Induced diploid gynogenesis and polyploidy in crucian carp, Carassius auratus gibelio (Bloch), x common carp, Cyprinus carpio L., hybrids.

Abstract. Results of a 16 year (1977–1992) study of hybrids obtained from crossing two cyprinid fish, crucian carp, Carassius auratus gibelio (Bloch) (bisexual form), and common carp, Cyprinus carpio L., are presented. The ability to produce diploid eggs in F₁ females (resulting from chromosome endoreduplication in early oogenesis) was responsible for the high yield of spontaneous diploids in gynogenetic progenies of F₁ females and for triploidy in hybrids from back-crosses of F₁ females with males of the parent species. Different types of hybrids, including diploid and triploid gynogenetic, tetraploid (amphidiploid) and androgenetic progenies, were obtained. Diploid and some triploid hybrids (females only) were reproduced inter se by induced gynogenesis in several subsequent gynogenetic generations. Amphidiploid hybrids were obtained by crossing triploid F₈ females with diploid common carp males or by crossing diploid gynogenetic females with diploid inverted hybrid males producing diploid sperm. Results of cytogenetic investigations and fish culture properties in hybrids are presented. The scientific and practical significance of the data obtained are discussed.     

Reproductive ability of triploid ornamental (koi) carp (Cyprinus carpio L.) × goldfish (Carassius auratus L.) hybrids and characteristics of their offspring

The purpose of this study was to investigate reproductive ability of backcross triploid koi (Cyprinus carpio L.) × goldfish (Carassius auratus L.) hybrids. These triploids have been obtained by crossing of F₁ hybrid females producing diploid eggs with males of parental species. Triploid hybrid females, when crossed with goldfish or koi males, produced mostly aneuploid fish with ploidy range from approximately 2.2n–3.2n with a mean value 2.5n; some fish in crosses of triploid females with koi males were tetraploid (4.0n). Since analysed fish had in their genomes one haploid set from parental males, the data indicate that triploid hybrid females mostly produced aneuploid eggs with ploidy range from approximately 1.2n–2.2n and a mean ploidy around 1.5n while some eggs were triploid. Triploid hybrid males were completely sterile and have not released any sperm after hormonal injection. Despite their low viability, some aneuploid fish obtained from triploid hybrid females were raised in indoor recirculating systems until the age of 2 years and their reproductive ability has been evaluated. One aneuploid female with ploidy 2.1n produced larvae with ploidy range from 2.9n to 3.4n with a mean ploidy of 3.1n when crossed with a koi male; about 60% of obtained larvae had ploidy from 3.0n to 3.2n. These data indicate that this female produced mostly eggs with unreduced ploidy level.     

Verification of mitotic gynogenesis in ornamental (koi) carp (Cyprinus carpio L.) using microsatellite DNA markers

The Japanese ornamental (koi) carp is a popular decorative fish all over the world. In koi, clones have not yet been obtained, although production of fish with identical colour patterns could be of commercial interest. Mitotic gynogenetic progenies are essential for subsequent production of clones in fish. However, resulting late‐shocked progenies may be contaminated with meiotic gynogens from spontaneous suppression of the second meiotic division in eggs. In this study, microsatellite DNA markers were used to confirm mitotic gynogenetic origin of obtained late‐shocked progenies. Recombination rate (y) and mapping distance relative to centromere (M‐C) of 10 microsatellite loci were determined based on percentage of heterozygotes in meiotic gynogenetic progenies. The range of y varied from 0.01 to 0.96 and the M‐C map ranged from 0.5 to 48 cM. The mean value of y over the 10 loci was 0.481. Six loci, which had y 0.47 and higher, were used as markers in two late‐shocked gynogenetic progenies. Complete homozygosity was revealed at all six microsatellite loci indicating mitotic gynogenetic origin of analysed progenies.     

