Adult Mayflies Research Articles

Mayfly Optimization Algorithm: A Nature-Inspired Approach with Advanced Termination for Efficient Minimization

The Mayfly Optimization Algorithm (MO), inspired by the swarming and mating behavior of adult mayflies, offers a promising approach for tackling minimization problems. However, traditional MO can suffer from unnecessary iterations and exploration of suboptimal regions in the search space. This paper addresses these limitations by introducing two key advancements: greedy selection and auto-termination. Greedy selection ensures the algorithm prioritizes solutions with lower fitness values during position updates, guiding the search towards the minimum more effectively. Auto-termination monitors fitness function changes over a defined window and terminates the algorithm if improvement stagnates, reducing computation time. We evaluate the performance of the enhanced MO algorithm on various benchmark minimization functions. The results demonstrate that the incorporation of greedy selection and auto-termination significantly improves the convergence speed and efficiency of MO compared to the traditional approach. This paves the way for MO to be a more competitive and efficient tool for tackling various real-world minimization problems. Index Terms— Mayfly Optimization Algorithm (MO), Minimization Problems, Greedy Selection, Auto-Termination, Fitness Function, Convergence Speed, Efficiency, Swarm Intelligence, Nature-Inspired Optimization

Mayfly Optimization for Real-World Problems: A Review of Applications and Challenges

The Mayfly Optimization Algorithm (MO), inspired by the swarming and mating behavior of adult mayflies, has emerged as a powerful tool for tackling optimization problems, particularly those seeking minimum values. This review paper delves into the core principles of MO, exploring its stages of swarming, velocity update, movement, mating, and selection. We analyze the strengths of MO, including its ability to balance exploration and exploitation during the search process, leading to well-converged solutions. Additionally, the paper examines recent advancements in MO that address potential limitations. We discuss how incorporating techniques like greedy selection and auto-termination can enhance the convergence speed and efficiency of the algorithm. Furthermore, the review explores various applications of MO across diverse fields, highlighting its potential for solving real-world minimization problems. Finally, we identify and discuss ongoing research directions, including hybridization with other algorithms and exploration of advanced termination strategies. This review paper aims to provide a comprehensive understanding of the Mayfly Optimization Algorithm, its capabilities, and promising areas for future development. Index Terms— Mayfly optimization, particle swarm optimization, swarm intelligence, nature inspired algorithm.

Mayflies see the world in a different light

Everyone gains new perspectives as they grow up, but insects that go through metamorphosis see with a completely different set of eyes as adults. Mayflies spend most of their lives under water as larvae before emerging as adults for one final day of speed dating in a last-ditch effort to produce the next generation. In order to compare how mayflies navigate the two different visual landscapes in which they live, Ádám Egri with Ádám Mészáros and György Kriska at the Eötvös Loránd Research Network Centre for Ecological Research, Hungary, measured how mayflies’ eyes respond to different wavelengths of light and compared what they found to the light levels where the insects tend to congregate.Adult mayflies don't have much time to travel so they spend most of their airborne life mingling around the local neighborhood. By reviewing footage from webcam videos, the researchers determined that Ephoronvirgo mayflies typically swarm in the evening when the sun elevation is low, about –15 to –7 deg below the horizon. They then measured the visual environment when the sun is at different elevations with a spectrophotometer, which measures the strength of light across a range of wavelengths. It turned out that light levels when the adults congregate at dusk are low and the majority of the light is made up of short wavelength colours, closer to ultraviolet. In contrast, the water where the larvae grow up is murky, so longer wavelengths like visible green light are better able to permeate the darkness. These differences suggest that the insects’ eyes may be adapted to distinct environments throughout their life cycle.In order to measure what the insects can see, the team collected larval and adult wild mayflies to test their vision in the lab. Light is sensed when photons are absorbed by specialized cells in the eye that communicate with the brain via electrical signals. The researchers measured these electrical signals with a fine electrode probe while shining lights of different wavelengths onto the insects’ eyes. The adult mayfly's eyes were less sensitive to light that is visible to humans and instead picked up on short ultraviolet wavelengths that are invisible to us. Given that the adults emerge in the evening and die the following day, the reduced sensitivity to visual light suits the insects. However, the larvae living in muddy riverbeds sense light and darkness through simple eyes called ocelli, which absorb photons and send electrical signals to the brain, but can't resolve shapes. The researchers found that larval eyes were also sensitive to UV light, but they were most sensitive to light with longer wavelengths closer to green, which is fitting given the murky world they grow up in.Many insects can see ultraviolet, but these experiments shed light on the green sensitivity of larval ocelli. Although they can't see as well as other animals, the simple eyes of larval mayflies are well matched for the muddy riverbed conditions where they spend most of their lives. As adults, mayflies emerge and face their first and last evening of life above water with a fresh set of eyes that help them find a mate in the dark.

