Metformin Fish Behavior Study Retracted Over Falsified Animal Ethics Approval

PLOS One has retracted a 2018 study that reported environmental concentrations of the diabetes drug metformin altered aggressive behavior in the Siamese fighting fish, Betta splendens. The retraction notice, published on October 26, 2026, states that the paper's animal research approval was falsified and that no valid ethical authorization ever covered the experiments. The problems came to light after the corresponding author informed PLOS that the final paragraph of the Behavioral assay procedure subsection in the Materials and methods section was incorrect.

That paragraph had described the study's animal care and use approvals, a disclosure required under the journal's Animal Research policy. A representative of Merrimack College, the institution named in the study, told PLOS that a valid protocol approved by an Institutional Animal Care and Use Committee does not exist for the experiments reported in the paper. The representative further stated that approval from an external IACUC was never sought.

According to the retraction notice, this means the paragraph describing the approval was falsified. When those assurances turn out to be untrue, the journal's policy on Animal Research provides grounds for retraction, which is the basis the editors cited in this case. The retracted paper, authored by R. D. MacLaren along with K. Wisniewski and C. MacLaren, was published in May 2018 in PLOS One under the title reporting that environmentally relevant metformin concentrations affected aggressive behavior in Betta splendens.

The editorial process following the discovery was marked by non-response from the authors. According to the notice, RDM did not respond to the final editorial decision, while KW and CM either did not respond directly or could not be reached. The PLOS One Editors therefore proceeded with the retraction on the basis of the information provided by the corresponding author and the institutional representative.

The retraction notice carries the DOI 10.1371/journal.pone.0361363 and appears in volume 21, issue 10 of the journal. It links back to the original article, which was published in 2018 as PLoS One 13(5): e0197259 and indexed in PubMed under PMID 29763426. In this case, the editors identified the falsified ethics statement as the decisive concern under journal policy.

Subject of Research: Retraction of a 2018 PLOS One study on metformin exposure and aggressive behavior in Betta splendens due to a falsified animal ethics approval

Article Title: Retraction: Environmental concentrations of metformin exposure affect aggressive behavior in the Siamese fighting fish, Betta splendens

Article References: The PLOS One Editors (2026). Retraction: Environmental concentrations of metformin exposure affect aggressive behavior in the Siamese fighting fish, Betta splendens. PLOS One, 21(10), e0361363. https://doi.org/10.1371/journal.pone.0361363

Image Credits: AI Generated

DOI: 10.1371/journal.pone.0361363

Keywords: retraction, PLOS One, metformin, Betta splendens, animal research ethics, IACUC, Merrimack College, research integrity, pharmaceutical pollution, fish behavior, falsified approval, Environmental