A new type of insect infrared organ of low thermal mass

The Australian beetle Acanthocnemus nigricans is attracted by forest fires and has a pair of complex infrared (IR) receptor organs on the first thoracic segment. Each organ consists of a tiny sensory disc (diameter 120-130 µm) which serves as an absorbing structure for IR radiation. The disc is arranged above an air-filled cavity which is located just anteriorly to the coxae of the prothoracic legs. Inside the disc, about 30 multipolar thermoreceptors (warmth receptors) are tightly attached to the cuticle which is directed to the outside. The many dendrites of each multipolar neuron are tightly wrapped around the soma and contain a large number of mitochondria. Absorption of IR radiation by the disc causes an increase in temperature which is measured by the warmth receptors. Therefore, the IR receptors of A. nigricans can be classified as microbolometers with reduced thermal mass and in principle can be compared to the IR organs of pit vipers.     

The brain as a photoreceptor: intracerebral ocelli in the firefly

 This paper deals with the structure and function of the intracerebral ocelli in the caudal area of the brain of the Japanese firefly. A pair of epilaterally placed specialized pigmented organs was found at the caudal ends of the brains of the fireflies Luciola cruciata and L. lateralis. On the basis of light and transmission electron micrographs of both male and female individuals these organs seemed photoreceptive in nature. Intracellular and extracellular recordings were obtained from the intracerebral ocelli of the fireflies with microelectrodes. The physiological evidence revealed that the cells found in the brain were, indeed, photoreceptors. Received: 7 April 2000 / Accepted in revised form: 16 June 2000     

Microfluidic photomechanic infrared receptors in a pyrophilous flat bug

Infrared (IR) receptors are so far known only in boid and crotalid snakes and in three genera of pyrophilous beetles that seek out forest fires. Pyrophilous insects can also be found in other orders, however, so it can be hypothesised that IR receptors also occur in some of these species. We investigated the pyrophilous Australian flat bug Aradus albicornis and found a small number of dome-shaped sensilla (diameter 13 microm) on the prothorax, which have previously not been described. Ultrastructural investigations revealed that the sensilla are characterised by a fluid-filled inner compartment enclosed in a round cuticular shell. The cuticular apparatus is innervated by the dendrite of a ciliary mechanoreceptor, which is fluidically coupled to the inner compartment. Electrophysiological recordings demonstrated that the sensilla respond to brief warming by red laser light or to broadband IR radiation. Depending on the radiation intensity (4.4-549 mW/cm(2) tested, threshold measured as 11.3 mW/cm(2)), first spike latencies varied between 3.4 and 7.5 ms. Thus, our findings demonstrate that A. albicornis most probably possesses photomechanic IR sensilla resembling the metathoracic IR sensilla of buprestid beetles of the genus Melanophila. In the Melanophila sensillum, IR radiation causes thermal expansion of a fluid, which rapidly deforms the dendritic membrane of a mechanosensory cell. The existence of photomechanic IR receptors in both beetles and bugs demonstrates a remarkable convergent evolution towards this particular biophysical transduction mechanism and suggests that it provides selective advantages over other possible solutions.     

Seed drops and caches by the harvester ant Messor barbarus: do they contribute to seed dispersal in Mediterranean grasslands?

 To determine whether the harvester ant Messor barbarus acts as a seed disperser in Mediterranean grasslands, the accuracy level of seed processing was assessed in the field by quantifying seed drops by loaded foragers. In the vicinity of exploited seed patches 3 times as many diaspores were found as in controls due to seed losses by foragers. Over trails, up to 30% of harvested seeds were dropped, singly, by workers but all were recovered by nestmates within 24 h. Seeds were also dropped within temporary caches with very few viable diaspores being left per cache when ants no longer used the trail. Globally, ant-dispersed diaspores accounted for only 0.1% of seeds harvested by M. barbarus. We discuss the possible significance for grassland vegetation of harvester-ant-mediated seed dispersal. Received: 26 January 2000 / Accepted in revised form: 20 June 2000     

Hierarchy length in orphaned colonies of the ant <Emphasis Type="Italic">Temnothorax nylanderi</Emphasis>

Workers of the ant Temnothorax nylanderi form dominance orders in orphaned colonies in which only one or a few top-ranking workers begin to produce males from unfertilized eggs. Between one and 11 individuals initiated 80% of all aggression in 14 queenless colonies. As predicted from inclusive fitness models (Molet M, van Baalen M, Monnin T, Insectes Soc 52:247–256, 2005), hierarchy length was found to first increase with colony size and then to level off at larger worker numbers. The frequency and skew of aggression decreased with increasing size, indicating that rank orders are less pronounced in larger colonies.     

