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survival and to promote the growth of
P. monodon
nauplii. Later experiments from the same
authors showed a similar effect for the swimming crab larvae
Portunus trituberculatus
when
the probiotic was added daily to seawater from zoea 1 to zoea 3 (Nogami
et al.
1997). Interest-
ingly the level of the probiotic bacteria was recorded at 10
5
to 10
6
CFU ml
-1
in culture water
and a concomitant decrease in
V. anguillarum
concentration was measured in seawater. Large
scale experiments in commercial infrastructure in Japan confirmed this protective effect with
an average survival rate increased by twofold when the probiotic was added.
However, since then relatively few in-depth studies have been published on this topic and,
as previously reported in this chapter, most of the information available today comes from
practical and empirical experiences in commercial hatcheries.
Most of the investigations of probiotics in crustacean larviculture were motivated by the
need for alternative solutions to replace antibiotics. Also the reports available today gener-
ally demonstrate the ability of probiotic strains to improve the resistance of larvae and early
post larvae to diseases, especially those of bacterial origin such as vibriosis (Gomez-Gil
et al.
2000; Garriques and Arevalo 1995; Pai
et al.
2010; Panigrahi
et al.
2011). As presented in
Table 11.1, mainly Gammaproteobacteria,
Bacillus
sp. and LAB have been assessed as probi-
otics for crustacean larvae. The Gammaproteobacteria (
Vibrio
sp.) and
Bacillus
sp. probiotics
tested were almost exclusively isolated from the local environment while both autochthonous
and allochthonous LAB were considered.
An illustrative example is the previously quoted development of the
V. alginolyticus
probi-
otic (Ili strain) in Ecuadorian shrimp hatcheries. Recent studies have also evaluated the effect
of
Bacillus
on shrimp larvae or early post larvae. Ravi
et al.
(2007) isolated three strains from
the marine sediment according to their antagonistic activity against specific
Vibrio
spp. These
strains were identified as
Paenibacillus
sp.,
Bacillus cereus
and
Paenibacillus polymyxa
.The
inoculation of
Paenibacillus
sp. and
B. cereus
at two concentrations (10
4
and 10
5
CFU ml
-1
)
separately in the larval rearing tanks resulted in increased survival rates of
P. monodon
post
larvae challenged with pathogenic
V. harveyi
and other
Vibrio
spp. Lactic acid bacteria, and
specifically
lactobacilli
, were less frequently tested but showed improvement in both growth
performance and resistance to vibriosis of freshwater and marine shrimp larvae; this effect is
often attributed to an antagonism toward
Vibrio
spp. or enhancement of the immune response
(Viera
et al.
2007; Panigrahi
et al.
2011). It is also observed that the intensity of the effect
seemed to be dependent on the LAB species. Indeed Panigrahi
et al.
(2011) reported that
Lac-
tobacillus rhamnosus
and
Ped. acidilactici
strains were both able to improve the survival and
growth of
P. monodon
from mysis to PL-25 when administered at 10
5
CFU ml
-1
; however,
only the
Ped. acidilactici
strain was able to significantly protect PL-25 when subjected to a
V. anguillarum
infection. Similar findings were obtained by Viera
et al.
(2007), who reported
similar efficiency of two autochthonous LAB strains under 'unchallenged conditions', while
the
Lb. plantarum
strain was more effective at improving the resistance of
L. vannamei
mysis
to a pathogenic
V. harveyi
compared to unidentified LAB species.
The increased resistance of shrimps to vibriosis, or even WSSV, has also been linked to an
effect of probiotics on the immune response of the animal. However, very few authors have
comprehensively investigated this putative mode of action in crustacean larvae. In the study
of Liu
et al.
(2011b), the authors reported the effect of
B. subtilis
E20 on the up-regulation of
the expression of two proPO isoform genes (Söderhäll and Cerenius 1998). Interestingly these
results were coherent with a previous study from the same authors which showed that the same
probiotic was able to improve PO activity and phagocytic activity in
L. vannamei
juveniles;
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