Spatial Variation of Acanthophlebia cruentata (Ephemeroptera), a Mayfly Endemic to Te Ika-a-Māui-North Island of Aotearoa, New Zealand.

Simple SummaryPatterns of variation within a widespread species can provide evidence of population history. Adjacent stable populations with gene flow show clinal genetic divergence forming a pattern of isolation by distance. Populations that have grown due to an increase in potential habitat such as forest cover since the last glacial maximum will have low genetic variation showing patterns of range expansion. The mayfly Acanthophlebia cruentata of Aotearoa, New Zealand, is widespread in streams of North Island but absent from the cooler South Island. Mayfly nymphs are restricted to streams but adults fly, facilitating gene flow among catchments. We detected higher genetic diversity at lower latitudes of this mayfly’s range compared to most of its distribution, concordant with predictions of limited forest cover in New Zealand during Pleistocene glacial periods. A signature of recent range expansion was observed in the higher latitudes. Despite initial observation suggesting mayfly size correlated with latitude, we found sex, elevation and sampling date were significant predictors of size, and some size variation is also explained by three regional groups based on haplotype distribution.The mayfly Acanthophlebia cruentata of Aotearoa, New Zealand, is widespread in Te Ika-a-Māui North Island streams, but has never been collected from South Island despite land connection during the last glacial maximum. Population structure of this mayfly might reflect re-colonisation after volcanic eruptions in North Island c1800 years ago, climate cycling or conceal older, cryptic diversity. We collected population samples from 33 locations to estimate levels of population genetic diversity and to document phenotypic variation. Relatively low intraspecific haplotype divergence was recorded among mitochondrial cytb sequences from 492 individuals, but these resolved three geographic-haplotype regions (north, west, east). We detected a signature of isolation by distance at low latitudes (north) but evidence of recent population growth in the west and east. We did not detect an effect of volcanic eruptions but infer range expansion into higher latitudes from a common ancestor during the last glacial period. As judged from wing length, both sexes of adult mayflies were larger at higher elevation and we found that haplotype region was also a significant predictor of Acanthophlebia cruentata size. This suggests that our mitochondrial marker is concordant with nuclear genetic differences that might be explained by founder effect during range expansion.

Regulation of metamorphosis in neopteran insects is conserved in the paleopteran Cloeon dipterum (Ephemeroptera)

In the Paleozoic era, more than 400 Ma, a number of insect groups continued molting after forming functional wings. Today, however, flying insects stop molting after metamorphosis when they become fully winged. The only exception is the mayflies (Paleoptera, Ephemeroptera), which molt in the subimago, a flying stage between the nymph and the adult. However, the identity and homology of the subimago still is underexplored. Debate remains regarding whether this stage represents a modified nymph, an adult, or a pupa like that of butterflies. Another relevant question is why mayflies have the subimago stage despite the risk of molting fragile membranous wings. These questions have intrigued numerous authors, but nonetheless, clear answers have not yet been found. By combining morphological studies, hormonal treatments, and molecular analysis in the mayfly Cloeon dipterum, we found answers to these old questions. We observed that treatment with a juvenile hormone analog in the last nymphal instar stimulated the expression of the Kr-h1 gene and reduced that of E93, which suppress and trigger metamorphosis, respectively. The regulation of metamorphosis thus follows the MEKRE93 pathway, as in neopteran insects. Moreover, the treatment prevented the formation of the subimago. These findings suggest that the subimago must be considered an instar of the adult mayfly. We also observed that the forelegs dramatically grow between the last nymphal instar, the subimago, and the adult. This necessary growth spread over the last two stages could explain, at least in part, the adaptive sense of the subimago.

