Groups Of Aquatic Insects Research Articles

Dietary variation and food selection by mayfly grazers in a subtropical mountain stream

Abstract Background The classification of functional feeding groups of aquatic insects is often misleading in tropical/subtropical streams because their feeding habits are assumed to be the same as their temperate counterparts according to the mouthpart structure and foraging behavior. This study aimed to examine the diets and preferences of mayfly grazers (Baetis spp. and Rhithrogena ampla) in a subtropical mountain stream in the dry and wet seasons. Results In the stream, epilithic algal communities on insect-excluded bricks (as a grazer-excluded control) were dominated by small adnate diatoms, most likely due to the high current velocity. Both grazers preferred understory and small adnate diatoms, Achnanthes spp. and Achnanthidium pyrenaicum, in both seasons. However, the stalked diatoms Gomphonema spp. were preferred only by Baetis, but not by Rhithrogena, in the dry season when the current velocity became relatively slower. The results of pairwise tests further showed that the algal compositions on the insect-excluded bricks coincided with the diets of both grazers in the wet season but were distinct from those on the bricks in the dry season. Seasonal variations in the algal compositions of the diets of Rhithrogena and on the insect-excluded bricks were apparent, but not in the diets of Baetis. Conclusions The algal physiognomy was most likely attributed to the impact of the high current velocity in the stream. Our results suggest that the diet preference by mayfly grazers in the stream is potentially influenced by algal availability.

Longitudinal Distribution of the Functional Feeding Groups of Aquatic Insects in Streams of the Brazilian Cerrado Savanna.

We demonstrate that the distribution of the functional feeding groups of aquatic insects is related to hierarchical patch dynamics. Patches are sites with unique environmental and functional characteristics that are discontinuously distributed in time and space within a lotic system. This distribution predicts that the occurrence of species will be based predominantly on their environmental requirements. We sampled three streams within the same drainage basin in the Brazilian Cerrado savanna, focusing on waterfalls and associated habitats (upstream, downstream), representing different functional zones. We collected 2,636 specimens representing six functional feeding groups (FFGs): brushers, collector-gatherers, collector-filterers, shredders, predators, and scrapers. The frequency of occurrence of these groups varied significantly among environments. This variation appeared to be related to the distinct characteristics of the different habitat patches, which led us to infer that the hierarchical patch dynamics model can best explain the distribution of functional feeding groups in minor lotic environments, such as waterfalls.

Contaminants as habitat disturbers: PAH-driven drift by Andean paramo stream insects

Contaminants can behave as toxicants, when toxic effects are observed in organisms, as well as habitat disturbers and fragmentors, by triggering avoidance responses and generating less- or uninhabited zones. Drift by stream insects has long been considered a mechanism to avoid contamination by moving to most favorable habitats. Given that exploration and transportation of crude oil represent a threat for surrounding ecosystems, the key goal of the present study was to assess the ability of autochthonous groups of aquatic insects from the Ecuadorian paramo streams to avoid by drift different concentrations of polycyclic aromatic hydrocarbons (PAH) contained in the soluble fraction of locally transported crude oil. In the laboratory, different groups of insects were exposed to PAH for 12h. Three different assays, which varied in taxa and origin of the organisms, concentrations of PAH (0.6–38.8µgL−1), and environment settings (different levels of refuge and flow) were performed. For Anomalocosmoecus palugillensis (Limnephilidae), drift was a major cause of population decline in low concentration treatments but at higher concentrations mortality dominated. PAH was highly lethal, even at lower concentrations, for Chironomidae, Grypopterygidae (Claudioperla sp.) and Hydrobiosidae (Atopsyche sp.), and, therefore, no conclusion about drift can be drawn for these insects. Contamination by PAH showed to be a threat for benthic aquatic insects from Ecuadorian paramo streams as it can cause a population decline due to avoidance by drift and mortality.

