Natural infestation of an anchor worm, Lernaea sp. in cage culture of Asian Seabass, Lates calcarifer juveniles and its control using an anti-parasitic drug, emamectin benzoate.

Parasitic infestations and their control programmes are one among the challenges to be considered the most significant in aquaculture. A parasitic infestation was studied elaborately in Asian Seabass, Lates calcarifer juveniles with clinical signs, post-mortem findings, morphological and molecular identifications. In addition, those fish were also treated with emamectin benzoate (EMB) @ 50 µg kg-1 of fish body weight (BW) d-1 for 10 consecutive days under the controlled wet lab facility by feeding through the medicated feed at 4% BW. Results showed that the parasitic prevalence, parasitic intensity (PI) and mortality were 45.5%, 8.17 ± 0.15 per fish and 40% over a period of one week in that existing cage culture. The parasite was identified as a crustacean bloodsucker, anchor worm Lernaea sp. and EMB was found to be 100% effective with significant reduction in PI over a period of 10 days with improved survival rate of 90% against the untreated group. Infested but treated group revealed substantial haematological improvement in parameters such as RBC, WBC, Hb, PCV, large lymphocytes, small lymphocytes and total lymphocytes (P < 0.01). Similarly, comparative histopathology of vital organs also revealed no discernible lesions between the healthy and treated fish juvenile as compared to that of infested untreated group. Hence, EMB can be used to control the Lernaea sp. infestation in Asian Seabass.

In vitro fertilization and hybridization potential of the Indian white shrimp (Penaeus indicus).

Managing the reproduction of shrimp farmed in captivity is essential for selective breeding and interspecies hybridization. Procedures have not been developed for conducting in vitro fertilization in penaeid shrimp. In this study, the feasibility of in vitro fertilization (IVF) of the pre-ovulatory oocyte of Penaeus indicus was examined. Additionally, the processes of fertilization and possibility of hybridizing P. indicus with P. monodon with utilization of IVF procedures was also evaluated. The IVF was conducted by dissecting ovaries with fully developed follicles, and mixing these (~0.1 million oocytes) with 1 mL of a sperm suspension. Evaluations for fertilization and embryonic development occurred every l5 min. The eggs collected from the ovaries had the capacity for activation and fertilization. The hatching rate was 5.5 ± 1.1% of the total number of eggs fertilized, and 8.2 ± 4.8% of the nauplii developed to the post-larval stage. Results from the scanning electron micrograph evaluations provided detailed information about the changes occurring as a result of IVF in P. indicus. Interspecific hybridization of P. indicus with P. monodon did not result in hatching of embryos from the eggs, although 1% of eggs were fertilized. A reliable and inexpensive IVF procedure was developed, therefore, IVF could be an efficacious procedure for facilitation of intraspecific cross production in a penaeid breeding program. Furthermore, it was determined that IVF could be a possible procedure for interspecies hybridization between closely related species to circumvent prezygotic barriers in reproductive processes.

Broodstock development and captive maturation of hilsa (Tenualosa ilisha) in a brackishwater pond-based system.

Successful captive broodstock development of clupeid fish, hilsa, is one of the major challenges for the artificial propagation of this economically valued fish. The present study provides novel insights into the pond-reared captive broodstock development of hilsa using artificial feed. In the present study, wild collected hilsa fry (weight 1.35 ± 0.13 g, length 53.84 ± 0.95 mm) were reared in grow-out ponds for 6 months followed by maintaining them as broodstock in other ponds using formulated feed in both cases. After 6 months of pond rearing, the average body weight and length of fish were 66.76 ± 4.53 g and 184.75 ± 3.65 mm, respectively. In broodstock ponds, hilsa subadults fed with formulated feed (crude protein 41.06%) ensured significant advancement in ovarian maturity with gonado somatic index of 9.09%, enhanced secondary yolk stage oocytes of 91.66% and enlargement of oocyte diameters up to 570 µm. The broodstock reached somatic growth such as average body weight and average body length of 383.80 ± 27.38 g and 339.33 ± 9.68 mm, respectively, with a condition factor of 1.06 ± 0.15. Gut content analysis revealed the better acceptability of the artificial feed. Lipid profiling of muscle and ovary during gonadal maturation revealed mobilization of fat from muscle to ovary and selective retention of some fatty acids (i.e., C14:0, C18:0, C20:5, C22:6 and C20:4) in the ovary, which might help in gonadal maturation. STATEMENT OF SIGNIFICANCE: Successful rearing of wild-caught hilsa juvenile in captive condition using formulated feed showed its potential as aquaculture species in low saline conditions. Advance stage of maturation in low saline captive conditions showed the possibility for induced breeding of hilsa, a high priced anadromous fish. Mobilization of fat from muscle to ovary and selective retention of some fatty acids in the ovary showed the scope of dietary manipulation for broodstock development of hilsa.

Vibrio harveyi biofilm as immunostimulant candidate for high-health pacific white shrimp, Penaeus vannamei farming.

The study was to develop Vibrio harveyi biofilm-based novel microbial product and its oral delivery for high health Penaeus vannamei farming. Yield of bacterial biofilm was optimized on chitin substrate (size: <360, 360-850 and 850-1250 µm; concentration: 0.3, 0.6 and 0.9%) in tryptone soy broth (0.15%). The biofilm was characterized by crystal violet assay, SEM and LSCM imaging; protein profiling by SDS-PAGE and LC-ESI-MS/MS. The immune stimulatory effect of the biofilm in yard experiments was evaluated by relative quantification of immune genes using real-time PCR effect on overall improvement on health status under field trials. The highest biofilm yield (6.13 ±â€¯0.2 × 107 cfu/ml) was obtained at 0.6% of <360 µm chitin substrate. The biofilm formation was stabilized by 96 h of incubation at 30 °C. Protein profiling confirmed expression of six additional proteins (SDS-PAGE) and 11 proteins were differentially expressed (LC-ESI-MS/MS) in biofilm cells over free cells of V. harveyi. Oral administration of the biofilm for 48 h confirmed to enhance expression of antimicrobial peptides, penaeidin, crustin and lysozyme in P. vannamei. Further Oral administration of biofilm for two weeks to P. vannamei (1.8 ±â€¯0.13 g) improved the growth (2.66 ±â€¯0.06 g) and survival (84.44 ±â€¯1.82%) compared to control (2.15 ±â€¯0.03 g; 70.94 ±â€¯0.66%) Nursery trials showed a significant reduction in occurrence of anatomical deformities like antenna cut (12.67 ±â€¯0.66%), rostrum cut (4.66 ±â€¯0.87%), and tail rot (3.33 ±â€¯0.88%), compared to animals fed with normal diet which was 24.33 ±â€¯2.72; 14 ±â€¯1.52 and 10.66 ±â€¯1.45% respectively. In vitro and in vivo studies suggest inactivated biofilm cells of V. harveyi on chitin substrate express additional antigenic proteins and when administered orally through feed at regular intervals stimulates immune response and improve growth, survival and health status of shrimp.