15 DECEMBER 1999
M. Velasco, A.L. Lawrence, F.L. Castille
Postlarval (PL) Litopenaeus vannamei of 2.0 mg and L. stylirostris of 1.3 mg mean initial weight were reared for 21 days without water exchange in fiberglass tanks to test their ability to utilize bacteria to satisfy their requirements for vitamins. Four semi-purified diets containing vitamin mixture levels of 0.0, 0.15, 0.30 and 0.50 % were evaluated. Mean L. vannamei survival and growth were not significantly affected by vitamin mixture level. Mean L. stylirostris survival was significantly lower for diets containing 0.0 and 0.15 % vitamin mixture compared to the diet containing 0.5 %. Mean L. stylirostris growth was not significantly affected by vitamin mixture level; however, this may have been a consequence of cannibalism within tanks. It appears that L. vannamei, but not L. stylirostris, is able to obtain the required amounts of vitamins directly from the culture environment in these rearing conditions to support similar survival and growth as when fed a diet containing 0.5 % vitamin mixture. Whether L. vannamei is able to utilize bacteria as a source of vitamins more efficiently than L. stylirostris, or the better results obtained with L. vannamei are simply a reflection of a higher rate of loss of vitamins for L. stylirostris needs further research.
(Shrimp Mariculture Research Laboratory, Texas Agricultural Experiment Station, Texas A&M University System, 1300 Port St., Port Aransas, TX 78373, USA, e-mail: nivelasco@ecua.net.ec)