2.6 Vibrio challenge study with juveniles
The experimental tanks for juveniles rearing encompass ten
litre plastic tank containing six litre of filtered sea water (30
ppt). About eight healthy tiger shrimp juveniles with each an
average length: 6.5±0.5 cm and average weight 1.5±0.3 g were
maintained in five sets of tanks. The experimental setup
included treatments in duplicate and kept in such a way to
avoid cross contamination. The shrimps were individually
netted out and about 2 mm of a small wound (hereafter
wounded shrimp-WS) was made through the cuticle and into
the muscle of the third abdominal segment by pushing a
scalpel until it penetrated [17]. The pathogen (V. harveyi VSH5)
and probionts (AVP03 and AVP07, each separately) were
grown in 150ml marine broth and 200ml of TSB with 1.5%
NaCl respectively. The bacterial cells were harvested by
centrifugation at 6000 rpm and added to the experimental tank
water as PL treatment. About 20% of water in all the
treatments was replaced with filtered dechlorinated seawater
containing equal concentration of bacterial cells as in the
initial stage. The animals were fed with ad libitum commercial
feed and aerated continuously. Total plate count (TPC) and
presumptive vibrio count (PVC) in each experimental set up
was estimated. The survival percentage and the bacterial count
were examined for four days. Infected animals were confirmed
by its luminescence under dark.