Theses and Dissertations


Title: Physiological and nutritional requirements for the culture of the Pacific white shrimp, Litopenaeus vannamei, in low salinity waters

Name: Roy, Luke

Degree: PhD

Chair: D. Allen Davis

Resides: FAA

University: Auburn

Location: West, Alabama

Date: 2006

Pages: 140

Keywords: white shrimp, Litopenaeus, inland low salinity, culture, water quality

Abstract:

The culture of the Pacific white shrimp, Litopenaeus vannamei, in inland low salinity well waters (LSWW) is a promising, fledgling industry in Alabama. Despite the success of a small number of farmers in producing L. vannamei in LSWW on a commercial scale, a number of problems (high mortalities and poor growth) have arisen that prevent optimum growth and development of the industry. Preliminary investigations revealed water deficient in a number of ions essential for normal growth, survival, and osmoregulatory function, including potassium (K+) and magnesium (Mg2+). Experiments were designed to investigate technologies to solve these problems and aid shrimp farmers in west Alabama. Dietary supplementation of cholesterol and phospholipids was evaluated as a potential avenue of improving growth and survival under low salinity conditions. Laboratory and on-farm experiments were conducted to investigate the role of these two dietary supplements in excess of requirement under stressful (i.e. low K+ and Mg2+) rearing conditions. In both lab and farm trials no benefits from lecithin or cholesterol supplementation in excess of the dietary requirement were observed. Another potential means to improve growth and survival of L. vannamei in LSWW is dietary supplementation of minerals required for normal osmoregulatory function, including K+, Mg2+, and sodium chloride (NaCl) which may offset deficiencies in the water. Two separate 7-week experiments were conducted in 4.0 ppt (low K+, Mg2+) artificial low salinity water to evaluate dietary supplementation of these minerals. In trial 1, minerals were added in the form of purified chloride salts, while Trial 2 evaluated the use of a coating agent for the Mg2+ and NaCl treatments, while a K+ amino acid complex was utilized in the K+ treatments to reduce mineral leaching. Results suggest that chloride salts are no effective supplements while dietary supplementation of a K+ amino acid complex may help improve growth and survival of L. vannamei in low salinity waters. A series of experiments were carried out to evaluate the effects of several aqueous K+ and Mg2+ concentration/ratios on survival, growth, and respiration in juvenile L. vannamei. Four different levels of K+ (5, 10, 20, and 40 mg L -1) were utilized and a treatment of 4 ppt reconstituted seawater was used as a reference. In order to evaluate the effects of Mg2+ , five concentrations (10, 20, 40, 80, 160 mg L -1) were evaluated over a 6-week period. Results from the 7-week K+ growth trial indicated significant differences in survival and growth among treatments. Results from the Mg2+ trial revealed a difference in survival between the lowest Mg2+ treatment (60%) and all other treatments (90-97%). Shrimp respiration in the lowest Mg2+ treatment (10 mg L -1) was significantly higher than in the 80 mg L -1 treatment, possibly indicating stress. Upon transfer to high or low salinity, crustaceans must employ a variety of mechanisms to survive, including isosmotic intracellular volume regulation and an anisosmotic extracellular volume regulation. Carbonic anhydrase (CA) is involved in isosmotic extracellular volume regulation by catalyzing the following hydration /dehydration reaction (CO2 + H2O <–> H+ + HCO3-), which provides the counter ions H+ and HCO3- for exchanging Na+ and Cl-, respectively at the gills. Free amino acids can be measured colorimetrically using a total ninhydrin positive substance assay (TNPS) Two experiments were conducted to evaluate branchial CA activity and TNPS (abdominal muscle and hemolymph) upon exposure to low and high salinity. In the CA experiment shrimp were acclimated from 30 ppt to either 45, 15, or 5 ppt. After 7 days, branchial CA activity was highest in the anterior gills at all salinities. In the FAA experiment, shrimp were acclimated from 30 ppt to either 45.0, 15.0, 5.0, or 2.5 ppt. After 14 days, TNPS were measured in both abdominal muscle and hemolymph, revealing an increase in TNPS in the abdominal muscle of shrimp acclimated to 45 ppt and an increase in hemolymph TNPS at the lowest test salinity (2.5 ppt).

Download: Download

203 Swingle Hall | Auburn, Alabama 36849 | (334) 844-4786 |
Website Feedback | Privacy | Copyright ©