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Histopathological description of iridophoromas resembling skin nodule syndrome in Siamese fighting fish Betta splendens

Oros, J; Priestnall, SL; Suarez-Bonnet, A


J Oros

SL Priestnall

A Suarez-Bonnet


Intensive breeding of the Siamese fighting fish Betta splendens, a species that inhabits marshlands in Thailand and other countries in south-east Asia, was traditionally focused on game fighting because the males are very territorial, but has evolved to become mainly devoted to ornamental purposes. Recently, a preliminarily named 'skin nodule syndrome' (SNS) has been described affecting this fish species in Thailand, with multiple bacterial infections suggested, including 4 species of Mycobacterium spp., although the etiology remains elusive. Here we describe the histopathological and immunohistochemical characteristics of 2 iridophoromas in 2 male Siamese fighting fish that strongly resemble the lesions described for SNS. Immunohistochemical analysis yielded negative results for Melan-A, PNL-2, and S-100, likely due to species-specific reasons. The results for molecular detection of mycobacterial DNA were also negative in both cases. The published histological lesions of SNS are very similar to the 4 chromatophoromas that have been reported affecting this species since 2015. Taken together with the present cases, we hypothesize that the preliminarily named SNS in fighting fish may be characterized as invasive chromatophoromas, although the true etiology remains to be elucidated and could include infectious and non-infectious causes. Further studies are necessary to examine whether commercial breeding of Siamese fighting fish has resulted in a possible genetic origin.


Oros, J., Priestnall, S., & Suarez-Bonnet, A. (2022). Histopathological description of iridophoromas resembling skin nodule syndrome in Siamese fighting fish Betta splendens. Diseases of Aquatic Organisms, 151, 23-27.

Journal Article Type Article
Acceptance Date Aug 18, 2022
Online Publication Date Sep 1, 2022
Publication Date 2022
Deposit Date Aug 10, 2023
Publicly Available Date Sep 1, 2023
Print ISSN 0177-5103
Publisher Inter Research
Peer Reviewed Peer Reviewed
Volume 151
Pages 23-27
Keywords Betta splendens; Chromatophoroma; Immunohistochemistry; Iridophoroma; Siamese fighting fish; DIFFERENTIATION; MELANOMA


Histopathological Description Of Iridophoromas Resembling Skin Nodule Syndrome In Siamese Fighting Fish Betta Splendens (192 Kb)


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