Chromosome set manipulation and sex control in common carp: a review

The development of techniques for production of gynogenetic, androgenetic, polyploid, and monosex progenies in common carp (Cyprinus carpio L.) is described from a chronological perspective. Gynogenetic progenies were obtained either by suppression of the second meiotic division in eggs (meiotic gynogenesis) or by suppression of the first mitotic division in haploid embryos (mitotic gynogenesis). As a rule, gynogenetic progenies of common carp were all-female, revealing female homogamety (females—XX, males—XY) in this species. Induced gynogenesis results in increased homozygosity; the rate of increase depends on the type of gynogenesis. Inbreeding coefficient (F) for one generation of meiotic gynogenesis in common carp is about 0.6, while diploids obtained by mitotic gynogenesis are homozygous for all genes (F = 1.0). Mitotic gynogenesis was used for production of clones in common carp. In androgenetic progenies of common carp, YY males were identified, that after crossing with normal females (XX) produced all-male progenies. Triploids of common carp are characterized by a significant reduction in gonad development (especially ovaries). However, the reduction in gonad development did not result in an increase of somatic growth rate of fish. The procedure for androgen treatment to induce phenotypic sex reversal in genotypic females (XX) was elaborated. All-female progenies of common carp were produced on a large scale by crossing normal females (XX) with hormonally sex-reversed males (XX). Rearing of all-female progenies in conditions when fish normally reach sexual maturity before reaching of market size increased production yield by 7–8%. In a few cases distant hybridization resulted in polyploidy of fish without application of any physical treatment. The ability of hybrid females between crucian carp (Carassius auratus) and common carp to produce diploid (with unreduced chromosome number) gametes resulted in opportunities to produce triploid and tetraploid hybrid progenies.     

Reproductive ability of second generation ornamental (koi) carp (Cyprinus carpio L.) × goldfish (Carassius auratus L.) hybrids and characteristics of their offspring

The purpose of this study was to investigate the reproductive ability of second generation (F₂) koi (Cyprinus carpio L.) × goldfish (Carassius auratus L.) hybrids. Only diploid F₂ males and females were fertile and used in crosses. A significant increase was recorded in male fertility in F₂ versus F₁. In contrast with an earlier study in which only one fertile F₁ male was found, about 20% of F₂ males produced sperm. The observed reproductive ability of F₂ hybrids was similar to that demonstrated by the only fertile F₁ male and F₁ females. F₂ males produced diploid spermatozoa and generated triploids when crossed with koi females. All triploid fish in these progenies were males indicating that F₂ males had a sex chromosome constitution of XY. F₂ females produced diploid eggs and generated mostly triploids when crossed with koi males. In progenies obtained by crosses of F₂ males with F₁ and F₂ females, most of the surviving juveniles (63%–100%) were diploid; a minority of juveniles were aneuploid (ploidy ranged from 2.1n to 3.6n). Diploid fish in these progenies were presumably the result of spontaneous androgenesis and gynogenesis, by the same mechanisms observed earlier in progenies obtained by crossing the F₁ male with F₁ females.     

Gynogenesis and sex determination in large-scale loach Paramisgurnus dabryanus (Sauvage)

Gynogenesis was induced using heterologous sperms in large-scale loach, Paramisgurnus dabryanus (Sauvage), in which a ZW/ZZ sex determination was previously proposed. Three microsatellite loci were used to monitor exclusive maternal inheritance of gynogenetic progenies. The results showed that high percentages of meiogynogens were produced at 4 min post-fertilization and mitogynogens were produced at 18 min post-fertilization by heat shocks, while meiotic gynogenesis was induced by cold shocks within a wide period and high heterozygosity was even observed in gynogens produced at 24 min post-fertilization. The sex ratios of the F₁ progenies in three gynogenetic families were significantly deviated from 1:1 expectation with a female bias in two families and a male bias in one family (P < 0.05), and the other four gynogenetic families showed approximate 1:1 sex ratios. Moreover, the self-mating between gynogenetic F₁ progenies and mating between gynogenetic F₁ progenies and normal individuals produced all-female progenies or identical proportions of females and males. The data of sex ratios generally confirmed that the sex determination in large-scale loach was determined by the putative ZW/ZZ system, and the possible reasons causing the biased sex ratios are discussed.     

Genetic variability in meiotic gynogenetic muskellunge,Esox masquinongy (Mitchell), estimated from segregation of microsatellite alleles