An overview of the Hexagenitidae (Ephemeroptera) from the Crato Formation (Aptian, Lower Cretaceous) of Brazil, with the description of a new species

ABSTRACT Among mayflies, the Hexagenitidae is the most common family of the Cretaceous, including in the world-renowned Crato Formation (Aptian) of northeastern Brazil. However, most of the Crato mayfly fauna was described based on nymphs, which, due to their ontogenetic development, may present numerous continuous characters. As a consequence, many unclear taxa have been described, and their taxonomic position needs to be re-evaluated. We here present a checklist and revision of some previously described species from the Crato Formation and the description of new specimens. We propose a new species, Protoligoneuria heloisae sp. nov., based on a previously described adult erroneously referred to within Oligoneuriidae. Further adult specimens of Hexagenitidae are here described in detail, presenting new morphological data and variations that were, up to now, unknown for Hexagenitidae of the Crato Formation. Lastly, we briefly discuss the genus Cratohexagenites. Our new findings further add to the taxonomical and morphological diversity of the adult mayfly fauna of the Crato Formation.

The Ephemeroptera (Hexapoda, Insecta) from the Lower Cretaceous Crato Formation (NE Brazil): a new genus and species, and reassessment of Costalimella zucchii Zamboni, 2001 and Cratogenites corradiniae Martins-Neto, 1996

A new genus and species of Ephemeroptera, Astraeoptera cretacica gen. et sp. nov., is described from the Lower Cretaceous limestone of the Crato Formation (Brazil). The new taxon has the following diagnostic characters: veins MP2 e CuA straight at their bases, MA branching in the apical half of wing length, CuA not forked, cubital field with longitudinal veins sub-parallel to CuA. It was compared with other adult mayflies worldwide, both fossil and extant, and could not be assigned to any known ephemeropteran family. In addition, holotypes of other two mayfly species were reanalyzed, resulting in taxonomical changes. A new description of the Costalimella zucchii Zamboni, 2001 holotype is provided, indicating its placement within Hexagenitidae, rather than Siphlonuridae, as previously proposed. We also reanalysed the holotype of Cratogenites corradiniae Martins-Neto, 1996, providing new and more accurate information about the species and confirming its junior synonymy to Protoligoneuria limai Demoulin, 1955. Our results indicate that the diversity of Crato Formation mayflies, both at species and family level, is greater than previously thought, confirming the predominance of hexagenitids among Cretaceous ephemeropterans.

