Fertility and gamete ploidy of allopentaploid offspring of tetraploid dojo loach Misgurnus anguillicaudatus females and
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ORIGINAL ARTICLE Biology
Fertility and gamete ploidy of allopentaploid offspring of tetraploid dojo loach Misgurnus anguillicaudatus females and large‑scale loach Paramisgurnus dabryanus males Songqian Huang1,2 · Li Zhang3 · Xiaojuan Cao1 · Weimin Wang1 Received: 12 November 2018 / Accepted: 11 November 2019 © Japanese Society of Fisheries Science 2020
Abstract Artificial interspecific hybrids (3n) of tetraploid dojo loach Misgurnus anguillicaudatus (TTTT) and diploid large-scale loach Paramisgurnus dabryanus (PP) were viable. Allopentaploid loaches (TTTTP) were produced by cold-shocking the fertilized eggs of TTTT females fertilized with sperm of PP males. The TTTTP were viable and well developed. As there are currently no reports on the fertility and gamete ploidy of TTTTP, artificial propagation and ploidy analyses were conducted to determine them. The ovaries of TTTTP were well developed with primary oocytes and secondary oocytes; the testes were sterile with low-density sperm-like cells. By backcrossing with mature TTTT, TTTTP were found to be female fertile and male sterile. The fertility of female TTTTP was low; they produced few viable diploid eggs and a few inviable triploid and aneuploid eggs. Ploidy analysis of cold-shock-induced progenies of TTTTP × TTTT indicated that TTTTP could generate viable diploid eggs, along with diploid second polar bodies. The results of this study are helpful for further understanding of loach polyploidization and should encourage more investigations on hybridization and gamete formation in loaches. Keywords Hybridization · Fertility · Gamete ploidy · Polyploidy · Allopentaploid loach
Introduction Dojo loach Misgurnus anguillicaudatus and large-scale loach Paramisgurnus dabryanus are small freshwater fish widely distributed throughout Eurasia (Huang et al. 2017a). Loach is regarded as an excellent model for the analysis of polyploidy, unisexual reproduction and abnormal gamete formation in teleosts (Li et al. 2008; Arai and Fujimoto 2013; Huang et al. 2015). Five different levels of ploidy, * Xiaojuan Cao [email protected] 1
College of Fisheries, Engineering Research Center of Green Development for Conventional Aquatic Biological Industry in the Yangtze River Economic Belt, Ministry of Education, Huazhong Agricultural University, Wuhan 437000, Hubei, People’s Republic of China
2
Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113‑8657, Japan
3
Shanghai University of Finance and Economics, Shanghai 200433, People’s Republic of China
diploid (2n = 50), triploid (3n = 75), tetraploid (4n = 100), pentaploid (5n = 125) and hexaploid (6n = 150), have been found in loach caught in China (Li et al. 2008, 2012). Dojo and large-scale loach are sympatric in the wild, and their hybrid progenies are viable in natural ponds and experimental tanks (You et al. 2009; Cui et al. 2013). Many models have been developed to examine the fertility and gamete ploidy of polyploid loaches. A natura
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