Gas exchange pattern in the two‐spot ladybird beetle,Adalia bipunctata,differs in dry vs. moist air

Gas exchange patterns in the ladybird beetle, Adalia bipunctata (L.) (Coleoptera: Coccinellidae), were investigated using an infrared gaseous analyser (IRGA) and a coulometric O₂ respirometer (manometric–volumetric system). Before testing, the beetles were kept either in dry (dehydrated) or moist (hydrated) conditions for 1 day. Their subsequent gas exchange patterns did not depend on their state of humidity but rather were controlled by the humidity of the insect chamber during gas exchange measurement. If this chamber contained dry air, the beetles exhibited CO₂ release by burst, which we interpreted as cyclic gas exchange (CGE) with inter‐burst periods, but if the chamber was switched to contain moist air, then cyclic CO₂ release was soon abandoned and a pattern of continuous gas exchange appeared. Measurements with the coulometric respirometer in moist air showed that continuous gas exchange was often associated with weak abdominal pulsations, which we interpreted as active ventilation. Their metabolic rate was lower during gas exchange cycles than during continuous gas exchange. We revealed that in the ladybird beetle metabolic rate increased in moist air when the gas exchange pattern transitioned from cyclic to continuous.     

Habitat characteristics of grassland Pterostichus species (Coleoptera, Carabidae)

Abstract.

• 1 Pterostichus species were sampled on ninety-two sites distributed throughout north-east England using pitfall trapping.
• 2 The incidence of each species was related to measured site environmental variables using logistic regression.
• 3 Four species groups were identified on the basis of size. The extent of overlap in habitat types between species in each group varied. Two large species overlapped considerably whilst the smaller species showed different responses to one or more environmental variable.
• 4 Possible causes of the differences in habitat overlap between Pterostichus species are discussed.

     

Taxonomic studies of Pterostichus ishikawai Nemoto (Coleoptera: Carabidae)

A macrocephalic pterostichine carabid, Pterostichus ishikawai Nemoto, endemic to the Korean Peninsula, is taxonomically revised based mainly on the membranous parts of the genitalia (male endophallus and female vagina). Two species are separated from P. ishikawai (type locality: Mount Taebaegsan) and newly described: P. ishikawaioides (type locality: Mount Sobaeksan) and P. jiricola (type locality: Mount Jirisan). Since comparative male genital morphology does not support monophyly for these three species, the two novel species should be treated as distinct species, not subspecies of P. ishikawai.     

Notes on two species of the subgenus Lyrothorax Chaudoir (Coleoptera: Carabidae; genus Pterostichus), Pterostichus amagisanus Tanaka and Ishida and Pterostichus fujitai Tanaka and Ishida

Two species of the subgenus Lyrothorax Chaudoir (Coleoptera: Carabidae; genus Pterostichus ), Pterostichus amagisanus Tanaka and Ishida and Pterostichus fujitai Tanaka and Ishida, were revised based on the male endophallus (inner sac everted from aedeagus). P. amagisanus was newly recorded based on a single male from Kyushu, southwest Japan, far from its known distribution (Honshu; the Fuji-Hakone-Izu volcano area), although additional materials are necessary to confirm this record. Despite a highly disjunct distribution, no conspicuous difference was recognized in either external or genital characters between the materials from Honshu and Kyushu. The nominal species P. fujitai was separated into two species, P. fujitai (Honshu) and Pterostichus eoyoritomus sp. nov. (Shikoku; type locality: Mount Jingayama); these two species have some significant differences in the endophallic structures. Character states in male genitalia suggest a sister relationship between P. eoyoritomus sp. nov. and Pterostichus yoritomus Bates.     

