amino acid is found to be deterrent for the studied fishes. All studied fishes typically consume or reject pellets after a single intraoral testing; repeated grasping of pellets is extremely rare. The total time clariids spend on intraoral testing and consumption or rejection of one pellet is at most 3–5 s. Clariids captured in their natural environments (C. macrocephalus and C. batrachus) require considerably more time for acclimation to aquarium conditions than clariids taken from the aquaculture (C. gariepinus and the hybrid): at least one month and several days, respectively. The stress response to handling in wild fish includes the release of large amounts of skin mucus.