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Abstract Larval stages of the Pacific white shrimp, Litopenaeus vannamei (Boone) were fed standard live diets of mixed microalgae from the first to the third protozoea (PZ1 to PZ3), followed by Artemia nauplii until post-larvae 1 (PL1). Trypsin enzyme activity for each larval stage was determined using N-α-p-toluenesulphonyl-l-arginine methyl ester (TAME) as a substrate. Results were expressed as enzyme content to assess ontogenetic changes during larval development. Tissue trypsin content (IU µg[sup -1] DW for each larval stage) was significantly highest at the PZ1 stage and declined through subsequent stages to PL1. This contrasts with previously observed patterns of trypsin development in Litopenaeus setiferus (Linnaeus) and other penaeid genera, which exhibit a peak in trypsin activity at the third protozoea/first mysis (PZ3/M1) larval stage. Litopenaeus vannamei larvae transferred to a diet of Artemia at the beginning of the second protozoea (PZ2) stage were significantly heavier on reaching the first mysis stage (M1) than those fed algae, while survival was not significantly different between treatments. At both PZ2 and PZ3 stages, trypsin content in larvae feeding on Artemia was significantly lower than in those feeding on algae. The rapid decline in trypsin content from PZ1 and the flexible enzyme response from PZ2 suggest that L. vannamei is physiologically adapted to transfer to a more carnivorous diet during the mid-protozoeal stages. [ABSTRACT FROM AUTHOR]

Abstract The present work evaluates the effectiveness of partial or total replacement of microalgae with artificial diets [CAR Frippak, experimental Dry Immune Selco (DIS, with vitamins C, E, HUFA and immunostimulants)] administered together with a single dose of live algae (SDLA) for the protozoeal stages of the Pacific white shrimp Litopenaeus vannamei (Boone) (expt 1). In expt 2, Artemia enriched with DIS were fed to mysis 1–postlarvae 1 to assess diet performances. The results indicate that highest survival and growth is obtained when larvae at the N6-PZ1 moult are administered DIS (2 mg L[sup -1] day[sup -1]) + CAR (2 mg L[sup -1] day[sup -1]) and SDLA (20 cells μL[sup -1] mixed algae, Chaetoceros muelleri and Isochrysis galbana, 70%:30% respectively) as a first feed, and DIS + CAR (2 mg L[sup -1] day[sup -1] each) thereafter until PZ3 (survival 91.2%), as opposed to live microalgae control (81.9%). A significantly better total length was achieved by larvae fed the live microalgae control (2.51 mm) or the above artificial diet regime (2.44 mm) than in all other treatments. Larvae administered this artificial diet treatment were significantly heavier (0.039 mg larvae[sup -1]) than those fed the algal control (0.023 mg larvae[sup -1]) or any other treatment. This may result from the combined effect of the artificial diet together with vitamins C, E and HUFA in the booster DIS. These results demonstrate for the first time the impact that a single first feed at the N6-PZ1 moult may have on later development, as all larval groups received the same diet from the PZ1 to PZ3 stages. The results from expt 2 indicate that the administration of Artemia enriched with DIS during mysis 1–post-larvae 1 for L. vannamei larvae results in a significant increase in survival (88.6%), total length (5.24 mm) and weight (0.155 mg larvae[sup -1]) in comparison with other enrichments, such as DIS 5V1 (without vitamins, but with HUFA) or non-enrichment. [ABSTRACT FROM AUTHOR]