2,3-Dimethyl-5-(2-methylpropyl)pyrazine, a trail pheromone component of Eutetramorium mocquerysi Emery (1899) (Hymenoptera: Formicidae)

 The ant Eutetramorium mocquerysi (Myrmicinae) is endemic to the island of Madagascar. During foraging and nest emigration the ants lay recruitment trails with secretions from the poison gland. We identified three pyrazine compounds in the poison gland secretion: 2,3-dimethyl-5-(2-methylpropyl)pyrazine 1, 2,3-dimethyl-5-(3-methylbutyl)pyrazine 3, 2,3-dimethyl-5-(2-methylbutyl)pyrazine 4. Only the first component elicited trail-following behavior in the ants. We were unable to investigate whether the other pyrazine components have a synergistic function. Received: 21 February 2000 / Accepted in revised form: 27 June 2000     

Nectar production dynamics and sugar composition in two <Emphasis Type="Italic">Mucuna</Emphasis> species (Leguminosae,Faboideae) with different specialized pollinators

Nectar is secreted in particular rhythms throughout the lifespan of a flower, which allows determining the nectar production dynamics. This paper compares nectar features in Mucuna japira and Mucuna urens describing: dynamics of nectar production, floral response to nectar removal, resorption, nectar sugar composition, and variation in nectar sugar composition. M. japira inflorescence bears 12–21 yellow flowers, which are in anthesis for 7 days, whereas M. urens inflorescence bears 36–54 greenish flowers, but only 1–3 flowers are in anthesis simultaneously that last one night. Nectar volume and sugar concentration were measured, and the amount of sugar was estimated. Qualitative and quantitative nectar sugar composition was determined. Both species had a constant nectar sugar concentration (ca. 10% for M. japira and ca. 16% for M. urens) and secreted high volumes of nectar (ca. 340 μl per flower for M. japira and 310 μl per flower for M. urens), during 5 days for M. japira and 6 h for M. urens, but after the first removal, i.e., when flower opening mechanism is triggered, nectar production stops immediately. Nectar resorption occurred in both species. Nectar sugar composition showed some similarities between the species. Variation in nectar sugar composition occurred in both species. The Mucuna species are dependent on their pollinators to produce fruits and seeds, and they have different strategies to promote the necessary interaction with birds or bats, especially related to nectar and flower characteristics.     

Variability of Fire Behavior, Fire Effects, and Emissions in Scotch Pine Forests of Central Siberia

As part of the Russian FIRE BEAR (Fire Effects in the Boreal Eurasia Region) Project, replicated 4-ha experimental fires were conducted on a dry Scotch pine (Pinus sylvestris)/lichen (Cladonia sp.)/feathermoss (Pleurozeum schreberi) forest site in central Siberia. Observations from the initial seven surface fires (2000-2001) ignited under a range of burning conditions quantified the different fuel consumption and fire behavior characteristics (e.g., rate of spread, fireline intensity, etc.) possible in this particular forest fuel type. Experimental results and dendrochronological study of local fire history both support the dominance of local fire regimes by low to moderate-intensity surface fires. Carbon released by the experimental fires ranged from 4.8 to 15.4 t C ha^{− 1} depending on fuel conditions and fire severity. Preliminary emission data show a strong correlation between carbon dioxide (CO₂) and carbon monoxide (CO) emissions, which should facilitate accurate estimates of fire impacts on atmospheric chemistry. Carbon concentration in smoke samples was related to fire severity. The short landscape-scale fire-return interval (50 years), combined with typically low fire severity, in pine ecosystems of central Siberia is often associated with low tree mortality and relatively rapid buildup of litter and understory fuels after a fire.     

