Induced triploids and tetraploids in bighead carp, Hypophthalmichthys nobilis, verified by multi-embryo cytofluorometric analysis

Triploid and tetraploid bighead carp, Hypophthalmichthys nobilis, were produced by applying a hydrostatic pressure shock of 500 atm of 90 s duration. The optimum time of pressure shock after fertilization for triploid and tetraploid production was 4 min and 36 min, respectively. Egg quality as measured by survival in control groups related directly to percent triploids produced. Eighty to 100% triploids were produced when control viability exceeded 59%. No triploids were produced when control viability was less than 40%. Conventional techniques to determine ploidy require labor intensive karyotyping methods or fish large enough to obtain a blood sample for analysis in a particle counter. This paper describes a cytofluorometry technique developed to determine ploidy from fish embryonic tissue. Multiembryo homogenates analyzed 24–28 h after fertilization were used to determine ploidy distribution for each treatment group.