Wing-dimorphism and population expansion of Pterostichus melanarius (Illiger, 1798) at small and large scales in central Alberta, Canada (Coleoptera, Carabidae, Pterostichini)

A study spanning ten years revealed changes in wing-morph ratios corroborating the hypothesis that the wing-dimorphic introduced carabid, Pterostichus melanarius Ill.,is spreading through flight, from the city of Edmonton, Canada and establishing populations in natural aspen forest of more rural areas 45-50 km to the East. Comparison of wing-morph ratios between Pterostichus melanarius and the native wing dimorphic species Agonum retractum LeConte suggests that the spatial variation in ratios for Pterostichus melanarius does not reflect underlying environmental variation, but instead the action of selective forces on this wing-dimorphic species. About ten years after its earliest detection in some rural sites the frequency of macropterous individuals in Pterostichus melanarius has decreased c. five-fold, but it is still above the level seen in European populations in which the two wing-morphs are thought to exist in equilibrium. Pterostichus melanarius is expanding its range in native aspen forest much faster than three other introduced species Clivina fossor L.), Carabus granulatus O.F. Müllerand Clivina fossor L also encountered in this study. The two Carabus species are flightless, but Carabus fossor can be dimorphic. Although these four non-native ground beetle species comprise >85% of the carabids collected at sites in urban Edmonton, activity-density of native carabids was similar across the urban-rural gradient, suggesting little direct impact of introduced species on the local abundance of native species. In a second study conducted at a smaller scale near George Lake, Alberta, macropterous individuals of Pterostichus melanarius have penetrated furthest and most rapidly into native aspen forest. Furthermore, the percentage of micropterous individuals has increased markedly in areas first colonized a decade previously. Overall, these studies support the idea that macropterous beetles in wing-d dimorphic species are important vanguards for early colonization of unexploited territory, but that flightless individuals replace the flying morph relatively rapidly once populations are established.     

Cryptic species of the subgenus Morphnosoma Lutshnik (Coleoptera: Carabidae; genus Pterostichus) from Japan

Pterostichus thunbergi Morawitz and its related species of Japan are revised based on the structure of membranous parts of their genitalia for the first time, under the name of the thunbergi species group. This species group is monophyletic and is placed in the subgenus Morphnosoma Lutshnik. The monotypic subgenus Moritapterus Berlov, erected for P. thunbergi, is synonymized with Morphnosoma. Comparative study of the endophallus revealed that P. thunbergi michinoku Nakane is a junior synonym of P. habui and that four species should be recognized in this group. Three of them are sympatric with P. thunbergi and one of them, Pterostichus (Morphnosoma) robustistylis, is described as a new species. Molecular phylogeny based on the COI gene (mitochondrial [mt]DNA) supported its independence as a distinct species. The resultant trees of mtDNA and comparative study of morphology revealed that P. thunbergi is probably non‐monophyletic. In the present study we suggest the presence of further cryptic species of Morphnosoma in Japan.     

荒漠昆虫天花吉丁虫的呼吸及体内水分损失特征

为研究荒漠地区昆虫的呼吸及水分损失特征,以专性寄生在荒漠植物梭梭上的天花吉丁虫Julodis variolaris Pallas为对象,采用LI-6400光合分析仪测定在20℃下天花吉丁虫的呼吸量,并采用重量法测定了不同温度下其水分散失率。结果表明:天花吉丁虫呼吸为典型的不连续气体交换循环（discontinuous gas exchange cycle, DGC）的模式,DGC平均周期约需12.96 min,爆发间期历时平均约占整个DGC历时的80%,CO₂平均释放率为23.45 μL/min。在25℃、30℃、35℃和40℃恒温条件下,单位时间内水分散失随温度升高而增加,10 h内25℃和30℃之间的水分损失率无显著差异,但25℃和30℃与35℃、40℃之间的水分损失率具有显著性差异;10～24 h内25℃、30℃、35℃之间的水分损失率具有显著性差异。荒漠昆虫天花吉丁虫在高温下的高脱水率和高死亡率说明,其在没有水分来源的情况下很难存活,而不连续呼吸模式是其适应高温干旱环境的对策之一。     

Preliminary experiments on the olfactory responses of Pterostichus melanarius Illiger (Coleoptera: Carabidae) to intact plants

1 In two successive years, the olfactory responses of Pterostichus melanarius Illiger (Coleoptera: Carabidae) to intact cabbage and white clover plants were studied, using a four‐arm olfactometer. 2 The first set of experiments tested the response to the odours of cabbage, white clover and the two plants grown together against potting compost; in the second and third sets of experiments, white clover and cabbage were tested, respectively. 3 The results indicate that female P. melanarius individuals are arrested by the combined odours of cabbage and white clover, spending significantly more time in the cabbage with white clover odour field than in either the cabbage, white clover or control odour fields. 4 Similar results were not found for males. 5 Cabbage plants alone did not elicit significant responses in either sex. 6 White clover alone did not elicit significant responses by females and the responses of males were not uniform in the two successive years.     

