Efecto de la Ablación del Pedúnculo Ocular Sobre Variables Reproductivas, Inmunológicas y Metabólicas en Hembras Reproductoras de Macrobrachium americanum

Abstract

We evaluated the effect of eyestalk ablation in reproductive females of Macrobrachium americanum on reproductive, immunological and metabolic variables. The main goal was to analyze if removing the X Organ Sinus Gland reduce the time of moulting cycle and reproduction periods to obtain a greater number of spawnings per female. Two groups was arranged, the first group was a control and was not ablated (NA) n= 20 Females. The second group was unilaterally ablated (EA) n= 17 Females. Variables were recorded as time of moulting cycle, number of seedlings and the number of spawnings per organisms. For immunological variables (hemolymph clotting time, total number of hemocytes, and total phenoloxidase and profenoloxidasa), feeding rate, and metabolites (oxygen consumption, and concentration in haemolymph of glucose, lactate, total protein and triglycerides). Haemolymph samples were taken four days after hatching in each group. The 20 organisms in the NA group had 1 moulth, and then only 5 moulted a second time. While the 17 females EA had 1 first moult, 11 females presented a second moult, and a third molt occurred just in 1 organism. The average in time for moulting cycle in NA females was 31.2± 3.4 days, meanwhile for the group EA was 29.3 ± 5.4 days, no significant difference was detected P=0.212. Both groups showed only one spawn per female. Clotting time of hemolymph was not significantly different (P=1.00) between the EA group (41 seconds) and NA (36 seconds).Significant higher concentration of total number of hemocytes was observed in the EA group (P=0.0022). The NA group showed a mean activity of 4.19 of total proPO activity units ±2.4 in 20 μL of sample (SLH), the EA group showed 4.6±2.4 units of activity. Similar results were presented in the activity of the total FO. In both cases there were no significant differences (P=0.330 and P=0.521, respectively). Significant differences in the rate of food intake (P=0.007) with a higher consumption in the EA group (0.05±0.02 g food/g animal/day) than in NA (0.04 ± 0.01 g food/ g animal/day). Concentration of glucose in plasma of the EA group (28.9 ± 21.20 mg/dL) was lower, but not significant (P=0.166) when compared with the NA group (38.12 ± 17.3 mg / dL). In contrast, concentration of lactate, was lower in group NA (34.08 ± 14.5 mg/dL) and was not significantly different (P = 0.632) from EA group. Protein concentration in NA females was 417±182 mg/dL and it was not significant (P=0.935) from compared with EA group. Concentration of triglycerides was significantly lower (P=0.022) in the group NA (64.5±17.2 mg/dL). These results indicate that the ablation technique in order to generate greater number of larvae in less time is not recommended for this species as the molting cycle could not be reduced although by the presence of triglycerides in hemolymph, gonadal maturation was carried out, but these two processes were not synchronized, causing an unbalance in females limiting the production of eggs.