Comparative study of heat shock and pressure shock for triploidy induction in rainbow trout (Oncorhynchus mykiss)

Abstract

The study was aimed to explore the effective physical treatment for successful triploidy
induction to take the advantage of improving growth in coldwater aquaculture candidate
fish, rainbow trout Oncorhynchus mykiss. Comparison was made between two common
physical treatments viz.,, heat shock and pressure shock to prevent the extrusion of second
polar body in newly fertilised eggs. Heat shock was given on the fertilised eggs at three
temperature levels viz., 26, 28 and 30ºC with four exposure timings of 5, 8, 10 and 12 min.
Pressure shock was applied at three different levels of pressure i.e 9000, 9500 and 10000 psi
for 3 different exposure times of 3, 5 and 7 min. Poidy verification of the treated eggs was
done by counting the chromosome number in karyotyping. Results of the field operations
reflected 86-90% triploidy induction for pressure shock at9500 psi for exposure time of 5 min
with 72-80% survival from fertilisation to swim-up fry stage and 80% triploidy induction for
heat shock at 280C for 10 min with 60-66% survival from fertilisation to fry stage. Appropriate
centigrade temperature minutes (CTM) was calculated as 300-375 min, which is variable at
different locations and environmental conditions. Study concluded that pressure shock is
more effective over heat shock for triploidy induction in rainbow trout.

CTM, Heat shock, Karyotyping, Pressure shock,
Triploidy induction