Abstract

Beneficial microorganisms isolated from the gut of adult shrimp, Litopenaeus vannameiand adult Cortez oyster, Crassostrea corteziensis was tested to determine larval survival of whiteleg shrimp L. vannamei. The isolates were characterized through tests for hemolytic and antagonism to select potential beneficial strains. Strains YC5-8, Y02-1, YC5-1 and YPD10-4 were selected from in vitro assays and evaluated in larval cultures at 1 × 10⁵ CFU/ml. Pseudomonas aeruginosa (strain YC5-8) and Burkholderia cepacia(strain Y02-1) were selected and two subsequent bioassays were performed to evaluate these two strains on shrimp larvae. At the first bioassay, two concentrations of the strains were used: 1 × 10⁴ and 1 × 10⁶ CFU/ml. During the second trial, two mixed concentrations (1:1) and an antibiotic were tested: 1 × 10⁴ CFU/ml; 1 × 10⁵ CFU/ml; oxytetracycline at 4 mg/l. A significant increase in larval survival following treatment with YC5-8 and YO2-1 at 1 × 10⁴ and 1 × 10⁶ CFU/ml was registered. Shrimp larvae exposed to mixed strains and oxytetracycline also had significantly higher survival than the control group.

Key words: Pseudomonas sp., Burkholderia sp., Litopenaeus vannamei, larvae, probiotics.