金纹细蛾的发育起点温度和有效积温

在自然变温条件下,研究金纹细蛾LithocolletisringoniellaMatsumura各虫态发育历期。结果表明,成虫产卵前期、卵、幼虫、蛹及全世代的发育起点温度分别为7.5,5.2,10.4,11.3和7.1℃,有效积温分别为40.6,59.7,102.2,15.4和203.1日.度。根据有效积温法则,预测该虫在山东省1年发生4~6代,第1、2代成虫发生期分别为5月下旬和6月下旬。     

Kinetics of spermatogenesis in the white-lipped peccary (Tayassu pecari)

This study aimed to characterize the stages of the seminiferous epithelium cycle by the tubular morphology method, and to determine the number of differentiated spermatogonia generations in the adult white-lipped peccary. Twenty adult white-lipped peccaries, obtained from commercial slaughterhouse, were used. Fragments of the testicular parenchyma were fixed in 3% glutaraldehyde and embedded into a methacrylate resin. The number of germ and Sertoli cells was estimated by the analysis of cell populations in 50 transversal sections of seminiferous tubules in different stages of the cycle. The tubular morphology method allowed the identification of cellular associations characteristic of the eight stages of the seminiferous epithelium cycle in white-lipped peccaries. The results showed the presence of six generations of differentiated spermatogonia in white-lipped peccaries, and that the cell composition of the eight stages of the seminiferous epithelium cycle in this species is very similar to that described for collared peccaries.     

龙眼角颊木虱生物学特性及防治研究

龙眼角颊木虱是龙眼的主要害虫,以成虫和若虫为害龙眼新梢嫩叶。在厦门市同安区一年发生六代,主害代为经一代于３月下旬至４月中旬和第五代于９月中旬至１０月上旬。本报道了该虫在不同温度下各虫态的发育历期,发现各个世代若虫都有滞育的现象,研究分析了若虫滞育对越冬虫源,主害代虫源等种群动态的影响,并探讨了龙眼角颊木虱的为害损失测定及药剂防治试验。     

Time scales of divergence and speciation among natural populations and subspecies of Arabidopsis lyrata (Brassicaceae)

? Premise of the study: Plant populations that face new environments adapt and diverge simultaneously, and both processes leave footprints in their genetic diversity. Arabidopsis lyrata is an excellent species for studying these processes. Pairs of populations and subspecies of A. lyrata represent different stages of divergence. These populations are also known to be locally adapted and display various stages of emerging reproductive isolation. ? Methods: We used nucleotide diversity data from 19 loci to estimate divergence times and levels of diversity among nine A. lyrata populations. Traditional distance-based methods and model-based clustering analysis were used to supplement pairwise coalescence-based analysis of divergence. ? Key results: Estimated divergence times varied from 130000 generations between North American and European subspecies to 39000 generations between central European and Scandinavian populations. In concordance with previous studies, the highest level of diversity was found in Central Europe and the lowest in North America and a diverged Russian Karhum?ki population. Local adaptation among Northern and central European populations has emerged during the last 39000 generations. Populations that are reproductively isolated by prezygotic mechanisms have been separated for a longer time period of ～70000 generations but still have shared nucleotide polymorphism. ? Conclusions: In A. lyrata, reproductively isolated populations started to diverge ～70000 generations ago and more closely related, locally adapted populations have been separate lineages for ～39000 generations. However, based on the posterior distribution of divergence times, the processes leading to reproductive isolation and local adaptation are likely to temporally coincide.     

