Ventral polarization vision in tabanids: horseflies and deerflies (Diptera: Tabanidae) are attracted to horizontally polarized light

Adult tabanid flies (horseflies and deerflies) are terrestrial and lay their eggs onto marsh plants near bodies of fresh water because the larvae develop in water or mud. To know how tabanids locate their host animals, terrestrial rendezvous sites and egg-laying places would be very useful for control measures against them, because the hematophagous females are primary/secondary vectors of some severe animal/human diseases/parasites. Thus, in choice experiments performed in the field we studied the behavior of tabanids governed by linearly polarized light. We present here evidence for positive polarotaxis, i.e., attraction to horizontally polarized light stimulating the ventral eye region, in both males and females of 27 tabanid species. The novelty of our findings is that positive polarotaxis has been described earlier only in connection with the water detection of some aquatic insects ovipositing directly into water. A further particularity of our discovery is that in the order Diptera and among blood-sucking insects the studied tabanids are the first known species possessing ventral polarization vision and definite polarization-sensitive behavior with known functions. The polarotaxis in tabanid flies makes it possible to develop new optically luring traps being more efficient than the existing ones based on the attraction of tabanids by the intensity and/or color of reflected light.     

Torpor and energetic consequences in free-ranging grey mouse lemurs (Microcebus murinus): a comparison of dry and wet forests

Many endotherms save energy during food and water shortage or unpredictable environment using controlled reductions in body temperature and metabolism called torpor. In this study, we measured energy metabolism and water turnover in free-ranging grey mouse lemurs Microcebus murinus (approximately 60 g) using doubly labelled water during the austral winter in the rain forest of southeastern Madagascar. We then compared patterns of thermal biology between grey mouse lemurs from the rain forest and a population from the dry forest. M. murinus from the rain forest, without a distinct dry season, entered daily torpor independent of ambient temperature (T _a). There were no differences in torpor occurrence, duration and depth between M. murinus from the rain and dry forest. Mouse lemurs using daily torpor reduced their energy expenditure by 11% in the rain forest and by 10.5% in the dry forest, respectively. There was no significant difference in the mean water flux rates of mouse lemurs remaining normothermic between populations of both sites. In contrast, mean water flux rate of individuals from the dry forest that used torpor was significantly lower than those from the rain forest. This study represents the first account of energy expenditure, water flux and skin temperature (T _sk) in free-ranging M. murinus from the rain forest. Our comparative findings suggest that water turnover and therefore water requirement during the austral winter months plays a more restricting role on grey mouse lemurs from the dry forest than on those from the rain forest.     

Evidence of earliest human occurrence in Europe: the site of Pirro Nord (Southern Italy)

Some flint lithic artifacts were discovered in the fissure fillings of the well-known Pirro Nord site (Apulia, Southern Italy). The lithic industry, composed by three cores and some flakes, has been found to be associated to an Early Pleistocene vertebrate fossil assemblage. The fossil association contains a wide range of micromammals, including Allophaiomys ruffoi and Episoriculus gibberodon and large mammals including Bison degiulii and Equus altidens together with African elements as the gelada baboon Theropithecus and the saber-toothed cat Megantereon whitei. It defines the latest Villafranchian chronological unit (Pirro Nord Faunal Unit) in the Western European mammal biochronology. The lithic industry of Pirro Nord represents the oldest occurrence of the genus Homo in Europe as it is attributable to a chronological interval between 1.3 and 1.7 Ma. This supports the hypothesis that the genus Homo, with Oldowaian technology, extended its range in Europe, probably from western Asia, during the first half of the Early Pleistocene. The new discovery from Pirro Nord changes the chronology of the first arrival of hominids in Europe and offers new perspectives in the debate about the human dispersal in the Early Pleistocene.     

水位变化对消落带氨氧化微生物丰度和多样性的影响

南水北调来水进入密云水库将直接引起水库水位上涨,这必将影响消落带土壤中氨氧化微生物的丰度和多样性,从而影响消落带中氮循环过程.采用分子生物学方法,探讨了水位变化对消落带氨氧化细菌(AOB)和古菌(AOA)的生物多样性和丰度的影响.Real-time PCR结果显示,2015年9月消落带岸上/水陆界面土壤和沉积物中AOA和AOB的丰度范围分别为1.00×10~7~3.91×10~7copies·g~(-1)和5.49×10~6~9.77×10~6copies·g~(-1).2015年11月水位比9月上升3 m,淹没区土壤/沉积物中AOA和AOB的丰度范围分别为5.80×106~1.56×10~7copies·g~(-1)和2.14×10~6~4.40×106copies·g~(-1),比被淹没前有所下降,但AOA的丰度始终高于AOB,说明AOA比AOB更适合在低氨氮的消落带环境中生长,并且更能适应低氧环境.水位上升3 m后,水陆交界面土壤中AOA和AOB的多样性均有所增加,而在沉积物中多样性减少.水位上涨之前,AOA大多数OTU属于Nitrososphaera、Nitrosopumilus,而水位上涨之后,大多数OTU归属于土壤簇Nitrososphaera,即在低氧消落带环境中土壤簇Nitrososphaera为优势AOA菌.对于AOB,水陆交界面土壤和沉积物中Nitrosopira和Nitrosomonas分别在氨氧化过程中发挥作用.     

