Ploidy manipulations aimed to produce androgenetic Japanese ornamental (koi) carp, Cyprinus carpio L.

Androgenesis in Japanese ornamental (koi) carp was induced in batches of Yu goslavian common (mirror scaled) carp eggs. Eggs were immersed in a synthet ic (SOF) or carp natural (cNOF) ovarian fluid and placed in Petri dishes on a relating shaker (60 rpm) during irradiation with a UV-dose of 2000, 2500 or 3000 J/m(2). The treated eggs were fertilized with koi sperm and the pa ternal genome was diploidized by heat (40+/-1 degrees C/2 min) or pressure shock (7500 psi/2 min), during the first mitotic division. The highest yiel ds (7.8%) of androgenetic hatched larvae (androgenotes), indicated by a pat ernal color marker (lack of melanophores), were obtained in batches heal-sh ocked at the embryonic age of tau=1.5 tau(0). Eggs irradiated in cNOF showe d two to three-fold higher survival than eggs irradiated in SOF. The extrem ely low survival of androgenotes in all experiments can be attributed to lo ss of viability from irradiation or elevated mortality from shock treatment s and greater likelihood of homozygous mutation. In two preliminary trials, batches of koi and carp eggs (15,000 and 17,000, respectively) were activa ted with Yugoslavian (mirror) carp or koi (fully scaled) sperm, respectivel y, and diploidized by late cold shock (2-4+/-1 degrees C/45 min). The femal e carpX male koi group yielded 17 androgenetic larvae, recognized by the co lor marker. No androgenotes hatched from the reciprocal group (female koix male carp). All putative androgenetic offspring, that carried the paternal (mirror) scalation, were examined at the size of 3-5 cm and were found to b e fully scaled, indicating hybrids rather than androgenotes. Further examin ation of cold-shock induction is planned. It is recommended that further ex periments be conducted to optimize the method.