Reproductive compatibility between populations of the citrus red mite,Panonychus citri (McGregor) (Acarina: Tetranychidae)

Reproductive compatibility was studied among populations of different types of the citrus red mite, Panonychus citri (McGregor ), i.e., the diapausing type from pear (DP), the non-diapausing type from citrus (C) and that from pear (NP). Copulation was also observed between mates of different types (DP and C). Only in crosses between C ♀ and DP ♂, was copulation occasionally broken off prematurely; duration of copulation varied considerably between pairs and the average duration was much shorter than that between DP ♀ and C ♂ and than that in crosses between mates of the same types. No F₁ adult females were produced at all from crosses between DP and C, showing that there was a complete reproductive isolation between the two types. There was a significant reciprocal difference in the egg hatchability and survival rate of immatures in the F₁ progeny; mortality in the eggs and that in the immature stage were significantly higher in crosses between DP ♀ and C ♂, as compared to those in the reciprocal cross. This suggested that fertilization may have occurred in the former cross, whereas it seemed that eggs were not fertilized in crosses between the C ♀ and DP ♂. The NP was compatible with the C, whereas it was completely incompatible with the DP. Thus, there was a complete reproductive incompatibility between the diapausing and non-diapausing type of P. citri.     

Biological evaluation of the systematic validity of the African Argas (Persicargas) Arboreus and the Asian-Australian A. (P.) Robertsi (Ixodoidea: Argasidae)

Khalil G. M., Hoogstraal H. and Oliver J. H. Jr. 1980. Biological evaluation of the systematic validity of the African Argas (Persicargas) arboreus and the Asian-Australian A.(P.)robertsi (Ixodoidea: Argasidae). International journal for Parasitology10: 253–259. The closely related A. (P.)arboreus (Ethiopian Faunal Region) and A. (P.) robertsi (Oriental and Australian Faunal Regions) interbreed readily and produce partially fertile progeny. Intrahybrid crosses are much less productive than P₁ homogamic crosses. Results of backcrosses indicate that the progeny of the robertsi ♂ × arboreus ♀ cross are less fertile than the progeny of the reciprocal cross. The fertility of F₁ hybrid progeny is lower than that of the P₁ pure species as expressed in lower female fecundity, egg hatch, and/or viability of immature stages. These 2 species probably originated from a common ancestor and geographic isolation caused genetic incompatibility.     

Hybridization and F1 backcrosses between two closely related tropical species of sea urchins (genus Echinometra) in Okinawa

Summary

Four species of sea urchins of the genus Echinometra, designated species A, B, C, and D, occur along the coast of Okinawa; they are distinguished by color pattern and other characteristics. The two most distinct species, Echinometra sp. A (Ea) with white-tipped spines and Echinometra sp. D (Ed) with nearly black spines (possibly E. oblonga), were examined for potential hybridization through a series of fertilization experiments and rearing of the resulting hybrids. Fertilization was reciprocally asymmetrical; Ed ova were readily fertilized by sperm of Ea, but less than 20% of the ova of Ea were fertilized by sperm of Ed. Nevertheless, hybrids resulting from crosses in both directions developed normally through larval and juvenile stages to produce sexually mature adults. Larvae of Ed♀×Ea♂ and Ed♂×Ed♀ were larger than those of Ea♂ × Ed♀ and Ea♂ × Ea♀, reflecting the larger eggs of Ed. However, Ea♂×Ea♀ juveniles and later stages, up to maturity, were consistently larger than those of equivalent ages of the other crosses; largest to smallest were Ea♂×Ea♀, Ed♂×Ea♀, Ea♂ × Ed♀, and Ed♂×Ed♀, respectively. Ova and sperm of the hybrids were viable and fertilizable in all combination of crosses, although fertilization of those of Ed♂×Ea♀ hybrids was consistently higher than those of Ea♂ × Ed♀ hybrids. These experiments represent the first reported successful production of hybrid sea urchins with viable gametes. They indicate that reproductive isolation is achieved by prezygotic isolating mechanisms in these two species. Of these mechanisms, gametic incompatibility is probably only partly involved, if at all, and differences in spawning times, habitat segregation, or other factors appear to be important for maintaining reproductive isolation in these closely related species.     