Gas exchange and nutrition patterns during the life cycle of an artificial wheat crop

The growth, mineral and shoot and root CO₂ exchange of wheat plants ( Triticum aestivum L. cv. Courtot) cultivated in growth chambers have been studied during the complete life cycle. The life cycle could be divided into 4 periods according to the patterns of CO₂ exchange: exponential increase, linear increase, stabilization and decline of photosynthesis. These patterns are analysed in relation to light interception, tillering, competition between plants and ageing of the leaves, all of which constitute successive limiting factors. Root metabolism seemed to be subordinated to the demand of the shoot for minerals. Ion uptake from the nutrient solution was particularly pronounced in young plants, which were higher in minerals and nitrogen than older ones. The ratios of K and P uptake varied with plant age, and the charge balance in ion exchange was equlibrated by H uptake. Rhythmic patterns appeared in all exchanges and varied with plant age. The highest amplitude of rhythm was found in root respiration. After taking the losses due to respiration and photorespiration into account, the maximum rate of photosynthesis approached the theoretical value calculated from the light energy absorbed.     

Interference competition,not predation,explains the negative association between wood ants (Formica rufa) and abundance of ground beetles (Coleoptera: Carabidae)

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Discontinuous gas exchange patterns of beet armyworm pupae, Spodoptera exigua (Lepidoptera: Noctuidae): effects of Bacillus thuringiensis Cry1C toxin, pupal age and temperature

Abstract. Changes in the discontinuous gas exchange cycle of pupal beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae), exposed or not to Cry1C Bacillus thuringiensis toxin, are examined against developmental age (1–7 days) and at different temperatures (10–25 °C) using flow through respirometry. Both exposed and nonexposed pupae exhibit discontinuous gas exchange, but only at 10 °C; the frequency of cyclic release of CO₂ increases with increasing temperatures. The three phases of the discontinuous gas exchange cycle are distinct for both treatment groups. However, the duration of each phase is significantly greater for pupae exposed previously to toxin. The closed phase is 40 ± 14% longer, the flutter phase 23 ± 19% longer, and the open phase is 28 ± 12% longer when pupae were exposed to toxin. Respiratory water loss is 4.5 ± 1.3% for toxin exposed pupae and 2.1 ± 2.4% for unexposed pupae. Furthermore, the exposed pupae have significantly greater cuticular permeability (26.01 ± 1.9 µg cm⁻² h⁻¹ mmHg⁻¹) than the nonexposed pupae (9.64 ± 0.9 µg cm⁻² h⁻¹ mmHg⁻¹). However, in both strains, cuticular transpiration (>93%) far exceeds respiratory transpiration. Overall, total water loss is significantly greater in pupae whose larvae are exposed to toxin compared with pupae from nontreated larvae. Toxin exposed pupae have a mean cycle duration of 60 ± 2.5 min whereas that of nonexposed pupae is 42 ± 1.8 min.(ml g⁻¹ h⁻¹) of the open phase is greater earlier in pupal life followed by a minimum at mid-pupal stage and an increase at late-pupal development in both treatment groups. Combining all 7 days, closed, flutter and open phase (ml g⁻¹ h⁻¹), pupae exposed to toxin produce significantly more CO₂ during each phase. On average, toxin exposed pupae produce 52 ± 12, 43 ± 10 and 15 ± 37% more CO₂ than the untreated pupae during the closed, flutter and open phases, respectively. Therefore, the present study reinforces the need to use insects of similar developmental age in studies of insect respiration patterns and energy metabolism.     

