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Abstract:
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The fresh water prawn, Macrobrachium rosenbergii, has proven potential for use as an
aquaculture species (Hanson & Goodwin, 1997; Kurup, 1984). In India alone, culture of
this species of prawn in low saline areas requires about 200 million seed per year
(Kurup, 1984). In hatcheries poor survival rate has been associated with vibriosis at
di#erent stages of the larval cycle. Members of the family Vibrionaceae associated with
the larvae of M. rosenbergii were shown to be pathogenic under laboratory conditions
(Bhat et al., 2000, in press). Vibrios have been associated with mortality of penaeid
prawns by several workers (Aquacop, 1977; Hameed, 1993; Karunasagar et al., 1994).
Two methods have been suggested to protect both the larvae and juveniles from
vibriosis; one is the administration of bacterins prepared from pathogenic strains
(Itami et al., 1989, 1991; Adams, 1991; Song & Sung, 1990; Sung et al., 1991) and the
other is the utilization of yeast 1-3 and 1-6 glucans as immunostimulants for
enhancing the non-specific defense system (Sung et al., 1994; Song et al., 1997). In the
light of these observations it was hypothesised that bacterins and yeast glucans may
also be e#ective in protecting the larvae of M. rosenbergii from vibriosis as has been
achieved in the case of penaeids. To examine this hypothesis, the ability of bacterins
and an extracellular glucan-producing yeast to increase the overall survival and
metamorphosis of larvae in a hatchery, as well as to protect against an experimental
challenge under laboratory conditions, was evaluated |