Ephemeroptera Nymphs Research Articles

Composição e distribuição da fauna de Ephemeroptera (Insecta) em área de transição Cerrado-Amazônia, Brasil

O objetivo deste trabalho foi responder se existe padrão na distribuição espacial das ninfas de Ephemeroptera em diferentes córregos e rios da bacia do Rio Suiá-Miçú, MT, e como os córregos estudados estão classificados de acordo com a composição de espécies. Na coleta foram amostrados 12 córregos e rios, em três períodos do ano. Foram coletados 1356 indivíduos, distribuídos em sete famílias, 31 gêneros e 42 espécies e/ou morfoespécies. Os locais mais abundantes foram ambientes semi-lênticos, com pouco sombreamento no leito, sugerindo que a maior entrada de luz disporia, além do material alóctone, material autóctone como fonte de alimento. A maior riqueza de espécie e/ou morfoespécie, estimada, foi em ambientes lóticos enfatizando que os Ephemeroptera apresentam maior riqueza nestes locais uma vez que a correnteza é essencial para transportar a matéria orgânica particulada. Tanto na análise de agrupamento (TWINSPAM) como na ordenação (DCA) observou-se a separação entre ambientes lóticos e semi-lênticos quanto a composição de espécies. Percebeu-se um gradiente na similaridade de composição dos ambientes lóticos de pequeno porte para ambientes lóticos de grande porte e, por fim, os semi-lênticos. Os resultados deste estudo demonstram que a estrutura física dos ambientes aquáticos afeta a composição de espécies. Dessa forma, a retirada das matas ciliares e o represamento dos córregos podem levar à perdas significativas na diversidade.

Widespread omnivory and low temporal and spatial variation in the diet of fishes in a hydrologically variable northern Australian river

This article examines the trophic ecology of freshwater fishes (22 species in 15 families) in a wet and dry tropical Australian river of high intra-annual and interannual hydrological variability. Seven major trophic groups were identified by cluster analysis; however, four food items (filamentous algae, chironomid larvae, Trichoptera larvae and Ephemeroptera nymphs) comprised almost half of the average diet of all species. The influence of species, fish size, spatial effects and temporal effects on food use was investigated using redundancy analysis. Size, time and space accounted for little of the perceived variation. Ontogenetic changes in diet were minor and limited to a few large species. Spatial variation in trophic composition of the fish assemblages reflected the effects of the Burdekin Falls and dam, a major geographic barrier, on species distributions. Little spatial variation in diet was detected after accounting for this biogeographical effect. Temporal variations in flow, although marked, had little effect on variations in fish diet composition due to the low temporal diversity of food resources in physically monotonous sand and gravel channels. Species identity accounted for<50% of the observed variation in food choice; omnivory and generalism were pronounced. The aquatic food web of the Burdekin River appears simple, supported largely by autochthonous production (filamentous and benthic microalgae, and to some extent, aquatic macrophytes). Allochthonous food resources appear to be unimportant. The generalist feeding strategies, widespread omnivory and absence of pronounced trophic segregation reported here for Burdekin River fishes may be common to variable and intermittent rivers of subtropical and tropical northern Australia with similar fish communities and may be a general feature of rivers of low habitat diversity and characterized by flow regimes that vary greatly both within and between years.

Feeding Ecology and Development of Juvenile Black Ducks in Maine

Feeding Ecology and Development of Juvenile Black Ducks in Maine

Ecological significances of ontogenetic shifts in the stream‐dwelling catfish, Hatcheria macraei (Siluriformes, Trichomycteridae), in a Patagonian river

Abstract – The relationship between ontogenetic changes and both feeding and habitat preferences was studied in a stream catfish population of Argentine Patagonia. Fish capture, as well as habitat data recording, was performed during a 1‐year long period. Larvae–juvenile transition was determined between 22.4 and 29.4 mm standard length (SL), on the basis of the relative growth changes and morphogenesis, and juvenile–adult shift was established between 61 and 65 mm SL using a macroscopic criterion of gonadal development and gonadosomatic index. Spawning period was estimated to be in the summer season, from December to February. Larvae preferred shallow marginal pools and fed mainly on small Chironomidae larvae, while juveniles and adults inhabited riffles and preyed on Ephemeroptera nymphs and Chironomid larvae. Morphological constraints during the larval period were related to habitat and feeding preferences. A complete development of fins allowed juveniles to colonise faster water habitats while a bigger mouth gape permitted them to prey on new items and on a larger size prey range.

