Simultaneous production of triploid and haploid eggs by triploid Squalius alburnoides (Teleostei: Cyprinidae).
The hybrid minnow Squalius alburnoides comprises diploid and polyploid forms with altered modes of reproduction. In the present paper, we report a cross where a triploid female generated both large, triploid and small, haploid eggs simultaneously, which were fertilized with S. pyrenaicus sperm. Although the large eggs were rarer (15%), they originated offspring with higher survivorship, so that tetraploids were dominant among the surviving siblings. The cross yielded apparently all female progeny. Inheritance patterns were inferred using four microsatellite markers and NORs (Nucleolus Organizer Regions) phenotypes, and suggested that haploid eggs were probably produced by an atypical hybridogenesis, in which the elimination of the unmatched genome permitted random segregation and recombination between the homospecific genomes, while the triploid eggs were clonal. The present results suggest that the occurrence of triploid unreduced eggs may be a new route for the natural tetraploidization in the complex.
Alves
M Judite
MJ
Museu Bocage, Museu Nacional de História Natural, Universidade de Lisboa, Rua da Escola Politécnica 58, 1269-102 Lisbon, Portugal. mjalves@fc.ul.pt
Gromicho
Marta
M
Collares-Pereira
M João
MJ
Crespo-López
Elena
E
Coelho
M Manuela
MM
D000818:Animals; D002871:Chromosome Banding; D003433:Crosses, Genetic; D003530:Cyprinidae / Q000235:genetics* / Q000502:physiology*; D005260:Female; D005453:Fluorescence; D018895:Microsatellite Repeats / Q000235:genetics; D009697:Nucleolus Organizer Region / Q000235:genetics; D010063:Ovum / Q000166:cytology*; D011003:Ploidies; D011174:Portugal; D012098:Reproduction / Q000235:genetics*