Energy partitioning into growth, respiration, excretion and exuvia during larval development of the shrimp Farfantepenaeus paulensis
2001
Lemos, D. | Phan, V.N.
Energy channeled into growth (P), metabolism maintenance (R), excretion (E) and exuvia (E(v)) were quantified in feeding larval stages of Farfantepenaeus paulensis reared under commercial practices at 26 +/- 1 degrees C and 34 +/- 1 per thousand S. Dry weight, oxygen consumption, ammonia-N excretion and energy content were determined in protozoeal (PZ I-PZ III) and mysid (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 metabolism (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 by excretion (E) and exuvia (E(v)) presented lower values compared to P and R. From the total energy assimilated between PZ I and M III, growth comprised 42% while metabolism 52%. The percentage of assimilated energy channeled into growth (net growth efficiency or K2) was approximately 50% in PZ I and PZ II, reaching the highest value in PZ III (K2 = 69.9%). In the following stages, K2 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 individual energy content (P/B > 100%), while M II and M III presented lower results (P/B = 12.8-18.6%). Energetics of larval development indicated a planktonic phase with intense swimming activity and high metabolic rate, ingestion and growth (PZ I-PZ III). The transition to a benthic existence was marked by decreased metabolic rate and growth (M I-M III). These energetic parameters may be used as condition indices for cultured larvae as they help to explain how hatchery practices may affect metabolism and growth of the organisms.
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