LATERAL DISPERSAL OF ADULT AQUATIC INSECTS FOLLOWING EMERGENCE FROM THE MIDDLE REACHES OF THE CHIKUMA RIVER(HONSHU ISLAND,JAPAN)IN RELATION TO WATERFRONT VEGETATION

To clarify the role of waterfront vegetation of floodplains for adult aquatic insects, Trichoptera and Diptera (Tipulidae and Chironomidae), in the middle reaches of the Chikuma River from May to July, an investigation of the number of these insects was conducted by trapping in each type of vegetation using board traps.A total of 2608.5 adults/m 2 were collected, and we identified a total of 26 species belonging to three taxa,i.e., seven species of Trichoptera, four species of Tipulidae and 15 species of Chironomidae. The most abundant species was Psychomyia acutipennis in Trichoptera (95.7%). There was a significant difference between the number of P.acutipennis in the all vegetation area (especially, Salix subfragilis) and the control area (no vegetation) during the investigation periods (P<0.05, Mann-Whitney U-test). Other taxa did not show a significant difference between the all vegetation area and the control. Moreover, the numbers of adult P. acutipennis showed a significant difference in height on each vegetation. In the case of Vicia villosa varia and V. villosa varia plus dead Phragmites australis, the highest number was caught in the traps set in the boundary between one plant and the plant above (P<0.05, Steel-Dwass Test) in May.On the other hand, in the case of almost all vegetation during the investigation periods (except of S.subfragilis in May, Melilotus officinalis plus dead P.australis in June), the highest number was caught in the traps set up within the vegetation (P<0.05, Steel-Dwass Test).As a result, a significant difference was observed in the number of trapped P.acutipennis according to the vegetation and its height.It is suggested that the existence of multiple types of vegetation in the floodplain plays an important role for maintaining the diversity of the fauna there.

Divergence and constraint in the thermal sensitivity of aquatic insect swimming performance

Environmental temperature variation may play a significant role in the adaptive evolutionary divergence of ectotherm thermal performance curves(TPCs).However,divergence in TPCs may also be constrained due to various causes.Here,we measured TPCs for swimming velocity of temperate and tropical mayflies(Family:Baetidae)and their stonefly predators(Family:Perlidae)from different elevations.We predicted that differences in seasonal climatic regimes would drive divergence in TPCs between temperate and tropical species.Stable tropical temperatures should favor the evolution of"specialists"that perform well across a narrow range of temperatures.Seasonally,variable temperatures in temperate zones,however,should favor"generalists"that perform well across a broad range of temperatures.In phylogenetically paired comparisons of mayflies and stoneflies,swimming speed was generally unaffected by experimental temperature and did not differ among populations between latitudes,suggesting a maintenance of performance breadth across elevation and latitude.An exception was found between temperate and tropical mayflies at low elevation where climatic differences between latitudes are large.In addition,TPCs did not differ between mayflies and their stonefly predators,except at tropical low elevation.Our results indicate that divergence in TPCs may be con strai ned in aquatic in sects except under the most differe nt ther・mal regimes,perhaps because of trade-offs that reduce thermal sensitivity and increase performance breadth.

Water Striders:The Biomechanics of Water Locomotion and Functional Morphology of the Hydrophobic Surface(Insecta:Hemiptera-Heteroptera)

Water striders are insects living on the water surface, over which they can move very quickly and rarely get wetted. We measured the force of free walking in water striders, using a hair attached to their backs and a 3D strain gauge. The error was calculated by comparing force and data derived from geometry and was estimated as 13%. Females on average were stronger （1.32 mN） than males （0.87 mN）, however, the ratio of force to weight was not significantly different. Compared with other lighter species, Aquarius paludum seems stronger, but the ratio of force to weight is actually lower. A. paludum applies about 0.3 mN.cm^-1 to 0.4 mN.cm 1 with its mid-legs, thus avoiding penetrating the surface tension layer while propelling itself rapidly over the water surface. We also investigated the external morphology with SEM. The body is covered by effectively two layers of macro-and micro-hairs, which renders them hydrophobic. The setae are long （40 μm-60μm） and stiff, being responsible for waterproofing, and the microtrichia are much smaller （〈10μm）, slender, and flexible, holding a bubble over the body when submerged.