Muskellunge, Esox masquinongy, is an important recreational freshwater fish native to North America. Since muskellunge populations are often maintained through stocking efforts, advances in muskellunge reproductive technologies are of direct relevance to fishery enhancement. We evaluated the efficiency of inbreeding through induced meiotic diploid gynogenesis. Eggs from six female muskellunge were manually stripped and activated using ultra violet‐irradiated yellow perch, Perca flavescens, sperm. Hydrostatic pressure shocking regimes (48 263 kPa) were then applied to the eggs to prevent second polar body expulsion producing unambiguous meiotic gynogens. Six female dams and samples of 12–20 of their gynogenetic progeny were genotyped at seven polymorphic microsatellite loci. Chromosomal recombination frequencies of microsatellite loci based on retention of heterozygosity among gynogens ranged from 0.043 to 0.839 (0.576 ± 0.237). There were no statistical differences in recombination frequency among females at any of the loci. The average inbreeding coefficient (F‐value) ranged from 0.581 to 0.979, equivalent to three to fourteen generations of full‐sibling crosses respectively. The average F‐value overall was 0.712, equivalent to between five and six generations of full‐sibling crosses. Centromere map distances of the seven microsatellite loci ranged from 2.15 to 41.95 cM and meiotic gynogenesis was useful in eliminating heterozygosity at loci proximal to the centromere, but not distal. Since the age at maturity of female muskellunge is approximately 5 years, gynogenesis may pose an expeditious alternative to traditional breeding strategies for creation of homozygous pedigrees for some loci that may be outcrossed to introduce positive heterozygosity effects in the offspring.     

Production of meiotic gynogenetic and triploid sea bass, Dicentrarchus labrax L.: 1. Performances, maturation and carcass quality

Meiotic gynogenetic and triploid sea bass were produced by pressure shocks according to a previously published protocol. Pressure-treated groups did not survive as well as controls during early development and larval rearing. Performances, sexual maturation and carcass quality were examined over a period of 34–45 months. At the age of 34 months, growth of the gynogenetic fish was comparable to that of the control but inferior in the triploid fish. A predominance of male fish was found within the triploid groups, while diploid and meiotic gynogenetic fish showed equal proportions of the sexes. Gonadal maturation in triploid fish was significantly impaired, particularly in the females that showed rudimentary ovaries. Triploid males exhibited primary maturation but proved to be gametically sterile. Pressure-induced triploids did not grow as well as diploids, but these results might be ascribed to specific on-growing conditions (communal rearing). The performance of gynogenetic sea bass was comparable to that of control. The superiority of diploid fish over their triploid counterparts was confirmed during the final growing period and more clearly so in females. Performances of triploids varied according to their maternal origin. Overall, striking qualitative differences between diploid and triploid fish were found at the age of 34 and 45 months, although the results varied in a gender-specific manner. A strong maternal effect was also observed. The potential advantages of triploid sea bass for aquaculture purposes are discussed.     

微卫星分离模式显示雄性三倍体鲫产生非整倍体精子

三倍体鲫(Carassius auratus)行天然雌核发育,其自然种群中却有较高比例的雄性个体,这些雄性个体的性腺发育正常,能产生有活力的精子。而且其精子的DNA含量约为体细胞的一半,显示三倍体鲫精子发生过程中可能经历了均等的减数分裂。流式细胞术虽然能够较准确地测定细胞群的平均DNA含量,但是却很难检测到单个精子中的个别染色体增减,要明确回答雄性三倍体鲫产生的精子是否为整倍体需要定量地检测单个精子的遗传组成。本研究用微卫星标记检测以雌性鲤(Cyprinus carpio)与雄性三倍体鲫为亲本构建的杂种家系的基因型,结果发现母本鲤的多态位点在子代中呈孟德尔分离,父本三倍体鲫具有三套鲫基因组,其等位基因在子代中呈随机分离。上述研究结果提示:三倍体鲫起源于二倍体鲫的同源加倍,而非二倍体鲫和鲤的种间杂交;三倍体鲫通过染色体的随机分离产生非整倍体的精子,其精子发生过程中没有均等的减数分裂。三倍体鲫行雌核发育生殖,却可能并非起源于种间杂交且群体中的雄性个体可育,因而是单性生殖鱼类中的一个特例。     

RAPD and microsatellite analysis of diploid gynogens from allotetraploid hybrids of red crucian carp (Carassius auratus)×common carp (Cyprinus carpio)