Acceptability and suitability of Tuta absoluta eggs from irradiated parents to parasitism by Trichogramma nerudai and Trichogramma pretiosum (Hymenoptera: Trichogrammatidae)

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Body size,duration of parental care,and the intrinsic rate of natural increase in eutherian and metatherian mammals

Summary The intrinsic rate of natural increase (r _m), conception to weaning time (t _cw), age of first reproduction (t_mat), and components of fecundity were compared between ecologically similar groups of 42 metatherian (=marsupial) and 42 eutherian mammals. Marsupial t _cw s average 50% longer than those of eutherians. Small marsupials (<400 g) mature later, and have lower and r _ms than eutherians; large marsupials (>10,000 g) do not mature later but also have lower r _ms. At body sizes of 1,000–3,500 g, marsupials and eutherians have similar t _mat s and t _cw s but marsupials have greater r _ms. Marsupials compensate for their longer t _cw s by a variety of methods including embryonic diapause, larger litter sizes, and short periods between weaning and maturity. Although the greatest similarities in marsupial and eutherian life histories are at body sizes of 1–5 kg, compensation for long t _cw may be seen at any marsupial body size. Other ecological factors not withstanding, marsupial reproduction is neither inherently inferior to that of eutherians nor obviously more advantageous in unpredictable environs.     

我国新疆和湖南棉铃虫种群的遗传学研究

采自湖南衡阳(HY)和新疆哈密(HM)的棉铃虫Helicoverpa armigera(Hubner)种群被室内杂交和回交,杂交F₁代和回交F₂代雌成虫的产卵量、卵孵化率和产卵时间等繁殖力参数均无明显的变化。在22℃下,HM、HY、HM♀×HY♂、HY♀×HM♂和(HY♀×HM♂)×HY♂后代蛹滞育的临界光周期分别为13h 35 min,11 h,11 h 45 min,11 h 43min和11 h9min。在一15℃下,HM、HY、HM♀×HY♂、HY♀×HM♂、HY♀×(HY♀×HM♂)♂和(HY♀×HM♂)♀×HM♂后代滞育蛹的致死中时间(LT”)分别是159.7h、34.27h、100.65 h、116.75h、90.78h和135.58h,亲本F₁代显性度D(HM♀×HY♂)和D(HY♀XHM♂)分别为0.3998和0.5926。遗传分析表明棉铃虫滞育蛹的抗寒性由多个不完全显性的基因控制。     

Reproductive isolating mechanisms contributing to asymmetric hybridization in Killifishes (Fundulus spp.)

When species hybridize, one F1 hybrid cross type often predominates. Such asymmetry can arise from differences in a variety of reproductive barriers, but the relative roles and concordance of pre-mating, post-mating prezygotic, and post-zygotic barriers in producing these biases in natural animal populations have not been widely investigated. Here, we study a population of predominantly F1 hybrids between two killifish species (Fundulus heteroclitus and F. diaphanus) in which >95% of F1 hybrids have F. diaphanus mothers and F. heteroclitus fathers (D♀ × H♂). To determine why F. heteroclitus × F. diaphanus F1 hybrids (H♀ × D♂) are so rare, we tested for asymmetry in pre-mating reproductive barriers (female preference and male aggression) at a common salinity (10 ppt) and post-mating, pre-zygotic (fertilization success) and post-zygotic (embryonic development time and hatching success) reproductive barriers at a range of ecologically relevant salinities (0, 5, 10, and 15 ppt). We found that F. heteroclitus females preferred conspecific males, whereas F. diaphanus females did not, matching the observed cross bias in the wild. Naturally rare H♀ × D♂ crosses also had lower fertilization success than all other cross types, and a lower hatching success than the prevalent D♀ × H♂ crosses at the salinity found in the hybrid zone centre (10 ppt). Furthermore, the naturally predominant D♀ × H♂ crosses had a higher hatching success than F. diaphanus crosses at 10 ppt, which may further increase their relative abundance. The present study suggests that a combination of incomplete mating, post-mating pre-zygotic and post-zygotic reproductive isolating mechanisms act in concert to produce hybrid asymmetry in this system.     