Dietary variation and food selection by mayfly grazers in a subtropical mountain stream

The classification of functional feeding groups of aquatic insects is often misleading in tropical/subtropical streams because their feeding habits are assumed to be the same as their temperate counterparts according to the mouthpart structure and foraging behavior. This study aimed to examine the diets and preferences of mayfly grazers (Baetis spp. and Rhithrogena ampla) in a subtropical mountain stream in the dry and wet seasons. In the stream, epilithic algal communities on insect-excluded bricks (as a grazer-excluded control) were dominated by small adnate diatoms, most likely due to the high current velocity. Both grazers preferred understory and small adnate diatoms, Achnanthes spp. and Achnanthidium pyrenaicum, in both seasons. However, the stalked diatoms Gomphonema spp. were preferred only by Baetis, but not by Rhithrogena, in the dry season when the current velocity became relatively slower. The results of pairwise tests further showed that the algal compositions on the insect-excluded bricks coincided with the diets of both grazers in the wet season but were distinct from those on the bricks in the dry season. Seasonal variations in the algal compositions of the diets of Rhithrogena and on the insect-excluded bricks were apparent, but not in the diets of Baetis. The algal physiognomy was most likely attributed to the impact of the high current velocity in the stream. Our results suggest that the diet preference by mayfly grazers in the stream is potentially influenced by algal availability.

Effects of environmental factors on community structure of Leptophlebiidae (Insecta, Ephemeroptera) in Cerrado streams, Brazil

We analyzed the effects of environmental factors on abundance, species richness, and functional group richness of Leptophlebiidae in 16 sampling points along four Cerrado streams. Across three periods of 2005, we collected 5,492 larvae from 14 species in stream bed substrate. These species belong to three functional feeding groups: scrapers, filtering collectors and shredders. The abundance and species richness were not affected by water quality, but habitat quality related to presence of riparian vegetation had positive effects on the abundance of shredders. Our results add important information on the natural history of the species and functional groups of aquatic insects and also provide relevant data for the monitoring and conservation of streams in the Brazilian Cerrado.

Diversity and Density of Aquatic Insects in the Lower Reach of River Moirang, Manipur, North East India

A study on the diversity and density of aquatic insects in the lower reach of river Moirang, Manipur, India was conducted using aquatic insects as bio indicator to ascertain the pollution status of the river as it discharges into the Loktak lake (Ramsar site), the lifeline of people of Manipur. The study revealed the presence of three orders, nine families, twelve genera and eighteen species of aquatic insects in the lower reach of the river. The orders were Hemiptera, Odonata and Coleoptera. There was total absence of sensitive groups of aquatic insects like Ephemeroptera, Plecoptera and Trichoptera. According to Engelmann’s scale, Diplonychus rusticus (Fabricius) was found eudominant followed by five subdominant and six recedent species. No species was found in the dominant range. Species diversity and evenness indices fluctuated throughout the year and Shannon H′<1 in all the months indicated a stressed and disturbed environment. This is confirmed by the record of low dissolved oxygen (DO), high biological oxygen demand (BOD) and high phosphate in the water of the river. Among the heavy metals, the ranges of both lead and mercury were found to exceed the WHO maximum permissible limit. Significant positive correlation of rainfall with pH, DO, BOD, nitrate, phosphate, Berger Parker dominance index (d) and significant negative correlation with diversity index (Shannon H′) indicated that rainfall is one of the important parameters in the ecology of the system. Canonical correspondence analysis (CCA) revealed that the important physico-chemical attributes of the ecosystem were air temperature, water temperature, depth, rainfall, BOD, DO, salinity, sodium, total alkalinity, iron and lead.