Formation of sperm bundles in Pterostichus nigrita (Coleoptera: Carabidae)

The formation and structure of sperm bundles (spermiozeugmata), and the structure of the vas deferens where bundles are formed, in Pterostichus nigrita is described by light and electron microscopy. The spermiozeugmata are of the sheet-like type consisting of a central rod (about 3?mm long) of electron-dense material (the spermatostyle), to which two bundles of spermatozoa (about 95 per bundle) are attached. The spermatostyle has a spoon-shaped head, and the rod material is differentiated into an electron-dense core and a more electron-lucent cortex. Spermatozoa (about 340?µm long) are attached to the anterior portion of the rod only. Spermiozeugma formation occurs in the upper vas deferens (before the seminal vesicle region) with the secretion of rod material by epithelial cells, which are characterized by well developed rough endoplasmic reticulum with distended cisternae, abundant mitochondria and Golgi bodies. Some cells contain numerous myeloid structures thought to be precursors of rod material, and coated vesicles. During spermiozeugma development, the heads of spermatozoa become embedded in the developing rod material, the anterior of which sits in one of the many diverticula of the mid-region of the vas deferens. Elongation of the rod proceeds by addition of material posteriorly.     

A test of the oxidative damage hypothesis for discontinuous gas exchange in the locust Locusta migratoria

The discontinuous gas exchange cycle (DGC) is a breathing pattern displayed by many insects, characterized by periodic breath-holding and intermittently low tracheal O(2) levels. It has been hypothesized that the adaptive value of DGCs is to reduce oxidative damage, with low tracheal O(2) partial pressures (PO(2) ≈ 2-5 kPa) occurring to reduce the production of oxygen free radicals. If this is so, insects displaying DGCs should continue to actively defend a low tracheal PO(2) even when breathing higher than atmospheric levels of oxygen (hyperoxia). This behaviour has been observed in moth pupae exposed to ambient PO(2) up to 50 kPa. To test this observation in adult insects, we implanted fibre-optic oxygen optodes within the tracheal systems of adult migratory locusts Locusta migratoria exposed to normoxia, hypoxia and hyperoxia. In normoxic and hypoxic atmospheres, the minimum tracheal PO(2) that occurred during DGCs varied between 3.4 and 1.2 kPa. In hyperoxia up to 40.5 kPa, the minimum tracheal PO(2) achieved during a DGC exceeded 30 kPa, increasing with ambient levels. These results are consistent with a respiratory control mechanism that functions to satisfy O(2) requirements by maintaining PO(2) above a critical level, not defend against high levels of O(2).     

The effects of forestry on carabid beetles (Coleoptera: Carabidae) in boreal forests

As compared to natural forests, managed boreal forests are younger, more homogeneous in terms of tree age and species composition, and consist of smaller fragments. Here we examine the effects of such characteristics caused by forestry on carabid beetles (Coleoptera, Carabidae) in the boreal region. The main results are the following. (1) Fragmentation of forests and the size of a fragment appear not to be crucial for the survival of the majority of forest carabids, as they tend to be distributed over various successional stages, but species requiring old-growth habitats suffer. (2) For carabids there appear to be no or very few edge specialist species, and forest-open land edges appear to be effective barriers for species associated with forest or open habitat. However, generalist species easily cross the edge, and edges of forest fragments may be invaded by species from the surrounding open habitat. (3) Habitat change following clear-cutting dramatically changes the composition of carabid assemblages: species restricted to mature forests disappear and open-habitat species invade, while habitat generalists survive at least in the short term. Carabid diversity can probably best be maintained if forest management mimics natural processes, maintains natural structures and includes the natural composition of vegetation and other structural elements (such as dead wood) within the stands, provided that these forest features can be maintained and recreated through forest management practices. At a larger scale, the whole spectrum of forest types and ages (especially old-growth forests), and different successional processes (especially fire) should be maintained. These require the development and use of innovative logging methods, and the planning, implementation, and assessment of landscape-scale ecological management strategies.     

The control of reproductive diapause in Nebria salina (Coleoptera: Carabidae)

