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The phylogenetic relationship of Ephemeridae (Insect: Ephemeroptera) remains hotly debated using mitochondrial (mt) genomes. All previously reported mt genomes of Ephemeridae belong to the genus Ephemera. This study provides the first complete mt genome sequence from the genus Hexagenia with an analysis of the mitogenome of Hexagenia rigida Mc Dunnough, 1924 (Ephemeroptera: Ephemeridae) and providing new information to discuss the phylogenetic relationships within Ephemeroptera. The complete mt genome of H. rigida was a circular molecule of 16,159 bp in length, containing 37 genes (2 rRNA genes, 13 protein-coding genes, 22 tRNA genes), which showed the typical mt gene arrangement of insects. The AT content of the whole genome was 70.0% and the length of the control region was 1091 bp. All protein-coding genes used ATN as the start codon, and most PCGs used TAA/TAG as the stop codons excluding COI, COII, ND5 and Cyt b that used T as the stop codon. BI and ML phylogenetic trees constructed from 27 species of 13 families showed that Ephemeridae is a sister clade to the clade Polymitarcyidae.

Background: The stem-group of Ephemeroptera is phylogenetically important for understanding key steps in evolutionary history of early pterygote insects. However, these taxa have been mostly studied from the taxonomy point of view focused on the pattern of wing venation and often using only classical optical microscopy devices. In-depth studies on detailed morphology of the different body structures are scarcely performed, although the results are critical for elucidation of life history traits and their evolutionary pattern among the basal pterygotes. Results: New information is presented on the morphology of two species of Misthodotes, which are stem-mayflies from the Early Permian. Based on new results obtained from a re-examination of the type specimens and supplementary material, we infer the life history traits of both the adult and larval stages of these Palaeozoic insects and reconsider previous interpretations. For the first time, we report the structure of the thoracic pleura and the articulation at the base of the wing in a stem-group of Ephemeroptera and compare them with those of extant mayflies. We also provide additional support for the systematic placement of investigated taxa and an amended diagnosis of the genus Misthodotes. Conclusions: Adult Misthodotes sharovi and Misthodotes zalesskyi had chewing mouthparts, which enabled them to scavenge or feed on plants. The wing apparatus was adapted for slow powered flapping flight and gliding, using long caudal filaments for steering. The wing base does not have rows of articulary sclerites as previously hypothesized for some Palaeozoic taxa but inflexible axilla similar to that found in modern mayflies. The structure of the thoracic pleura is also similar to that in the crown group of Ephemeroptera, while differences in the course of sutures may be explained by an evolutionary trend towards more powerful dorsoventral flying musculature and forewing-based flight (anteromotorism) in modern taxa. There is no evidence for swarming behaviour and mating in the air as occurs in modern mayflies as they had none of the associated morphological adaptations. Putative larvae of Misthodotes can not be unambiguously associated with the adults. They also exhibit some morphological specializations of Protereismatidae like 9 pairs of abdominal tracheal gills supporting their benthic lifestyle with legs adapted to burrowing. [ABSTRACT FROM AUTHOR]

The phylogenetic relationship of Ephemeridae (Insect: Ephemeroptera) remains hotly debated using mitochondrial (mt) genomes. All previously reported mt genomes of Ephemeridae belong to the genus Ephemera. This study provides the first complete mt genome sequence from the genus Hexagenia with an analysis of the mitogenome of Hexagenia rigida Mc Dunnough, 1924 (Ephemeroptera: Ephemeridae) and providing new information to discuss the phylogenetic relationships within Ephemeroptera. The complete mt genome of H. rigida was a circular molecule of 16,159 bp in length, containing 37 genes (2 rRNA genes, 13 protein-coding genes, 22 tRNA genes), which showed the typical mt gene arrangement of insects. The AT content of the whole genome was 70.0% and the length of the control region was 1091 bp. All protein-coding genes used ATN as the start codon, and most PCGs used TAA/TAG as the stop codons excluding COI, COII, ND5 and Cyt b that used T as the stop codon. BI and ML phylogenetic trees constructed from 27 species of 13 families showed that Ephemeridae is a sister clade to the clade Polymitarcyidae. [ABSTRACT FROM AUTHOR]

