Energy metabolism is well-studied in vertebrate systems, providing insights on the genes and mechanisms involved in different pathways necessary for the survival of an organism. Yet, such studies are still lacking in invertebrate systems much more in shrimp. An earlier study has showed several contigs from the black tiger shrimp to be homologous to white spot syndrome virus (WSSV), a devastating pathogen in shrimp, including contig 31-WSSVORF82 (c31) and contig 34-WSSVORF21 (c34). This study aims to unveil the roles of three genes: c31, c34 and protein kinase (PK) in the shrimp system and its possible role in WSSV-infection. Rapid amplification of cDNA ends-polymerase chain reaction or RACE-PCR was used to obtain the full-length sequence of c31 and c34, followed by in vivo gene silencing using RNAi technology, and intramuscularly injecting dsRNA to WSSVchallenged Macrobrachium rosenbergii and Penaeus (Marsupenaeus) japonicus. Gene expression followed for healthy shrimps and dsRNA-treated shrimps. Mrc31 was revealed to be the enzyme lactase dehydrogenase (LDH), commonly released during tissue damage and is a marker for disease. The most parsimonious tree pictured Mrc31 to be sister clades to LDH of other shrimp species, Penaeus monodon and P. vannamei, supported with 100% and 72% bootstrap values, respectively. Mrc34 was highly homologous to the glycogen phosphorylase (GP) enzymes of other organisms including that of another shrimp, M. japonicus, bearing a bootstrap value of 99%. For PK, phylogenetic analysis revealed that the three open reading frames (ORFs) from P. monodon, M. rosenbergii and P. japonicus have 30% homology to WSSV-PK supported by a 98% bootstrap value. Mortality data from dsRNA-treated and WSSV-infected shrimps showed that treatment with dsRNA-LDH, GP and PK had significantly higher survival rates compared to that of the controls, Phosphate Buffered Saline (PBS) and Green Fluorescent Protein (GFP). Silencing the three genes in the shrimp has rendered some protective effect against the virus. Gene expression showed that all three genes are present in immune-related organs such as the gills, hepatopancreas and hemocyte. This study is the first to report the possible identities and functions of contigs 31, 34 and PK providing valuable data on the shrimp's genome.

The giant trevally, maliputo (Caranx ignobilis), a highly prized and most popular indigenous migratory fish in Taal Lake, Batangas, Philippines, was induced to spawn using various hormones (to assess hormone efficacy on spawning performance). Different feeding regimes used in the larval rearing of this species were also evaluated. Sexually mature breeders, 5 to 7 years old with at least 0.5 mm oocyte diameter and 60% of ova at GVM stage were injected intramuscularly, in two doses, with: (a) 1,000 IU/kg BW human chorionic gonadotropin (HCG); (b) 100 µg/kg BW luteinizing hormone releasing hormone analogue (LHRHa); and (c) 5 mg/kg BW carp pituitary extract (CPE), at five breeders per hormone treatment. Uninjected fish served as the control. Treated fish were released and allowed to spawn spontaneously in 40-ton (5m diameter) circular tanks. Successful spawning was achieved during the months of March to July (28-30 ppt salinity; 27.6-29.25°C). Maliputo eggs are pelagic, clear and spherical, with a single oil globule and mean diameter of 0.8 mm. Ovulation period was 24-36.5 hours after 2nd injection in HCG-treated fish and 25-52 hours for LHRHa-injected fish. Only one of the CPE-treated fish spawned after 27 hours but eggs were not fertilized. Uninjected control fish did not spawn. Eggs were hatched in 11-13 hours in HCG treatment and 11-17 hours in LHRHa. Mean number of spawned eggs (3,500-4,000 eggs•gram-1) was higher in HCG treatment (223,068 eggs•kg-1 breeder at 58.27g•kg-1 breeder) than LHRHa (176,524 eggs•kg-1 breeder at 50.44 g•kg-1 breeder). Fertilization and hatching rates were both higher in LHRHa (60.88% and 71.07%, respectively), than HCG treatment (30.53% and 43.06%). Mean number of produced larvae was higher in LHRHa treatment (56,040 larvae•kg-1 breeder) compared to HCG-treated fish (41,547 larvae•kg-1 breeder). Hatched larvae (1.6 mm mean length) reared for 30 days in 3m x 3m concrete tanks using the standard protocol for marine finfish hatchery attained a maximum survival of 4.47%. Complete metamorphosis was observed after 26-28 days (8.1 mm mean length). Successful larval rearing was attained using greenwater (Nannochloropsis sp.) technology fed with live food (Brachionus sp. and Artemia salina). Critical periods were days 1-7 and days 19-22 when heavy mortalities were observed. Being the first recorded spawning in captivity of Caranx ignobilis in the Philippines, the results of this study provides an important baseline data and is a major step towards the development of a hatchery technology for maliputo in the country as well as for seed enhancement of its natural habitat. The project has provided 400,000 maliputo larvae to private hatcheries for larval rearing trials while 100,000 larvae were seeded in Balayan Bay and 5,000 fingerlings released in Taal Lake.

Various post-larval rearing methods were compared to determine which scheme would give the most yield of newly settled (visible) juvenile stage (> 1mm body length). Five types of postlarval rearing methods were tested: T1- planktonic diatom only (Chaetoceros calcitrans, Cc), T2-benthic diatom Navicula (Nsp) as biofilm and concentrate, T3- Navicula as biofilm + Cc, T4Spirulina as paste on settling plate + Cc, and T5- Spirulina (Sp) as paste on settling plates + Nsp concentrate. An experiment was conducted in small (3-li) aquaria using a cohort of Day 14 (postfertilization) sandfish larvae. Simultaneously, three of the 5 post-larval rearing methods (i.e. T2, T3 and T4) were done in medium scale (30-li) aquaria to determine how a conventional method (T2) employed in a pilot sea cucumber hatchery in Central Philippines compared with method observed in Viet Nam (T3) or with a hybrid method (T4). Visible post-settled juveniles were counted weekly for the next three weeks and expressed as percentage yield. After three days of rearing, transparent but visible early settled juveniles were observed. Mean percentage (%) juvenile yield in week 1 was highest in T1 (Cc only)(17% + 1.3) followed by T3 (Sp + Cc) (14% + 1.6) in a 3 li scale. Yield increased and peaked in week 2 especially for rearing methods with Nsp while those without (e.g T1 and T2) declined dramatically by week 3. In the 30-li scale, the highest mean yield was consistent with T5 (Nsp + Cc) until Week 3 (12% + 11.2). The mean juvenile yield on the 2nd and 3rd week were better than the 2% average for this stage or the 2.5% benchmark based on experiences in the Philippines and Viet Nam as indicated in published references.