SEX DETERMINATION IN DIPLOID-TRIPLOID CROSSES OF SPINACIA OLERACEA

Mahoney , D. L. Jules Janick , and E. C. Stevenson . (Purdue U., Lafayette, Ind.) Sex determination in diploid-triploid crosses of Spinacia oleracea. Amer. Jour. Bot. 46(5): 372–375. 1959.—Segregation for sex in spinach was studied in a series of diploid pistillate × triploid staminate crosses. The genetic data indicated that the functional gametes from staminate triploids were not confined to n and n + 1 types. Cytological analyses of progenies from a number of 2n ♀ × 3n (XYY and XYY) ♂ crosses revealed similar but non-homogeneous types of chromosome segregation. These crosses produced 49.3% diploids, 17.9% trisomies, 0.5% with 14 chromosomes, 1.2% with 16 chromosomes, 11.4% with 17 chromosomes, 18.9% triploids, and 0.8% with 19 chromosomes. The reciprocal crosses produced a higher percentage of aneuploid types including 1.7% with 15 chromosomes. Segregation for sex in each of the various chromosome numbered progeny of diploid-triploid crosses was presented and analyzed.     

Inheritance of Cry1Ac resistance and associated biological traits in the cotton bollworm, Helicoverpa armigera (Lepidoptera: Noctuidae)

The analysis of reciprocal genetic crosses between resistant Helicoverpa armigera strain (BH-R) (227.9-fold) with susceptible Vadodara (VA-S) strain showed dominance (h) of 0.65-0.89 and degree of dominance (D) of 0.299-0.782 suggesting Cry1Ac resistance as a semi-dominant trait. The D and h values of F₁ hybrids of female resistant parent were higher than female susceptible parent, showing maternally enhanced dominance of Cry1Ac resistance. The progeny of F₂ crosses, backcrosses of F₁ hybrid with resistant BH-R parent did not differ significantly in respect of mortality response with resistant parent except for backcross with female BH-R and male of F₁ (BH-R × VA-S) cross, suggesting dominant inheritance of Cry1Ac resistance. Evaluation of some biological attributes showed that larval and pupal periods of progenies of reciprocal F₁ crosses, backcrosses and F₂ crosses were either at par with resistant parent or lower than susceptible parent on treated diet (0.01 μg/g). The susceptible strain performed better in terms of pupation and adult formation than the resistant strain on untreated diet. In many backcrosses and F₂ crosses, Cry1Ac resistance favored emergence of more females than males on untreated diet. The normal larval period and the body weight (normal larval growth) were the dominant traits associated with susceptible strain as contrast to longer larval period and the lower body weight (slow growth) associated with resistance trait. Further, inheritance of larval period in F₂ and backcross progeny suggested existence of a major resistant gene or a set of tightly linked loci associated with Cry1Ac sensitivity.     

Genetic Control of Resistance to the Sterol 14α-Demethylase Inhibitor Fungicide Prochloraz in the Cereal Eyespot Pathogen Tapesia yallundae

Sexual crosses were used to determine the genetic basis of resistance to the sterol 14 α-demethylase inhibitor fungicide prochloraz in the cereal eyespot pathogen Tapesia yallundae. Three different crosses between sensitive parental strains (22-432 and 22-433 [the concentration required to inhibit growth by 50% {IG₅₀} for each was ≤0.03 mg/liter]) and field isolates from France and New Zealand with differing levels of resistance (PR11 [IG₅₀ = 0.5 mg/liter], PR1 [IG₅₀ = 1.0 mg/liter], and 11-3-18 [IG₅₀ = 2.4 mg/liter]) yielded progeny showing a bimodal distribution, with an even number of sensitive and resistant progeny. This indicated the segregation of a single major gene for resistance in each cross, which was confirmed by the use of backcrosses, crosses between F₁ progeny, and control crosses between sensitive parents. However, there was also evidence of additional quantitative genetic components responsible for the increased IG₅₀s of the more resistant isolates. A further cross was made between isolate PR11 and an F₁ progeny arising from isolate 11-3-18, and this also yielded progeny which were entirely prochloraz resistant. This suggested that resistance genes were allelic in these two isolates, with resistance conferred by a gene at the same locus (or closely linked loci), despite the fact that the isolates (PR11 and 11-3-18) originated from different continents.     