Polytene chromosomes of Chironomidae (Diptera) as a bioassay of trace-metal-induced genome instability

Chironomids are a ubiquitous group of aquatic insects that are very sensitive to environmental stress. Due to the presence of polytene (‘giant’) salivary gland chromosomes, it is possible to define the genome response of several Chironomid species to various stress agents. The aim of this study was to assess the genotoxic changes in populations of widely distributed chironomid species from aquatic basins in Bulgaria, Italy, Russia, U.K. and Poland, which were exposed to high concentrations of trace metals. We analyzed the structural and functional alterations of polytene chromosomes of the salivary glands of larvae belonging to three different cytocomplexes of the genus Chironomus (“thummi”, “lacunarius”, “pseudothummi”), and genera Glyptotendipes and Kiefferulus. Somatic structural chromosome rearrangements (para- and pericentric heterozygous inversions, deletions, deficiencies and amplifications) were used to estimate a Somatic index (S) for each population. The highest S indexes were detected in Chironomus riparius populations from locations with high concentrations of trace metals in the sediment. Each species showed specific genome responses to stress agents which we discussed in the light of the specific DNA structures and cytogenetic characteristics of the species. In larvae from polluted sediments two key structures of the salivary gland chromosomes (Balbiani Rings and Nucleolar Organizer) sharply reduced their activity to levels below those observed under non-polluted conditions. It is concluded that polytene chromosomes can be used as tools for evaluating the genotoxicity of the aquatic environment. Structural and functional chromosome alterations provide cost-effective early-warning signals of genotoxic concentrations of environmental pollutants.doi: 10.5324/fn.v31i0.1355.Published online: 17 October 2012.

学校プールに形成される水生昆虫相の成立要因に関する研究

学校プール内に生息している水生昆虫相の種，個体数について，東京都及び千葉県内の 4 地域計 32 校において，2007 年 5 月～2008 年 5 月までの使用期間外に各校月 1 回程度調査を実施した。調査の結果を TWINSPAN で解析したところ，東京都と千葉県が異なるグループに分類された。ヒメゲンゴロウ，コシマゲンゴロウ，ミズカマキリ，ショウジョウトンボは東京都の学校プールで確認することができなかった。種数に差が確認された要因として，種の供給源となる学校プール周辺の水田面積や周囲の樹木の有無などが考えられた。主にトンボ目の個体数の差に影響を与える要因としては，学校プール周囲の植生から供給される落葉である可能性が示唆された。

Checklist de Ephemeroptera do Estado de São Paulo, Brasil

Os Ephemeroptera constituem um dos mais importantes grupos da entomofauna aquática, ao lado de Plecoptera e Trichoptera (EPT) e muitos Diptera. Ocorrem em ambientes aquáticos continentais lênticos e lóticos, sendo sua maior diversidade encontrada em rios de pequena ordem, com fundo rochoso e acúmulo de folhas, e água oligotrófica a mesotrófica. A última lista de Ephemeroptera para o Estado de São Paulo feita por Hubbard &amp; Pescador (1999) registrou apenas 8 espécies e nenhum pesquisador trabalhando com taxonomia do grupo. Atualmente 53 espécies são registradas para o Estado de São Paulo, distribuídas em 9 famílias: Baetidae (15 spp.), Caenidae (1 sp.), Ephemeridae (1 sp.), Euthyplociidae (2 spp.), Leptohyphidae (12 spp.), Leptophlebiidae (16 spp.), Melanemerellidae (1 sp.), Oligoneuriidae (1 sp.) and Polymitarcyidae (3 spp.), e pelo menos 4 pesquisadores Doutores brasileiros trabalhando diretamente com taxonomia e distribuição de Ephemeroptera.