Oxygen doesn't limit mayflies when the temperature soars

As air breathers, we probably don't appreciate how difficult it is for aquatic creatures to breathe. ‘The oxygen concentration in water is only about 3% that in air and the oxygen diffusion rate in water is 3×105 times lower’, says David Funk from the Stroud Water Research Center, USA, explaining that aquatic animals have to work ∼15 times harder than terrestrial creatures to breathe. And the situation for cold-blooded (exothermic) creatures is even more perilous when the temperatures rise and their metabolism begins running faster. ‘The temperature-dependent performance of animals is believed to be shaped by the capacity for oxygen delivery in relation to oxygen demand’, Funk explains, adding that oxygen availability was thought to be the factor that sets the highest temperatures at which fish and aquatic insects can survive. Knowing that adult mayflies that develop in warm conditions tend also to be smaller, possibly as a consequence of running low on oxygen, Funk, Bernard Sweeney and John Jackson, also from Stroud Water Research, decided to find out how oxygen availability affects the development and survival of mayflies over a range of temperatures. But the team didn't stop at investigating one species of mayfly: Neocloeon triangulifer nymphs only thrive in well-oxygenated streams over a narrow temperature window of 8°C, while two robust populations of Cloeon dipterum are capable of surviving in relatively stagnant water in their comfort zone of 14–30°C. Allocating 50 larvae from each species to individual 1.8 l miniaquaria, Funk created environments with high (45%) oxygen, down to normal (∼20% oxygen), while the temperature ranged from 20°C up to 32°C – the temperatures at which the females are unable to produce offspring. ‘We raised over 4400 hatchlings through their entire lives in 90 separate vessels housed in four giant water baths’, Funk says with a smile.Monitoring the hottest youngsters with access to 45% oxygen, it was clear that the souped-up oxygen supply didn't compensate for the challenge of developing in hot water: the youngsters failed to thrive. If oxygen was limiting the nymphs’ ability to survive in hot water, then those with access to unprecedented amounts of oxygen (45%) should have flourished. In short, the availability of oxygen does not limit the mayflies’ ability to survive and grow in sizzling conditions. Some other factor is responsible for their high mortality when the mercury rises.Then Funk monitored how a lack or abundance of oxygen affected the youngster's development, paying close attention to their gills, eyes and leg length. ‘The most technically difficult thing was measuring the gill size’, says Funk, recalling how he had to be on hand as the youngsters transformed into adults, so that he could retrieve the discarded skins to measure the size of all seven pairs of gills. Comparing the nymphs’ growth at high and low temperatures (25 and 20°C), they found the hottest nymphs were always smallest, even in 45% oxygen. Oxygen availability wasn't restricting the nymph's growth either. However, the team was astonished by the impact that low oxygen had on the youngsters’ gills. ‘I noticed that mayflies reared in hypoxic conditions responded by greatly increasing the size of their gills. We had no idea they could do this, but quickly realised that gill size could be a valuable indicator of oxygen stress’, says Funk.So, oxygen availability doesn't seem to be the factor that restricts mayfly nymph growth and survival when the temperature soars, but the aquatic insects do respond to low oxygen by increasing the size of their gills to make the most of the meagre levels.

The turquoise killifish: a genetically tractable model for the study of aging

Lifespan is a remarkably diverse trait in nature, ranging from just hours in adult mayflies to hundreds of years in the Greenland shark and quahog clam. Great disparities in lifespan are often observed even among somewhat closely related species; for example, in the laboratory, wild-derived strains of the common house mouse have a maximum observed lifespan of approximately 6 years, while a similarly sized rodent, the naked mole rat, can live for over 30 years. Comparative biology of aging across the tree of life provides a tremendous opportunity for understanding the molecular and genetic basis underlying lifespan and aging. However, a lack of molecular and laboratory tools has limited the ability of researchers to take full advantage of the incredible diversity of aging phenotypes in nature. Recent developments in genomic technology have made it increasingly possible to study non-canonical model organisms for aging. One promising new genetic model organism amenable to a range of experimental interventions is the turquoise killifish (Nothobranchius furzeri). This fish species has a naturally short lifespan and undergoes a wide range of aging-related transformations. These fish have a fully sequenced genome and transcriptome, and killifish embryos are accessible to transgenesis and genome editing. Furthermore, different killifish species and populations show striking differences in lifespan, providing the opportunity for comparative analysis of aging. This Review introduces the natural life history of the turquoise killifish, its emerging applicability as an aging model system, the genetic tools that have been developed to study aging for this species and a summary of recent studies facilitated by these new tools.

Small alteration - big impacts: effects of small-scale riparian forest management on host-parasite dynamics in streams.