Phenoloxidase and Melanization Innate Immune Activities in Green Darner Dragonfly Nymphs (Anax junius)

Insects in the Order Odonata are highly subject to infection by gregarine parasites. However, despite the important ecological roles that insects play in every ecosystem in which they exist, little research has been devoted to the description of insect immunity. Insects rely heavily on the rapid actions of innate immune mechanisms to prevent infection. We characterized the melanization response in the hemolymph of green darner dragonfly (Anax junius) nymphs. Incubation of chymotrypsin-activated hemolymph with L-DOPA resulted in volume- and time-dependent production of dopaquinone via the phenoloxidase (PO) enzyme, with biphasic accumulation of product. The PO activity was temperature-dependent, with a stepwise increase from 20℃ - 35℃ and maximum activity measured at 35℃ - 40℃. The formation of product was also inhibited in a concentration-dependent manner by diethylcarbonate, a specific inhibitor of PO activity, which indicated that the observed activity was due to the presence of PO enzyme. The rate of formation and quantity of melanin was dependent on exposure to different titers of bacteria. This is the first characterization of both PO activity and melanization response in green darner dragonflies.

Habitat Characterization of Black Flies(Diptera:Simuliidae)in the Tafna Catchment of Western Algeria

Physical Habitat characterization of black flies was performed in the Tafna Basin of Algeria, based primarily on stream size, substrate, and aquatic and riparian vegetation. A total of 143 samples were taken between April and October 2009 at 11 sampling sites in the Tafna catchment. Dams exerted an effect through a slowdown of flow and sedimentation of fine particles, eliminating coarse microhabitats favorable for black flies. Stream and substrate characteristics are key parameters that determined the microhabitats of the species. Of 10 species considered, four were widely present with significant plasticity for the stream and substrate. Four other species were more closely associated with faster streams and eroded substrate. A greater rheophilic tendency was found for Simulium bezzii (Corti), Simulium sergenti Edwards, Simulium quadrifila Grenier, Faure and Laurent and Simulium galloprovinciale Giudicelli, which represents a new record for Algeria.

Role of climatic variability in shaping intraspecific variation of thermal tolerance in Mediterranean water beetles

The climatic variability hypothesis(CVH)predicts that organisms in more thermally variable environments have wider thermal breadths and higher thermal plasticity than those from more stable environments.However,due to evolutionary trade-offs,taxa with greater absolute thermal limits may have little plasticity of such limits(trade-off hypothesis).The CVH assumes that climatic variability is the ultimate driver of thermal tolerance variation across latitudinal and altitudinal gradients,but average temperature also varies along such gradients.We explored intraspecific variation of thermal tolerance in three typical Mediterranean saline water beetles(families Hydrophilidae and Dytiscidae).For each species,we compared two populations where the species coexist,with similar annual mean temperature but contrasting thermal variability(continental vs.coastal population).We estimated thermal limits of adults from each population,previously acclimated at 17,20,or 25℃.We found species-specific patterns but overall,our results agree with the CVH regarding thermal ranges,which were wider in the continental(more variable)population.In the two hydrophilid species,this came at the cost of losing plasticity of the upper thermal limit in this population,supporting the trade-off hypothesis,but not in the dytiscid one.Our results support the role of local adaptation to thermal variability and trade-offs between basal tolerance and physiological plasticity in shaping thermal tolerance in aquatic ectotherms,but also suggest that intraspecific variation of thermal tolerance does not fit a general pattern among aquatic insects.Overlooking such intraspecific variation could lead to inaccurate predictions of the vulnerability of aquatic insects to global warming.