A Study of the Behaviour of the Australian Field Cricket Teleogryllus commodus (Walker) (Orthoptera: Gryllidae) in the Field and in Habitat Simulations

The behaviour of T. commodus (Walker) in the field and in simulated natural habitats is described. Regular predictable sequences of behaviour are represented by an ethogram. Most behaviour was centred around burrows or sheltered sites. Burrows appeared to be a limiting resource and there may be behavioural dimorphism in ♂ ♂ (burrower and non-burrower strategies). Individuals were found to form gregarious clusters and appeared to be attracted to areas already occupied by crickets. Territorial spacing and other social interactions occurred within these clusters. ♂ ♂ and ♀ ♀ were found to be mobile, and moved continually between sites. The movement of ♂ ♂ and ♀ ♀ between burrows (calling sites) was measured. Adult ♂ ♂ never remained at a burrow for longer than two days. In simulated natural habitats ♂ ♂ moved in response to two factors: first, and most common, as a result of eviction by other ♂ ♂ second, as a response to the absence of ♀ ♀. When cricket density was increased in habitat simulations crickets clustered at calling sites. The adaptive significance of T. commodus behaviour is discussed.     

Survival,growth and feed utilization of two clariid catfish (Clarias gariepinus,Burchell 1822 and Heterobranchus bidorsalis,Geoffroy, 1809) and their reciprocal hybrids

An experiment was conducted to determine the survival rate, fertilization rate, growth performance and feed utilization of two African clariid catfish Clarias gariepinus and Heterobranchus bidorsalis and their reciprocal hybrids. Four genetic crosses were made: C. gariepinus♀ × C. gariepinus♂, H. bidorsalis♀ × H. bidorsalis♂, C. gariepinus♀ × H. bidorsalis♂ and H. bidorsalis♀ × C. gariepinus♂. The experiment was divided into two phases: artificial propagation of the fish species using a synthetic hormone and rearing the fry for 14 days, then further rearing the 14‐day‐old fry for an additional 35 days. In the first phase of the experiment, fry survival was estimated in each experimental unit (genetic cross); in the second phase, growth and nutrient utilization were investigated. Results revealed that the highest percentage of fertilization, hatching rate and percentage of survival was in the hybrid (H. bidorsalis♀ × C. gariepinus♂) followed by the purebred H. bidorsalis (H. bidorsalis♀ × H. bidorsalis♂). These three factors were significantly different (P < 0.05) among the genetic crosses. The purebred H. bidorsalis (H. bidorsalis♀ × H. bidorsalis♂) had the highest percentage values of weight gain, specific growth rate and protein efficiency ratio and that these three parameters were significant (P < 0.05) among the four genetic crosses. Based on the results of this study, the purebred H. bidorsalis is recommended for commercial aquacultural practices.     

Effects of triflumezopyrim on the reproduction of brown planthopper,Nilaparvata lugens