Composition and diversity of Ephemeroptera (Insecta) nymph communities in the middle section of the Jacuí River and some tributaries, southern Brazil

The taxonomic composition and diversity of assemblages of Ephemeroptera nymphs of four lotic environments in the central region of State of Rio Grande do Sul, a subtropical area in southern Brazil, were evaluated. Samplings were done monthly, with a Surber sampler, from June 2001 to May 2002, in the Jacuí River and three of its tributaries. The total number of nymphs collected in the four sampling sites was 11,007 in five families and 19 genera, of these, 11 are new records for the State. The highest diversity occurred in Point 4 (H'=2.41) and the lowest in Point 2 (H'=1.69). Point 4 had the highest environmental stability, conservation of the riparian vegetation and the lowest anthropic impact, while Point 2 presented a large environmental simplification due to a direct anthropic influence (e.g. domestic sewerage, trampling by cattle). The diversity of nymphs observed in the total area is high, compared to the estimated maximum theoretical diversity; a result of the high evenness and richness recorded. Rarefaction curves, calculated for a sample of 1,018 specimens, showed a similar expectation of richness for the four sampling sites. This result seems to be associated with the overall environmental homogeneity of the region caused by long-term alterations (land use and deforestation). In summary, higher diversity of Ephemeroptera nymph assemblages seems to be associated with habitat complexity, a good vegetation cover and a lower anthropic influence.

Harpellales in the digestive tracts of Ephemeroptera and Plecoptera nymphs from Veracruz, Mexico

This is the first report of Harpellales (Zygomycota) from Mexico, including herein only the endosymbiotic species of gut fungi in the digestive tracts or shed exuviae of Plecopteran and Ephemeropteran nymphs. Four new species are described: Allantomyces zopilotei, Bojamyces olmecensis, Gauthier-omyces viviparus and Graminella ophiuroidea. Among previously known Harpellales, Lancisporomyces nemouridarum and Zygopolaris ephemeridarum are southern range extremes and new records for Mexico. All species are illustrated and discussed relating to biogeographic implications of the new reports from Mexico, as well as the particular environmental circumstances of the Harpellales in the tropics.

Alimentação de &lt;em&gt;Rhinodoras dorbignyi&lt;/em&gt; (Kröyer, 1855) (Siluriformes: Doradidae) no rio Ibicuí, Rio Grande do Sul, Brasil

The study of the feeding ecology of Rhinodoras dorbignyi was conducted in three sites of the Ibicuí river, Rio Grande do Sul, Brazil, from December 1999 to January, 2003. The specimens were sampled bimonthly. The feeding spectrum was determined combining the frequency of the occurrence with the volume of each alimentary item, in order to obtain the feeding index (IAi). The spatial analysis was based on the diet and distribution of R. dorbignyi in the three sampling points, and also in their different biotopes. Temporal changes on diet and capture of the specimens were evaluated considering the seasons and the daily feeding rhythm. The intensity of spatial-temporal feeding intake was analyzed using the average stomach fullness. Significance level of 0.05 was used in the analyses. Ephemeroptera nymphs belonging to the family Polymitarcyidae represented the main feeding item (62.48%). The feeding spectrum of R. dorbignyi showed significant differences regarding sampling points, seasons, and biotopes. The species showed highest abundance in lotic environments, during the spring and summer and after sunset. No statistically significant results were observed with regard to spatial and temporal differences in feeding intake.

New species and summary of Iberian Harpellales

The occurrence of three new species of Harpellales in the Iberian Peninsula is reported. Capniomyces celatus was found in Nemouridae (Plecoptera) nymphs, Stipella latispora in Simuliidae (Diptera) larvae and Legeriomyces dolabrae with Baetidae (Ephemeroptera) nymphs. These species are differentiated from others by thalli and/or reproductive structures. Geographic range extensions for other species of Harpellales also are reported; these are Graminella bulbosa, Pennella angustispora, Spartiella barbata, Stachylina euthena, St. grandispora, St. pedifer, St. penetralis, St. prolifica, St. robusta and Stipella vigilans. All are compared with related taxa and are illustrated with photographs. Finally a summary of the known Harpellales occurring in the Iberian territory is provided with data on their distribution and ecology.

