Molecular investigation on the presence of monodon slow- growth syndrome (MSGS) in the green tiger shrimp Penaeus semisulcatus in Egypt; biofloc as a control measure

Juveniles of Penaeus semisulcatus were sampled from shrimp farms and were sorted into four categories; small-negative, large-negative, small-positive and large-positive groups based on the size of the shrimp. Levels of MIH-1 and CHH-1 transcripts, peptide, ecdysteroid, glucose and glycogen were determined. The highest levels of MIH-1 were noticed at early pre-molt stage, while the lowest was noticed at inter-molt stage. However, the relative expression level of CHH-1 transcript in the optic lobe from the inter-molt stage of all different shrimp categories (large-negative, small-negative, large-positive and small-positive, was significantly different (P<0.05). Rabbit anti-MIH-1 antibody at 1:10,000 dilutions was bound to rMIH-1 without cross reactivity to with rCHH-1 or rGIH, whereas the anti-CHH antibody was bound to rCHH-1, without cross reactivity to rMIH or rGIH. The haemolymph ecdysteroid level was 90-100 ng/ml at late pre-molt stage and significantly different (P<0.001) from the post-molt, inter-molt and early pre-molt stages. The average glycogen concentration of the hepatopancreas of large-positive shrimp was not significantly different (P>0.05) from small- and large-negative shrimp. Similarly, no significant difference (P>0.05) was noticed in the average glycogen concentration of hepatopancreas between small-negative and large-negative shrimps. The average glucose concentration in haemolymph of large-positive shrimp was not significantly different (P>0.05) from small-negative and large-negative shrimps. Two low protein diets (^~20BFd_20.13 and ^~22BFd_22.20) and two biofloc (BFd_Sucrose and BFd_Glucose) were prepared in addition to control (35% crude protein). The lowest glucose concentration was estimated in the control (13.45±2.15 µg/ml), and the highest glucose concentration was found in BFd_Glucose (75.01±2.31 µg/ml), followed BFd_Sucrose (45.32±1.32 µg/ml), ^~20BFd_20.13 (43.51±3.21 µg/ml) and ^~22BFd_22.20 (40.21±3.12 µg/ml). Pleopod tissues from shrimp P. semisulcatus grown in biofloc, low protein diets, and control were tested by RT-PCR. LSNV was not detected in P.semisulcatus grown in biofloc, low protein diets, compared to control. This study revealed that biofloc treatments and low protein diets could enhance growth rates and control MSGS in P. semisulcatus.