Fertility signals in the bumblebee Bombus terrestris (Hymenoptera: Apidae)

In eusocial Hymenoptera, queen control over workers is probably inseparable from the mechanism of queen recognition. In primitively eusocial bumblebees (Bombus), worker reproduction is controlled not only by the presence or absence of a dominant queen but also by other dominant workers. Furthermore, it was shown that the queen dominance is maintained by pheromonal cues. We investigated whether there is a similar odor signal released by egg-laying queens and workers that may have a function as a fertility signal. We collected cuticular surface extracts from nest-searching and breeding Bombus terrestris queens and workers that were characterized by their ovarian stages. In chemical analyses, we identified 61 compounds consisting of aldehydes, alkanes, alkenes, and fatty acid esters. Nest-searching queens and all groups of breeding females differed significantly in their odor bouquets. Furthermore, workers before the competition point (time point of colony development where workers start to develop ovaries and lay eggs) differed largely from queens and all other groups of workers. Breeding queens showed a unique bouquet of chemical compounds and certain queen-specific compounds, and the differences toward workers decrease with an increasing development of the workers' ovaries, hinting the presence of a reliable fertility signal. Among the worker groups, the smallest differences were found after the competition point. Egg-laying females contained higher total amounts of chemical compounds and of relative proportions of wax-type esters and aldehydes than nest-searching queens and workers before the competition point. Therefore, these compounds may have a function as a fertility signal present in queens and workers.     

Evidence for a male-produced pheromone in <Emphasis Type="Italic">Tetropium fuscum</Emphasis> (F.) and <Emphasis Type="Italic">Tetropium cinnamopterum</Emphasis> (Kirby) (Coleoptera: Cerambycidae)

(E)-6,10-dimethyl-5,9-undecadien-2-ol (geranyl acetol), termed here fuscol, was identified as a male-produced pheromone emitted by Tetropium fuscum (F.) and Tetropium cinnamopterum Kirby. In field experiments, traps baited with synthetic fuscol alone were not significantly attractive, but the combination of fuscol plus host volatiles (a synthetic blend of monoterpenes plus ethanol) attracted significantly more male and female T. fuscum and female T. cinnamopterum than did host volatiles alone. This is the first homoterpenoid alcohol to be described in the Cerambycidae, and the first pheromone reported from the sub-family Spondylidinae.     

Anatomic and acoustic sexual dimorphism in the sound emission system of Phoenicoprocta capistrata (Lepidoptera: Arctiidae)

Both sexes of Phoenicoprocta capistrata have functional tymbals. The scanning electron microscopy revealed differences in the morphology of these organs in males and females. Male tymbals have a well-developed striated band, constituted by 21 ± 2 regularly arranged striae whereas female tymbals lack a striated band. This type of sexual dimorphism is rare in Arctiidae. The recording of the sound produced by moths held by the wings revealed that while males produced trains of pulses organized in modulation cycles, females produced clicks at low repetition rate following very irregular patterns. Statistically, there are differences between sexes in terms of the duration of pulses, which were 355 ± 24 μs in the case of males and 289 ± 29 μs for females. The spectral characteristics of the pulses also show sexual dimorphism. Male pulses are more tuned (Q ₁₀ = 5.2 ± 0.5) than female pulses (Q ₁₀ = 2.7 ± 0.5) and have a higher best frequency (42 ± 1 kHz vs. 29 ± 2 kHz). To our knowledge, this is the first report on an arctiid moth showing sexual dimorphism in tymbal’s anatomy that leads to a best frequency dimorphism. Males produce sound at mating attempts. The sounds recorded during mating are modulation cycles with the same spectral characteristics as those recorded when males are held by the wings. The morphological and acoustic features of female tymbals could indicate a process of degeneration and adaptation to conditions under which the emission of complex patterns is not necessary. Frank Coro no longer works at Universidad de La Habana.     

Homing in the wolf spider Lycosa tarantula (Araneae, Lycosidae): the role of active locomotion and visual landmarks

Previous studies on the homing of the wolf spider Lycosa tarantula have shown that it is carried out by path integration. Animals using this mechanism must measure the distance walked and the angles turned. This study aims to understand if wolf spider L. tarantula is able to estimate the walked distance in an outward path. As this information is more likely obtained by proprioceptive mechanisms, active or passive displacements have been performed. An active locomotion was found essential to estimate distances. During passive locomotion, spiders searched for their burrows near the release point while when displaced actively the inbound journey was longer than the outbound one. The possible use of visual landmarks near the burrow was also tested as a cue to complete the inbound journey. Our results did not show that L. tarantula used these visual landmarks to find the burrow. L. tarantula seems to use only proprioceptive information obtained during the outbound path to estimate the distance traveled.     