Anatomical localization and stereoisomeric composition of <Emphasis Type="Italic">Tribolium castaneum</Emphasis> aggregation pheromones

We report that the abdominal epidermis and associated tissues are the predominant sources of male-produced pheromones in the red flour beetle, Tribolium castaneum and, for the first time, describe the stereoisomeric composition of the natural blend of isomers of the aggregation pheromone 4,8-dimethyldecanal (DMD) in this important pest species. Quantitative analyses via gas chromatography–mass spectrometry showed that the average amount of DMD released daily by single feeding males of T. castaneum was 878 ± 72 ng (SE). Analysis of different body parts identified the abdominal epidermis as the major source of aggregation pheromone; the thorax was a minor source, while no DMD was detectable in the head. No internal organs or obvious male-specific glands were associated with pheromone deposition. Complete separation of all four stereoisomers of DMD was achieved following oxidation to the corresponding acid, derivatization with (1R, 2R)- and (1S, 2S)-2-(anthracene-2,3-dicarboximido)cyclohexanol to diastereomeric esters, and their separation on reversed-phase high-performance liquid chromatography at −54°C. Analysis of the hexane eluate from Porapak-Q-collected volatiles from feeding males revealed the presence of all four isomers (4R,8R)/(4R,8S)/(4S,8R)/(4S,8S) at a ratio of approximately 4:4:1:1. A walking orientation bioassay in a wind tunnel with various blends of the four synthetic isomers further indicated that the attractive potency of the reconstituted natural blend of 4:4:1:1 was equivalent to that of the natural pheromone and greater than that of the 1:1 blend of (4R,8R)/(4R,8S) used in commercial lures.     

In vivo measurements of the internal pH of Hediste (Nereis) diversicolor (Annelida, Polychaeta) exposed to ambient sulphidic conditions using pH microelectrodes

 The effect of different ambient sulphide concentrations on the internal pH regime of Hediste (Nereis) diversicolor was studied under in vivo conditions using liquid membrane pH microelectrodes, a method which is new to marine sciences. As a case study, the hypothesis was tested whether organisms exposed to ambient sulphidic conditions are able to lower their internal pH which, in effect, would reduce sulphide influx into the animals and thus could represent an effective detoxification mechanism. It was shown that a significant lowering of the internal pH occurred within only 20 min after adding sulphide. This pH lowering appeared to be dependent on the external sulphide concentration of the ambient medium and showed a saturation beyond a threshold level of about 130 μM. It is discussed whether this sulphide-induced pH drop is an active regulatory mechanism and acts as an effective protection mechanism against sulphide during short-term exposures. Received: 1 June 1999 / Accepted in revised form: 3 May 2000     

饮水型砷暴露对小鼠多系统脏器的毒性作用

为揭示饮水型砷暴露对机体的毒性,系统研究了砷摄入对实验动物基础生理和多系统脏器的毒性损伤作用.选雄性ICR小鼠为受试动物,以自由饮用含砷10 mg·L^-1的水溶液进行染毒,连续染毒60 d后检测发现,饮水砷暴露对小鼠一般体征和体重无显著影响,肝脏脏器系数显著降低,心脏、肺脏、肾脏和睾丸脏器系数降低,但无统计学意义.砷染毒组血清谷丙转氨酶（ALT）和谷草转氨酶（AST）活性显著升高,总胆固醇（TC）和甘油三酯（TG）含量显著升高,高密度脂蛋白胆固醇（HDL-C）含量显著降低,低密度脂蛋白胆固醇（LDL-C）含量显著升高;肝脏、小肠、心脏、肺脏、肾脏和睾丸组织中还原型谷胱甘肽（GSH）含量和超氧化物歧化酶（T-SOD）活性显著降低,过氧化氢（H₂O₂）和丙二醛（MDA）含量显著升高,并出现程度不同的组织形态结构损伤.研究结果表明,饮水砷暴露可诱发实验小鼠肝脏功能异常、生理代谢紊乱,导致消化系统、循环系统、呼吸系统、泌尿系统与生殖系统等多系统脏器组织的氧化损伤和结构病变,砷暴露对机体的毒性作用存在组织器官差异性,对肝脏的损伤较严重.     

Discovery of mycangia and the associated xylose-fermenting yeasts in stag beetles (Coleoptera: Lucanidae)

Most wood-feeding insects need an association with microbes to utilize wood as food, and some have special organs to store and convey the microbes. We report here the discovery of the microbe-storage organ (mycangium) in stag beetles (Coleoptera: Lucanidae), which develop in decayed wood. The mycangium, which was discovered in the abdomen, is present in all adult females of 22 lucanid species examined in this study, but absent in adult males. By contrast, adult insects of both sexes of selected Passalidae, Geotrupidae, and Scarabaeidae, which are related to Lucanidae, lacked mycangia similar to those of the lucanid species. Yeast-like microbes were isolated from the mycangium of five lucanid species. DNA sequence analyses indicate that the microbes are closely related to the xylose-fermenting yeasts Pichia stipitis, Pichia segobiensis, or Pichia sp. known from the gut of a passalid species.     