New species and summary of Iberian Harpellales

The occurrence of three new species of Harpellales in the Iberian Peninsula is reported. Capniomyces celatus was found in Nemouridae (Plecoptera) nymphs, Stipella latispora in Simuliidae (Diptera) larvae and Legeriomyces dolabrae with Baetidae (Ephemeroptera) nymphs. These species are differentiated from others by thalli and/or reproductive structures. Geographic range extensions for other species of Harpellales also are reported; these are Graminella bulbosa, Pennella angustispora, Spartiella barbata, Stachylina euthena, St. grandispora, St. pedifer, St. penetralis, St. prolifica, St. robusta and Stipella vigilans. All are compared with related taxa and are illustrated with photographs. Finally a summary of the known Harpellales occurring in the Iberian territory is provided with data on their distribution and ecology.

The Diet of the Brown Trout Salmo trutta (L.) during the Reproductive Period: Size‐Related and Sexual Effects

AbstractWe investigated the autumnal diet of the brown trout Salmo trutta, in a Prepyrenean stream (NW Iberian Peninsula) focusing on intraspecific dietary differences related to size and sex. The diet of trout included 18 types of prey, with Plecoptera and Ephemeroptera nymphs and Diptera larvae as the most consumed taxa. Large trout ate larger prey, than did small trout, and also increased the consumption of terrestrial‐surface prey with respect to aquatic‐benthic prey. As terrestrial‐surface preys were larger than aquatic‐benthic prey, the size‐related differences in the diet of trout were related to gape‐limitations. Although male and female trout did not differ in size, we found that males foraged on a more diverse type of prey than females, probably owing to male territoriality during the reproductive period. This study provides new evidence of dietary plasticity in the brown trout and confirms the importance of local dietary studies to better understand factors which drive trophic ecology of predators. (© 2006 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Functional feeding groups of Brazilian Ephemeroptera nymphs : ultrastructure of mouthparts

In order to assign 18 mayfly taxa found in streams in the Macae River basin into Functional Feeding Groups, the anatomy of their feeding apparatus was examined through scanning electron microscopy. Also, habitat preference and field observations of feeding behaviour were made to assure FFG assignment. Ephemeropteran taxa were classified into five FFGs: Passive Filterers - Hylister plaumanni; Active Filterer Lachlania boanovae and Campylocia sp.; Brushers - Askola froehlichi, Farrodes carioca, Hagenulopsis spp., Massartela brieni, Miroculis froehlich, Miroculis sp., and Thraulodes spp; Grazers - Cloeodes spp., Americabaetis spp., Camelobaetidius spp.and Baetodes spp.; Scrapers Leptohyphes pereirae, Leptohyphes spp., Tricorythodes spp. and Tricorythopsis spp. Species of the three best represented mayfly families in south-east Brazil were assigned to different FFGs (Leptophlebiidae - Brushers; Baetidae - Grazers and Leptohyphidae - Scrapers), with one exception, Hylister plaumanni (Leptophlebiidae; Active filterers). This information is useful to understand the role of mayflies in stream ecosystems, and to help the development of ecological theories for tropical streams.

Alimentação e fator de condição de peixes characidiíneos no sistema do Ribeirão Grande, Sudeste do Brasil

Feeding, seasonal changes in visceral fat and condition factor were compared in two species of characidiin fishes, Characidium lauroi and C. alipioi from Ribeirão Grande system, southeastern Brazil. Five streams of Ribeirão Grande system were sampled (22o 47’ 08’’ S, 45o 28’ 17’’W). The samples were taken four times per site, from July, 2001 to April, 2002: winter (July 2001), spring (October 2001), summer (February 2002) and autumn (April 2002). Quantitative collections were made with an electro-fishing device powered by a generator with maximum capacity of 1,500 V and 8.7 A of 60 Hz alternating current. Ephemeroptera nymphs, Diptera larvae (Chironomidae, Simuliidae), Plecoptera nymphs, Trichoptera larvae (Hydroptilidae, Psychoyiidae), terrestrial insects (Coleoptera, Isoptera, Hemiptera [Heteroptera, Homoptera]), Megaloptera larvae (Corydalidae), Arachnida, Ostracoda and vegetal debris were found in both species’ diets. Visceral fat declined in February, coinciding with the decline of the condition factor in both species. The increased feeding from summer to fall provides fat accumulation. During subsequent seasons, fish may utilize visceral fat reserves for maintenance and reproduction

The Biology of &lt;i&gt;Pellonula leonensis&lt;/i&gt; Boulenger, 1916 (Osteichthyes: Clupeidae) in Anambra River, Nigeria

