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Triploidy could reduce breeding activity in tilapia without the use of hormones. In this study, the effect of triploidy on survival, growth, and gender of a line of red hybrid tilapia (Oreochromis mossambicus X Oreochromis niloticus) was assessed relative to the performance of diploid siblings. Triploidy was induced by preventing second polar body extrusion by applying either heat or cold shock. Growth was similar for both ploidies during the first 90 days of culture. However, at the age of 120 days, the average body weight of triploids produced by heat shock (215.5 ± 3.61 g) was significantly higher than that of cold shock (192.7 ± 2.6 g) and the diploid control (191.9 ± 1.74 g). Survival among triploids was inferior to diploids. Percentage of males in the triploid population was 82.9% in the heat-shocked treatment group, 54.8% in the cold-shock treatment, and 50% in the diploid control. Maximum attainable weight of red tilapia was calculated by applying the Ford-Walford growth plot: 650 g (heat-shocked ...

Summary The polychaete Perinereis cf. nuntia, a tropical species endemic in Thailand, was cultured in captivity as follows: eggs and sperm from sexually mature (epitokous) P. cf. nuntia, were artificially fertilized, and settled into a sand bed about 30 cm deep at the nectochaete stage. The sand beds were supplied with seawater at 30-ppt salinity and the nectochaetes reared for five months after which time some adults were becoming epitokes. The culture method yielded 3–4 kg polychaetes at an atokous stage per m2 of culture area. Because the polychaetes were to be used to feed shrimp broodstock, samples of the worms were screened for the presence of white-spot syndrome and yellow-head viruses using polymerase chain reaction (PCR) methods prior to introduction to the system as founders and at monthly intervals during their culture. Morphological details of P. cf. nuntia from fertilization to nectochaete stage are described using light microscopy, transmission (TEM) and scanning electron microscopy (SEM). T...

–The effect of photoperiod on growth of juvenile giant freshwater prawns, Macrobrachium rosenbergii de Man, was tested. The prawns were divided into four groups and each group was reared under one of the following light-dark conditions: continuous darkness (L0:D24), 12 hr light: 12 hr dark (L12:D12), 16 hr light: 8 hr dark (L16:D8), and 20 hr light: 4 hr dark (L20:D4). Body size was determined at the age of 45, 75, and 110 days by measuring total length, orbital length, and carapace length; body weight was determined at the age of 110 days. At 110 days of age, the prawns reared under L0:D24 photoperiod were significantly longer and heavier than those reared under other light-dark conditions. The survival rate of the prawns reared under L0:D24 photoperiod was also higher than that of other groups. This study indicates a positive effect of continuous darkness on growth and survival rate of juvenile giant freshwater prawns, M. rosenbergii.