Applied Ecophysiology: An Integrative Form to Know How Culture Environment Modulates the Performance of Aquatic Species from an Energetic Point of View - Aquaculture and the Environment: A Shared Destiny - page 175

were statistically similar. This is probably due lipids in the digestive gland being used
during the first 3 hours of fasting, allowing for animals to have sufficient energetic reserves
to tackle the salinity change Rosas et al . , (1995). This study concluded that movement of
lipids to satisfy the energetic demand of osmoregulation could be operating in shrimp of
this species.
4.2 Physiological condition and immune system of shrimp
The shrimp immune system has a solid protein base and hemocyanin plays an important role
in its function. Recent studies have demonstrated that in addition to its multifunctional role
(oxygen transporter, storage protein, carotenoids carrier, osmolite, ecdysone transporter)
hemocyanin has a fungistatic Destoumieux et al . ,(2001) and prophenol oxydase-like function
Adachi et a l. , (2003). Proteins are also involved in recognizing foreign glucans through
lipopolysaccharide binding protein (LPSBP) and β glucan binding protein (BGBP)
Destoumieux et al . , (2000); Vargas-Albores & Yepiz-Plascencia, (2000). A clotting protein (with
the change of fibrinogens to fibrin) is involved in engulfing foreign invading organisms and
prevents blood loss upon wounding Hall et al . , (1999); Montaño-Pérez et al., (1999). Defense
reactions in shrimp are often accompanied by melanization. Prophenoloxidase (ProPO)-
activating system, mediated by hemocytes, is a zymogen of phenoloxidase (PO) enzyme that
catalyzes both o-hydroxylation of monophenols and oxidation of phenols to quinones leading
to synthesis of melanin Sritunyalucksana & Söderhall, (2000). Conversion of ProPO to PO
occurs through a serine protease called prophenoloxidase-activating enzyme (ppA) regulated
by another protein, a-2 macroglobulin, a trypsin inhibitor Perazzolo & Barracco, (1997). The
innate immune response of shrimp also relies upon a production, in hemocytes, of
antimicrobial peptides called peneidins that are active against a large range of pathogens
essentially directed against Gram-positive bacteria via a strain-specific inhibition mechanism
Destoumieux et al . , (2000).
In order to reach effects of dietary protein level on energetic balance we probe two protein
levels in a range of optimal reported levels of 15% and 40% (equivalent to 15 and 40g DP/kg
body weight/day [g DP/kg BWd]) and one extremely low (5% equivalent to 5g DP/kg
BWd) were used to feed juveniles for 50 days. Dietary protein level enhanced ingestion rate
in shrimp fed 5g DP/kg BWd compared to shrimp fed 40g DP/ kg BWd, however, daily
growth coefficient (DGC,%) of L. vannamei juveniles was high in shrimp fed 40g DP/kg
BWd. An inverse relation between wastes (H+U) and dietary protein level was observed
indicating that shrimp lose 81% of ingested energy when fed 5g DP/kg BWd and only 5.6%
when fed 40g DP/kg BWd. A higher assimilation and production efficiency (P/As) was
obtained when shrimp were fed 40g DP/kg BWd, than obtained in shrimp fed 15 or 5g
DP/kg BWd. An increase in Oxy hemocyanin was observed with increasing dietary protein
levels indicating that shrimp accumulated protein as hemocyanin. A reduction of hemocytes
occurred when shrimp were fed sub-optimal dietary protein; same patron was observed in
the respiratory burst. The compensatory mechanism used by L. vannamei to respond
nutritional stress, sub-optimal dietary protein level (5 and 15g DP/kg BWd) induced not
only a severe reduction in growth rate and assimilation efficiency but also in immune
capacities Pascual et al., (2004).
In an attempt to know how the protein level modulates catabolism and its effects on the
immune response, we studied juvenile L. vannamei that had been starved for varying period