Black spot disease related to a trematode ectoparasite causes oxidative stress in Xyrichtys novacula

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Xyricthys novacula is very popular fish species in the Balearic Islands and a main target for recreational fishing. Over the last years, spots were observed on many individuals, which seems to be progressively more common. The aim of the present study was to identify the parasite, determine its abundance in a marine protected area (MPA) and in a non-protected one with more anthropic influence, and to evaluate the antioxidant and immune responses to this parasite presence by studying biomarkers in both liver and epithelial mucus. Analysis of genetic sequences established with 98.6–98.4% certainty that the parasite is a digenean fluke Scaphanocephalus sp. An average abundance of 12.3 ± 11.3 and 1.3 ± 1.3 parasites per individual was found for the non-protected area and the MPA, respectively. The activities of lysozyme and superoxide dismutase and total immunoglobulin concentration were significantly higher in mucus of X. novacula with more parasites. Similarly, in liver, a higher parasite load is related to higher activities of catalase, glutathione peroxidase and glutathione S-transferase, whereas malondialdehyde remained similar. In conclusion, Scaphanocephalus sp. affects X. novacula, inducing an immune and antioxidant response in epithelial mucus and in liver. The potential influence of the environment on parasite transmission, prevalence and abundance require further research to determine whether it makes fish more susceptible to infections.

This research was funded by Direccio ´ General de Política Universitaria ` i Recerca, Comunitat Autonoma ` de les Illes Balears AP_2021_012), by DG Pesca, Conselleria d'Agricultura i Pesca, Govern de les Illes Balears and, by the Biodibal project within the framework of the Collaboration Agreement between the University of the Balearic Islands and Red Electrica de Espana. ˜ A. Solomando was supported by an FPU contract with the Ministry of Science, Innovation and Universities from the Spanish Government (FPU18/04689). A. Sureda and S. Tejada were granted by the Programme of Promotion of Biomedical Research and Health Sciences, Instituto de Salud Carlos III (CIBEROBN CB12/03/30038).

Peer reviewed