Genetic variation was comparatively analyzed between the artificially induced diploid gynogen population from F₁₀ allotetraploid hybrids of red crucian carp (♀) (Carassius auratus red var., 2n=100)×common carp (♂) (Cyprinus carpio L., 2n=100) and the normal F₁₀ allotetraploid hybrid population used as the control, using random amplified polymorphic DNA (RAPD) assay and microsatellite analysis. The specific 600-bp fragment for diploid gynogen population was detected by S45 and the specific 900-bp fragment for allotetraploid F₁₀ hybrid population was detected by S134. The results from RAPD assay and microsatellite analysis were in agreement with each other, that is to say, the diploid gynogens presented lower level of polymorphism than allotetraploid F₁₀ hybrids. Furthermore, as expected, microsatellite analysis revealed more detailed information on genetic diversity than RAPD assay. The mean percentage of polymorphic loci (12.71%) and Shannon's index of phenotypic diversity (0.25) from RAPD data for diploid gynogen population were significantly lower than those (30.69% and 0.63, respectively) for F₁₀ allotetraploid hybrid population. The mean number of alleles per microsatellite locus (1.73) in diploid gynogen population was considerably lower than that (2.55) in F₁₀ allotetraploid hybrid population. The average observed (0.36) and expected heterozygosity (0.26) in diploid gynogen population were lower than those (0.58 and 0.40, respectively) in F₁₀ allotetraploid hybrid population, indicating that the diploid gynogens presented lower genetic diversity than the allotetraploids. In addition, the mean effective number of alleles at 11 microsatellite loci (1.60) in diploid gynogen population was lower than that (1.88) in F₁₀ allotetraploid hybrid population. The significant differences between two populations in the average observed and expected heterozygosity, mean number of alleles and effective number of alleles, suggested that the effect of gynogenesis resulted in rather higher genetic homogeneity in diploid gynogens. The comparative RAPD analysis of diploid gynogens and their parents was performed with 34 primers. The identical RAPD pattern was detected between diploid gynogens and their female parent, however, some clear specific RAPD bands were detected between diploid gynogens and their male parents, but not detected in their female parent. The result indicated that heterologous genetic material had incorporated into diploid gynogenetic fish (G₁).     

黄姑鱼异质雌核发育子代的遗传分析

为了解黄姑鱼（Nibea albiflora）异质雌核发育子代的基因纯合情况,利用微卫星标记（SSR）和扩增片段长度多态性标记（AFLP）对黄姑鱼异质雌核发育家系进行遗传鉴定和分析。结果显示：（1）雌核发育家系在4个SSR位点和5对AFLP引物组合扩增出的位点均未发现父本特异性等位条带,表明雌核发育体比率为100%。（2）用于遗传分析的7个SSR位点在雌核发育家系和正常交配家系中均未见完全纯合的情况,雌核发育家系7个SSR位点的平均纯合度为0.382,是正常交配家系（0.161）的2.37倍。雌核发育家系各个体的纯合位点数为0~6个,纯合位点所占比例为0~85.7%。（3）5对AFLP引物共扩增出182条清晰的扩增条带,其中有21条父本特异性条带和16条母本特异性条带。16条母本特异性条带中有7个条带在雌核发育家系中显著偏分离（P<0.05）。雌核发育家系和正常交配家系多态性条带比例分别为14.7%和20.3%。（4）雌核发育家系与母本的遗传相似度高于与正常交配家系的遗传相似度,正常交配家系同父本和母本的遗传距离大致相同。研究结果表明,黄姑鱼异质雌核发育二倍体家系的遗传纯合度显著高于正常交配家系,人工诱导雌核发育是促进基因纯合的一个有效途径,它不仅可以加速有利基因的纯合固定,还可以加速有害基因的淘汰,从而有效提高育种效率。     

Gynogenesis induction and sex determination in the Eurasian perch,Perca fluviatilis

In the present study, we used meiotic gynogenesis, widely used in studies on sex determination, to confirm female homogamety in Eurasian perch, Perca fluviatilis. Sperm irradiated with UV for 400 s was used to artificially fertilized eggs. The diploid of the resulting embryos was restored by a heat shock (30 °C) applied to the eggs 5 min postfertilization, for 25 min. Fertilization (ranging between 45% and 75%) and survival rates at hatching (ranging between 3.4% and 46.6%) were not significantly different (P>0.05) between the diploid control and gynogenetics. The diploid controls and two batches of gynogenetics contained 100% diploid larvae, whereas two other batches of gynogenetics contained 6.7% and 10.0% triploid larvae. The sex ratios of the diploid controls were not significantly different from 1:1, whereas all gynogenetic families were 100% female. These results confirm female homogamety in Eurasian perch, demonstrated by the use of hormonally mascilinized breeders in a previous study.     

Assessment of homozygosity and fertility in meiotic gynogens of the European sea bass (Dicentrarchus labrax L.)

