Effects of ploidy and nutritional conditions on muscle morphology, proliferation and myogenic proteins expression in Rhamdia quelen larvae

Abstract

Although Rhamdia quelen is a promising species for farming in South America, many aspects of its development and optimal conditions of culture remain unknown. In this sense, we explore muscle development and some proteins related to myogenic process in diploid and triploid larvae submitted to fasting-refeeding. Regarding muscle morphology, within diploid groups, fasted larvae (FD) showed a significant decrease in white muscle fiber area compared with control (CD) and refed (RD-1) groups. Then, when food was provided, area values restored nearly to control. Based on these results, it is probable that temporary muscle fiber atrophy takes place in fasted diploid fish. Conversely, no significant morphological changes were observed among triploid groups. When the effects of ploidy on somatic growth were assessed, FD and RT-1 groups registered a significantly higher percentage of fibers with an area smaller than 500 μm2 compared with fasted triploid larvae (FT) and RD-1 groups, respectively. Additionally, immunolocalization of the proliferating cell nuclear antigen (PCNA) decreased during starvation in fish of both ploidies and only recovered to normal after refeeding in triploid fish. An increase in PCNA related to ploidy was detected in CD and RD-1 compared with their triploid counterparts. In relation to myogenic proteins, Myog showed a significant increase expression in diploid larvae during starvation. Mstn was not affected by ploidy or alimentary variations. Our results show that diploid fish are more affected by short-term starvation than triploid fish, which could be indicative of differential physiological responses of diploid and triploid larvae to alimentary changes in culture. This might be relevant to optimize conditions of culture for both diploid and triploid fish.