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96 D. Lemos et al.rAquaculture 186 (2000 89–105
3. Results and discussion

Good growth performance of shrimp in ponds is associated with survival during
larval stages ŽCastille et al., 1993 . Looking for the production of good quality
.
postlarvae, research on larval nutrition has traditionally focused on the establishment of
suitable feeding protocols for the different developmental stages ŽLoya-Javellana, 1989;
Gallardo et al., 1995 .. Digestive enzyme activities were used as an index of the trophic
state in order to allow for suitable diet formulation ŽVan Wormhoudt, 1973; Laubier-
Bonichon et al., 1977; Lee et al., 1984; Galgani et al., 1985 .. It may also indicate
differences in the digestive potential among the life stages of cultured shrimp. Trypsin
specific activity of L. schmitti was low in egg and nauplius IV–V, increased in PZ I and
reached a peak in PZ III ŽFig. 2 . The activity decreased from mysis I, maintaining low
.
values during the initial postlarval stages. This activity pattern was found to be similar in
several penaeid species such as Marsupenaeus japonicus, Litopenaeus setiferus, Pe-
naeus monodon, L. Õannamei and F. paulensis ŽLaubier-Bonichon et al., 1977; Lovett
and Felder, 1990; Fang and Lee, 1992; Le Moullac et al., 1992; Lemos et al., 1999 .. The
mechanism of enzyme regulation remains unclear, but the variations seem to be closely
related to developmental events rather than changes in diet ŽLovett and Felder, 1989,
1990 .. The increased enzyme activity occurs at stages with intense energy turnover such
as protozoea, when swimming, ingestion and metabolic rates are high ŽEmmerson, 1980;
Loya-Javellana, 1989; Dall et al., 1990; Chu and Ovsianico-Koulikowsky, 1994 .. The

Fig. 2. Trypsin activity using TAME as substrate, during larval and postlarval development of L. schmitti.
Esegg, Nsnauplius, PZsprotozoea, Msmysis and PLspostlarva. Error barssstandard deviation. The
number of activity assays for each stage is denoted above the error bars. Eggs at the early nauplius embrionary
..
stage according to Primavera and Posadas Ž1981 Activity was expressed as U mg protein y1 based on an
2
extinction coefficient of 0.54 cm mmol y1 for the substrate TAME ŽRick, 1984 .
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