Diploid Males Research Articles

Genetic studies of tench ( Tinca tinca L.): induced triploidy and tetraploidy and first performance data

Triploidy was successfully induced with cold shocks of 0–2°C, lasting 35 min and starting 2–5 min after gamete activation and with hydrostatic pressure shocks with 1, 2 and 5 min exposure at 50.01–52.47 MPa starting 2–5 min after gamete activation. Tetraploidy was successfully induced with heat shocks of 40.5°C, lasting 1.5 min and starting 45 min after gamete activation and with hydrostatic pressure shocks starting 50 min after gamete activation without further changes in the remaining parameters. Temperature shocks were considered to be the most suitable treatments, based on observed proportions of viable polyploids and incubation rates. The τ 0 unit for tench was used for standardization of shock initiation. Results of rearing triploid and/or tetraploid tench in experimental earthen ponds were assessed. A sample of 19 4-year-old triploid and their 43 diploid siblings was used for analysis of weight differences, gonadosomatic index and dressing percentage. Triploid females displayed 13.52% higher live weight and 3.94% higher dressing percentage than diploid females ( P<0.001) and their gonadosomatic index reached 25.10% of that of diploid females ( P<0.001). Triploid males displayed 23.66% higher live weight than diploid males ( P<0.01). Their dressing percentage was 1.30% lower ( P<0.1) while gonadosomatic index reached 60.00% of that of diploid males. Differences in live weight and gonadosomatic index between triploid females and triploid males were found statistically significant ( P<0.01 and P<0.05, respectively) while no difference was found in dressing percentage.

Viability of diploid males in the parasitic wasp,Diadromus pulchellus (Hym.: Ichneumonidae)

In the HymenopteraDiadromus pulchellus diploid males have been observed in samples collected in the wild and bred in the laboratory. Using a yellow body color mutant strain, a protocol of crosses, involving inbred individuals, allows the routine production of such diploid males. These males result from the development of fertilized ova and emerge normally. Their preimaginal viability is similar to those of other individuals, and their imaginal viability does not differ from that of haploid males. Diploid males present normal external morphology and neither mosaicism nor intersexuality was observed. However, they are bigger than haploid males and have head size and wing length similar to those of females. The significance of diploid male viability in hymenopteran populations is discussed.

Sex determination in the hymenopteran Diadromus pulchellus (Ichneumonidae): validation of the one-locus multi-allele model

Males of the hymenopteran Diadromus pulchellus are normally haploid, but diploid males can be obtained by inbreeding. Inbred crosses within strains that are polymorphic at the enzymatic loci Pgm-2 and Ao-4 or that differ by a body colour mutation produce heterozygous diploid males in offspring. The genotypic distributions observed in such progeny were compared with expected results under the one-locus sex determination model or the two independent loci model. The results show that only the one-locus multi-allele model fits the data and allow a provisional estimate of ∼ 15 sex alleles. These conclusions generalize the case of existence of a single locus to determine sex in Hymenoptera and are discussed at the evolutionary level.

染色体操作によるサケ科魚類の三倍体及び雌性発生二倍体の生物学的特性と形質遺伝に関する研究―ＩＩ 三倍体ニジマス雄における血清および下垂体ホルモン量の変動と精巣の発達

Testicular development and hormone levels of triploid males of rainbow trout were compared with those of diploid males during three consecutive seasons. Changes in the levels of serum sex steroid hormones (testosterone, 11-ketotestosterone, and 17α, 20β-dihydroxy-4-pregnen-3-one) and pituitary and serum gonadotropin in triploids were similar to those in diploids. Although meiotic division first occurred in the July testes of both triploids and diploids, subsequent spermatogenesis was markedly delayed in the testes of triploids. During the natural spermiating season, a large number of atretic figures of spermatogenic germ cells were found in the testes of triploids with a sudden decrease in the gonadosomatic index. The amount of sperm was markedly less in triploids than in diploids. Some necrotic cells were invested by hypertrophied Sertoli cells lining the inner wall of the lobular lumen. Taken together, these results suggest that the cause of abnormality of spermatogenesis in triploids is the disruption of meiosis due to the odd number of chromosome sets.

Developmental abnormalities in triploid hybrids between tetraploid and diploid tree frogs (genus Hyla)

Crosses between tetraploid female grey tree frogs, Hyla versicolor, and diploid males of the same genus may provide information on developmental differences between the parental species. Crosses with Hyla cinerea males in 1988 produced a large number of vigorous offspring, but abnormalities in eye development indicated some incompatibility of the parental genomes. The degree of eye development of the hybrids varied, ranging from completely absent to fully functional. Repetition of this cross combination in 1989 resulted in similar variation in eye formation. Histological sections through developing eyes indicated that the abnormalities may be related to improper formation of the cornea, improper orientation of the lens, or lack of lens induction. This may reflect differences in the timing of development between the two parental species.

