Comparative Research Of Growth And Ingestion And Digestive Level Of Different Young Fish Of Siniperca Species

To further understand the physiological mechanism of growth speed of different mandarin fish, the relationship between growth rates and daily food intake, pepsin activities, relative expression of pepsinogen PG A1, PG A2, PG C in stomach of juveniles of S. chuatsi, S. scherzeri and their hybrids(S. scherzeri ♀×S. chuatsi ♂ F1) were compared and analyzed during 30 days experiment. Results showed that average growth weight(AGW) of the three species was(1.171± 0.180) g/d of S. chuatsi,(1.019± 0.104) g/d of hybrids,(0.433± 0.078) g/d of S. scherzeri respectively, their growth rates ranked as S. chuatsi > F1> S. scherzeri. Daily food intake of the three species was(6.1±0.31) g/d of S. chuatsi,(4.24±0.23) g/d of S. scherzeri and(5.26±0.33) g/d of hybrids respectively. S. chuatsi was higher than hybrids and S. scherzeri. The maximum specific pepsin activity was found in stomach, specific pepsin of the three species was(347.8±13.3) U/g of S. chuatsi,(272.1±10.9) U/g of S. scherzeri(303.4±12.1) U/g of hybrids respectively during later periods. Among the three species pepsin activities ranked as S. chuatsi > F1 >S. scherzeri. Gastric PGs m RNA expression of three species all increased during the experiment. Proportion of PGC: PGA1: PGA2 was 1.1:1.0:0.7.The highest expression level of PGs was observed in S. chuatsi, PGs expression of F1 was slightly higher than S. scherzeri(P<0.05). Growth rate was direct correlation with amount of food intake of the three Siniperca species, and there was a corresponding relationship between amount of food intake and digestive capacity.Structure characterization of stomach, intestines and pyloric caecum of Siniperca chuatsi, S. scherzeri and their hybrid(S. scherzeri ♀×S. chuatsi♂) was compared via paraffin section technique. Stomach wall consisted of mucous, sub mucosa and muscular layers, lamina propria could be seen in the mucous layer, three Siniperca species shared the same structure. Relative thickness of mucous layer of S. chuatsi and the hybrid was 0.30±0.09, 0.30±0.11 respectively, relative thickness of S. scherzeri was 0.21±0.13, which was much thinner than the other two species. Intestines consisted of villus, mucous, submucosa, and muscular layers. Inner wall formatted many wrinkles, and goblet cells existed in villus layer. There was no significant difference on wrinkle number and density of goblet cells between S. chuatsi and hybrid, while these data of S. scherzeri was significantly lower than S. chuatsi and the hybrid(P<0.05). The mean number of pyloric caecum of S. chuatsi, S. scherzeri and the hybrid was 213.8±17.3, 79.3±13.2 and 109.8±21.8, respectively. The structure of pyloric caecum was similar to intestines, there was no significant difference among three Siniperca species on wrinkle number, but density of goblet cells of S. scherzeri was significantly lower than that of S. chuatsi and the hybrid(P<0.05). The distribution characterization of oxynticopeptic cells of three Siniperca species was compared via in situ hybridization technique. The deep purple hybridization signals of three pepsinogen probes(PG A1, A2 and C) were all detected in the gastric cell of mucous layer. Within the same species, there was no significant difference among hybridization signal cells of PG A1, A2 and C probes(P>0.05). Among three Siniperca species, density of hybridization signal cells by the gene probes(PG A1, A2, and C) ranked from high to low as: S. chuatsi = hybrid > S. scherzeri, and there was significant difference among them(P<0.05). Structure difference of digestive tract and distribution characterization of oxynticopeptic cells provided some scientific base for further study of fish digestion physiology.