ABSTRACT
Ecdysis is a common phenomenon that happens throughout the life phase of the giant freshwater prawn Macrobrachium rosenbergii. It is vital to better understand the correlation between cannibalism and biochemical compound that exists during the moulting process. The objective of the present study was to determine the amino acid profile released by M. rosenbergii during the ecdysis process that promotes cannibalism. To accomplish this, changes in amino acid levels (total amino acid (TAA) and free amino acid (FAA)) of tissue muscle, exoskeleton, and sample water of culture medium from the moulting (E-stage) and non-moulting (C-stage) prawns were analysed using high-performance liquid chromatography (HPLC). Comparison study revealed that among the TAA compounds, proline and sarcosine of tissues from moulting prawn were found at the highest levels. The level of FAA from water that contains moulting prawns (E-stage) was dominated by tryptophan and proline. Significant values obtained in the present study suggested that these amino acid compounds act as a chemical cue to promote cannibalism in M. rosenbergii during ecdysis. The knowledge of compositions and compounds that were released during the moulting process should be helpful for better understanding of the mechanism and chemical cues that play roles on triggering cannibalism, and also for future dietary manipulation to improve feeding efficiencies and feeding management, which indirectly impacts productivity and profitability.
ABSTRACT
As one of the most important aquatic fish, Micropterus salmoides suffers lethal and epidemic disease caused by rhabdovirus at the juvenile stage. In this study, a new strain of M. salmoides rhabdovirus (MSRV) was isolated from Yuhang, Zhejiang Province, China, and named MSRV-YH01. The virus infected the grass carp ovary (GCO) cell line and displayed virion particles with atypical bullet shape, 300–500 nm in length and 100–200 nm in diameter under transmission electron microscopy. The complete genome sequence of this isolate was determined to include 11 526 nucleotides and to encode five classical structural proteins. The construction of the phylogenetic tree indicated that this new isolate is clustered into the Vesiculovirus genus and most closely related to the Siniperca chuatsi rhabdovirus. To explore the potential for a vaccine against MSRV, a glycoprotein (1–458 amino acid residues) of MSRV-YH01 was successfully amplified and cloned into the plasmid pFastBac1. The high-purity recombinant bacmid-glycoprotein was obtained from DH10Bac through screening and identification. Based on polymerase chain reaction (PCR), western blot, and immunofluorescence assay, recombinant virus, including the MSRV-YH01 glycoprotein gene, was produced by transfection of SF9 cells using the pFastBac1-gE2, and then repeatedly amplified to express the glycoprotein protein. We anticipate that this recombinant bacmid system could be used to challenge the silkworm and develop a corresponding oral vaccine for fish.