Environmental changes and ecological disturbances can have large and unpredictable effects on parasite dynamics. Increasing human impacts on freshwater ecosystems through land use may thus modify the distribution and abundance of parasites and have cascading effects on host populations. Here we tested the effects of small-scale riparian forest management on the nematode Cystidicoloides ephemeridarum and its insect intermediate host Ephemera danica in forested streams. We assessed the impacts of harvesting riparian trees on parasite prevalence and abundance concomitantly with host densities. We also looked at upstream and downstream reaches to document potential cascading effects on unaltered stream sections mediated by aerial dispersal of adult mayfly or downstream drift of E. danica larvae. We show that host densities and parasite levels (prevalence and abundance) increased significantly following riparian tree removal. Overall, parasite densities showed a 6- to 66-fold increase in harvested reaches compared to upstream, pristine reaches. Similar effects were also clear downstream of the disturbance. Thus, despite the small extent of riparian forest alteration along the study streams, both parasite and intermediate host were strongly affected. Small-scale riparian forest management may thus have large, unforeseen impacts on some aspects of freshwater ecosystem structure and functioning that are often ignored. Generally, understanding how human perturbations influence parasites is vital when trying to predict overall impacts on ecosystem structure and functioning, and how changes in infection dynamics may further affect host species.

<strong>A simple, inexpensive artificial stream for rearing Ephemeroptera from sandy substrates</strong>

We describe a simple, inexpensive artificial stream to rear mayflies from sandy bottom streams. It consisted of a 151 L tub containing sand and water from a local stream. A small submersible pump circulated the water and netting was placed over the tub to collect adults. The stream was operated in a heated greenhouse. This artificial stream was remarkably productive. We collected over 2100 adult mayflies representing 6 genera along with several Trichoptera and Diptera adults. This stream was productive for 55 weeks with minimal maintenance.

Spatial and temporal variation in the distribution of burrowing mayfly nymphs (Ephemeroptera: Hexagenia limbata and H. rigida) in western Lake Erie

In the early 1990s, burrowing mayfly species reappeared in sediments of the western basin of Lake Erie after an absence of over 30years due to episodic hypoxia at the sediment–water interface. Long-term monitoring of adult mayflies at shoreline areas had revealed that Hexagenia rigida was more abundant than Hexagenia limbata during the initial recolonization period, but was gradually replaced by H. limbata. We hypothesized that this shift in dominance would be confirmed by the distribution and abundance of nymphs. We identified nymphs collected each spring throughout western Lake Erie from 1997 to 2004. The relative abundances of H. rigida and H. limbata nymphs exhibited the same temporal sequence as adults. Furthermore, the number of sites in the western basin in which H. rigida occurred decreased as the occurrence frequency of H. limbata increased. H. limbata were dominant in the basin by 2004. Hexagenia limbata nymphs persisted in the center-most part of the basin, whereas H. rigida did not, possibly due to differences in tolerance to hypoxia. There were no significant differences in body size between the two populations. Differences in dispersal distance from source populations and the timing and success of egg hatching likely accounted for the initial colonizing success of H. rigida, but the differential ability of H. limbata eggs to overwinter in sediments and possible tolerance of nymphs to hypoxia has possibly led to its current dominance in the western basin.

Using group-specific PCR to detect predation of mayflies (Ephemeroptera) by wolf spiders (Lycosidae) at a mercury-contaminated site

Bioaccumulation of contaminants can occur across ecosystem boundaries via transport by emergent aquatic insects. In the South River, Virginia, USA, aquatic mercury has contaminated songbirds nesting in adjacent riparian forests. Spiders contribute the majority of mercury to these songbirds’ diets. We tested the hypothesis that massive annual mayfly emergences provide a vector for mercury from river sediments to the Lycosid spiders most frequently eaten by contaminated songbirds. We designed mayfly-specific PCR primers that amplified mtDNA from 76% of adult mayflies collected at this site. By combining this approach with an Agilent 2100 electrophoresis system, we created a highly sensitive test for mayfly predation by Lycosids, commonly known as wolf spiders. In laboratory spider feeding trials, mayfly DNA could be detected up to 192h post-ingestion; however, we detected no mayfly predation in a sample of 110 wolf spiders collected at the site during mayfly emergence. We suggest that mayfly predation is not an important mechanism for dietary transfer of mercury to wolf spiders and their avian predators at the South River. Instead, floodplain soil should be considered as a potential proximate source for mercury in the terrestrial food web.

