白垩纪中期克钦琥珀毛蚊科(双翅目:毛蚊总科)昆虫一新属新种

毛蚊科是双翅目长角亚目的一类昆虫,其种类丰富,广布世界各地.毛蚊化石记录较为丰富,但往往都是保存于湖相沉积地层中,琥珀中的化石较为罕见.本文根据缅甸北部克钦地区产出的白垩纪中期琥珀中保存的昆虫标本建立了 1新属新种——缅甸白垩叉毛蚊(Cretpenthetria burmensis gen.et sp.nov.),归入...     

Structure of the coxa and homeosis of legs in Nematocera (Insecta: Diptera)

Construction of the middle and hind coxae was investigated in 95 species of 30 nematoceran families. As a rule, the middle coxa contains a separate coxite, the mediocoxite, articulated to the sternal process. In most families, this coxite is movably articulated to the eucoxite and to the distocoxite area; the coxa is radially split twice. Some groups are characterized by a single split. The coxa in flies is restricted in its rotation owing to a partial junction either between the meron and the pleurite or between the eucoxite and the meropleurite. Hence the coxa is fastened to the thorax not only by two pivots (to the pleural ridge and the sternal process), but at the junction named above. Rotation is impossible without deformations; the role of hinges between coxites is to absorb deformations. This adaptive principle is confirmed by physical modelling. Middle coxae of limoniid tribes Eriopterini and Molophilini are compact, constructed by the template of hind coxae. On the contrary, hind coxae in all families of Mycetophiloidea and in Psychodidae s.l. are constructed like middle ones, with the separate mediocoxite, centrally suspended at the sternal process. These cases are considered as homeotic mutations, substituting one structure with a no less efficient one.     

Twisted rhabdomeres in the compound eye of a tipulid fly (Diptera)

Summary The individual rhabdomeres of the outer retinular cells (R1–6) in the tipulid fly, Ptilogyna, twist about their long axes. Proximally, the rhabdoms become partitioned off by processes from the retinular cells, so that the basal region of each rhabdomere is enclosed in a pocket formed by its own cell (Fig. 2). This organisation of the rhabdom enables each rhabdomere to twist while supported within its own retinular cell, and while the cell itself maintains its orientation with respect to the entire ommatidium. Theory predicts that the rhabdomeral twisting should significantly reduce the polarisation sensitivity of R1–6, but have little effect on the efficiency with which unpolarised light is absorbed.     

Sexual dimorphism in cuticular hydrocarbons of the Australian field cricket Teleogryllus oceanicus (Orthoptera: Gryllidae)

Sexual dimorphism is presumed to reflect adaptive divergence in response to selection favouring different optimal character states in the two sexes. Here, we analyse patterns of sexual dimorphism in the cuticular hydrocarbons of the Australian field cricket Teleogryllus oceanicus using gas chromatography. Ten of the 25 peaks found in our chromatographs, differed in their relative abundance between the sexes. The presence of sexual dimorphism in T. oceanicus is discussed in reference to a review of sexual dimorphism in cuticular hydrocarbons of other insects. We found that this trait has been examined in 103 species across seven different orders. Seventy-six of these species (73%) displayed sex specificity of cuticular hydrocarbons, the presence/absence of which does not appear to be directly linked to phylogeny. The occurrence of sexual dimorphism in cuticular hydrocarbons of some but not other species, and the extent of variation within genera, suggest that this divergence has been driven primarily by sexual selection.     

The growth of Bibio johannis (L.) and Dilophus febrilis (L.) (Diptera: Bibionidae) larvae in the field

Bibionid larvae were extracted from soil samples collected from June 1985 to March 1987. Each larva was identified, weighed and measured for maximum head capsule width. Both Bibio johannis and Dilophus febrilis have six larval instars. Bibio johannis grew slowly in late summer and early autumn but rapidly from October to January. Early and late instar larvae of D. febrilis occurred simultaneously and it was concluded that this species was not bivoltine but may exist as two separate cohorts with distinct flight periods.     

