Use of bacteria as biological control agent against microbial diseases in shrimp (Penaeus monodon) and crab (Scylla serrata) hatcheries: Part I. Isolation and selection of bacteria for biological control in crustacean hatcheries
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2005-03Page views
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Abstract
A study aimed at obtaining a biological control agent against bacterial diseases of hatchery-reared shrimps and crabs was conducted. Bacteria were isolated from crustacean rearing environments where luminescent vibriosis was not observed, from natural food, and from various feed ingredients. From hundreds of purified strains, 80 bacterial isolates were tested in one-on-one mixed cultures in seawater for their ability to suppress the growth of luminescent Vibrio harveyi. Of the 10 isolates exhibiting that capability, two strains were further studied: C1 from Chlorella culture and P9 from a commercial probiotic preparation. However, due to the indigenous nature of C1 strain from the unicellular alga Chlorella sp. more studies were done on it. Its biochemical characteristics and pathogenicity against crab larvae was determined. Several static bath tests were simultaneously conducted to compare the pathogenicity of luminescent Vibrio harveyi and the benign effect of potential probiotic bacteria on various stages of crab zoeae and shrimp postlarvae. Mortality in all treatments with probiotic bacteria was lower than those challenged with luminescent V. harveyi and the control indicating its benign effect. Initial bacterial inocula of 102 and 103 colony-forming-units (cfu)/mL in ultraviolet-sterilized seawater resulted in a hundred-fold increase in bacterial numbers after 24 hr, proving that in static bath bacterial bioassays, growth and replication of bacteria occurs in the test chambers. However, when the bacterial inocula were 105 to 106 cfu/mL, no significant change in bacterial numbers occurred. Furthermore, control chambers with no bacteria inoculated, were found to harbor between 104 to 105 cfu/mL of mixed bacterial population after 24 hr, part of which was luminescent Vibrio. Since the tests were conducted without feeding, results proved that bacteria associated with the test larvae also proliferated in significant numbers during the experimental period. Thus, monitoring of bacteria should not be done only on the initial hour of inoculation, but the following day as well to show microbial interactions during the experiment.
Suggested Citation
Lavilla-Pitogo, C. R., de la Peña, L. D., & Catedral, D. D. (2005). Use of bacteria as biological control agent against microbial diseases in shrimp (Penaeus monodon) and crab (Scylla serrata) hatcheries: Part I. Isolation and selection of bacteria for biological control in crustacean hatcheries. In K. Nagasawa (Ed.), Recent Advances in Diagnosis and Prevention of Fish and Shrimp Diseases in Southeast Asia (pp. 129–137). Tigbauan, Iloilo, Philippines: Aquaculture Department, Southeast Asian Fisheries Development Center.
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9718511732Related items
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Selection of probiotics for shrimp and crab hatcheries
(Aquaculture Department, Southeast Asian Fisheries Development Center, 2002)A study aimed at obtaining a biological control agent against bacterial diseases, specifically luminescent vibriosis, of hatchery-reared shrimps and crabs was done to find an alternative for chemotherapy as a disease prevention and control method. Bacteria were isolated from crustacean rearing environments where luminescent vibrosis was not observed, from natural food, and from various feed ingredients. From hundreds of purified strains, 80 bacterial isolates were tested in one-on-one mixed cultures in seawater for their ability to suppress the growth of luminescent Vibrio harveyi. Of the 10 isolates exhibiting that capability, two strains were further studied: C1 from chlorella culture and P9 from a commercial probiotic preparation. However, due to the indigenous nature of C1 strain from the unicellular alga Chlorella sp. and the ease in distinguishing it from other bacteria owing to its colony morphology, more tests were done on C1 strain. To determine the suitability of C1, and to some extent P9, as biocontrol bacteria, their pathogenicity against crab larvae and shrimp postlarvae, and their ability to become associated or incorporated into the larvae were determined. Incorporation into the rotifer, Brachionus, was also tested. Due to the positive results obtained in the incorporation experiments, the growth of strain C1 in microbiological media and unrefined media prepared from agricultural by-products was also tested. -
Research on crustaceans
(Aquaculture Department, Southeast Asian Fisheries Development Center, 1995)Crustacean research at the SEAFDEC Aquaculture Department during the last three years focused mostly on the tiger shrimp Penaeus monodon. Studies were done along six problem areas: (1) developing spawning techniques for captive broodstock, (2) defining physico-chemical levels tolerable by larvae or postlarvae, (3) finding alternative feeds or fertilizers for extensive culture, (4) reducing the cost and evaluating the quality of formulated feeds for semiintensive culture, (5) preventing and controlling disease, and (6) documenting the chemicals used in shrimp culture and their effects on the environment. To reduce feed costs, substitutes for expensive feed components were screened and the specific nutrient requirements of tiger shrimp during culture were determined. A few studies were made on other crustaceans. The vitellogenin levels during maturation of the white shrimp P. indicus were measured. The digestibility of feedstuffs was also tested in the white shrimp. Culture techniques are being developed for the mudcrab Scylla serrata in ponds, pens, and cages. -
Bacterial loads in hatcheries and virulence of Vibrio spp. to larvae of the tiger shrimp Penaeus monodon
(Bureau of Agricultural Research, Department of Agriculture, 2007)Shrimp hatcheries are high-density systems and are prone to diseases. A small-scale and a large-scale hatchery for the tiger shrimp Penaeus monodon in Iloilo, Philippines were monitored over two months for water quality and shrimp survival. Water quality (water temperature, pH, salinity, dissolved oxygen, and specific gravity) was not significantly different between the two hatcheries. However, the small hatchery seemed to favor survival of eggs to early postlarval stages, whereas the large hatchery favored the survival of late postlarvae. The normal microflora and bacterial loads of tiger shrimp eggs, larvae, postlarvae, and rearing water were determined to identify the dominant bacteria and potential pathogens. Shrimp eggs harbored the lowest heterotrophic bacterial counts. The counts increased from the nauplii to the mysis stages, decreased during the mysis stage, and then gradually increased in the older larvae. Bacterial loads in the rearing water reflected those in raw sea water and reservoir-aged sea water. Vibrio, Pseudomonas, and Aeromonas were not detected in eggs but were found in postlarvae. Ubiquitous in sea water, these bacteria increased with the build-up of organic matter. The bacterial load in the water adversely affected larval survival. Forty bacterial strains were isolated from tiger shrimp eggs, larvae, postlarvae, from the feeds, and from the rearing water. These were tested for biochemical characteristics and segregated into eight groups or genera. Six genera were found in the mysis and five genera in the postlarvae. The Vibrio species were dominant. Only Escherichia spp. were present in feeds, whereas five genera were present in the rearing water. Only Vibrio and Pseudomonas were present in both larvae and water. Moraxella, Aeromonas, and Klebsiella were found in larvae but not in rearing water. Micrococcus and coryneforms were found only in rearing water. Four Vibrio isolates were tested for virulence against shrimp postlarvae at inoculation densities of 102 and 107 cfu/ml. The four Vibrio species caused mortality of postlarvae, and more at the higher inoculation density. The most virulent was Vibrio anguillarum—30% of postlarvae died after 24 h exposure to a bacterial density of 102 cfu/ml, and all larvae died after 48 h at 107 cfu/ml. Shrimp hatcheries must have protocols for hygiene and sanitation and for disease prevention and control.