Analysis and Prediction for Spatial Distribution of Functional Feeding Groups of Aquatic Insects in the Geum River

The aim of this study is to define a correlation between spatial distribution of functional feeding groups of aquatic insects and their habitat types in the Geum River based on the theory of River Continuum Concept (RCC). For that object we had classified habitat types of the study area according to various environmental factors and examined closely their distribution characteristics by correlation analysis between biota community and the environmental factors. And then, a probabilistic method named Frequency Ratio Model (FRM) and spatial analysis function of GIS were applied to produce a predictive distribution map of biota community considering their distribution characteristics according to the environmental factors as related variables. As a result, 6 major environmental factors that might affect the classification of habitat types were extracted. Finally, we had compared the predicted distribution map with prior survey database from other researches and then could find out a high correlation between them. The results of this study might be used to develop a new estimation method for aquatic ecosystem with functional feeding groups of aquatic insects and also be used as preliminary data for conservation and restoration of stream habitats.

Water beetle biodiversity in Mediterranean standing waters: assemblage composition, environmental drivers and nestedness patterns

Abstract. 1. Nowadays, it is widely accepted that increasing human activity is highly related to the current biodiversity loss, this fact being especially worrying in aquatic ecosystems, mainly in semi‐arid areas. To date, studies on the biodiversity of small standing waters are focused on Central and Northern Europe, Mediterranean regions being poorly documented.2. Here, data for aquatic Coleoptera in SE Iberia have been used to: (i) explore the relative contribution of standing waters to regional aquatic biodiversity, (ii) identify the environmental drivers structuring beetle assemblages, (iii) determine the degree to which standing water assemblages are nested subsets, and (iv) make recommendations for the conservation and management of the habitats studied.3. Water beetles are a hyperdiverse group of aquatic insects which represent good surrogates of aquatic biodiversity. A total of 95 sites across eight habitat types were sampled, 174 species being recorded (11% were Iberian endemics).4. Habitat types generally had distinct aquatic beetle faunas; a combination of conductivity, anthropogenic impact and altitude best explaining differences in assemblages across sites. Beetle faunas were significantly nested, this being the case across all sites, and for both fresh and saline systems independently. Disturbance was identified as a key driver of nestedness across sites overall, and particularly in freshwaters, whereas conductivity was more important in saline waters.5. Our study identifies the biodiversity importance of lentic inland waters in the Iberian southeast, and points to the influence that human activities already exert on the invertebrate faunas of western Mediterranean wetlands.

Sub‐fossil Chironomidae as indicators of palaeoflow regimes: integration into the PalaeoLIFE flow index

AbstractThe sub‐fossil head capsules of larval Chironomidae have been widely exploited as palaeoecological indicators of lentic ecosystems but their value in the interpretation of the evolution of lotic systems has been underutilised by comparison. Recent research has demonstrated that the remains of Chironomidae are abundant within fluvial sequences and that they offer a valuable record of channel change and floodplain evolution that may complement that derived from existing biological and sedimentological techniques. This paper demonstrates the use of Chironomidae in characterising the palaeoflow regime of a large mid–late Holocene floodplain palaeochannel (5470–4960 to 1530–1350 cal. a BP) of the River Trent (Derbyshire, UK). Using expert knowledge and published information regarding flow preferences, larval Chironomidae were incorporated into the PalaeoLIFE (Lotic‐invertebrate Index for Flow Evaluation) methodology. The results clearly demonstrate that the sub‐fossil record provided by Chironomidae can be used to characterise changes in the flow regime within palaeochannel sections. At the scale of the channel section, species‐ and generic‐level ecological associations can provide useful information regarding habitat characteristics, including the presence of instream vegetation, mineral substrates and woody debris. The ability to undertake environmental reconstruction and channel evolution history was significantly enhanced through the application of a multi‐proxy approach, by incorporating other aquatic insect groups (Trichoptera and Coleoptera) into the PalaeoLIFE metric, together with sedimentological data. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Towards a comprehensive barcode library for arctic life - Ephemeroptera, Plecoptera, and Trichoptera of Churchill, Manitoba, Canada