Baltic amber fossils reveal early evolution of sexual dimorphism in stalk-eyed flies (Diptera: Diopsidae)

A cladistic analysis of 16 species of extant and amber fossil stalk-eyed flies of the family Diopsidae places the fossil †Prosphyracephala succini (Loew) as the sister group of all other Diopsinae, the subfamily in which eye stalks occur. The study is based on a scoring including five old and 23 new finds of †P. succini from Baltic amber, and for the first time allows a morphometric analysis of eye span and various body size parameters in this species. The data indicate that sexual dimorphism of the eye stalks already existed in †Prosphyracephala, suggesting that this feature evolved early in the Diopsinae. Contrary to recent views that the ancestral condition of diopsine eye stalks was monomorphic, the new results suggest that sexual selection was involved in the evolution of eye stalks from the very beginning of the lineage.     

Sexual dimorphism in desiccation responses of the sand scorpion Smeringurus mesaensis (Vaejovidae)

The osmoregulatory and respiratory responses of male and female Smeringurus mesaensis (Vaejovidae) to prolonged desiccation were measured. No significant effect of sex on mass-loss rates (MLRs) was found. Still, females maintained their haemolymph osmolality when desiccated to 10% mass loss, whereas that of males increased significantly after loss of as little as 5% of initial mass. Females had a 3-fold larger hepatopancreas, significantly higher hepatopancreas water content and higher metabolic rates when adjusted to hepatopancreas-free dry mass. Thus, females not only store more water in the hepatopancreas but also mobilise it to the haemolymph at a higher rate during desiccation, thus maintaining haemolymph osmolality. Gas exchange rates of both males and females decrease as desiccation progresses. An initial respiratory exchange ratio (RER) of approximately 0.9 is followed by a significant increase at mass loss levels of 7.5% and higher. RER values greater than 1.0 may result from partial shift to anaerobic catabolism, which allows closure of the book lung spiracles for longer duration, thus minimising respiratory water loss. The effects of gas exchange rates on rates of water mobilisation between body compartments and water loss to the environment suggest a trade-off between maintaining osmotic stability and conserving body water stores under stressful conditions.     

The apelinergic system: Sexual dimorphism and tissue-specific modulations by obesity and insulin resistance in female mice

It has been proposed that the apelinergic system (apelin and its receptor APJ) may be a promising therapeutic target in obesity-associated insulin resistance syndrome. However, due to the extended tissue-distribution of this system, the therapeutic use of specific ligands for APJ may target numerous tissues resulting putatively to collateral deleterious effects. To unravel specific tissular dysfunctions of this system under obesity and insulin-resistance conditions, we measured the apelinemia and gene-expression level of both apelin (APL) and APJ in 12-selected tissues of insulin-resistant obese female mice fed with a high fat (HF) diet. In a preliminary study, we compared between adult male and female mice, the circadian plasma apelin variation and the effect of fasting on apelinemia. No significant differences were found for these parameters suggesting that the apelinemia is not affected by the sex. Moreover, plasma apelin level was not modulated during the four days of the estrous cycle in females. In obese and insulin-resistant HF female mice, plasma apelin concentration after fasting was not modified but, the gene-expression level of the APL/APJ system was augmented in the white adipose tissue (WAT) and reduced in the brown adipose tissue (BAT), the liver and in kidneys. BAT apelin content was reduced in HF female mice. Our data suggest that the apelinergic system may be implicated into specific dysfunctions of these tissues under obesity and diabetes and that, pharmacologic modulations of this system may be of interest particularly in the treatment of adipose, liver and renal dysfunctions that occur during these pathologies.     

Sexual dimorphism and the influence of artificial elevated temperatures on body size in the imago of Nemoura trispinosa (Plecoptera: Nemouridae)

Our study site was composed of a spring that was divided lengthwise from its source into two equally wide channels, with water temperature in the experimental channel being increased by 2.0–3.5°C relative to that of the control channel. We examined sexual dimorphism in overall body size and eight morphological traits in the stonefly Nemoura trispinosa Claassen, and whether body size varies according to site of emergence (upstream versus downstream) and/or the thermal regime in which they undergo nymphal development. Univariate tests showed that females were significantly larger than males in all eight traits, and multivariate analyses (Principal Components Analysis) demonstrated that females were larger in overall body size. Both univariate and multivariate tests showed that adults emerging from the control and downstream portions of the stream were larger than those from heated and upstream reaches, respectively. We discuss possible hypotheses contributing to the female-biased sexual dimorphism observed in this species.     

