Aquatic animals like fishes are living in both freshwater and salt water. They are herbivores, carnivores, or omnivores. The foods are different, depending on the fish species. The behaviors of smelling, touching or intaking things into mouth are different, owing to their utmost chemo-receptors of the fish species. Some species are well at smelling, touching, or tasting the foods or non-foods. Although the different species eat different kinds of foods, the feeding behavior of them are mostly followed with three basic stages.
The first stage of feeding consists of a visually directed orientation to the pellet followed by rapid intake into the fish mouth or oropharynx. The intake was produced by protrusion and opening of the fish jaws, along with depression of the floor of the branchial region. The pellet was transported immediately to the anterior pharynx, where it could be trapped between the palatal organ and the floor of pharyngeal cavity.
The second stage of feeding involves in sorting the edible or inedible things, which are consisted of two apparent behaviors. The first sorting behavior was rinsing, where adduction of the lower jaw and opercula produced a flow of water through the mouth and out the gill slits. The second behavior is back-washing, which is involved with adducting the opercula, protrusion of the upper jaw without opening the mouth, and depression of the floor of the oropharyngeal cavity. This behavior produces a reverse flow of water through the gill slits into the oropharyngeal cavity. Both sorting behaviors are infrequent and brief with unflavored pellets.
The third stage of feeding consists of the conclusion of the feeding sequence through either ingestion or rejection of the foods. Following sorting, the fish transported the unflavored foods to the posterior mouth, where the foods were masticated and swallowed. Rejection consists of compression of the oropharyngeal cavity and protrusion of the mouth, resulting in the foods being forcefully ejected from the oral cavity. Often, once the rejected food is outside of the fish mouth, the fish continues to seek other foods and follow the above consequence feeding behaviors.
Generally, when the fish feels hungry, it appears to seek foods and when the stomach is distended, the information of fullness in the stomach sends to the brain to reduce feeding response to the point of cessation. Since the foods are digested and passed through the intestine, the fullness of the stomach reduces and the brain causes to search for more foods. The time to empty the foods in the stomach influences the return of appetite, which assesses how many times the fish will feed within one day period.
This article is reviewed from: Gustatory control of feeding behavior in goldfish (Charles F. Lamb & Thomas E. Finger, 1995).
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