34 SEPTEMBER 2016 • WORLD AQUACULTURE • WWW.WAS.ORG Portunid crabs are commercially important crustaceans. One of the major obstacles to the growth of crab aquaculture is the low supply of hatchery-produced seed due to bacterial diseases and high mortality rates. Currently, antibiotics are used extensively in crab larviculture to improve survival, but their use poses numerous risks, including the development of antibiotic resistance in bacteria, higher levels of virulence, and accumulation of restricted chemicals in the flesh of farmed animals. This article assesses the potential of using Bacillus and Lactobacillus as probiotics on the culture performance of crab larvae. Using probiotics is a promising way to increase survival rates and culture performance in a sustainable way. This article also discusses the negative effects of vibrio bacteria on larval crabs because vibriosis is a serious disease issue in crustacean culture worldwide. The Use of Probiotics in Aquaculture The focus on probiotics as an environmentally safe option for disease control is increasing and their use is now based on practical experience and research. Worldwide demand for probiotic components, supplements and feeds reached US$15.9 billion in 2008 and was around US$ 19.6 billion by 2013, with a yearly increase of 4 percent. There are now many commercial probiotic products that include single or multiple species. The need for options to the use of antibiotics is ongoing and the field of probiotics for aquaculture is now attracting considerable attention. The methods of infection by many fatal pathogens have been elaborated and experience indicates improved survival of culture animals challenged with bacterial pathogens when probiotics are used. Probiotics can be provided as feed supplements and culture The Potential Use of Bacillus and Lactobacillus as Probiotics in Portunid Crab Larviculture Kwong Kok Onn, Anita Talib, Md. Arif Chowdury, Khairun Yahya and Wan Mustaffa Wan Din water additives. Using probiotics results in modification of bacterial communities in tank water, improving growth and survival of larval crustaceans and bivalves. Regular application of probiotics is necessary to achieve and maintain artificial dominance by the probiotic bacteria. Thus, it is feasible to alter the makeup of bacterial flora in culture through probiotic supplementation, but sustained additions are needed for the beneficial effect to occur. Many papers have been published on the use of probiotics in aquaculture systems to control water quality, especially ammonia levels. A mixture of probiotics in solution and particle form is typically added to high-density aquaculture tanks. The mixture enhances water quality in crustacean cultures by reducing the concentration of organic matter and ammonia. Adding Bacillus to culture environments can enhance water quality. Indigenously isolated B. subtilis has been used for aquaculture. Some were isolated from shrimp ponds that had lower ammonia compared to those without probiotic application. During passage through the digestive tract, probiotics can attach and proliferate in the gut, enhancing digestive enzyme activity and larval development. Attachment of probiotic bacteria to the intestinal surfaces of cultured animals is associated with stimulation of the immune system and inhibitory activities toward enteropathogens. Probiotics improve the digestibility of dietary energy, resulting in greater growth rates of cultured animals. Preinoculation with probiotics can prolong the dominance of the desired bacteria in the culture environment. This can lower the mortality as a result of the improved capacity of larvae to survive infections from pathogenic bacteria. FIGURE 1. Female Scylla paramamosain broodstock. FIGURE 2. Gram stained, rod-shaped Bacillus licheniformis (40 x magnification).
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