BackgroundThis study reports progress in assembling a DNA barcode reference library for Ephemeroptera, Plecoptera, and Trichoptera ("EPTs") from a Canadian subarctic site, which is the focus of a comprehensive biodiversity inventory using DNA barcoding. These three groups of aquatic insects exhibit a moderate level of species diversity, making them ideal for testing the feasibility of DNA barcoding for routine biotic surveys. We explore the correlation between the morphological species delineations, DNA barcode-based haplotype clusters delimited by a sequence threshold (2%), and a threshold-free approach to biodiversity quantification--phylogenetic diversity.ResultsA DNA barcode reference library is built for 112 EPT species for the focal region, consisting of 2277 COI sequences. Close correspondence was found between EPT morphospecies and haplotype clusters as designated using a standard threshold value. Similarly, the shapes of taxon accumulation curves based upon haplotype clusters were very similar to those generated using phylogenetic diversity accumulation curves, but were much more computationally efficient.ConclusionThe results of this study will facilitate other lines of research on northern EPTs and also bode well for rapidly conducting initial biodiversity assessments in unknown EPT faunas.

Aquatic insect faunas and communities of a mountain stream in Sapa Highland, northern Vietnam

Aquatic insect communities were investigated from the Muonghoa Stream in the Sapa Highland (highest peak 3,143 m), a subtropical mountain stream in northern Vietnam. Field investigations for quantitative (Surber net 50 cm × 50 cm, mesh size 0.2 mm, riffle and pool/run) and qualitative (hand net, mesh size 1 mm) sampling were conducted at nine sites along the watercourse between 27 November and 2 December 2005. As a result, a total of 216 species (the majority of them undescribed) belonging to 139 genera, 61 families, and nine orders were recognized: 53 Ephemeroptera species (24.5%), nine Odonata species (4.2%), 15 Plecoptera species (6.9%), seven Hemiptera species (3.2%), 35 Coleoptera species (16.2%), one Megaloptera species (0.5%), 29 Diptera species (13.4%), 66 Trichoptera species (30.6%), and one Lepidoptera species (0.5%). Trichoptera, Ephemeroptera, and Coleoptera represented the major aquatic insect groups with regard to taxonomic and individual richness, whereas Hemiptera and Odonata were relatively less diverse and abundant than in studies of other tropical Southeast Asian streams. The dominance, richness, and diversity indices (H′) fell within the following ranges [mean ± standard deviation (SD)]: 0.18–0.76 (0.42 ± 0.19), 4.13–9.19 (7.06 ± 1.45), and 1.61–3.22 (2.67 ± 0.55), respectively. Riffle habitats generally yielded numbers of aquatic insect species and individuals approximately twice that sampled in pool/run habitats. Shredders were relatively larger in proportion within the headwater reach, whereas scrapers and collector-gatherers were more abundant in the middle and lower stream reaches. This functional feeding group composition is characteristic of temperate streams in East Asia. The results of detrended correspondence analysis and Bray–Curtis cluster analysis indicated that aquatic insect compositions at the sampling sites were very reflective of the reach characteristics, which evidence gradual changes with altitude and stream order along the stream watercourse. This is the first comprehensive investigation of aquatic insects in highland Southeast Asian regions.

Fauna of Macroinvertebrates and Composition of Functional Feeding Groups about the Aquatic Insects to Microhabitats from the Geum River, Korea