Bibionids (Diptera: Bibionidae) in agricultural land: a review of damage, benefits, natural enemies and control

Records of crop damage caused by Bibionidae are reviewed together with evidence for their beneficial activities, natural enemies and control methods. Bibionids are sporadic and infrequent pests. Although grass and cereals are most vulnerable, a wide range of crops is attacked. Damage is most severe after grass or when plants are under stress. The presence of organic matter during oviposition increases the likelihood of damaging populations. Many natural enemies exist but their impact on adult or larval populations has not been quantified. Given the pattern of attacks and lack of approved insecticides, cultural control methods are more appropriate than chemical. The role of adult bibionids in pollination and of larvae involved in soil processes could be of greater importance than any damage caused by the group.     

Sexual dimorphism in shells of Cochlostoma septemspirale (Caenogastropoda, Cyclophoroidea, Diplommatinidae, Cochlostomatinae)

Sexual dimorphisms in shell-bearing snails expressed by characteristic traits of their respective shells would offer the possibility for a lot of studies about gender distribution in populations, species, etc. In this study, the seven main shell characters of the snail Cochlostoma septemspirale were measured in both sexes: (1) height and (2) width of the shell, (3) height and (4) width of the aperture, (5) width of the last whorl, (6) rib density on the last whorl, and (7) intensity of the reddish or brown pigments forming three bands over the shell. The variation of size and shape was explored with statistical methods adapted to principal components analysis (PCA) and linear discriminant analysis (LDA). In particular, we applied some multivariate morphometric tools for the analysis of ratios that have been developed only recently, that is, the PCA ratio spectrum, allometry ratio spectrum, and LDA ratio extractor. The overall separation of the two sexes was tested with LDA cross validation.The results show that there is a sexual dimorphism in the size and shape of shells. Females are more slender than males and are characterised by larger size, a slightly reduced aperture height but larger shell height and whorl width. Therefore they have a considerable larger shell volume (about one fifth) in the part above the aperture. Furthermore, the last whorl of females is slightly less strongly pigmented and mean rib density slightly higher. All characters overlap quite considerably between sexes. However, by using cross validation based on the 5 continuous shell characters more than 90% of the shells can be correctly assigned to each sex.     

Sexual size dimorphism in the ontogeny of the solitary predatory wasp Symmorphus allobrogus (Hymenoptera: Vespidae)

Sex-specific patterns of individual growth, resulting in sexual size dimorphism (SSD), are a little studied aspect of the ontogeny related to the evolutionary history and affected by the ecology of a species. We used empirical data on the development of the predatory wasp Symmorphus allobrogus (Hymenoptera, Vespidae) to test the hypotheses that sexual differences of growth resulting in the female-biased SSD embrace the difference in (1) the egg size and the starting size of larva, (2) the larval development duration, and (3) the larval growth rate. We found that eggs developing into males and females have significant differences in size. There was no significant difference between the sexes in the duration of larval development. The relative growth rate and the food assimilation efficiency of female larvae were significantly higher than compared to those of male larvae. Thus, the SSD of S. allobrogus is mediated mainly by sexual differences in egg size and larval growth rate.     

菲菊头蝠回声定位声波频率的性二态有利于性别识别

许多动物的叫声频率呈现性二态现象。蝙蝠夜间活动,主要利用声音信号导航空间、追踪猎物、传递交流信息。本研究选择成体菲菊头蝠作为研究对象,检验回声定位声波频率性二态是否有利于性别识别。研究发现,菲菊头蝠回声定位声波频率参数具有显著性别差异。播放白噪音、雄性回声定位声波及雌性回声定位声波期间,实验个体的反应叫声数量依次递减。播放白噪音、雌性回声定位声波及雄性回声定位声波后,实验个体的反应叫声数量依次递增。白噪音诱导反应叫声强度高于回声定位声波诱导反应叫声强度。研究结果表明,菲菊头蝠回声定位声波的频率参数编码发声者性别信息,有利于种群内部的性别识别。本研究暗示,回声定位声波可能在蝙蝠配偶选择中扮演一定作用。     

