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 174

Digestive Gland
Dietary CHO

Muscle

E
P
I
D
E
R
M
I
S
C
h
y
t
i
n

Starch

Glucose 6 P

Glycogen

Energy

Glucosamine to epidermis
Glutamine to gill

Glucose + NH4+

Energy

Piruvate + NH4+

Blood

Glucose 6 P

Piruvate

Glycogen

Peptides + AA Peptides + AA

Hemocyanin

Protein
synthesis
+ NH4+

Energy
+
NH4+
NH3

Glucose

S
y
n
t
h
e
s
i
s

Dietary
Protein

Peptides

+
NH4+

Immune
Response

Growth

Glucosamine

Blood

Osmotic
Regulation

Free AA Pool
Glutamine to gill

Gills

Free AA Pool Free AA Pool

Glutamate
+ NH4

NH4+ - NH3

Blood

Fig. 5. Diagram showing a summary of the relationship between dietary proteins and
carbohydrates and the metabolic pathways involved in the uptake of ingested nutrients.

shrimp may require lower protein levels than those they require at low salinity. This is
because at concentrated environments ammonia produced by the degradation of dietary
amino acids may be toxic. At low salinity degraded amino acids are transformed to
ammonia and used for ion exchange, whilst at concentrated environments ammonia
molecules are trapped in the blood and cannot be released as rapidly and efficient.
Notwithstanding the high tolerance of crustaceans to high ammonia in blood Schmitt &
Uglow, (1997), levels above 12 mg l -1 could inhibit growth, delay moult and reduce
breathing capacity of shrimp Danford et al . (2001). High levels such as those can easily be
attained when the diet contains more than 35% proteins and shrimp are kept at salinities
higher than 40 UPS Rosas et al., (2000)

The effect of salinity on lipid metabolism in has neither been studied in depth. In a recent
study the effect of salinity on shrimp survival, the activity of the Na/K bomb and lipids was
examined Palacios et al . , (2004). In that study 20 day old fed and unfed (3 and 24 h fasting)
postlarvae were compared to demonstrate the effect of energy reserves on survival and
osmoregulatory mechanisms. Activity of the Na + -K + ATPase was 5 times higher in posterior
gills than in anterior ones, a response associated with the osmoregulatory function of this
organ. In addition, a non-significant increase in anhydrase activity was observed in
postlarvae exposed for 20 days to 10 UPS. This is explained by the role of this enzyme in the
hydration of CO 2 produced in respiration. Under low salinity conditions, the internal media
dilutes and the output of Na + decreases. Na + in then exchanged for H + and Cl - for HCO 3 ,
provided by CO 2 through the carbonic anhydrase. In that same study total lipids in
digestive gland were significantly lower in fasting than in fed PL 20, whereas triacyl glycerids