Effect of UV radiation on the genetic inactivation of sperm of the bullseye puffer Sphoeroides annulatus (Jenyns, 1842)

Abstract

 Genetic (DNA) inactivation of fish sperm with ultraviolet irradiation is generally accompanied by a paradoxical effect on survival rates (Hertwig effect). In the present study, sperm samples from ten male bullseye puffer fish (Sphoeroides annulatus) were diluted 1:50 using Cortland's extender solution and used to test the effect of nine ultraviolet doses (0.2–1.0 J cm–2) on motility time in seconds, motility index, and embryo survival rate after fertilizing eggs from five bullseye puffer females. Motility time of sperm irradiated with 0.2–0.9 J cm–2 were not statistically different from the controls, but sperm irradiated with a dosage of 1.0 J cm–2 dosage had significant lower motility time. Motility indices (MI) allowed for the statistical differentiation of four groups in relation to their response to different radiation doses: the first had high MI, and included the controls and 0.2–0.3 J cm–2 treatments; the second had lower MI and included the 0.4–0.7 J cm–2 treatments; the third showed recovery of MI and included the 0.8–0.9 J cm–2 treatments; and the fourth showed the lowest MI with the 1.0 J cm–2 treatment. Embryo survival was highest for the controls and 0.2 J cm–2 treatment, decreasing in the 0.3–0.4 J cm–2 treatments, increasing again in the 0.5–0.8 J cm–2 treatments, until reaching lowest survival in the 0.9–1.0 J cm–2 treatments. These results indicate that the best ultraviolet dosage to achieve genetic inactivation of sperm of this species is close to 0.7 J cm–2, a dosage in which fish fry showed typical haploid syndrome characteristics.