CHROMOSOMAL INHERITANCE PATTERNS OF INTERGENERIC HYBRIDS OF ICTALURIDCATFISHES - ODD DIPLOID NUMBERS WITH EQUAL PARENTAL CONTRIBUTIONS

Hybrid chromosomal compositions of channel catfish Ictalurus punctatus x black bullhead Ameiurus melas and channel catfish x flathead catfis h Pylodictis olivaris were analysed by a computer-based method. The ka ryotype of each hybrid was highly asymmetric, and the diploid numbers and arm numbers were intermediate to the parental types. The hybrid of fspring of channel catfish x black bullhead possessed a diploid number of 59 chromosomes, with an arm number estimate of 87. The hybrid offs pring of the channel catfish x flathead catfish cross possessed a dipl oid number of 57 chromosomes, also with an arm number estimate of 87. Nucleolus organizer regions (NORs) were located on a single pair of ch romosomes with symmetric staining intensity in channel catfish and in black bullhead, and on a single pair of chromosomes with asymmetric st aining intensity in flathead catfish. The channel catfish x black bull head hybrid had two unpaired chromosomes that stained positively for N ORs. The channel catfish x flathead catfish had three unpaired chromos omes that stained positively for NORs. Specific marker chromosomes wer e identified in each hybrid. There was no evidence of androgenesis, gy nogenesis, polyploidy or aneuploidy in the hybrids. Results of this st udy, plus information reported previously, indicate that chromosomes o f ictalurid catfishes are inherited stably in a haploid pattern with a n equal contribution to the genomes of F-1 hybrids, even in intergener ic crosses involving divergent numbers of parental chromosomes. (C) 19 97 The Fisheries Society of the British Isles.