Haematological and metabolic profiles associated with age and sex in giant kokopu (Galaxias argenteus) (Gmelin 1789) broodstock

Abstract

This study characterized selected peripheral blood (PB) haematological parameters, liver, serum and muscle metabolic features in 3-and 5-year-old male and female giant kokopu (Galaxias argenteus) broodstock reared indoor at 16 C. Sex and age did not affect PB total cell count and haematocrit values. Nonetheless, higher erythrocytes in 5-year-old fish, elevated thrombocyte and lymphocyte counts in 3-year-old fish indicate age-specific cellular regulation. Higher thrombocyte counts in female fish suggest sex-specific regulation. At a metabolic level, liver abundance for long chain saturated fatty acids (FAs) was higher in males, whereas females had elevated levels of polyunsaturated FAs. Essential and non-essential amino acids (AAs) in liver and serum were also elevated in females compared to males. These findings suggest differential allocation of FAs and AAs to reflect requirements for gonadal, development and provisioning. Similarly, age significantly resulted in higher liver and serum abundances of some non-essential AAs in 3-year-olds compared to 5-year-old fish, suggesting higher metabolism in younger fish. Overall, results enhance our understanding of sex-and age-based differences in fish haematology, muscle, liver, and serum metabolite profiles in healthy G. argenteus. Future studies should carefully consider potential age-and sex-specific differences in metabolic responses.

Haematological and metabolic profiles of brooder giant kokopu, Galaxias argenteus (Gmelin 1789) based on sex and temperature

“…Assessment of selected peripheral blood haematological parameters and metabolite profiling of liver, muscle and serum samples were performed in 3‐year‐old male and female G. argenteus that had been cultured at 12°C and 16°C. Similar to previous findings by Valdebenito et al (2011) in G. maculatus , erythrocytes, thrombocytes, lymphocytes, monocytes and neutrophils were observed in G. argenteus blood (Lulijwa, Alfaro, Venter, et al, 2021; Lulijwa, Alfaro, Young, et al, 2021).…”

“…The lack of temperature‐specific effect on haematological parameters may suggest within range acclimation temperatures (12°C and 16°C), stress absence or adaptation. However, mean haematocrit values were within the typical 20%–35% range for G. maculatus and most teleosts (Clark et al, 1979; Lulijwa, Alfaro, Venter, et al, 2021; Lulijwa, Alfaro, Young, et al, 2021; Urbina & Glover, 2012). Haematocrit values are a stress signal and increase with stressful acclimation temperatures (Cho et al, 2015; De et al, 2019).…”

“…Previous studies show that sex influences the teleost liver metabolome (Lulijwa, Alfaro, Venter, et al, 2021; Ong et al, 2009; Qiao et al, 2016). In this study, the sex‐specific liver metabolites can be linked to AA metabolism.…”

“…Metabolomics is already being used in aquaculture with promising application potential (Raposo de Magalhães et al, 2020). Fish metabolism can equally be influenced by sex (Johnston et al, 2020; Lulijwa, Alfaro, Venter, et al, 2021; Qiao et al, 2016) and water temperature (Costas et al, 2012; Malekar et al, 2018; Song et al, 2019).…”

“…Selected haematology and physiological analyses have been conducted with inanga ( Galaxias maculatus ) (Urbina & Glover, 2012; Urbina et al, 2013; Valdebenito et al, 2011), but not G. argenteus . Although G. argenteus is economically important to New Zealand (Wylie et al, 2016), literature on haematology and metabolism remains sparse (Lulijwa, Alfaro, Venter, et al, 2021). Moreover, fundamental information is needed to enable comparative monitoring of health status in wild and cultured stocks.…”