It's All Life History

It's All Life History

Extended larval development compensates for sublethal effects of fish predation in a mayfly population (Rhithrogena semicolorata, Ephemeroptera)

Abstract Many predation experiments in streams are carried out in enclosures. Hence, the relevance of their results to predict population dynamics is often unclear due to the relatively small spatial and temporal scale of the experiments. To enhance the transferability of experimental results on the ecosystem scale the impact of fish predators on a prey population was observed in a reach scale approach over 2 years in a natural stream. A 400-m reach inhabited by the small benthivorous fishes gudgeon ( Gobio gobio ) and stone loach ( Barbatula barbatula ) was compared with a fishless reference reach. It was shown that fish predation may affect the population of the grazing mayfly Rhithrogena semicolorata on the ecosystem scale. Although the larvae grew slower in the fish reach than in the fishless reach, the adults reached the same size and fecundity because they emerged 2–3 weeks later. By this compensation, the prey species avoided a reduction of their individual fecundity. On the other hand, the extended exposure to the fish predators resulted in an enhanced mortality and a reduced density of adult mayflies. Thus, there was obviously a trade-off between maximising fecundity and minimising mortality from fish predation. The observed differences were almost certainly caused be fish predation and not by natural differences of the reaches. This was concluded from results gained after eliminating all benthivorous fish from the former fish reach. With the help of scenario analyses based on our empirical data and simple model assumptions we could demonstrate that compensating the potential loss in fecundity by extending development time led to higher average fitness of the prey population than emerging at an earlier fixed time to avoid additional predation losses. Therefore, we concluded that this strategy was adaptive in the presence of benthivorous fish.

Spatial-temporal patterns of recolonizing adult mayflies in Lake Erie after a major disturbance

This 12-year study of Hexagenia male imagos documents the recovery of two species of burrowing mayflies, Hexagenia limbata and Hexagenia rigida in western Lake Erie after a 30-year absence due to hypoxia, resulting from cultural eutrophication. Annual adult mayfly collections were made at night during the peak emergence period at four sites along the north shore of the western basin of Lake Erie, 1997 to 2008. H. rigida, the dominant species in upstream riverine waterbodies, was the early colonizer, representing about 90% of all male imagos sampled in 1997. In 2000, when the two species were co-dominant, both inland aerial dispersal (5.5 km) and lakeward (0.25 to 4 km) oviposition patterns confirmed species co-existence. Twice weekly collections throughout the extended emergence period at one site confirmed that H. rigida was the dominant species in 1997, H. limbata and H. rigida were co-dominant in 2000, and H. limbata was dominant in 2002. Once H. limbata became the dominant species (> 90%) in 2000 to 2002 (depending on the site), it remained so. Both species followed a similar inland dispersal pattern, decreasing in density with increasing distance from shore; most mayflies were present within 1 km from shore. There was no significant difference in mean egg density of the two species among the sites extending lakeward in 2000 when the two species were equally abundant. The transition from the dominance of H. rigida to H. limbata may have resulted from several factors, including differential competition and growth between species or predation effects.

The antennal sensilla of adult mayflies: Rhithrogena semicolorata as a case study

The present paper reports on an ultrastructural investigation of the sensilla on the antennal flagellum of the imago (SEM and TEM) and subimago (SEM) of the mayfly Rhithrogena semicolorata. Sensilla coeloconica of two different sizes, named big and small pegs, are distinguishable in both stages. The big pegs are lobe-shaped with a porous cuticle. The small pegs are more or less conical with a smooth cuticle. TEM seriate sections revealed that the big pegs are innervated by three neurons, which enter the peg. The dendrite sheath opens at the entrance to the peg and leaves the dendrites in contact with the outside through pores and pore tubules. This structure is in agreement with that reported for single-walled olfactory receptors. The small pegs may be innervated by two or four neurons. In both cases, two unbranched dendrites enter the peg and are in close association with the peg wall. These show features typical of hygroreceptors. In the small pegs innervated by four neurons, the other two neurons stop short of entering the peg, and one of them branches. This last could constitute the thermoreceptive unit. The function of the fourth neuron is unknown.The presence of olfactory sensilla in adult mayflies, such as Paleoptera, is relevant to the study of evolutionary trends in insect odour perception. Hygro–thermoreceptors are important in such fragile aquatic insects, which need a moist environment for moulting and reproduction.

