Energy partitioning into growth, respiration, excretion and exuvia during larval development of the shrimp Farfantepenaeus paulensis

Energy channeled into growth (P), metabolism maintenance (R), excretion (E) and exuvia (E,) were quantified in feeding larval stages of Farfantepenaeu s paulensis reared under commercial practices at 26 +/- 1 degreesC and 34 /- 14 parts per thousand S. Dry weight, oxygen consumption, ammonia-N excre tion and energy content were determined in protozoeal (PZ I-PZ III) and mys id (M I-M III) stages. In stages PZ III and M I, a higher weight increment (P) was observed compared to other larval stages. Energy expended in metabo lism (R) increased through each subsequent stage, showing higher increment in the intervals PZ II-PZ III (1.7-fold) and PZ III-M I(1.8-fold). Losses b y excretion( E) and exuvia (E,) presented lower values compared to P and R. From the total energy assimilated between PZ I and M LII, growth comprised 42% while metabolism 52%. The percentage of assimilated energy channeled i nto growth (net growth efficiency or K-2) was similar to 50% in PZ I and PZ II, reaching the highest value in PZ III (K-2 = 69.9%). In the following s tages, K-2 remained between 33.3% and 49.8%. The metabolism (R) and growth (P) ratio showed higher growth investment in PZ III (R/P = 44.9%) compared to other stages. PZ I and PZ III exhibited higher growth in relation to ind ividual energy content( P/B > 100%), while M II and M III presented lower r esults (P/B = 12.8-18.6%). Energetics of larval development indicated a pla nktonic phase with intense swimming activity and high metabolic rate, inges tion and growth (PZ I-PZ III). The transition to a benthic existence was ma rked by decreased metabolic rate and growth (M I-M III). These energetic pa rameters may be used as condition indices for cultured larvae as they help to explain how hatchery practices may affect metabolism and growth of the o rganisms. (C) 2001 Elsevier Science B.V. All rights reserved.