Daily rhythms of leukocytes populations, biochemical and enzymatic blood parameters in a carnivorous freshwater catfish (Lophiosilurus alexandri)

ABSTRACT

The aim of this study was to investigate the daily rhythms of hematological, biochemical and enzymatic parameters of the blood of a nocturnal model of fish (Lophiosilurus alexandri) bred in the laboratory (F1). Thirty-six juveniles were stocked in six tanks of a recirculation aquaculture system for 20 days. The fish were exposed to a light:dark cycle of 12:12 h and were fed 1% of biomass twice a day with commercial diet. The daily rhythms of hematological, biochemical and enzymatic parameters were then measured at six sampling times “zeitgeber time = ZT” at four-hour intervals under light:dark 12:12 h (lights on = ZT0, at 8.00 a.m). No differences were observed to alkaline phosphatase, glucose, cortisol, aspartate aminotransferase, superoxide dismutase, total protein and hematocrit (p > 0.05). However, white blood cell count, Lymphocytes (LYN), Neutrophils (NEU), Eosinophil and Neutrophils to Lymphocytes ratio were significant different between sample times (p < 0.05). Also, a significant difference in alanine transaminase was observed, with a peak of production at nighttime. In contrast, glutathione peroxidase peaked at 8:00. Uric acid, magnesium and Calcium (Ca⁺⁺) showed statistically significant differences (p < 0.05). A significant difference was observed (p < 0.05), with a peak of albumin at 08:00 and triglycerides at 12:00, while cholesterol was low (p < 0.05) at 08:00 and higher from 12:00 to 04:00. Cosinor analysis revealed also rhythmicity to SOD, UA, Mg and Ca⁺⁺, ALB and CHO (p < 0.05). In conclusion, the time of day must be considered a key factor when using blood parameters as biomarkers for disease, health and welfare in the L. alexandri aquaculture.

KEYWORDS:

• Biological rhythms
• fish physiology
• homeostasis
• immune system
• stress oxidative enzymes

Acknowledgments

We thank Conselho Nacional de Desenvolvimento Científico e Tecnológico-CNPq-Brazil, Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – CAPES-Brazil, and Fundação de Amparo a Pesquisa de Minas Gerais-FAPEMIG-Brazil for financial support and funding for the authors, including Ronald K. Luz (CNPq –Proc. 305048/2015-5) and Rodrigo Fortes (Produtividade em Produtividade-PQ CNPq –No.305734/2016-4 and 401416/2014-3).

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Conselho Nacional de Desenvolvimento Científico e Tecnológico [305048/2015-5,305734/2016-4,401416/2014-3].