International Journal of Aquaculture, 2024, Vol.14, No.1, 9-19 http://www.aquapublisher.com/index.php/ija 14 organelles can undergo breakdown, releasing stored fatty acids into the cellular environment, thereby causing a decrease in the overall fatty acid levels (Meyers et al., 2019). Previous studies in copepods have shown an increase in the number of intracellular membranes under cold conditions. This is believed to be a compensatory mechanism that reduces the diffusion path length of metabolites, thereby counteracting the reduced diffusivity constants (Mäkinen et al., 2017; Werbrouck et al., 2017). Ectotherms maintain physiological functions by restructuring the lipid composition of biological membranes when temperatures keep changing (Martin-Creuzburg et al., 2012;). When copepods are exposed to both starvation and heat, it is observed that their storage fatty acid (FA) pool loses its buffering function, leading to increased mortality rates (Werbrouck et al., 2017). The fatty acid profile of Thermocyclop sp. in the present study was dominated by SFAs and MUFAs with lower concentrations of PUFAs at different storage temperatures. Similar studies (McKinnon et al., 2015) observed that the FA composition of Calanoid copepods Bestiolina similis and Parvocalanus crassirostris were dominated by SFAs (16:0, 18:0, 14:0) and MUFAs (22:1, 20:1) and that the EFA, DHA, and EPA were present in smaller proportions and lipid peroxidation was identified as the main cause of this phenomenon (Camus et al., 2021). Among the various classes of fatty acids (FAs), polyunsaturated fatty acids (PUFAs) are particularly susceptible to lipid peroxidation. Once lipid peroxide radicals are formed, they can initiate an autocatalytic chain reaction of lipid peroxidation (Gladyshev et al., 2015; McKinnon et al., 2015). Additionally, the short-term storage minus feeding at 12 °C reduced SFA composition compared to 4 °C. Cold temperatures are also thought to increase the membrane lipid order but can be compensated by first and second cis-double bond insertions in the fatty composition of the cyclopoid membrane. Therefore, this might explain the higher levels of SFAs in the copepods under 4 °C in this study (Werbrouck et al., 2017). The composition of palmitic acid remained higher than other SFAs across all temperatures. As such, the storage of copepods at the study temperatures might have not compromised palmitic acid levels which is a key metabolite in fish growth (Osibona et al., 2006). Furthermore, the higher composition of PUFAs observed in this study at 8 °C and 12 °C storage temperatures demonstrate the viability of storing the copepods at these temperatures. Similar results were observed in copepod Eudiaptomus gracilis, with higher levels of PUFAs especially EPA and DHA (Koussoroplis et al., 2014). It is imperative to note that essential fatty acids like EPA and DHA in copepods form a cornerstone of the nutritional requirements for larval fish. The presence of these essential nutrients in copepod diets directly influences larval development, health, immune function, and overall success in both natural ecosystems and aquaculture settings. Besides these fatty acids are responsible for maintaining copepods’ membrane fluidity (Gladyshev et al., 2015). 2.4 Implications of the study The study offers a pathway towards optimizing copepod-based feeding strategies, a critical component in aquaculture. Given the essential role of copepods in the diets of fish larvae, understanding how storage conditions influence their fatty acid profiles allows fish farmers to make informed decisions. This optimization can result in healthier and faster-growing fish larvae, contributing to the success of aquaculture operations. By implementing optimal storage conditions for Thermocyclop sp., aquaculture operations align with the broader goals of sustainable aquaculture. The efficiency gained in live feed management not only improves economic viability but also reduces environmental impact and promotes the responsible use of resources, contributing to the long-term sustainability of the industry. Economically, implementing optimal storage conditions for copepods can have positive implications for aquaculture operations. Improved survival rates and enhanced nutritional quality may translate into more efficient and cost-effective practices, positively impacting the economic viability of the aquaculture industry. 3 Materials and Methods 3.1 Culture of Micro-algae The culture of micro-algae was achieved following the protocol from (Izaara et al., 2020). Initial stock of the micro-algae was sourced from Sewerage treatment lagoons of the National Water and Sewerage Corporation (NWSC)-Entebbe. Serial dilution followed by multiple sub-cultures using Bold’s Basal Medium (BBM) was used to achieve a pure stock of the micro-algae as modified by Izaara et al. (2020). Rectangular glass tanks (25 L) were utilized for the culture of the micro-algae. To facilitate maximum exposure of the micro-algae to light for better
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