The brown planthopper, Nilaparvata lugens Stål (Hemiptera: Delphacidae), is a notorious pest on rice in Asia and has evolved serious resistance to traditional chemical insecticides in recent years. Triflumezopyrim, a newly commercialized mesoionic insecticide, exhibited an excellent control effect on sucking insects, including N. lugens. However, the effects of triflumezopyrim on the reproduction of N. lugens have not yet been fully elucidated. In this study, we investigated the impacts of different concentrations of triflumezopyrim (LC₁₀, LC₅₀ and LC₉₀) on the reproduction and the reproduction related genes of N. lugens exposure to the insecticide via systemic and contact route. The results indicated that the preoviposition periods of N. lugens females in the LC₅₀ and LC₉₀ triflumezopyrim-treated groups (♀ t × ♂ t) were prolonged in contact toxicity treatment, compared with control (acetone treatment). The fecundities for three pair combinations (♀ c ×♂ t, ♀ t ×♂ c and ♀ t ×♂ t) treated with LC₅₀ and LC₉₀ concentrations of triflumezopyrim showed a significant decrease compared to water/acetone-treated control via contact and systemic route. No significant effects of LC₁₀ triflumezopyrim on preoviposition period and fecundity were found in contact and systemic toxicity treatments. However, the triflumezopyrim did not influence the egg hatchability. By microscope observation, the LC₅₀ and LC₉₀ triflumezopyrim impended the ovarian development in females. qRT-PCR analysis showed that the vitellogenin (NlVg) relative expression level of female adults exposed to LC₅₀ and LC₉₀ triflumezopyrim decreased by 30.3 – 39.5% in two toxicity treatments. The titers of another reproduction related hormones juvenile hormone III (JH III) in LC₅₀ and LC₉₀ triflumezopyrim-treatments were 27.4% and 25.8% lower than control in contact toxicity treatment and 27.08% and 37.18% lower than control in systemic toxicity treatment. In summary, these results suggested that the median lethal and high lethal concentrations of triflumezopyrim inhibited the reproduction and reduced the expression of NlVg and JH III in N. lugens. This study provided a reference for the efficient and scientific utilization of triflumezopyrim in the field.     

Effect of acclimated temperature on thermal tolerance,immune response and expression of HSP genes in Labeo rohita,Catla catla and their intergeneric hybrids

The ability of a species and population to respond to a decrease or an increase in temperature depends on their adaptive potential. Here, the critical thermal tolerance (CTmax and CTmin) of four populations: Labeo rohita, Catla catla, and their reciprocal hybrids L. rohita♀× C. catla♂ (RC) and C. catla♀ × L. rohita♂ (CR) being acclimatized at four acclimation temperatures (22, 26, 30 and 34 °C) were determined. All populations indicated substantial variations (P < 0.05) in CTmax and CTmin values. L. rohita displayed, comparatively the highest CTmax with largest total and intrinsic polygon zones as well as the upper and lower acquired thermal tolerance zones followed by RC and CR hybrids, while C. catla showed significantly the highest CTmin value and the smallest intrinsic and acquired thermal tolerance zones. Both hybrids illustrated low parent heterosis (≤11%). Additionally, the highest expression of Hsp70 and Hsp90 (heat shock proteins) genes, serum lysozyme level, respiratory burst activity and lowest lipid peroxidation level under lower and higher temperature shock further illustrated strong physiological mechanism of L. rohita in contrast to C. catla, to deal with acute temperature, while hybrids, especially F1 RC hybrid appeared as a good option to replace C. catla in relatively higher and lower temperature areas.     

Sexual Reproduction in Aspergillus flavus Sclerotia: Acquisition of Novel Alleles from Soil Populations and Uniparental Mitochondrial Inheritance

Aspergillus flavus colonizes agricultural commodities worldwide and contaminates them with carcinogenic aflatoxins. The high genetic diversity of A. flavus populations is largely due to sexual reproduction characterized by the formation of ascospore-bearing ascocarps embedded within sclerotia. A. flavus is heterothallic and laboratory crosses between strains of the opposite mating type produce progeny showing genetic recombination. Sclerotia formed in crops are dispersed onto the soil surface at harvest and are predominantly produced by single strains of one mating type. Less commonly, sclerotia may be fertilized during co-infection of crops with sexually compatible strains. In this study, laboratory and field experiments were performed to examine sexual reproduction in single-strain and fertilized sclerotia following exposure of sclerotia to natural fungal populations in soil. Female and male roles and mitochondrial inheritance in A. flavus were also examined through reciprocal crosses between sclerotia and conidia. Single-strain sclerotia produced ascospores on soil and progeny showed biparental inheritance that included novel alleles originating from fertilization by native soil strains. Sclerotia fertilized in the laboratory and applied to soil before ascocarp formation also produced ascospores with evidence of recombination in progeny, but only known parental alleles were detected. In reciprocal crosses, sclerotia and conidia from both strains functioned as female and male, respectively, indicating A. flavus is hermaphroditic, although the degree of fertility depended upon the parental sources of sclerotia and conidia. All progeny showed maternal inheritance of mitochondria from the sclerotia. Compared to A. flavus populations in crops, soil populations would provide a higher likelihood of exposure of sclerotia to sexually compatible strains and a more diverse source of genetic material for outcrossing.     