The main objective of this study is to find out the fauna of macroinvertebrate and composition of functional feeding groups about the aquatic insects to microhabitat from the Geum River, Korea. This study is based on investigations of the main channel of Geum River, Korea which is upstream of Daecheong Dam, and carried out in the spring and autumn of 2004. Collections from all the sites were 39,532 individuals, 130 species, 54 families, 16 orders, 7 classes, and 4 phyla of macroinvertebrates. Aquatic insects were composed of 90.76% (118 species) and 98.88% (39,088 individuals) of all the identified species. Among the microhabitats, the riffles were collected 26,293 individuals and 92 species, and the runs were collected 12,329 individuals and 89 species. Finally, the pools were collected 494 individuals and 41 species. In this survey, the proportions of functional feeding groups of aquatic insects were as follows (percent of identified): predators 37.65%, gathering-collectors 23.53%, scrapers 16.47%, filtering-collectors 11.76%, shredders 9.41% and plant-piercers 1.18%. Also, the functional feeding groups were sorted according to microhabitat, in the riffles 30.65% were predators and 29.03% were gathering-collectors; in the run 30.3% were predators, and 28.79% were gathering-collectors; while in the pools 36.67% were predators, and 30.0% were gathering-collectors. In all microhabitats, gathering collectors and predators were predominant, because most of the survey sites are in the midstream. Also, the scrapers were shown more frequently in the riffle (17.74%) and run (18.18 %) than pool (13.13%), the filtering-collectors were shown more frequently in the riffle (14.52%) and the run (12.12%) than the pool (6.67%), and the plant-piercers (3.33%) were found only in pools. But the shredders weren't a difference in the run (10.61%), the pool (10.0%) and the riffle (8.06%), because of the characteristic. Microhabitats (riffle and run) are much alike in composition ratio of functional feeding groups and pool was very lower out of composition ratio in microhabitats. But riffle is very important than run, because most of individual occur in streams. Besides, pool was diverse to composition ratios, considering the number of individuals.

Diversity of chironomid larvae in palustrine wetlands of the coastal plain in the south of Brazil

The Chironomidae of tropical South America are a very rich species, but are scarcely known. The range of environmental conditions under which chironomids are found is more extensive than that of any other group of aquatic insects. The objectives of this study were to carry out a diversity survey of chironomid larvae in wetland systems of the coastal plain in the south of Brazil and to analyze the effects of area, altitude, water conductivity, nitrate and phosphorus concentrations, and the life form of the dominant plant species on chironomid richness and composition. Collections were carried out from March to April in 2002. A total of 30 taxa (23 morphospecies and 7 species) distributed along 23 genera were found, and the Chironominae showed the greatest richness, followed by Tanypodinae and Orthocladiinae. The chironomid richness was higher in the emergent than in the multistratified wetland class. The wetland area, altitude, nitrate and phosphorus concentrations, and water conductivity did not influence the richness of Chironomidae. The Chironomidae genera and species were present in both the wetland classes (emergent and aquatic bed vegetation). However, while Chironominae were more frequent in the emergent than in the aquatic bed wetlands, no difference was observed for Tanypodinae. The aquatic vegetation was an important environmental predictor for chironomid larvae richness in the studied wetlands in the south of Brazil.

Dieta de &lt;em&gt;Bryconamericus iheringii&lt;/em&gt; (Ostariophysi: Characidae) em riachos da bacia do rio Tibagi, Estado do Paraná

Individuals of Bryconamericus iheringii (Boulenger, 1887), collected in the streams of Cambé, Taquari, Água da Floresta and Baroré, which belong to the Tibagi river basin (Parana Sate, Brazil), were analyzed for the purpose of diet study. The collection procedures were standardized in every stream. The stomach contents of the individuals were analyzed qualitative and quantitatively. The food items consumed by the species varied in number, and the main food item consumed differed in each stream. Thus, it was found: vegetable remains and debris, in Cambé; debris, in Taquari; filamentous algae and vegetable remains, in the Água da Floresta; and debris and remains of insects, in Baroré stream. The behavior shift from generalist to specialist strategy as well as the use of detritus as the main food, which can only be found in the river bottom, can indicate that stretches of streams with slower and deeper waters are not preferred by B. iheringii, as neither they are for some groups of aquatic insects which are used as food resource by this fish species

Clave taxonómica para larvas de las familias del orden Trichoptera (Insecta) de Costa Rica