Effect of the synergist, piperonyl butoxide, on the development of deltamethrin resistance in yellow fever mosquito, Aedes aegypti L. (Diptera: Culicidae)

The larvae and adults of Aedes aegypti were tested for the potential to develop resistance to the synthetic pyrethroid, deltamethrin, alone or a combination of deltamethrin with the synergist, piperonyl butoxide (PBO). Although continuous larval selection for 40 generations resulted in 703-fold resistance, the resistance ratio in the adults was only 1.3. Similarly, adult selections with deltamethrin showed a resistance ratio of less than four after 40 generations, indicating differential response to deltamethrin selection in the two developmental stages of the insect. When the susceptible larvae were subjected to selection pressure of deltamethrin and PBO in the ratio of 1:5 for 20 generations, the speed of selection for deltamethrin resistance slowed down by 60%. The F24 larvae obtained from the strain selected with deltamethrin alone were further subjected to selection pressure with synergized deltamethrin, which resulted in 89% reversal in deltamethrin resistance in just one generation. However, long-term selection with the insecticide-synergist combination returned resistance close to original levels in 15 generations. The data indicate the involvement of cytochrome P450-dependent detoxification as the primary mechanism of development of resistance to deltamethrin in the larvae. Implications of the results on the management of larval and adult stages of Ae. aegypti are discussed.     

Life cycles of two isopora species in the canary, Serinus canarius Linnaeus

The endogenous stages of Isospora serini Arog?o and Isospora canaria Box are described from experimentally infected canaries, Serinus canarius Linnaeus. Unlike other Coccidia, the first part of the I. serini life cycle takes place in mononuclear phagocytes. Five asexual generations are described from this cell type; 2 additional asexual generations and the sexual stages take place in the intestinal epithelium. Isospora canaria, on the other hand, has a conventional coccidian life cycle in that all of the endogenous stages are in the epithelium of the small intestine, with 3 asexual generations and the sexual generation described in the duodenal epithelium. The 2 species differ in their position relative to the nucleus of the intestinal epithelial cell. Isospora serini is usually on the lumenal side of the nucleus while I. canaria is below the nucleus, toward the basement membrane. The prepatent period is 4-5 days for I. canaria and 9-10 days for I. serini. Patency lasts for 11-13 days in I. canaria infections, but duration of oocyst output is more chronic in I. serini infections, persisting for as long as 231 days. Both species have a diurnal periodicity of oocyst discharge which occurs in late afternoon and evening.     

Grandparental effects in marine sticklebacks: transgenerational plasticity across multiple generations

Nongenetic inheritance mechanisms such as transgenerational plasticity (TGP) can buffer populations against rapid environmental change such as ocean warming. Yet, little is known about how long these effects persist and whether they are cumulative over generations. Here, we tested for adaptive TGP in response to simulated ocean warming across parental and grandparental generations of marine sticklebacks. Grandparents were acclimated for two months during reproductive conditioning, whereas parents experienced developmental acclimation, allowing us to compare the fitness consequences of short‐term vs. prolonged exposure to elevated temperature across multiple generations. We found that reproductive output of F1 adults was primarily determined by maternal developmental temperature, but carry‐over effects from grandparental acclimation environments resulted in cumulative negative effects of elevated temperature on hatching success. In very early stages of growth, F2 offspring reached larger sizes in their respective paternal and grandparental environment down the paternal line, suggesting that other factors than just the paternal genome may be transferred between generations. In later growth stages, maternal and maternal granddam environments strongly influenced offspring body size, but in opposing directions, indicating that the mechanism(s) underlying the transfer of environmental information may have differed between acute and developmental acclimation experienced by the two generations. Taken together, our results suggest that the fitness consequences of parental and grandparental TGP are highly context dependent, but will play an important role in mediating some of the impacts of rapid climate change in this system.     

柏小爪螨发育起点温度和有效积温的研究

在恒温条件下测定了柏小爪螨Oligonychusperditus卵、幼螨、若螨历期 ,成螨产卵前期和世代发育历期 ,用直线回归法和李典谟直接最优法分别计算了柏小爪螨各螨态和 1代的发育起点温度和有效积温 ,并根据有效积温法则预测了该螨在山东泰安地区 1年可能完成代数为 1 1代左右     

广州地区亚非草蛉的研究

亚非草蛉`Chrysopa boninensis`` Okamoto是果树、花木和蔬菜害虫的重要天敌。在广州地区一年完成10—11代,世代重叠。在田间没有越冬滞育现象。 本文叙述了该虫的生物学及其发生与环境的关系。释放试验结果表明,该虫控制害虫效果显著。有一定的应用价值。     

Production of mosaic lethals in different germ cell stages of drosophila by N-methyl-N'-nitro-N-nitrosoguanidine.