Genetics of Sex Determination and the Improvement of Biological Control Using Parasitoids

Diploid males are known to occur in several braconid and ichneumonid species. These diploid males are the result of a single-locus, sex-determination mechanism. Heterozygotes at this sex locus develop into females, whereas hemizygotes (haploids) and homozygotes (diploids) develop into males. Diploid males have a low fertility and their frequency drastically increases with small populations or inbreeding. The implications of this sex-determining mechanism for the use of parasitoids in biological control are explored. Production of diploid males leads to male-biased sex ratios and can reduce rates of establishment and population growth. Taxa in which a single-locus sex determination has been found (e.g., Ichneumonidae and Braconidae) often experience extreme male-biased sex ratios in mass rearing and have been more difficult to establish than taxa with other modes of sex determination (e.g., Chalcidoids). The effect of laboratory rearing on the number of sex alleles, frequency of diploid males, and population growth rates is explored by computer simulation. Methods of rearing and release that can enhance the number of sex alleles and the establishment of parasitoids are discussed. Furthermore, additional small-scale releases may enhance the effectiveness of already established populations by increasing number of sex alleles and the rate at which their population grows.

Expression of cis-regulatory mutations of the white locus in metafemales of Drosophila melanogaster.

At the white eye colour locus, there are a number of alleles that have altered expression between males and females. To test these regulatory mutations of the white eye colour locus for their phenotypic expression in metafemales (3X; 2A) compared to diploid females and males, eleven alleles or transduced copies of white were analysed. Two alleles that exhibit dosage compensation between males and females (apricot, blood) also exhibit dosage compensation in metafemales. White-ivory and white-eosin, which fail to dosage compensate in males compared to females, but that are distinct physical lesions, also show a dosage effect in metafemales. Two alleles with greater expression in males than females (spotted, spotted-55) exhibit even lower expression in metafemales. Lastly, five transduced copies of white carrying three different lengths of the white promoter, but that all exhibit higher expression in males, show reduced expression in metafemales, exhibiting an inverse correlation between the level of expression and the dosage of the X chromosome. Because these alleles of white respond to dosage compensation in metafemales as a continuum of the male and female responses, it is concluded that the same basic mechanism of dosage compensation is involved and that the dosage of the X chromosome conditions the sexually dimorphic expression.

Hybridization of chromosome-polymorphic populations of the inquiline ant,Doronomyrmex kutteri (Hym., Formicidae)

The workerless, inquiline ant,Doronomyrmex kutteri has isolated populations with a haploid chromosome number ofn=23 both in the Alps (Swiss and South Tyrolean Alps) and in Sweden, and a population withn=25 in southern Germany. Crossbreeding of sexuals from all populations proved successful. Backcrosses of F1-females with males from the parental populations produced F2-females, and hybrid males withn=23, 24, or 25 chromosomes. The chromosome polymorphism is not due to B-chromosomes. Probably then=25 karyotype originated from then=23 karyotype by two Robertsonian fissions (2 ¯M → 4 ¯A), since then=25 karyotype was found in only one of the populations. Diploid males occurred frequently in colonies from four out of five sites investigated.

X‐linked gene expression and sex determination in Caenorhabditis elegans

The signal for sex determination in the nematode Caenorhabditis elegans is the ratio between the number of X chromosomes and the number of sets of autosomes (the X/A ratio). Animals with an X/A ratio of 0.67 (a triploid with two X chromosomes) or less are males. Animals with an X/A ratio of 0.75 or more are hermaphrodites. Thus, diploid males have one X chromosome and diploid hermaphrodites have two X chromosomes. However, the difference in X-chromosome number between the sexes is not reflected in general levels of X-linked gene expression because of the phenomenon of dosage compensation. In dosage compensation, X-linked gene expression appears to be 'turned down' in 2X animals to the 1X level of expression. An intriguing and unexplained finding is that mutations and X-chromosome duplications that elevate X-linked gene expression also feminize triploid males. One way that this relationship between sex determination and X-linked gene expression may be operating is discussed.

