Survival, growth and feeding efficiency of Litopenaeus vannamei protozoea larvae fed different rations of the diatom Chaetoceros muelleri.

摘要

The survival, development and growth of Litopenaeus vannamei protozoea (PZ) larvae were evaluated in three experiments during which they were fed five different rations of the diatom Chaetoceros muelleri, from emerging PZ I larvae until the day of change to mysis I. The total amount of food and energy supplied in 5 days to each larva ranged from 85.5 to 223.2 micro g larva-1 (ash-free dry weight) and between 2.25 and 5.88 J larva-1. After 2 days, the development index (DI) showed that some of the larvae fed the highest ration had reached the stage of PZ III. At the end of the experiment the mean DI ranged from 2.9+or-0.2 to 3.2+or-0.3 and the differences among treatments were not significant. The mean percentages of survival ranged from 35.8% to 51.7% and were not statistically different, but total length was progressively higher with increasing ration. The final values were 1.91+or-0.54, 2.10+or-0.53; 2.34+or-0.36; 2.45+or-0.37 and 2.55+or-0.42 mm and were all statistically different with the exception of treatment 4, that was intermediate between treatments 3 and 5. However, the highest final organic weight (26.0+or-1.7 micro g larva-1) was treatment 4, which was different from the values obtained with the two lower rations. Treatments 3 and 5 had intermediate values. The percentages of the food ingested did not vary with the rations supplied or with the age of the larvae and ranged from 74% to 86%. Food ingestion (Fi) was a function of the food supplied (Fs), according to the equation Fi=0.848Fs-4.025 (R2=0.992; P<0.001). Using the amount of food supplied and ingested with each feeding regime and the respective organic weight gains, it was calculated that the percentages of Fs and Fi used for body growth were 14.4% and 17.9% with the lowest ration and 6.9% and 8.3% with the highest, whereas the three intermediate rations gave similar efficiencies (9.8% to 10.2% of Fs and 11.8% to 12.5% of Fi). However, the weight and energy gains obtained with the highest food utilization efficiency were lower than those obtained with the higher rations, indicating that cautious overfeeding is a more convenient alternative for L. vannamei PZ culture..