Social stress adversely affects digestive function in subordinate cichlid fish

In the study of Central American convict cichlid fish, CBN scientists Ryan L. Earley, Ph.D. and Matthew Grober, Ph.D. of Georgia State University, and Lawrence Blumer, Ph.D. of Morehouse College, compared bile retention and gall bladder size in dominant and subordinate males that had eaten equal amounts of food.

The scientists discovered not only were the gall bladders in the subordinate fish much larger, they were filled with dark "bad bile," unlike the pale bile in the dominant fish. The difference in gall bladder function also likely contributed to subordinate fish growing more slowly than the dominant ones. Cichlids have rigid dominance hierarchies, providing excellent models for the study of social stress. Previous cichlid studies have determined that the chronic stress of social subordination has other physiological consequences, including changes in body weight and hormones.

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