Allozyme variation, linkage disequilibrium and diploid male production in a primitively social bee Augochlorella striata (Hymenoptera; Halictidae)

A population of the primitively eusocial bee Augochlorella striata was surveyed for allozyme variation at 47 loci for 35 enzyme systems with a mean number of haploid genomes sampled of 76 per locus. The expected heterozygosity (mean ± S.E.) was 0·107 ± 0·004, the highest found for any bee species, solitary or social, studied to date. This result indicates that low levels of genetic variation are not ubiquitous in bees. No differences in allele frequencies between males and females were found. One diploid male was detected providing a maximum likelihood estimate of the frequency of diploid males in the population of 2·6 per cent. Strong linkage disequilibrium was detected between the loci Dia-2 and Lap. Under a genetic drift explanation for disequilibrium and realistic assumptions for the recombination rate between the two loci, the predicted population size is in broad agreement with that suggested from field studies

Genome elimination in diploid and triploid Rana esculenta males: cytological evidence from DNA flow cytometry

Cytological aspects of hemiclonal (meroclonal) inheritance in diploid and triploid males of the hybridogenetic frog Rana esculenta (Rana ridibunda x Rana lessonae) have been studied by DNA flow cytometry. The fact that the R. ridibunda genome contains 16% more DNA than the R. lessonae genome provides the ability to discern cells containing genomes of any species from the water-frog complex under study. Data are presented showing that elimination of the R. ridibunda genome occurs in hybridogenetic males from certain populations. In triploid males, the cytogenetic mechanism of hemiclonal inheritance is simpler than in diploids: after the elimination of a genome (always the genome in the minority in the triploid set; "homogenizing elimination"), no compensatory duplication of the remaining genetic material is necessary, as it is in diploids. The process of elimination can be visualized in triploid males by using DNA flow cytometry to identify cells in the special phase of the spermatogonial cell cycle that we termed the E phase.

DIPLOID MALES IN A PRIMITIVELY EUSOCIAL BEE, LASIOGLOSSUM (DIALICTUS) ZEPHYRUM (HYMENOPTERA: HALICTIDAE).

Hymenoptera are characterized by a haplo-diploid mechanism of sex determination. Females are diploid and males are haploid. However, in many species diploid males may occur if individuals are homozygous at a sex determining locus. Diploid males were found in three out of four populations (nest aggregations) of the primitively eusocial, halictine bee Lasioglossum zephyrum for which samples of males were examined electrophoretically. The frequency of diploid males was greater in a small, geographically isolated population (the "Robinson" nest aggregation) than in a large population that had nearby neighboring populations (the "Salmon Creek A" nest aggregation). In addition, the proportion of polymorphic loci was lower in the Robinson nest aggregation suggesting that a bottleneck event or loss of alleles due to small population size occurred in the Robinson population that involved a loss in the number of alleles at the sex determining locus.

Esterase isozymes in a solitary bee,Megachile rotundata (fab.): Characterization, developmental multiplicity, and adult variability

This study describes the biochemical characterization and genetic variation of cytosolic esterases in the alfalfa leafcutting bee, Megachile rotundata (Fab.). Esterase isozymes were separated by nondenaturing polyacrylamide gel electrophoresis and isoelectric focusing and characterized by inhibition with eserine sulfate, EDTA, paraoxon, and p-hydroxymercuribenzoate. Based on inhibition patterns and substrate specificity, there are major differences between adults and immature forms and more subtle differences between male and female adults. M. rotundata esterases are largely organophosphate sensitive and the two major adult allozymes were highly variable within the population examined. Differences in esterase expression between life stages with respect to niche and the occurrence of diploid males are discussed.

The evolution of polyandry by queens in social Hymenoptera: the significance of the timing of removal of diploid males

Multiple mating by queens in social Hymenoptera with single locus sex determination may be an adaptation to reduce the effect of genetic load caused by the production of diploid males, if there is a concave relationship between queen fitness and the proportion of diploid male offspring in the colony. In this situation queens should be selected to reduce the variance in the production of diploid male offspring by multiple mating. It has been suggested that this concave relationship occurs in species such as the honey bee, Apis mellifera, in which reproduction occurs near the peak of colony population. This paper suggests that the timing of diploid male removal may influence mating frequency, with early removal of diploid males favoring multiple mating and late removal of diploid males favoring single mating. This idea is explored in two ways. A mathematical model shows that cell use in the brood area of species that rear young in cells will be more efficient with multiple mating. This would favor multiple mating in species, such as the honey bee, in which brood rearing is constrained by the usable area of the brood chamber. Secondly, comparison of polyandrous honey bees (early removal of diploid males as young larvae) with monandrous fire ants, Solenopsis invicta, and Melipona bees (non-removal of immature diploid males) suggests that in the species without diploid male removal, variance reduction may reduce queen fitness. Suggestions are made for testing this hypothesis.

