Determination of triploidy
Ploidy level was verifed via erythrocyte nuclei size
measurements as described by Piferrer, Cal, Alvarez-
Blazquez, Sanchez and Martinez (2000) in unshocked
control, shock-induced triploid and hybrid
groups. Blood smears were prepared from 20 ¢sh by
the conventional method for each group. Red blood
cell and nuclear dimensions were measured at
1000 magni¢cation with a calibrated ocular micrometer
and light microscope (Olympus BX51, Tokyo,
Japan). Twenty arbitrary erythrocytes were
analysed per sample.