Unisexual polyploid vertebrates are commonly known to reproduce by gynogenesis, parthenogenesis, or hybridogenesis. One clone of polyploid Carassius gibelio has been revealed to possess multiple reproduction modes of unisexual gynogenesis and sexual reproduction, but the cytological and developmental mechanisms have remained unknown. 

Recently, research team led by Prof. GUI Jianfang at Institute of Hydrobiology, Chinese Academy of Sciences (IHB) confirmed for the first time the normal meiosis completion by spindle co-localization of β-tubulin and Spindlin in gibel carp.  

Moreover, by DAPI staining and BrdU-incorporated immunofluorescence detection during the first mitosis in the fertilized eggs by three kinds of different sperms, they also revealed three types of various nuclear events and development behaviors. They included normal sexual reproduction in response to sperm from the same clone male, typical unisexual gynogenesis in response to sperm from the male of another species Cyprinus carpio, and an unusual hybrid-similar development mode in response to sperm from another different clone male.  

Based on these findings, they had discussed cytological and developmental mechanisms on multiple reproduction modes in the polyploid fish, and highlighted evolutionary significance of meiosis completion and evolutionary consequences of reproduction mode diversity in polyploid vertebrates. 

This study was performed by IHB doctoral student ZHANG Jun and SUN Min who is working in Shanxi University. The corresponding author is Prof. GUI Jianfang. This work was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences, the earmarked fund for Modern Agro-industry Technology Research System and the National Key Basic Research Program. And the paper was published in Scientific reports with the title of "Meiosis completion and various sperm responses lead to unisexual and sexual reproduction modes in one clone of polyploidCarassius gibelio". 

FigureSchematic diagram of normal meiosis completion and various sperm response reproduction modes.(Left) Sexual reproduction mode in response to the sperm from the same clone male. (Middle) Hybrid-similar reproduction mode in response to the sperm from different clone male. (Right) Unisexual reproduction mode of gynogenesis in response to the sperm from another species male. Different sperm nucleus and the corresponding male pronucleus are shown by the corresponding colors. 1st pb and 2nd pb indicate the first polar-body and the second polar-body. The main key steps during meiosis and the first mitosis, including first meiosis completion, second meiosis completion, genome replication and fusion, genome replication, and a hypothesized extra endoreplication, are indicated in the corresponding positions.All the images of fish were drawn by ZHANG Jun and scanned into digital pictures.