Reducing the potential copper toxicity of concentrates to sheep by the use of molybdenum and sulphur supplements

A high copper (Cu) diet (45.3 μg Cu/g DM) was given to three groups of animals, ♂ or ♀ Scottish Blackface and ♂ Finnish Landrace lambs, without added molybdenum (Mo), or with 2, 4, 8 or 16 mg Mo/kg DM added in a 3 × 5 factorial experiment lasting 18–27 weeks. Sodium sulphate, providing 2 g S/kg, was added with each Mo supplement.Six of the nine lambs not given supplementary Mo + S died of Cu poisoning but those given Mo + S survived. Histological evidence of subclinical hepato-toxicity was found in Mo + S supplemented lambs but it decreased in severity as the level of added Mo increased. Plasma aspartate amino-transferase (PAAT) concentrations were elevated in unsupplemented lambs from week 9 and in lambs given 2 mg Mo/kg from week 12 but they remained normal in lambs given 4–16 mg Mo/kg DM. Successive increments in dietary Mo reduced the increase in liver Cu after 18–20 weeks from 1450 to 735, 483, 445 and 131 μg/g DM. The proportion of ingested Cu (y%) retained in the liver was related to dietary Mo (x, mg/kg DM) by the equation y = 2.6 ? 1.66 log x ± 0.21 (r = 0.98; 2 d.f.).Finnish Landrace lambs retained 50% less Cu in their livers, had lower PAAT levels and showed less histological evidence of liver damage than ♂ Scottish Blackface lambs. The latter had higher PAAT levels and a higher mortality from Cu poisoning than ♀ Scottish Blackface lambs although the two sexes retained similar proportions of ingested Cu in their livers.The results are discussed in relation to the practical use of Mo + S to prevent Cu poisoning in sheep.     

Melanization plasticity of Drosophila kikkawai,Drosophila leontia and reciprocal hybrids under different temperatures

Drosophila (Sophophora) kikkawai, Burla, 1954 and Drosophila (Sophophora) leontia, Tsacas & David 1978 are closely related sibling species, the former being cosmopolitan and the latter is restricted to tropical localities. We investigated the influence of introgressive hybridization on phenotypic diversity of the two sibling species in the present study. How hybridization supports the relative abundance of pure species according to latitudinal cline is the aim of this study because hybrids show a tendency to acquire geographical location of their parent species in equal or greater abundance. How hybridization supports the plasticity for melanization of hybrids is not explored yet. The two species can cross and generate hybrids. For this, we crossed true breeding strains of both species to obtain the hybrids i.e. dark female (♀) of D. kikkawai (D. k) with males (♂) of D. leontia (D. l) in cross I and light ♀ of D. k with ♂ of D. l in cross II along with their reciprocal crosses. Finally, we studied the plasticity of both species and their hybrids at 6 growth temperatures (14, 17, 21, 25, 28 and 31 °C). We found that there is no plasticity for melanization in true breeding darker and lighter strain of D. kikkawai as well as D. leontia whereas hybrids of both species showed high phenotypic plasticity. Significant differences in slope values across temperatures in parental and hybrid lines suggest plastic effects. Phenotypic variation in abdominal melanization in hybrids can be interpreted as a result of gene introgression with D. kikkawai. We conclude that introgressive hybridization might be an important, although underestimated, mechanism shaping species distribution and adaptation.     

A developmental analysis of the histone patterns of two species of Xenopus and their hybrids

The histone patterns in Xenopus laevis and X. borealis have been examined at various developmental stages using acid-urea polyacrylamide electrophoresis. Qualitative differences between the two species have been demonstrated in the H1 fraction. These differences are not affected by alkaline phosphatase digestion. Quantitative changes during development in both H1 and H4 fractions have also been observed. In addition, histones from hybrids of the two species have been examined. H1 histones characteristic of both species are present by the neurula stage in laevis ♀ × borealis ♂ hybrids. Quantitative changes observed in borealis development are mimicked in laevis ♀ × borealis ♂ hybrid development.