Complete Genome Sequence of Macrobrachium rosenbergii Golda Virus (MrGV) from China

In a meta-transcriptome study of the giant freshwater prawn Macrobrachium rosenbergii sampled in 2018 from a hatchery, we identified a variant of Macrobrachium rosenbergii golda virus (MrGV) in postlarvae without clinical signs. The virus belongs to the family Roniviridae, and the genome of this MrGV variant, Mr-18, consisted of 28,957 nucleotides, including 4 open reading frames (ORFs): (1) ORF1a, encoding a 3C-like protein (3CLP) (4933 aa); (2) ORF1b, encoding a replicase polyprotein (2877 aa); (3) ORF2, encoding a hypothetical nucleocapsid protein (125 aa); and (4) ORF3, encoding a glycoprotein (1503 aa). ORF1a overlaps with ORF1b with 40 nucleotides, where a −1 ribosomal frameshift with slippage sequence 5′-G14925GGUUUU14931-3′ produces the pp1ab polyprotein. The genomic sequence of Mr-18 shared 97.80% identity with MrGV LH1-2018 discovered in Bangladesh. The amino acid sequence identities between them were 99.30% (ORF1a), 99.60% (ORF1b), 100.00% (ORF2), and 99.80% (ORF3), respectively. Phylogenetic analysis of the RNA-dependent RNA polymerase (RdRp) proteins revealed that they clustered together and formed a separate cluster from the genus Okavirus. The finding of MrGV in China warrants further studies to determine its pathogenicity and prevalence within the region.

Assessment of Tilapia–Freshwater Prawn Co-Culture Schemes in Tanks and Lake-Based Cages for Increased Farm Production

The technical viability of tilapia (I-ExCEL strain Nile or red) and giant freshwater prawn (GFP) co-culture in cages-within-tanks was evaluated while appropriate feeding protocols for tilapia-GFP co-culture in cages in a eutrophic lake were determined. Specifically, production parameters in all test species grown for five months in tank co-culture (where only tilapias were fed) were compared, while the best feeding protocol from among the following treatments: (a) Tfed—fed tilapias; (b) GFPfed—fed prawns and (c) T-GFPfed—both species fed, were defined. I-ExCEL Nile tilapias grew faster in tank co-culture whether reared singly or otherwise. However, red tilapia-GFP tank co-culture gave the best results considering key production traits in all test species (red tilapia —2.52%/day specific growth rate or SGR, 83.3% survival; GFP—1.17%/day SGR, 72.85% survival). Lake-based co-culture was technically feasible at stocking densities of 12.5/m2 for tilapia and 2.4 to 4/m2 for prawns even when only tilapias were fed; prawns grew to desired marketable sizes by thriving mainly on detritus and natural food organisms in the lake. However, further refinements can still be made to optimise the co-culture schemes to make them more sustainable and provide artisanal fish farmers options in increasing farm yields through multi-species aquaculture.

Features of arthropod cultivation in the closed water supply installations on the example of a giant freshwater prawn

The cultivation of arthropods in closed water supply installations is a promising area for the development of commercial aquaculture in Russia. The giant freshwater prawn Macrobrachium rosenbergii is gradually becoming an aquaculture species of great commercial value, since it is the largest representative of its genus. In experiment for the prawn containing 3 tanks of the same size were used. The shrimps in the first tank were fed mainly plant food, but with a small proportion of animal food. In the second tank, animal feed was used. In the third tank, the shrimp diet consisted of 80% balanced artificial feed. The percentage of losses was 30, 20 and 7%, respectively. From the experiment, it became clear that main problems characteristic of all decapods, including the giant freshwater prawn, are the lack of high-quality and balanced artificial feeds, as well as problems associated with a decrease in the genetic diversity of artificial populations, which makes it more difficult and expensive to obtain seeding material. Cultivation of giant freshwater prawn in Russia can be quite cost-effective when using closed water supply installations, however, in order to achieve maximum benefits, it is necessary to develop artificial, optimized feeds designed specifically for crustaceans.

Lentiviral-Transduced Ectopic Expression of Androgenic Hormone in a Crustacean Hematopoietic Primary Cell Culture

Novel monosex biotechnologies in crustacean aquaculture involve the induction of sex reversal through manipulations of the androgenic gland (AG), and its most prominent factor, the insulin-like androgenic gland (IAG) hormone, during early developmental stages. In the giant freshwater prawn Macrobrachium rosenbergii, all-female populations are desirable for aquaculture, since the females can be stocked at higher densities and exhibit more uniform growth than males. Recently, a novel biotechnology for all-female aquaculture was developed based on injection into post-larvae of suspended primary AG cells from mature M. rosenbergii males. However, this biotechnology depends on the availability of appropriate male donors and it requires delicate surgical procedures on the small endocrine AG to produce appropriate quantities of cells for the sex manipulation. We therefore established a new platform for the production of M. rosenbergii IAG (Mr-IAG) in hematopoietic cells. The method rests on the induction of ectopic Mr-IAG expression under the white spot syndrome virus (WSSV) immediate-early 1 (IE1) promoter via a novel lentiviral vector. Our results demonstrate that M. rosenbergii primary cells infected with the Mr-IAG lentiviruses are capable of transcription, translation, and secretion of Mr-IAG in culture. Our new platform, which produces easy-to-harvest cells in abundance, could replace the AG cells used in the first step of the above-mentioned biotechnology for all-female aquaculture and, importantly, pave the way for producing monosex populations in other edible crustacean aquaculture species. In addition, a lentiviral system for crustacean cells provides a useful tool for basic and applied research in crustacean species.

MINI WHEEL APPLICATION ON HOUSEHOLD SCALE AQUACULTURE OF GIANT FRESHWATER PRAWNS (Macrobranchium rosenbergii)

Giant freshwater prawns, one of the freshwater aquaculture commodities which has high economic value and has wide market opportunity. Dissolved oxygen on giant freshwater prawn aquaculture is the one of necessary part on a prawn weight gain. Availability of dissolved oxygen can be increased by optimalization on mini wheel and blower use. Mini Wheel is a part of aquaculture technology application, especially on household scale aquaculture of giant freshwater prawn (M. rosenbergii). This assembly used recycle material which can still be used. This mini wheel was modified by 3 treatments, that A (blower without mini wheel pond treatment); B (one-propeller mini wheel pond treatment); C (two-propeller mini wheel pond treatment). This research used quantitative method and every treatment should has three repetitions. Aquaculture a household scale by applying mini wheel designed to find out its effect on water quality and growth of giant freshwater prawn (M. rosenbergii), with parameter ABW (Average Body Weight), ADG (Average Daily Growth), FCR (Feed Convertion Ratio) and SR (Survival Rate). This research showed that there is a significant difference between two-propeller mini wheel pond treatment, one-propeller mini wheel pond treatment and blower without mini wheel pond treatment. The optimum Dissolved Oxygen value on two-propeller mini wheel pond treatment was about 9 mg/L (morning and afternoon testing), Pond temperature on range 280C, and also pH has stability on 7. The best growth was found in two-propeller mini wheel pond treatment with Survival Rate (SR) 93%, Average Body Weight (ABW) 10 g/prawn, Average Daily Growth (ADG) 0.11 g/prawn, and Feed Convertion Ratio (FCR) 1.5.