The delayed effect of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was studied in Drosophila melanogaster by the proportion of mosaic progeny produced after this treatment. Following injection of the chemical into wild type males, complete and mosaic sex-linked recessive lethals were scored by the Muller-5 method, in five successive broods representing the different stages of spermatogenesis. All broods showed significant increase over the control in the frequencies of complete lethals with gradual decrease in mutation rate from the post-meiotic stages to the pre-meiotic ones. In the case of mosaic lethals, too, the post-meiotic stages were generally more sensitive; but the increase over the control was significant only for the mature spermatozoa. The extension of the experiment to F4 generation showed that a mosaic F1 female may produce further mosaic progeny. The production of lethal mutations in successive generations after treatment with MNNG supports the view that chemically induced instabilities can be transmitted as such over several generations.     

Host-feeding and oviposition by parasitoids in relation to host stage: Consequences for parasitoid-host population dynamics

Among parasitoids which host-feed destructively, there is a tendency for females to partition their feeding and oviposition behaviour in relation to different host stages, feeding preferentially or exclusively on earlier host stages and ovipositing preferentially or exclusively in (or on) later ones. We explored the dynamic implications of this behaviour for parasitoid-host population dynamics, using modifications of the age-structured simulation models of Kidd and Jervis (1989, 1991). Using the new versions of the models, we compared the situation where parasitoids practice host stage discrimination with respect to feeding and oviposition, with the situation where they do not. Additionally, we examined the effects of host stage discrimination on populations by (a) having generations either discrete or overlapping, (b) varying initial age structure, (c) having varying degrees of density dependence acting on host adult mortality, and (d) varying parasitoid develoment times in relation to the length of host development. With either discrete or overlapping generations of the host population, a reduction in the parasitoid development time had a destabilizing influence on the parasitoid-host population interaction. With discrete generations stage discrimination had no effect on the risk of extinction, irrespective of either the degree of density dependence acting on the host population, or the initial age structure of the host population. When parasitoid search was uncoupled from the insect's adult energy requirements, the interaction was always unstable. With continuous generations, stage discrimination affected stability at certain parasitoid development times, but not at others. The relative lengths of parasitoid and host development times also influenced the tendency of the host population to show discrete or overlapping generations.     

Seasonal size distribution of developmental stages of sub-antarctic copepod

Drepanopus pectinatus, the most numerous species of Copepod in the Kerguelen Archipelago completes 4 generations a year. The succession of generations follows the hydrological seasons. Each generation may be characterized by the cephalothorax length of the developmental stages C1 to C6. The mean lengths of stages C2 to C6 are shown to be significantly different (P > 0.05) between seasons (i.e. between generations). The size-classes have a unimodal distribution from stages C1 to C4. For copepodite C5 and adults, bimodal histograms reflect the differentiation of males and females.A reverse trend of the development pattern of lengths is demonstrated in this subantarctic species: a decrease with decreasing temperatures (6° to 2°) from April to September, and an increase with the rising temperatures (2° to 7°) from October to February.Two populations of females are distinguishable in spring and summer, by their small (0.950–1.299 mm length of cephalothorax, 55%) or large (1.300–1.800 mm, 45%) size, respectively.The differences in mean length cannot be explained by their relation to the mean temperature alone. Pigment content is suspected to play a role.     

Missing generations of spermatocytes and spermatids in seminiferous epithelium contribute to low efficiency of spermatogenesis in humans.