Analysis of 5–6 microsatellite loci was used to measure the increment of homozygosity in two meiogynogenetic progenies (A and B) of sea bass with respect to their mother. In progeny A and B, 20% and 12% of the meiogynogens retained heterozygosity for all investigated maternal loci, respectively, while complete homozygosity was observed only in 6% of B and in none of A, indicating the occurrence of significant allelic recombination during meiosis. The overall increment of homozygosity for the investigated loci was 27% for A and 47% for B. Although survival at hatching of meiogynogens was about half that of controls, they subsequently grew as controls and displayed the same onset of puberty and reproductive potential at adulthood during three consecutive years when crossed between themselves (11 crosses) or with control fish (13 crosses). In particular, meiogynogenetic females (n=24) underwent vitellogenesis and yielded eggs of good quality upon stimulation with LH–RH analogue similarly to normal fish. Sperm released by meiogynogenetic males (n=23) was equivalent to that of controls in terms of volume, quality and fertilization capability.Second generation meiogynogens were obtained by chromosome set manipulation from meiogynogenetic females and found to be morphologically normal at 3 years of age. Interestingly, under our culture conditions, the percentage of meiogynogenetic males in the second generation was 7% as opposed to 39% in the first generation.     

Microsatellite–centromere mapping in walking catfish Clarias macrocephalus (Günther, 1864) using gynogenetic diploids

Thirty new microsatellite loci were isolated from a microsatellite‐enriched genomic library of walking catfish Clarias macrocephalus. The CA motif was the most abundant, although several other motifs were also isolated. Two gynogenetic diploid families, each consisting of a female and 50 offspring, were genotyped at 56 microsatellite loci, including 30 loci developed in the present study and 26 loci reported in the previous study. Overall, 33 anonymous microsatellites derived from genomic library and 11 EST‐linked microsatellites were mapped to their centromeres. High levels of chiasma interference were apparent in the walking catfish genome as indicated by an average frequency of second‐division segregation (y) of 0.643 ± 0.248. Twenty‐six loci (59%) showed a high microsatellite–centromere recombination, with a frequency >0.67, and three loci had recombination frequencies >0.9. This study demonstrated that gene–centromere mapping provided a rapid method for the expansion of the initial linkage map of walking catfish.     

Induction of meiotic gynogenesis in the stinging catfish Heteropneustes fossilis (Bloch) and evidence for female homogamety

This study reports the results on induced meiotic diploid gynogenesis and female homogametic nature in the Indian catfish, Heteropneustes fossilis. The eggs of H. fossilis were inseminated with conspecific sperm. The sperm suspension was diluted to 1 × 10⁷ sperm mL⁻¹ in Hanks balanced salt solution. Sperm were irradiated under UV light, with the exposure time ranging from 15 to 360 s (7500 ergs mm⁻² for 60 s). The genetic inactivation of paternal chromosomes was confirmed by chromosome counting from the larval cells and the larvae also had a characteristic haploid syndrome. A typical ‘Hertwig effect’ in the yield of hatched larvae was observed with doses of UV exposure >75 s (9375 ergs mm²). Larvae resulting from sperm UV irradiated above 120 s (15 000 ergs mm²) were 100% haploids. Application of heat shock to the activated eggs was effective in suppressing the release of the second polar body (meiotic gynogenesis) and resulted in diploid gynogenetic larvae morphologically identical to those of the control. The best yield of diploid gynogens (49.3% with respect to the control) was found to be at 6 min after egg activation and the heat shock at 41 °C for a 1-min duration, at an ambient water temperature of 27 °C. A total of 113 diploid gynogenetic fry from seven different female fish were reared and subjected to sexing. All gynogenetic fish were female in contrast to the control, which had a mean sex ratio of 56.7% females (which was not significantly different from 50% female). From these results, the sex determination mechanism in H. fossilis was presumed to be female homogamety.     

利用SSR﹑EST-SSR、SNP标记对鲤食物转化率、体厚、体质量3种性状的分析

利用Windows Map Manager2.0的标记回归法对鲤(Cyprinus carpio L.)F2群体进行单标记定位分析.用91个SSR标记、33个EST标记、364个SNP标记对鲤进行全基因组扫描,结果得到与食物转化率、体厚、体质量3个性状显著相关(P＜0.05)的标记,分别为27、35、27个,其中与食物转化率相关的标记SNP0041、SNP0044,其相关性达到极显著水平(P＜0.001),贡献率分别达到15%、16%.这些标记可作为分子标记辅助育种的参考标记.将得到的与食物转化率显著相关的EST座位HLJEl4、HLJE253和与体质量显著相关的HLJE253座位在NCBI上进行BLAST比对,结果显示HLJE253与斑马鱼上编码ORF2结构蛋白的基因相关,相关程度达61%.将得到的与3种性状相关的SNP标记在NCBI上进行序列查找,通过Blast比对找到相关的基因,并对可能的功能作了注释.     

