Association of foreign DNA with sperm of gilthead seabream, Sparus aurata,after sonication, freezing, and dimethyl sulfoxide treatments

The association of foreign DNA with gilthead seabream (Sparus aurata) sperm was enhanced relative to simple coincubation by sonication, freezing, dime thyl sulfoxide and polyethylene glycol treatments. Sonication yielded the s trongest dot blot signals, equivalent to 250 to 380 foreign DNA copies per spermatozoa. We are unaware of previous reports attempting to associate DNA with ultrasound for fish or elsewhere. However, no or negligible foreign D NA was evident in 1- and 2-day-old fish larvae resulting from eggs fertiliz ed with sonicated or frozen sperm.