Stem cell proliferation and muscle hyperplasia continue during nutrient starvation in the atherinid fish Odontesthes bonariensis.

SIMO, I.; SCIARA, A.A.; ARRANZ, S.E.

Santiago de Compostela

Simposio; The International Symposium on Genetics in Aquaculture XII; 2015

Growth rateis the most important trait in aquaculture. Postembryonic muscle growth dependson proliferative myogenic precursor cells (MPCs). Refeeding after nutrientstarvation  is followed by a phase ofaccelerated growth known as compensatory growth. Although fish  show a particularly robust capacity for catchup growth, the biological mechanisms and the role of MPCs in this process remain elusive.To giveinsight into the basis of this process, pools of 200 mg fishes were set: acontrol group  was continuously fed and atreated group was starved for 2 weeks. At 7 and 10 days after  the start of the experiment fishes receivedan intra peritoneal injection of 5-ethynyl-2?-deoxyuridine in order to trackand label MPCs. Both weight and length of starved fishes were  significantly lower than controls(p<0.01). After starvation, a significant increase in the percentage offibers with a diameter lower than 20 µm was observed compared to control  group (p<0.01). Interestingly, the numberof fibers did not change between groups showing that hyperplasia but not hypertrophy continues during the fastingperiod. By quantifying the  MPCs wedemonstrated that proliferation continued during starved periods. In order togain insight into the relationship between body mass and muscle growth duringrefeeding, a new experiment was performed. Two different pools of 550 mg fisheswere set. A control group was continuously fed, while the second pool wasstarved for 2 weeks and then refed for another 2 weeks. Both weight and lengthof starved fishes were significantly lower than control group (p<0.01) but at the end of the experiment nosignificant differences  were observed.Like in previous experiment, the percentage of fibers with diameter lower  than 20 µm was significantly higher instarved fishes than in controls (p<0.01). The number  of muscle fibers increased along theexperimental period in both groups and did not differ  between them. At the end of the experiment nosignificant difference were observed on fiber muscle sizes of control and reefed fishes. The results show that themuscle gain during compensatory growth is mainly due to a compensatoryhypertrophy of small fibers generated during starvation.