This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Schooling fish have long fascinated us with their mesmerizing collective movements and seemingly perfect coordination. But a new study on clonal mollies suggests that this behavior is not innate.
During their first days of life, the fish still display distinct individual behaviors, and it is only around one month of age that they begin to form cohesive shoals, developing the coordinated movements characteristic of the group. However, several shoals of genetically identical clones begin to behave differently after a few weeks. The study was conducted by the Cluster of Excellence "Science of Intelligence (SCIoI)," the Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB), Humboldt Universität zu Berlin and UC Davis and published in Current Biology.
In the study, the research team analyzed the behavior of the Amazon molly (Poecilia formosa), a naturally clonal fish. Because these fish share an identical genetic heritage, they provide a unique opportunity to study how behavior develops. Using video recordings, the scientists observed 10 groups of four siblings over 55 days.
All the fish were reared together from birth under identical environmental conditions. Despite this standardization, significant differences in behavior developed between the groups. "A swarm is more than the sum of its parts.
This study of clonal fish shows that social experiences during development play a key role in the emergence of group behavior," said Dr. David Bierbach, an author of the study from the Cluster of Excellence "Science of Intelligence." The young mollies did not immediately behave as they typically do in cohesive groups of older fish. During the first two weeks of life, the distance between group members was largely what would be expected if the fish were moving independently.
From around three weeks onward, however, the fish increasingly began to stay together, with particularly pronounced changes beginning around day 30. Their movements also became more correlated, indicating that individuals were increasingly responding to one another. This gradual convergence suggests that social interactions become more important with age.
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