Abstract

We report unusual occurrences of retinal neoplasia in aquarium-housed striped bass (12/51 - prevalence of 23% over a 2.5-year period) and pajama cardinalfish (6/6 - prevalence of 100% over 1 year). These wild-born fish have been maintained in saltwater indoor closed systems at 12°C for bass and 25°C for cardinalfish. Unilateral exophthalmia/buphthalmia, due to retro-retinal masses often extending into the retro-orbital space, was the usual clinical presentation of this syndrome. Enucleations and resections of the retro-orbital masses were performed on 11 bass and five cardinalfish. Histologically, these masses originated from retinal cells and had characteristic features of retinoblastoma-like tumors, including Flexner-Wintersteiner rosette formations. Based on the ability of fish retinal cells to regenerate (as opposed to mammals), a diagnosis of non-embryogenic retinal neoplasm was given. Post-surgery survival was 1–545 days (median 225) for bass and 1–176 days (median 21) for cardinalfish. Two bass are still alive 15 and 18 months post-surgery. Reoccurrence of the tumor was the main cause of death. The cause of these ocular tumors is unknown. Nevertheless, it is speculated that the exposure to high-energy blue light waves produced by metal-halide lamps might induce retinal damage, which would elicit retinal regeneration and could therefore promote the development of retinal neoplastic changes. The absence of this syndrome in bass and cardinalfish from the same cohorts housed in a different lighting set-up supports this hypothesis. Due to their nocturnal adaptation, cardinalfish might be more sensitive to retinal damages by blue light waves than other species of reef fish.

* Presenting author