The biology of the commercially important clupeid, Pellonula leonensis, was studied from May 1998 to March 1999 in the Anambra river. In the atalla fishery of this river, the clupeid was the dominant species in terms of number and weight. Total length (TL) ranged from 3.4 to 8.5 cm and weight from 0.3 to 4.6 g; males were not longer or heavier than females. The mean exponent (b = 2.66) of the length-weight relationships of 12 populations indicated negative allometric function. Mean monthly Fulton's condition (K) was not dependent on season. There was little variability in the mean monthly gonadosomatic index (GSI) and breeding occurred throughout the year. Maturity occurred earlier in males than females; 50% of both sexes matured at 4.7 cm TL. Fecundity ranged from 126 to 1580 oocytes (mean 896 ± 477 oocytes). Total length was a better predictor of fecundity than ovary weight. Index of food significance (IFS) showed that Insecta (51:67%) was the dominant food group, followed by Algae (15.66%) and plant detritus (8.02%). Food items of primary importance were Ephemeroptera nymphs, Chironomidae, unidentified insects, fish, Microcystis, plant detritus and sand grains. Food richness and diet breadth were dependent on season. Key Words: Pellonula, Leonensis, Anambra River Bio-Research Vol.1(2) 2003: 33-50

The duct connecting Malpighian tubules and gut: an ultrastructural and comparative analysis in various Ephemeroptera nymphs (Pterygota)

Malpighian tubules proper are connected to the gut by ducts called trunks, the organization of which is described at ultrastructural level in the nymphs of various mayfly species, namely Ecdyonurus venosus (Heptageniidae), Ephemerella ignita (Ephemerellidae), Choroterpes picteti (Leptophlebiidae), and Caenis luctuosa (Caenidae). Trunks are luminal tubes varying in arrangement, number, shape, and length. The main cell type of the trunk wall is represented by cells that are bordered by a thin cuticle along their luminal side (type-A cells). Whereas these cells are exclusive in the long trunks (such as those of C. picteti and C. luctuosa), in the shorter ones (such as those of E. venosus and Ephemerella ignita) cells with a microvillous luminal border (type-B cells) are also encountered. These cells are located close to the entrance of the collecting duct of the Malpighian tubules proper, and their long microvilli form a dense filamentous mesh filling up the lumen. Both cell types exhibit fine structural features that are characteristics of ion-transporting epithelia. Ultrastructural investigations show that trunks are not a simple conducting system but are involved in the regulation of the ionic composition of the primary urine for producing a fluid hypo-osmotic with respect to the hemolymph.

Fungi living in the guts of larval aquatic insects in northwestern Argentina

Nine species of Harpellales (Zygomycota: Trichomycetes) and one species of Amoebidiales are reported from the northwestern provinces of Tucuman, Salta, and Jujuy in Argentina. New species included Smittium urbanum and Stachylina jujuyensis from Chironomidae larvae and Paramoebidium argentinense from Ephemeroptera nymphs. Harpella tica, previously known only from Costa Rica and Puerto Rico, was found in Simuliidae larvae, sometimes in the same streams with H. meridianalis, a fungus common in simuliids in more southern regions of Argentina and Chile. The warmer stream waters in the northwestern provinces had an impoverished insect fauna and we found fewer species than in the colder streams of Patagonia.

Fungi Living in the Guts of Larval Aquatic Insects in Northwestern Argentina

Nine species of Harpellales (Zygomycota: Trichomycetes) and one species of Amoebidiales are reported from the northwestern provinces of Tucu- man, Salta, and Jujuy in Argentina. New species in- cluded Smittium urbanum and Stachylina jujuyensis from Chironomidae larvae and Paramoebidium argen- tinense from Ephemeroptera nymphs. Harpella tica, previously known only from Costa Rica and Puerto Rico, was found in Simuliidae larvae, sometimes in the same streams with H. meridianalis, a fungus com- mon in simuliids in more southern regions of Argen- tina and Chile. The warmer stream waters in the