Daily sperm production per gram parenchyma (DSP/g) in humans is only 25 or 35% of that for most species including rats and nonhuman primates. To explain the low efficiency of spermatogenesis in humans, the number of generations of germ cells (spermatocytes and spermatids) and the number of these germ cells in each generation were determined for each spermatogenic stage in men with varied efficiencies. Testes were obtained at autopsy, fixed by vascular perfusion with glutaraldehyde, further fixed in osmium, and embedded in Epon 812 before 0.5-micron sections were stained with toluidine blue. Tubular cross sections were photographed, and spermatogenic stages were determined by two observers. Testes were divided into three groups on the basis of DSP/g. The number of generations of spermatocytes and spermatids was greater (p < 0.05) in the high (2.01 +/- 0.05) and intermediate (1.77 +/- 0.04) than in the low (1.45 +/- 0.15) DSP/g group. All groups had a lower number of generations of spermatocytes and spermatids compared to the optimum value of three. The number of these generations per cross section was related (r = 0.85; p < 0.01) to DSP/g in these men. The number per cross section of spermatocytes, spermatids, and the combined number of germ cells was higher (p < 0.01) in the high than in the low DSP/g group. The combined number of germ cells per cross section was related (r = 0.85; p < 0.01) to DSP/g. The combined number of germ cells was higher in the high versus the low DSP/g group in stages I through V, but this difference was significant only in stages IV and V.(ABSTRACT TRUNCATED AT 250 WORDS)     

Progeny selection for agronomic characters in early generations of a potato breeding programme

 Repeatabilities of progeny means, and the univariate cross prediction method were used to study the effectiveness of progeny selection for agronomically important characters in early generations of potato (Solanum tuberosum L.) breeding. The study was based on 90 progenies (72 crosses+18 selfs) evaluated for three successive generations, i.e. seedling, first clonal and second clonal generations. Repeatabilities of progeny means were measured as correlation coefficients between generations. In the univariate cross prediction method, progeny means and within-progeny standard deviations were used to calculate the proportions of clones exceeding the target values, and correlation coefficients between generations for predicted and observed proportions of clones, were calculated. Population means varied from generation to generation. Correlation coefficients between generations for progeny means for most of the characters were significant, but moderate. These were higher than the correlation coefficients between predicted and observed proportions of clones exceeding the target values. The possibility of using progeny means as a selection parameter to reduce the number of genotypes to be examined in later stages by rejecting the poor crosses in seedling generation is discussed. Received: 8 January 1997/Accepted: 28 February 1997     

Statistical characteristics of the density-independent population fluctuation and the evaluation of density-dependence and regulation in animal populations

In this study it was proved that the “density-independent population” shows the following characteristics if the analysis is made using time-series samples:

1. The slope b in the density-on-density regression between successive developmental stages has a general tendency to become smaller than 1, though the bias approaches zero if one or more of the following three conditions are satisfied: (a) the data cover a large number of generations, (b) the variance of the rate of population change for the period concerned is small relative to that for the residual period in a whole generation, and (c) the population has a distinct trend to either increase or decrease over generations.
2. The variance for the generation-to-generation population fluctuation increases continually as the number of generations is increased, even if the population has no inherent trend to increase or decrease. For a fixed number of generations, however, the variance remains constant among different developmental stages.

On the basis of these theoretical results, a modified method for detecting density-dependence from time-series samples was presented, together with a new, tentative technique of variance analysis to evaluate the regulation of numbers directly. The results of applying these methods to some sets of data from both hypothetical and actual populations illustrated their validity for use in population studies.     

Mortality factors affecting the leaf-mining stages of Phyllonorycter (Lepidoptera: Gracillariidae) on oak and birch 1. Analysis of the mortality factors

Mortality of life stages of Phyllonoycter species in mined leaves of oak and birch was investigated in a Cheshire locality during 1974. Phyllonotycter species are mostly bivoltine, but P. cavella is univoltine. Parasitism and host-feeding (predation) by Hymenoptera caused most mortality. Parasitism was heaviest in the first generations, with ectoparasitism predominating, although endoparasitism caused inore mortality in the second generations. The incidence of host-feeding increased to leaf-fall when more mines contained host-fed remains than either parasites or healthy Phyllonoycter . Host-feeding occurred particularly in the first three (sap-feeding) larval instars; ectoparasitism affected mainly the two subsequent (tissue-feeding) larval stages and pupae; and endoparasitism occurred in all stages although affected hosts are killed only from the fourth larval instar onwards. Highest mortality was suffered by tissue feeders in the first generation but by sap feeders in the second. Total mortality was greatest in second generation mines and, in a given generation, survival curves for Phyllonotycter were similar on both tree species. The observed density of second generation mines relative to first in the sample was higher than predicted from first generation mortality levels, and this is discussed.     