Experiments inducing prospective polar body nuclei to participate in embryogenesis of the sawfly Athalia rosae (Hymenoptera)

Mature eggs dissected from ovaries of unmated females of Athalia rosae (Hymenoptera: Tenthredinidae), if placed on a filter-paper soaked with distilled water, are activated and develop to haploid males. Occasionally, however, diploid females develop from these artificially activated eggs. Treatment of mature unfertilized eggs dissected from diploid females with ice-cold temperatures immediately before activation and with a high temperature (36° C) upon and immediately after activation resulted in the production of diploid males, diploid females, triploid females and gynandromorphs at high frequency. The same treatment of mature unfertilized eggs dissected from triploid females resulted in the production of only triploid survivors. These results, together with the results on the segregation of a marker mutation, yellow fatbody (yfb), appear to indicate that meiotic divisions were complete in the treated eggs, and that all four nuclei became potentially capable of participating in development with or without automictic fusion.

Egg fertility, early development and survival from crosses of diploid female × triploid male grass carp ( Ctenopharyngodon idella)

Ova obtained from diploid grass carp females were inseminated with sperm from diploid and triploid males, during three consecutive spawning seasons (1986, 1987, 1988), with reproducible results. Fertilization success was significantly lower in diploid × triploid crosses (27, 38 and 25%) compared with diploid × diploid crosses (49, 84 and 82%). Hatching embryos from diploid × triploid crosses had significantly ( P < 0.05) smaller body and yolk sac areas, and utilized their yolk more slowly than embryos from diploid × diploid crosses. Most diploid × triploid embryos surviving to hatch, suffered from notochord deformities and died before exogenous feeding began. Survival of juveniles from diploid × triploid crosses from hatching to 5 months was 0.21% and 0.125% for 1987 and 1988, compared with 95% and 84%, for diploid × diploid crosses. Coulter Counter ploidy determination for nine (five in 1987, four in 1988) diploid × triploid juvenile survivors revealed a diploid genome.

Induction of vitellogenin synthesis and maturation of transplanted previtellogenic eggs by juvenile hormone III in males of the sawfly, Athalia rosae

Both haploid and diploid adult males of the hymenoptera, Athalia rosae (Symphyta, Tenthredinidae), produced the two vitellogenins, L and S, in their haemolymph following topical application of juvenile hormone III. Previtellogenic ovaries transplanted into the abdoment of haploid adult males which were then given juvenile hormone III topically, maturated and the eggs upon in vitro activation successfully completed embryonic development.

Coexistence of pseudogamous and sexual planthoppers of the genus Ribautodelphax (Homoptera, Delphacidae)

ABSTRACT. The occurrence of pseudogamous triploid females in populations of the diploid species Ribautodelphax pungens (Ribaut) was studied throughout Europe. Considerable differences in triploid frequencies were found between populations but no regular geographic pattern was discerned. Within populations triploid frequencies proved to be stable from generation to generation. The twofold reproductive advantage of the pseudogamous triploid females is counterbalanced by active mate discrimination by diploid males against the pseudogamous triploid females in populations with high triploid frequencies. Sexual diploid and pseudogamous triploid females showed no differences in phenology. Differential winter mortality was found between diploid and triploid larvae.

Chromosome studies of progenies of tetraploid female rainbow trout

Nine induced tetraploid females were artificially inseminated by UV-irradiated sperm collected from diploid males, in order to induce the gynogenetic development of their ova. Most of the resulting embryos were diploid (or minor aneuploids). Several gynogenetic tetraploids, likely to issue from unreduced ova, were also detected in these progenies. The same females fertilized by normal sperm of diploid males gave a majority of triploids and several pentaploids, while the fertilization by normal sperm of tetraploid males gave rise to a majority of tetraploids and one hexaploid. The same crosses, after the eggs had been heat-shocked to double the maternal genetic contribution, yielded about three-quarters pentaploids and one quarter haploids (normal sperm of diploids), or three-quarters hexaploids and one quarter diploids (normal sperm of tetraploids). These haploids and diploids are likely to result from androgenesis.

Diploid male production ? a significant colony mortality factor in the fire ant Solenopsis invicta (Hymenoptera: Formicidae)

Two forms of the fire ant, Solenopsis invicta, occur in North America; the monogyne form has colonies with a single functional queen while the polygyne form has colonies containing many functional queens. Field surveys indicate that diploid males are common in natural populations of the polygyne form but absent from monogyne populations, in contrast to laboratory data showing that similar frequencies of queens producing such males occur in the two types of populations. Our results show that mature monogyne colonies with adopted queens rear diploid males in the laboratory, so it is unlikely that the absence of these males from monogyne colonies in the field is due to discrimination against them by monogyne workers. On the other hand, incipient monogyne colonies that produce diploid males exhibit significantly higher mortality and significantly slower rates of growth (Figs. 1–3) than colonies producing workers only. These results suggest that the observed distribution of male diploidy in S. invicta can be explained by differential mortality of diploid male producing colonies of the two forms, with such colonies of the monogyne form experiencing 100% mortality early in development. The mortality differences due to this factor are shown to be related to the different social structures and modes of colony founding characterizing the two forms.