Diel vertical movements by lotic mayfly nymphs under variable predation risk

Summary1. The diel foraging periodicities of two grazing mayfly (Ephemeroptera) nymphs, Heptagenia dalecarlica and Baetis rhodani, under variable fish (European minnow) predation risk were examined in a series of laboratory experiments.2. Heptagenia dalecarlica were almost exclusively nocturnal in their use of feeding areas on stone tops. There was a sharp increase in the proportion of nymphs out of refuge at nightfall, both in the control and fish‐odour treatments. In a treatment with freely moving fish, H. dalecarlica decreased their activity during both the day and night. In feeding trials with three freely foraging minnows, nymphs were completely safe when they had access to refuges beneath stones, whereas almost half the nymphs were consumed when no refuges were available.3. Baetis rhodani nymphs reduced their use of stone tops when exposed to four caged minnows or a freely moving fish, but this occurred both day and night. In feeding trials, B. rhodani were captured only while in the water column, and their mortality risk was independent of refuge availability.4. It is suggested that because H. dalecarlica lack efficient post‐encounter defences, they must rely on pre‐encounter mechanisms to reduce the threat of fish predation. It appears that in order to dwell sympatrically with fish, H. dalecarlica have evolved a coexistence by hiding strategy. In contrast, Baetis are vulnerable to fish attacks only if they enter drift in daylight, and are thus able to remain on stone tops both during the day and at night.

Captures, Body Mass and Diet of Platypuses in a Subalpine Tasmanian Lake.

Studies into the ecology of the platypus have concentrated on populations inhabiting !otic waters on mainland Australia. This paper presents preliminary results of a study into the feeding ecology and energetics of the platypus in a subalpine lake in Tasmania. During the autumn, winter and early spring months 29 individual platypuses were captured (13 adult females, 13 adult males and 3 juveniles). Of these, 46% of the adult males, 31% of the adult females and one of the juveniles were recaptured between one and eight times. Catch per unit effort was similar for the 1800-2400hrs, 0600-1200hrs and 1200-1800hrs time periods (0.158, 0.161 and 0.156, respectively). However catch per unit effort was low (0.057) between 2400hr and 0600hrs. There was no significant difference in the mean body mass of adult males and females between autumn, winter and early spring, however the condition of the females, indicated by the tail fat index, decreased in early spring. The overall mean body mass for adult males and adult females caught during the autumn/winter and early spring months was 2293.21g ± 300 (1920-2740g) and 1375.22g ± 147 (1150-1580g), respectively. This supports the observation that platypuses in Tasmania are larger than those occurring in mainland water bodies. The timing of juvenile captures suggests that matings occur at Lake Lea between mid September through to January. This indicates that the breeding season may be later in Tasmania than on the mainland. The contents of cheek pouches were collected from individuals caught during the autumn, winter and early spring months for identification of food items. Food items identified so far include Trichoptera, Gastropod molluscs, Ephemeroptera nymphs, Coleoptera larvae and Diptera, with Trichoptera forming the dominant food item. Measurements of the daily energy expenditure of six adults were attempted during late winter and early spring using the doubly labelled water technique.

Stomach contents of trout, Salmo trutta L., caught by angling on Loch Dee, an acid water in south‐west Scotland PH16 5LB.

The stomach contents of 459 rod‐caught brown trout, Salmo trutta L., collected over a period of 7 years from Loch Dee, an acid water in south west Scotland, were identified. The relative importance of each item was assessed volumetrically. The range of taxa available to the fish was limited because of the loch’s acidity (annual pH means 5.1–5.6) but up to 25 taxa were recorded in the stomachs. Ephemeroptera nymphs, Trichoptera pupae and terrestrial insects formed the greatest bulk, but chironomid larvae and pupae were found in almost half the stomachs. Among the zooplankton, Bythotrephes longimanus was the most abundant species in the samples despite its scarcity (less than 1% of animals in net samples). Despite the adverse conditions of water chemistry and limited range of food, the loch is able to support a regular trout fishery.

Diet and feeding relationships of two Iberian cyprinids

The diet and feeding interactions of the Iberian roach, Rutilus alburnoides (Steindachner), and chub, Leuciscus pyrenaicus Günther, were studied in the Sorraia river system. Seasonal shifts in the diets were examined to determine trophic overlap between the two species. Dipteran larvae were the dominant item in the diet of roach with the exception of summer and early autumn when dipteran adults became important. Ephemeroptera nymphs and imagos were the two principal food categories in chub diet. Plant material and terrestrial insects were consumed by both species mostly in the summer and autumn, periods of low availability of aquatic invertebrates in temperate streams. A low dietary overlap was found, probably resulting from differences in their seasonal foraging activity, but also from a compromise between the consumption of highly abundant plant material and rare animal food items.