A New Cretaceous Mayfly from Burmese Amber (Ephemeroptera: Australiphemeridae)

The new genus and species, Nanophemera myanmarensis McCafferty and Santiago-Blay, is described from an adult mayfly of the extinct family Australiphemeridae imbedded in Burmese amber, probably of Upper Cretaceous age. Nanophemera is the fifth genus known in the Australiphemeridae (a Pangaean, Cretaceous family), which is hypothesized to represent a primitive group of small-sized, tusked, burrowing mayflies (Scapphodonta), possibly closely related to the extant family Potamanthidae. Nanophemera is among the smallest known burrowing mayflies at slightly over four millimeters in length, and it differs from related genera by details of its cubital and anal venation systems in the forewings. The newly described fossil is the second mayfly discovered from Burmese amber.

Towards environmental assessment of river ecosystems by analyzing energy reserves of aquatic invertebrates

Environmental preferences of invertebrates in larger rivers are assumed to be displayed in their upstream–downstream distribution and in their abundance. Near the limits of a species’ distribution, individuals must cope with rather hostile, energy consuming, environmental conditions. On the contrary, it is assumed that sites with high abundance are located more in the center of the distribution area and represent more optimal conditions. We hypothesized that at these sites also the fitness of the animals is better, which should be reflected by higher amounts of storage substrates. We measured the abundance and the energy storage (triglyceride and glycogen contents) of the mayfly Heptagenia flava (Ephemeroptera: Heptageniidae), the leech Glossiphonia complanata (Hirudinea: Glossiphoniidae), and the freshwater shrimp Dikerogammarus villosus (Crustacea: Gammaridae) along 560 km of the River Elbe during the summers of 2003 and 2004. H. flava and G. complanata reached highest densities upstream while D. villosus abundance increased continuously towards the river mouth. A model selection approach revealed that the factor sampling site was necessary to explain the data of energy storage for each species. In H. flava, triglycerides, the most efficient storage substrate, were observed to reach maximum levels at sites with high abundances. Although D. villosus and G. complanata followed a similar relation, both species displayed some exceptions from this pattern with highest triglyceride concentrations at their upstream distribution limit. It is speculated that storage substrates have the potential to become an important tool in environmental assessment because they yield long-term information about the fitness of a population, especially in merolimnic species, e.g. mayflies. As adult mayflies do not feed, the amount of accumulated energy reserves during the larval life is crucial for their reproductive success and therefore is a very good indicator for the assessment of a population's fitness. It is further assumed that the fitness of the other two species does not depend on the energetic status of a certain juvenile stage. Their storages can be refilled at any time, if enough food is available. Nevertheless, storage substrates as well as the total amount of available energy therein are appropriate criteria for the physiological fitness of both species. They result from long-term effects of the surrounding conditions, but may also reflect creeping changes in the environment, e.g. consequences of rising temperatures. Therefore, the use of those criteria as an assessment tool for the physiological fitness of invertebrate populations seems to be very promising.

Immortalizing the Mayfly: Permanent Ephemera: An Illusion or a (Virtual) Reality?

Ephemera (an underrepresented and underresourced area of librarianship for many years) are finally coming of age—changing from nymph to adult mayfly, one might say. To be taken seriously by such an august body as the American Library Association’s Rare Books and Manuscripts Section is something that ephemerists only dreamed of a decade ago. In preparing this article, it has been beneficial for me to address some of the issues surrounding ephemera: to think more generally (even philosophically) about what ephemera are, what we are trying to do with them, and for whom.I am privileged to be Librarian of ...