New species of spongillafly genus Sisyra Burmeister,1839(Neuroptera:Sisyridae)from China and Laos

Three new spongillafly species of Sisyra Burmeister,1839 from southern China and Laos are described,namely S.arcuata sp.nov.,S.nobilia sp.nov.,and S.stenoloma sp.nov.Notably,S.arcuata sp.nov.and S.nobilia sp.nov.have remarkable forewing marking pattern,which has never been reported in Sisyra.Additionally,the male of the rare species Sisyra yunana Yang,1986 is described for the first time.All these Sisyra species have a highly specialized male gonocoxites 9.

The influence of habitat heterogeneity and latitude on gamma diversity of the Nearctic Simuliidae, a ubiquitous group of stream-dwelling insects

Among the most prominent, large-scale patterns of species richness are the increases in richness with decreasing latitude and with increasing habitat heterogeneity. Using the stream-dwelling larval and pupal stages of North American black flies （Diptera： Simuliidae）, we address 3 broad questions about species richness： （i） Does a significant latitude-richness relationship exist？ （ii） How does habitat heterogeneity influence gamma diversity？ （iii） What is the sign （positive or negative） of the latitude-richness and the heterogeneity-richness relationships？ We found no evidence that habitat heterogeneity influences gamma diversity. The estimated peak species richness for black flies in North America was at 50-53°N, which also corresponds with peak generic richness. All plesiomorphic, extant lineages of the Simuliidae in the Western Hemisphere are found in cool mountainous environments of North America, suggesting that peak richness at 50-53°N might be a signature of this phylogenetic pattern and a reflection of underlying historical processes

Urban development and industrialization impacts on semiaquatic bugs diversity: A case study in eastern Amazonian streams

Landscape changes have caused the decline of biodiversity and affected the integrity of aquatic ecosystems.In this study,we assessed the influence of industrialization associated with urban development on aquatic environments and the biodiversity of semiaquatic bugs(Gerromorpha)at different scales(water quality,habitat,and landscape).Using the simple buffer method,we evaluated nine streams assessing water quality variables,habitat structure,and linear features(radius¼300 m,length¼600 m)for the percentage of land use and land cover.Our results found that species composition of Gerromorpha was mainly affected by primary forest cover,habitat integrity,leaves substrate,and water temperature(29%explanation),and the species richness was mostly influenced by the habitat integrity index(HII)and phosphorus concentrations.The model that best explained the variation in species richness showed a positive relationship with phosphorus concentrations and HII(43%variation).Therefore,our results show that those human activities are the main factors altering aquatic biodiversity from local to regional scales.Therefore,the retention of riparian forests–even in urban and industrialized areas–can maintain the diversity of semiaquatic insect species by providing suitable environments for the habitat,feeding,and reproductive requirements of these aquatic organisms.Finally,our results also show that the management of riparian vegetation in urban areas and industrial complexes promotes aquatic biodiversity conservation in regions under development in the Amazon.

Assessing physical habitat structure and biological condition in eastern Amazonia stream sites

The advance of agricultural frontiers and industrialization in Amazonia has increased natural resource deterioration,resulting in degraded physical habitat structure and reduced local aquatic biodiversity.We evaluated the relative sensitivities of the Biological Monitoring Working Party(BMWP)and Average Score Per Taxon(ASPT)biotic indexes based on EPT(Ephemeroptera,Plecoptera,Trichoptera)versus EPT taxa richness,EPT abundance,and Shannon-Wiener EPT diversity for evaluating anthropogenic impacts on Amazonian streams.We expected that EPT-BMWP and EPT-ASPT would be more sensitive in detecting environmental changes on stream biota than the other measures.We sampled 32 stream sites in eastern Amazonia distributed along an environmental gradient resulting from different land use intensities.All the biological metrics except EPT-ASPT were significantly responsive to anthropogenic pressures;however,EPT taxa richness was slightly more responsive.