A molecular phylogenetic analysis of the neotropical dart-poison frog genus Phyllobates (Amphibia: Dendrobatidae)

 A phylogenetic analysis of the Neotropical dart-poison frogs, genus Phyllobates, was performed based on mitochondrial cytochrome b sequences. Members of Phyllobates from South and Central America were found to form each an evolutionary lineage. Among the South American lineage, species with uniform dorsal coloration as adults form a derived monophyletic clade. Received: 26 June 2000 / Accepted in revised form: 8 November 2000     

Low chitinase activity in Acacia myrmecophytes: a potential trade-off between biotic and chemical defences?

 We determined chitinase activity in leaves of four myrmecophytic and four non-myrmecophytic leguminous species at the plants' natural growing sites in Mexico. Myrmecophytic plants (or 'ant plants') have obligate mutualisms with ants protecting them against herbivores and pathogenic fungi. Plant chitinases can be considered a reliable measure of plant resistance to pathogenic fungi. The myrmecophytic Acacia species, which were colonised by mutualistic ants, exhibited at least six-fold lower levels of chitinase activity compared with the non-myrmecophytic Acacia farnesiana and three other non-myrmecophytes. Though belonging to different phylogenetic groups, the myrmecophytic Acacia species formed one distinct group in the data set, which was clearly separated from the non-myrmecophytic species. These findings allowed for comparison between two recent hypotheses that attempt to explain low chitinase activity in ant plants. Most probably, chitinases are reduced in myrmecophytic plant species because these are effectively defended indirectly due to their symbiosis with mutualistic ants. Received: 16 August 2000 / Accepted in revised form: 28 October 2000     

Climate anomalies, Indonesian vegetation fires and terrestrial carbon emissions

There was a widespread misconception about the causes of vegetation and land fires in Indonesia. At a certain point, the public perceived that fires and the associated haze pollution were primarily caused by smallholders' agricultural activities. In fact, there was a variety of land-use activities including large-scale land clearing following deforestation for further land development. El Niño events and the associated dry weather were sometimes quoted by officials and the media as the cause of fires. The fire episodes from 1980 to 2000 were analysed in connection with climate anomalies and the implementation of land-use policies related to forest conversions. The analysis employs long-term climatic and sea surface temperature data to reconstruct climate distributions and anomalies including Southern Oscillation Index (SOI), Sea Surface Temperature (SST) and Outgoing Long-wave Radiation (OLR). In this study, the terrestrial carbon emissions from vegetation fires were estimated based on official statistical data on area burnt. The possible incentives for sustainable land management were discussed in the light of fire prevention. The underlying cause neglected in the discussion of Indonesian vegetation fires was forest and land development policy. Legitimated in the early 1980s, it drove massive forest conversions and the use of fires for land clearing. El Niño Southern Oscillation (ENSO) provided dry weather suitable for biomass burning and widespread fire, but it was hardly the cause of fires. The estimate of area burnt in the big fires in 1997 was about 11.6 Mha, resulting in carbon release of 1.45 Gt, equivalent to 0.73 ppmv of CO₂, or almost half the annual global atmospheric CO₂ growth. Based on the current carbon market price such emissions by the 1997 fire episode were worth around US$ 3.6 billion.     

The action spectrum for maximal photosensitivity of germination

 Fruits of Garden Lettuce, imbibed in 0.01 M KNO₃, were depleted of maternal active phytochrome B by saturating deep-red exposure and photosensitized by chilling for 1 week at 4  °C. Twenty saturated fluence-response curves for photoinduced germination were elaborated between 300 and 800 nm, using exposure periods from 6 to 600 s at 22.5  °C; there is linear and closely parallel regression in the logarithmic probability net. The reciprocals of the half-response fluences obtained gave the apparent conversion spectrum of the controlling pigments and this was corrected for the transmittance of the seed-coat. It is a phytochrome spectrum of P _r with photoconversion cross-sections of 1.2·10⁹ and 4.5·10³ m² mol^–1 at 666 and 800 nm, respectively. This means that for half-saturated germination of sensitized seed, fewer than 1 out of 200,000 phytochrome A molecules have to be photoconverted to P _fr, and no photo-reversibility by deep-red was found. Therefore, all spectral colours of nightly moon- or skylight should stimulate the germination of sensitized weed seeds if they are exposed at the soil surface between sequential tillage operations. Received: 28 April 2000 / Accepted in revised form: 28 July 2000     