Canopy compass in nocturnal homing of the subsocial shield bug, <Emphasis Type="Italic">Parastrachia japonensis</Emphasis> (Heteroptera: Parastrachiidae)

In contrast to an open environment where a specific celestial cue is predominantly used, visual contrast of canopies against the sky through the gap, known as canopy cues, is known to play a major role for visually guided insect navigators in woodland habitats. In this paper, we investigated whether a subsocial shield bug, Parastrachia japonensis, could gauge direction using canopy cues on a moonless night. The results show that they could perform the round trip foraging behaviour even in an experimental arena with only an artificial round gap opened in the ceiling of the arena and adjust their homing direction for a new azimuth when the gap was rotated. Thus, P. japonensis can use slightly brighter canopy cues as a compass reference but not complex landmarks during nocturnal homing behaviour.     

Effect of periphyton community structure on heavy metal accumulation in mystery snail (Cipangopaludina chinensis):A case study of the Bai River, China

The ratio of metal:P stoichiometry was used to identify the accumulation pathways of heavy metals (V, Cr, Co, Ni, Cu, Cd, and Pb) from periphyton to snails Cipangopaludina chinensis Gray (C. chinensis) in the Bai River watershed. The results showed that periphyton communities were mainly composed of two types of algae, filamentous green algae and unicellular diatoms. The proportion of unicellular diatoms in the periphyton community is a key factor that influences metal accumulation in C. chinensis. The V, Cr, Co, Ni, and Cd content of C. chinensis increased steadily as the corresponding metal content of periphyton increased, but Cu and Pb in the snail did not increase in the periphyton. Mechanisms of V, Cr, and Ni accumulation were found to be related to the proportion of diatoms, while Cd and Pb accumulation were dependent on the physiological characteristics of C. chinensis. The accumulation of Cu in C. chinensis was closely related to their grazing behavior. The metal:P stoichiometry revealed that Cr, Ni, and Cd can reduce the potential ecological risks associated with increased P inputs to the ecosystem. V and Co were considered to be relatively safe, regardless of the periphyton P content. Finally, Pb may not be prone to transfer to higher trophic levels, and may pose the lowest ecological risks of the studied heavy metals, but Cu can cause potential ecological risks when eutrophication has occurred.     

Costs of female odour in males of the parasitic wasp <Emphasis Type="Italic">Lariophagus distinguendus</Emphasis> (Hymenoptera: Pteromalidae)

The display of female traits by males is widespread in the animal kingdom. In several species, this phenomenon has been shown to function adaptively as a male mating strategy to deceive sexual rivals (female mimicry). Freshly emerged males of the parasitic wasp Lariophagus distinguendus (Hymenoptera: Pteromalidae) are perceived by other males as if they were females because of a very similar composition of cuticular hydrocarbons which function as a sex pheromone in this species inducing courtship behaviour in males. Within 32 h, however, males deactivate the pheromone and are no longer courted by other males. In this paper, behavioural experiments were performed to test hypotheses on potential costs and benefits associated with the female odour in young males. We did not find any benefits, but demonstrated that young males were significantly more often outrivaled in male-male contests when competing with two older males for a female. Also, young males were significantly more often mounted in homosexual courtship events during these contests. Thus, display of female traits by males is not necessarily beneficial, and in fact, can be disadvantageous. We suggest that these costs have favoured the evolution of the pheromone deactivation mechanism in L. distinguendus males. The function of cuticular hydrocarbons as a female courtship pheromone in L. distinguendus might have evolved secondarily from a primary function relevant for both genders, and the deactivation of the signal in males might have caused a shift of specificity of the chemical signal from the species level to the sex level.     

Caps and gaps: a computer model for studies on brood incubation strategies in honeybees (<Emphasis Type="Italic">Apis mellifera carnica</Emphasis>)

In addition to heat production on the comb surface, honeybee workers frequently visit open cells (“gaps”) that are scattered throughout the sealed brood area, and enter them to incubate adjacent brood cells. We examined the efficiency of this heating strategy under different environmental conditions and for gap proportions from 0 to 50%. For gap proportions from 4 to 10%, which are common to healthy colonies, we find a significant reduction in the incubation time per brood cell to maintain the correct temperature. The savings make up 18 to 37% of the time, which would be required for this task in completely sealed brood areas without any gaps. For unnatural high proportions of gaps (>20%), which may be the result of inbreeding or indicate a poor condition of the colony, brood nest thermoregulation becomes less efficient, and the incubation time per brood cell has to increase to maintain breeding temperature. Although the presence of gaps is not essential to maintain an optimal brood nest temperature, a small number of gaps make heating more economical by reducing the time and energy that must be spent on this vital task. As the benefit depends on the availability, spatial distribution and usage of gaps by the bees, further studies need to show the extent to which these results apply to real colonies. M. Fehler and M. Kleinhenz contributed equally to this work.