A taxonomic key to the families of caddisfly larvae (Insecta: Trichoptera) of Costa Rica. The use of aquatic macroinvertebrates as bioindicators for water quality and environmental degradation of aquatic ecosystems has become more and more important in Costa Rica during the past years. For this reason, taxonomic and ecological investigations on the different groups of bioindicators, such as aquatic insects, is gaining more and more importance and can be considered as indispensable in the use of indices for biomonitoring. One of the most abundant and diverse groups of aquatic insects are the caddisflies, with their larvae living in a great variety of the country’s varied aquatic habitats. Therefore, in this work a taxonomic key for the identification of the families of Trichoptera larvae of Costa Rica is presented. Additionally, commentaries on the taxonomic diversity and ecology of each family are included, in order to facilitate the use of this important group of bioindicators. Such publications also help fill the general need for taxonomic keys to many groups of insects from tropical countries. Rev. Biol. Trop. 54 (Suppl. 1): 273-286. Epub 2006 Sept. 30.

An Update on the Occurrence of Three Species of Mayflies (Ephemeroptera) in Maine

Mayflies, members of the order Ephemeroptera, are a diverse group of aquatic insects. Unlike many kinds of insects that spend most of their lives on land, mayflies spend most of their lives in the water as immature forms called nymphs. Adult mayflies are short lived and reproduce soon after they complete their development to the final winged stage called an imago. Mated adult females deposit their eggs in the waters of streams and ponds, where they hatch. After hatching, nymphs live on or among the sediments and submerged stems of aquatic plants. Nymphs can feed and grow for as much as two years before they complete their development to the first winged stage called a subimago, but often this development is accomplished in one year or less. The subimago is a winged terrestrial form that usually flies away from the water to a place of safety where it soon sheds its skin and becomes the imago. For further details of mayfly biology the reader is directed to publications by Edmunds et al. (1976) and McCafferty (1981). In the late 1980's an extensive survey of Maine's mayfly fauna was conducted (Burian and Gibbs 1990). The results of that work showed Maine to have a diverse mayfly fauna with a majority of its 160 species broadly distributed from the mountains of the Moosehead Plateau to the coast. However, about 41 species (26% of the fauna) were recorded from less than three sites. Species such as these may indeed be rare, endemic, or indicative of special habitats. But, they may have been simply overlooked at other sites or were collected in a life stage that could not be determined to species. In general, mayflies with few records have ranges and habitat requirements that are largely unknown. For these species each new record improves our understanding of its range and habitat. This is especially important for the purpose of habitat management and conservation because critical decisions, usually involving rare species, cannot be made without basic range and habitat information. In this paper new locality records are presented for Siphlonurus securifer McDunnough, Metretopus borealis Eaton, and Hexagenia rigida Eaton, which have few known localities in Maine. Siphlonurus

Mechanisms of Hemolymph Acid-Base Regulation in Aquatic Insects

Insects are an important and abundant component of the aquatic habitat They are used as indicators of water quality and provide food for fish and birds. The composition and abundance of insect assemblages are known to change with pH. The physiological mechanisms used by insects to cope with extreme environmental pH and regulate extracellular pH are virtually unknown. Evolutionarily, the movement into water from land has consequences with respect to gas transfer, as air has 20-40 times more oxygen per unit volume than water. Two functional respirator, systems have dezveloped within the aquatic insects to extract oxygen from water: water breathers, which use morphological gills; and air breathers, which obtain air from a bubble attached to the body or directly from the atmosphere. This article summarizes research to date pertaining to acid-base regulation in these two functional groups of aquatic insects and compares them with other aquatic ectotherms. Excretion appears capable of handling base removal in the feu alkaline-water-inhabiting species studied, and ion exchange mechanisms across the integumenzt may be involved in pH regulation of insects exposed to acid conditions. Future work should examine the use of respiratory processes in extracellular pH regulation to clarify the role dfferent tracheal systems play in insect acid-base balance. An understanding of the mechanisms involved in acid or alkali tolerance may help in the selection of species as bioindicators of water quality.