Aquaculture performance of triploid barfin flounder Verasper moseri

ABSTRACT:   To evaluate the aquaculture performance of triploid barfin flounder Verasper moseri , the sex ratio, maturation, growth and the relative proportion of body parts were examined. The sex ratio of triploids was similar to diploids under communal rearing conditions, but the proportion of female diploids was higher than that of triploids under separate rearing conditions. The gonadosomatic index of triploid females was very low even during the spawning season, and the ovaries were rudimentary. These results suggest that triploid barfin flounder females were sterile. In addition, triploid males produced a small quantity of milt containing very few spermatozoa with abnormal shapes. Spermatozoa obtained from triploids were aneuploidies. When normal eggs were fertilized with sperm from triploid males, no fry developed. These results suggest that triploid barfin flounder males were functionally sterile. Triploid males grew more slowly than diploid males, and triploid females showed similar or slower growth than diploid females, whether reared separately (23 months) or communally (35 months). The ratios of visceral weight to the edible parts for triploid males were similar to those for diploid males, but ratios for triploid females were higher than for diploid females during the spawning period. In conclusion, a significant improvement of growth was not found in triploid barfin flounders.     

Studies on sperm of diploid and triploid tench, Tinca tinca (L.)

The tench Tinca tinca is an interesting fish from the viewpoint of polyploidy and related atypical reproduction aspects. Triploid tench were produced artificially. Studies of spermiation as well as of sperm motility and structure were performed on several triploid and diploid males simultaneously with individual experimental crosses with diploid females to define their reproductive capacities. The testes of triploids visually looked less developed in the most of cases with lower sperm production (0.05 cm³ sperm per male), GSI and weight of testes compared to diploids (0.58 cm³ sperm per male). Analysis of variance showed significant influence of ploidy level on the percentage of motile spermatozoa. Triploidy did not change percentage of live spermatozoa and velocity of spermatozoa at the first time of sperm movement. The study of sperm structure by scanning electron microscopy revealed that most sperm cells were of normal structure with some anomalies. Sperm heads of triploid and diploid males were mostly round-shaped, 1.86±0.2 and 1.6±0.18 μm in diameter. The midpiece of triploid spermatozoa was slightly narrower than that of diploid ones with typical cylindrical shape. Flow cytometry revealed sperm cells of triploids to be largely aneuploid (1.47 n) with high mosaic DNA, oscillating from haploid DNA content (1.0 n) to diploid DNA content (1.9 n). Experimental crosses between triploid males and diploid females revealed that these males were capable to stimulate effective development with relatively high level of fertilization and hatching rates from 0 to 70%. In conclusion, triploidization does not seem to guarantee sterility of tench.     

Ovaprim treatment promotes oocyte development and milt fertilization rate in diploid and triploid African catfish (<Emphasis Type="Italic">Clarias gariepinus)</Emphasis>

Triploid fish are increasingly used in aquaculture because they are generally unable to reproduce successfully. Energy is channeled into somatic growth rather than gonadal development, and in the event of escape, the animals are unlikely to breed successfully among themselves or with wild conspecifics. This study tested the ability of recently matured triploid African catfish (Clarias gariepinus) to produce and fertilize eggs with and without ovaprim treatment. Triploid females did not show the increase in ovary size observed in diploid members of the same cohort between 8 and 9 months of age, or the coincident decrease in visceral fat deposits, and this was unaffected by up to 5 weekly i.m. injections of 0.5 ml kg⁻¹ Ovaprim. However, we observed advanced vitellogenin (Vtg) sequestration in oocytes of triploid females, albeit to a lesser degree and with lesser cortical alveoli, compared to oocytes from diploid cohort members. Histological sections revealed a positive trend of oocyte development up to the third weekly ovaprim injection followed by a negative gonadal development in weeks four and five. Milt from triploid males injected 9–12 h earlier with 0.25 ml kg⁻¹ ovaprim i.m. fertilized more diploid eggs than milt from untreated triploid males (30 vs. 20%), but none of the developing embryos of triploid paternity survived to hatch. In contrast, milt of diploid males fertilized 49% of eggs, and 20% of the developing embryos hatched successfully. These rates were improved in ovaprim-injected diploid males to 70% fertilization and 33% hatch. This study demonstrates potential of overcoming non-viability of eggs from triploid female African catfish, and enhancing the ability of triploid milt to fertilize eggs.