The improved tetraploids (G1×AT) were obtained by distant crossing and gynogenesis and the high-body individuals accounted for 2% among G1×AT. After mating with each other, the high-body in- dividuals produced three kinds of bisexual fertile diploid fishes: high-body red crucian carp, high-body fork-like-tails goldfish and gray common carp. The high-body red crucian carp mating with each other formed three types of improved crucian carp (ICC) including improved red crucian carp (IRCC), im- proved color crucian carp (ICCC) and improved gray crucian carp (IGCC). The phenotypes, chromo- some numbers, gonadal structure and fertility of the three kinds of ICC and their offspring were observed. All the three kinds of ICC possessed some improved phenotypes such as higher body, smaller head and shorter tail. The ratios of the body height to body length of IRCC, ICCC and IGCC were 0.54, 0.51 and 0.54, respectively. All of them were obviously higher than that of red crucian carp 0.41 (P<0.01). Three kinds of ICC had the same chromosome number as red crucian carp with 100 chromosomes. All the ICC possessed normal gonads producing mature eggs or sperm, which was important for the production of an improved diploid population. Compared with red crucian carp, all the ICC had stronger fertility such as higher gametes production, higher fertilization rate and higher hatchery rate. Three types of improved diploid fish population were generated from the three kinds of ICC by self-crossing, respectively. The ICC can serve as ornamental fish and edible fish. They are also ideal parents to produce triploids by mating with tetraploids. The new ICC plays an important role in biological evolution and fish genetic breeding.
WANG Jing, QIN QinBo, CHEN Song, LIU ShaoJun, DUAN Wei, LIU JinHui, ZHANG Chun, LUO KaiKun, XIAO Jun & LIU Yun Key Laboratory of Protein Chemistry and Developmental Biology of Ministry of Education of China, College of Life Sciences, Hunan Normal University, Changsha 410081, China
Bisexual fertile diploid androgenetic individuals(A_(0))(2n=100)were formed by androgenesis.In this way,the diploid spermatozoa from male allotetraploid hybrids(AT)(4n=200)of red crucian carp(Carassius auratus red var.)(♀)×common carp(Cyprinus carpio L.)(♂)were used to fertilize the UV-treated hap-loid eggs of goldfish(Carassius auratus),and living androgenetic diploid fish were developed.The A_(0)became sexually mature at the age of 2 years,and they fertilized with each other to form their offspring(A_(1)).In this study,we observed the chromosomal number,gonadal structure and appearance of A_(1)fish.The results are as follows:(1)In A_(1),there were 85%tetraploids(A_(1)-4n),10%triploids(A_(1)-3n)and 5%diploids(A_(1)-2n),suggesting that diploid A_(0)could produce diploid gametes.It was concluded that the formation of diploid gametes generated from diploid A_(0)was probably related to the mechanism of pre-meiotic endoreduplication.(2)Among A_(1),only A_(1)-4n possessed normal ovaries and testes.The mature males of A_(1)-4n produced white semen.Under the electron microscope,the head of diploid sperm generated by A_(1)-4n was bigger than that of haploid sperm generated by red crucian carp.In the testes of the A_(1)-4n,there were many mature normal spermatozoa with a head bearing plasma mem-brane and a tail having the typical structure of"9+2"microtubules.Between the head and the tail,there were some mitochondria.The ovaries of A_(1)-4n developed well and mainly contained II,III and IV-stage oocytes.The IV-stage oocytes were surrounded by inner and outer follicular cells.The micropyle was observed on the oolemma of follicular cells.There were abundant yolks and plenty of endoplasmic reticulum in the cytoplasm of IV-stage oocytes.Because A_(1)-2n and A_(1)-3n were distant crossing diploid hybrids and triploid hybrids respectively,they possessed abnormal gonads,and no mature semen and eggs were observed.(3)Compared with allotetraploids,the A_(1)-4n fish not only had advantages such as fast growth rate and strong re
Dmc1 (disrupted meiotic cDNA) is a functionally specific gene, which was firstly discovered in yeast and then found to encode a protein required for homologous chromosome synapsis during the process of meiosis. In this investigation, we cloned the partial cDNAs of Dmc1 of diploid red crucian carp, Japanese crucian carp, common carp, triploid crucian carp and allotetraploid hybrids by using a pair of degenerate primers based on the conservative sequence of amino acids of the DMC1 protein in yeast, mouse and human. The full length cDNAs were then obtained by rapid amplification of cDNA ends (RACE). Our data showed that the full length cDNAs of Dmc1 in the three diploid fishes are all 1375 bp long, while it is 1383 bp long in triploids and 1379 bp long in allotetraploids. And despite of the variation in length, all the cDNAs encode a protein of 342 amino acids. A high homology of 97.3% of the DMC1 protein can be drawn by comparing the amino acid sequences in the three diploids, which is also of 86%, 86% and 95% similarity to human, mouse and zebrafish, respectively. A comparative study of the expression pattern of Dmc1 was carried out by RT-PCR using specific primers against the same se-quences of coding regions in different ploidy cyprinid fishes, from which it was showed that Dmc1 was expressed only in gonads of these five kinds of fishes. The expression pattern of Dmc1 in both ovaries and testes from different ploidy fishes within breeding season was also studied by Real-time PCR, and the results showed that the expression of this gene was greatly different among the three different ploidy fishes, which was the highest of triploid and lowest of allotetraploids. The histological sections data showed matured gonads of both diploid red crucian carp and allotetraploids in breeding season, although the latter demonstrated a higher maturation, and no gonadal maturation could be observed in triploids. In conclusion, we suggest that Dmc1 is specifically expressed in the period of meiosis in all the ploidy cyprinid fishes
TAO Min, LIU ShaoJun, LONG Yu, ZENG Chen, LIU JiFang, LIU LiangGuo, ZHANG Chun, DUAN Wei & LIU Yun Key Laboratory of Protein Chemistry and Developmental Biology of State Education Ministry of China, College of Life Sciences, Hunan Normal University, Changsha 410081, China