Life Cycle of Culicospora magna (Kudo, 1920) (Microsporida: Culicosporidae) in Culex restuans Theobald with Special Reference to Sexuality1

The life cycle of Culicospora magna (Kudo, 1920) Weiser, 1977, consists of two major developmental sequences that alternate in host individuals of successive generations, each of the sequences starting with a sporoplasm and ending with spores. The first sequence occurs in larval, pupal, and adult stages of a parental generation of the host mosquito, Culex restuans Theobald; it begins with a sporoplasm from an ingested uninucleate spore and progresses through stages in gametogony, plasmogamy, nuclear association, merogony, karyogamy, and disporous sporulation with production of binucleate spores that discharge sporoplasms into the oocytes. The second sequence occurs in egg and larval stages of a filial generation of the same host species; it begins with the binucleate sporoplasm that entered the egg, includes stages in merogony, nuclear dissociation, and mictosporous sporulation, and ends with uninucleate spores. These spores are released into the environment following death of the host and are capable of infecting new parental generation host individuals. The life cycle is conceived as an alternation of generations related to haploidy and diploidy in the nuclei, the transition from haploidy to diploidy occurring with nuclear association and the transition from diploidy to haploidy occurring with nuclear dissociation.     

Experimental infection of the tick Amblyomma cajennense, Cayenne tick, with Rickettsia rickettsii, the agent of Rocky Mountain spotted fever

In the laboratory, Amblyomma cajennense (Acari: Ixodidae) (Fabricius) larvae, nymphs and adults were exposed to Rickettsia rickettsii by feeding on needle-inoculated animals, and thereafter reared on uninfected guinea pigs or rabbits. Regardless of the tick stage that acquired the infection, subsequent tick stages were shown to be infected (confirming transstadial and transovarial transmissions) and were able to transmit R. rickettsii to uninfected animals, as demonstrated by serological and molecular analyses. However, the larval, nymphal and adult stages of A. cajennense were shown to be partially refractory to R. rickettsii infection, as in all cases, only part of the ticks became infected by this agent, after being exposed to rickettsemic animals. In addition, less than 50% of the infected engorged females transmitted rickettsiae transovarially, and when they did so, only part of the offspring became infected, indicating that vertical transmission alone is not enough to maintain R. rickettsii in A. cajennense for multiple generations. Finally, the R. rickettsii-infected tick groups had lower reproductive performance than the uninfected control group. Our results indicate that A. cajennense have a low efficiency to maintain R. rickettsii for successive generations, as R. rickettsii-infection rates should decline drastically throughout the successive tick generations.     

The seminiferous epithelial cycle and spermat ogenesis in rams (ovis aries )

The efficiency of spermatogenesis and degenerations of different spermatogenic cells under normal conditions of the environment have been investigated in rams. The meiotic divisions and the position of first-generation spermatids in haematoxylin-eosin stained testicular preparations were used to identify eight stages of the seminiferous epithelial cycle (SEC). The stages of relatively long duration (i.e., 1,2,3,4,8) were sub-divided. The percent-ages of frequency for the 14 stages reported were also studied. Three generations of type A (A(1), A(2), A(3)), one generation of type intermediate (In) and two generations of type B (B(1), B(2)) spermatogonia were recognized. A(2) and B(2) spermatogonia as well as primary and secondary spermatocytes did not degenerate. Contrarily, A(1), A(2), A(3), In and B(1) spermatogonia showed 25, 13.7, 27.3 and 21.2% degenerations respectively. We concluded that compared with the previously used eight-stage classification, subdividing stages with long durations as done in this study facilitates investigating the degenerations of spermatogenic cells. The efficiency of spermatogenesis in rams was 47.58% since one A(3) spermatogonium produces 30.45 spermatids/spermatozoa against the expected number of 64.