Stereological quantification of placental villus vascularization and its relation to umbilical artery Doppler flow in intrauterine growth restriction

The aim of this study was to investigate the changes in the number of vessels within tertiary stem villi and intermediate/terminal villi which may be responsible for the abnormalities in placental vascular resistance and Doppler velocity index values in growth-restricted fetuses. The placentas of 20 cases with intrauterine growth restriction and 30 cases which were appropriate for gestational age were studied. The umbilical artery resistance index, pulsatility index and systolic to diastolic ratio were measured in each case. The vessels were quantified by a stereological method described previously and vascular surface density and the volume portion of the villi were calculated. The placentas of preterm and term cases with intrauterine growth restriction displayed significant reductions in the vascular surface density of stem and intermediate/terminal villi and volume portion of intermediate/terminal villi stroma when compared with gestation-matched normally grown cases (p<0.05). There was no significant correlation between Doppler index values of the umbilical artery and the stereological parameters of the intermediate/terminal and stem villi in the intrauterine growth restriction group (p>0.05). Some of the pregnancies with intrauterine growth restriction (six patients) with normal Doppler flow velocity waveforms had reduced vascularization in the placentas, and these pregnancies were found to have no perinatal complications. We conclude that,although the placental villi show reduced vascularization in pregnancies with intrauterine growth restriction, the Doppler indices may be normal and this normal flow pattern is related to reduced complication rate. Copyright © 2002 John Wiley & Sons, Ltd.     

A familial Xp+ chromosome detected during fetal karyotyping,which is associated with short stature in four generations of a Turkish family

The short-stature homeobox-containing gene (SHOX) on chromosome Xp22.3 was recently identified as an important determinant of the stature phenotype. Deletions of the SHOX gene, some of them due to structural chromosome abnormalities, have been described in patients with idiopathic short stature and Leri-Weill syndrome. Additionally, haploinsufficiency of SHOX is a main cause for short stature seen in patients with Turner syndrome. Here we report an unusual X-chromosome abnormality, which was detected during a fetal karyotyping performed because of a previous child with Down syndrome. GTG banding demonstrated an extra chromosome segment on the terminal part of the short arm of chromosome X in the index case (karyotype: 46,X,Xp+). The same chromosomal abnormality was found in the mother and the maternal grandmother. All carriers of this chromosomal abnormality presented with short stature but no other associated symptoms. Whole chromosome painting of X revealed a homogeneous painting of the abnormal X chromosome indicating that no other chromosome was involved. Additional FISH studies with probe DXS1140 (Kallmann probe at Xp22.3), Quint-Essential X-Specific DNA (DMD probe at Xp21.2), XIST (at Xq13.2), and Tel Xq/Yq were performed, and no abnormality was observed in the intensities or the localizations of the probes signals. However, applying a specific SHOX gene probe (derived from cosmid LLNONO3M34F5) showed a loss of signal on the derivative X chromosome. Our results show that the Xp+ generation led to a deletion of the complete SHOX gene and caused short stature in the presented family. Copyright © 2003 John Wiley & Sons, Ltd.     

Pheromonal contest between honeybee workers (Apis mellifera capensis)

 Queenless workers of the Cape honeybee (Apis mellifera capensis) can develop into reproductives termed pseudoqueens. Although they morphologically remain workers they become physiologically queenlike, produce offspring, and secrete mandibular gland pheromones similar to those of true queens. However, after queen loss only very few workers gain pseudoqueen status. A strong intracolonial selection governs which workers start oviposition and which remain sterile. The “queen substance”, 9-keto-2(E)-decenoic acid (9-ODA), the dominant compound of the queen's mandibular gland pheromones, suppresses the secretion of queenlike mandibular gland pheromones in workers. It may act as an important signal in pseudoqueen selection. By analysing the mandibular gland pheromones of workers kept in pairs, we found that A. m. capensis workers compete to produce the strongest queen-like signal. Received: 2 July 2000 / Accepted in revised form: 28 July 2000