[Studies on genetic diversity in gonochoristic offspring produced from mating between two different gynogenetic...

Based on the discovery of gonochoristic reproductive mode in silver crucian carp (Carassius auratus gibelio), 18 individuals from the mated offspring between clone F and clone D and their parents were analyzed using 11 RAPD primers. The mated offspring differentiated into three phenotypes. One phenotype is similar to that of clone F (SF). The second is similar to that of clone D (SD). The third shows a novel longer and thinner body type (NL). Electrophoretogram results show abundant polymorhic DNA fragments among individuals in the FD mated offspring. Obviously, the polymorphic DNA fragments originate from the genome recombination owing to the gonochoristic reproductive mode. The FD mated offspring amplify different fingerprints from maternal, and their fingerprints are different from each other. These different DNA fragments can be divided into four groups according to their origin. The average genetic distance among individuals from the FD offspring (0.23 +/- 0.123) is much higher than that of allogynogenetic offspring, which is only about 0.01. Of the three phenotypes in the FD offspring, the average distances among SD is the highest (0.235 +/- 0.097). The next is SF phenotype, in which the average distances is 0.148 +/- 0.073. The average distances among NL is the lowest (0.094 +/- 0.083). The gonochoristic reproductive mode introduces high genotypic variability and underlines genetic diversity. A dendrogram was constructed by NJTREE cluster analysis based on a total of 2320 distinguishable fragments (116 per individual). NL3 and maternal are most closely related, and SD3 and paternal are most closely related. The average genetic distances between SD and SF or NL (> 0.31) is higher than that of between SF and NL (0.124). Consistent with previous study, the genetic distance between maternal and paternal is 0.35. The average genetic distances between FD offspring and parents are both about 0. 32. But the similarities among the three phenotypes in mated group FD offspring and parents are different. The similarity between SF and maternal (71%) is higher than similarities among other phenotypes and maternal. The similarity between SD and paternal (70%) is higher than similarities among other phenotypes and paternal. The results suggest the similarities among three phenotypes in the FD offspring and parents are related with their phenotypes because some DNA fragments specific for phenotypes were amplified in this study. The revelation about reproductive diversity will be able to open the door in which complicated mechanism has been locked in unisexual organisms for long time, and establish the important roles of silver crucian carp in the studies on evolutionary genetics in unisexual or polyploid vertebrates.