First report of exocrine epithelial glands in oestroid flies: the tachinid sexual patches (Diptera: Oestroidea: Tachinidae)

Sexual patches are abdominal areas identifiable by modified setation, present in the males of several groups of Tachinidae (Diptera). We comparatively studied more than 40 species belonging to 24 genera representative of subfamilies known to bear these organs, using light microscopy and scanning (SEM) and transmission (TEM) electron microscopy. We provide a detailed characterization of the fine structure of the setae and microtrichia composing these sexual patches and of the underlying epithelium. Study of abdominal sections showed that, close to the patch area, the epidermis forms a thick layer composed of numerous secretory units of strictly associated cells, ending at the level of cuticular pores at the base of the setae. We hypothesize a secretory function of these structures. The segmental pattern of the sexual patches across the Tachinidae is defined and predictable. We note that almost all the segmental patterns share the presence of sexual patches on abdominal tergite 4, underscoring the diversity of male sexual specializations that occur on the fourth abdominal segment of muscomorph flies.     

The synaptic organization of visual interneurons in the lobula complex of flies

Summary The synaptic organization of three classes of cobalt-filled and silver-intensified visual interneurons in the lobula complex of the blowfly Calliphora (Col A cells, horizontal cells and vertical cells) was studied electron microscopically. The Col A cells are regularly spaced, columnar, small field neurons of the lobula, which constitute a plexus of arborizations at the posterior surface of the neuropil and the axons of which terminate in the ventrolateral protocerebrum. They show postsynaptic specializations in the distal layer of their lobula-arborizations and additional presynaptic sites in a more proximal layer; their axon terminals are presynaptic to large descending neurons projecting into the thoracic ganglion. The horizontal and vertical cells are giant tangential neurons, the arborizations of which cover the anterior and posterior surface of the lobula plate, respectively, and which terminate in the perioesophageal region of the protocerebrum. Both classes of these giant neurons were found to be postsynaptic in the lobula plate and pre- and postsynaptic at their axon terminals and axon collaterals. The significance of these findings with respect to the functional properties of the neurons investigated is discussed.     

Sexual dimorphism in the snub-nosed langurs (Colobinae: Rhinopithecus)

Sexual dimorphism in the dentition and skeleton of the four extant species of snub-nosed langurs, Rhinopithecus (R.) bieti, R. (R.) brelichi, R. (R.) roxellana and R. (Presbytiscus) avunculus, was studied. The species shared a similar general pattern of sexual dimorphism, but were found to differ in respects that appear to reflect the influence of disparate socioecological and environmental factors. All the species showed marked canine dimorphism, but the very high degree of canine dimorphism in R. bieti appeared to be due to the intensity of intermale competition for mates during a temporally restricted breeding season, and possibly also to the intensity of competition between males for other resources during other times of the year. Sexual dimorphism in the postcranial skeleton of Rhinopithecus species was also most pronounced in R. bieti and may be related to the relatively higher frequency of terrestrial locomotion in males of the species. © 1995 Wiley-Liss, Inc.     

Sexual dimorphism in two subspecies of Ethiopian baboons (Papio hamadryas) and their hybrids

Sexual dimorphism in mammals has been related to such variables as absolute body size, ecology, and various aspects of social behaviour. Attempts to relate dimorphism to any of these variables have necessarily used small heterogeneous samples to represent the relevant species. We are concerned by the inevitable exclusion of any measure of variability in dimorphism and the consequent impossiblity of assessing the significance of observed interspecific differences. In this paper we describe aspects of sexual dimorphism in anubis,hamadryas, and hybrid baboons from Ethiopia. Samples are large enough to permit a measure of intrapopulation variability. Hamadryas baboons are more dimorphic than anubis in epigamic features, but not in postcanine dentition, nor, contrary to previous reports, in body weight or canine tooth size. Hybrid males are more hamadryas-like and hybrid females more anubis-like, as would be predicted by the proposed mechanism for the establishment of the hybrid zone, namely the capture of anubis females by hamadryas males.