Abstract. 1. Adult male and female Nebria salina were collected in summer, when in reproductive diapause, and subjected to three different photoperiod regimes, LD 18:6 h, LD 12:12 h, and LD 6:18 h, to assess the role of light regimes on sexual development. 2. Two alternative hypotheses were tested: (i) development rates increase in response to time restriction and (ii) development rate is at a maximum on the day length approximating to that in the field during reproduction. 3. Gonad development was assessed after 1 and 2 months' exposure to the experimental day lengths. In female N. salina, photoperiod and length of time of exposure both influenced reproductive development. Females required at least 2 months' exposure to photoperiods of ≤ LD 12:12 h to mature. Development of the ovary did not take place on LD 18:6 h, irrespective of the length of exposure. Sexual development occurred in all the males after 2 months, irrespective of photoperiod. 4. At the end of the study the activity of the remaining beetles was measured and compared. Significantly higher activity levels were measured in periods of darkness, and consequently beetles exposed to the two shorter day lengths were found to be more active than those kept on the longest photoperiod. Comparing the 3‐h period 06.00 – 09.00, the last 3 h of darkness for all three regimes, activity was significantly higher on LD 12:12 h and LD 6:18 h than on the LD 18:6 h regime. 5. In order to place the experimental studies in context with the life cycle under natural conditions, pitfall traps were used to compare the seasonal activity of N. salina in the field.     

Landscape patterns of species-level association between ground-beetles and overstory trees in boreal forests of western Canada (Coleoptera, Carabidae)

Spatial associations between species of trees and ground-beetles (Coleoptera: Carabidae) involve many indirect ecological processes, likely reflecting the function of numerous forest ecosystem components. Describing and quantifying these associations at the landscape scale is basic to the development of a surrogate-based framework for biodiversity monitoring and conservation. In this study, we used a systematic sampling grid covering 84 km(2) of boreal mixedwood forest to characterize the ground-beetle assemblage associated with each tree species occurring on this landscape. Projecting the distribution of relative basal area of each tree species on the beetle ordination diagram suggests that the carabid community is structured by the same environmental factors that affects the distribution of trees, or perhaps even by trees per se. Interestingly beetle species are associated with tree species of the same rank order of abundance on this landscape, suggesting that conservation of less abundant trees will concomitantly foster conservation of less abundant beetle species. Landscape patterns of association described here are based on characteristics that can be directly linked to provincial forest inventories, providing a basis that is already available for use of tree species as biodiversity surrogates in boreal forest land management.     

意大利蝗不连续气体交换循环(DGC)呼吸周期历时对高温胁迫的响应

【目的】在前期研究高温胁迫下意大利蝗Calliptamus italicus呼吸代谢的变化特征基础上,为探明相关变化机制,本研究进一步从不连续气体交换循环(DGC)呼吸周期历时阐明其对高温胁迫的响应机制。【方法】以源自新疆伊犁察布查尔蝗区野生种群的意大利蝗成虫为材料,应用多通道昆虫呼吸仪测定意大利蝗DGC暴发间期、暴发期和呼吸周期三者历时随温度变化(21~42℃区间,3℃温度梯度)的响应特征。【结果】雌雄意大利蝗DGC呼吸周期中暴发间期历时随温度升高而缩短,21℃时暴发间期历时最长,雌雄分别为7.29±0.31和7.05±0.37 min,与24,27,30和33℃差异不显著(P0.05),超过33℃后迅速缩短;至39℃时最短,雌雄分别为0.42±0.01和0.70±0.03 min,与其他温度下的历时差异显著(P0.05)。暴发期历时亦随温度升高而缩短,21和39℃时,雌虫暴发期历时分别达到最长和最短,依次为1.55±0.14和0.45±0.01 min,与其他温度下的历时差异显著(P0.05);24和39℃时,雄虫暴发期历时分别达到最长和最短,依次为1.61±0.10和0.68±0.02 min,与其他温度下的历时差异显著(P0.05)。随温度升高,意大利蝗DGC呼吸周期历时呈减少趋势,且主要由暴发间期历时减少所致。21~33℃范围内,每升高3℃雌雄虫暴发间期历时分别平均减少0.174和0.121 min,DGC呼吸频率增幅一致,均为0.0022 Hz,不同温度间差异不显著(P0.05);超过33℃后,每升高3℃雌雄虫暴发间期历时分别平均减少2.197和2.189 min,DGC呼吸频率分别增加0.0120和0.0085 Hz,不同温度间差异显著(P0.05);39℃时暴发间期历时接近零,42℃时DGC呼吸模式消失。【结论】随温度升高,意大利蝗呈现出O2吸收量和CO2释放量增加的变化特征,这是通过减少暴发间期历时和增加DGC呼吸频率等机制而实现的。