Ephemera wuchowensis Hsu, 1937 is a commonly encountered and widely distributed burrowing mayfly species in China, but its biological traits are poorly understood. In this study, we investigated the life history of E. wuchowensis using the size-frequency method at three sites along a creek in Central China. Monthly samples of larvae were taken from January to December 2017. The life history of E. wuchowensis was found to be univoltine in this northern subtropical region, and there were no significant differences among the sites based on the size-frequency histograms. Unlike the emergence of congeneric species, which inhabit southern subtropical monsoon streams and are showed to be highly synchronised with a relatively short flight period, the adults of E. wuchowensis has a long emergence period from April to September with two distinct peaks of emergence: the first from April to June, and the second from August to September. [ABSTRACT FROM AUTHOR]

Abstract: This study investigated the phylogenetic relationships among seven burrowing mayfly families. Genetic data from four ribosomal DNA genes (12S, 16S, 18S and 28S) generated with Sanger sequencing, 448 protein‐coding loci generated using a novel hybrid enrichment probe set and available RNAseq and genome assembly for 19 ingroup taxa and four outgroup taxa. Maximum likelihood and Bayesian analyses were carried out to estimate phylogenetic relationships. The results indicated that Potamanthidae, Euthyplociidae, Behningiidae and Palingeniidae were recovered as monophyletic. Ephemeridae was not monophyletic. Mandibular tusks evolved in the common ancestor of burrowing mayflies and were lost in the lineage leading to Behningiidae. [ABSTRACT FROM AUTHOR]

In aquatic ecosystems, the cycling and toxicity of nickel (Ni) are coupled to other elemental cycles that can limit its bioavailability. Current sediment risk assessment approaches consider add-volatile sulfide (AVS) as the major binding phase for Ni, but have not yet incorporated ligands that are present in oxic sediments. Our study aimed to assess how metal oxides play a role in Ni bioavailability in surficial sediments exposed to effluent from two mine sites. We coupled spatially explicit sediment geochemistry (i.e., separate oxic and suboxic) to the indigenous macroinvertebrate community structure. Effluent-exposed sites contained high concentrations of sediment Ni and AVS, though roughly 80% less AVS was observed in surface sediments. Iron (Fe) oxide mineral concentrations were elevated in surface sediments and bound a substantial proportion of Ni. Redundancy analysis of the invertebrate community showed surface sediment geochemistry significantly explained shifts in community abundances. Relative abundance of the dominant mayfly (Ephemeridae) was reduced in sites with greater bioavailable Ni, but accounting for Fe oxide-bound Ni greatly decreased variation in effect thresholds between the two mine sites. Our results provide field-based evidence that solid-phase ligands in oxic sediment, most notably Fe oxides, may have a critical role in controlling nickel bioavailability. [ABSTRACT FROM AUTHOR]

Fifteen new district and regional records of mayflies (Ephemeroptera) are given for Kenora District and Northwestern Ontario, Canada, based upon new field work. Records are provided for species of Arthropleidae (1), Baetidae (3), Baetiscidae (1), Caenidae (2), Ephemeridae (3), Ephemerellidae (2), Heptageniidae (1), and Siphlonuridae (2). [ABSTRACT FROM AUTHOR]

This study describes the sperm morphology of the mayfly Hexagenia ( Pseudeatonica) albivitta ( Ephemeroptera). Its spermatozoon measures approximately 30 μm of which 9 μm corresponds to the head. The head is composed of an approximately round acrosomal vesicle and a cylindrical nucleus. The nucleus has two concavities, one in the anterior tip, where the acrosomal vesicle is inserted and a deeper one at its base, where the flagellum components are inserted. The flagellum is composed of an axoneme, a mitochondrion and a dense rod adjacent to the mitochondrion. A centriolar adjunct is also observed surrounding the axoneme in the initial portion of the flagellum and extends along the flagellum for at least 2 μm, surrounding the axoneme in a half-moon shape. The axoneme is the longest component of the flagellum, and it follows the 9+9+0 pattern, with no central pair of microtubules. At the posterior region of the flagellum, the mitochondrion has a dumb-bell shape in cross sections that, together with the rectangular mitochondrial-associated rod, is responsible for the flattened shape of the flagellum. An internal membrane is observed surrounding both mitochondrion and its associated structure. [ABSTRACT FROM AUTHOR]

Burrowing mayflies (Ephemeroptera: Ephemeridae) are sensitive to pollution and have been used as environmental indicators in the Great Lakes.Hexagenia limbataandEphemera simulanspopulation abundance and biomass estimates from Chequamegon Bay, Lake Superior, were compared between the years 2002 and 2012 as well as inside and outside the Northern States Power Lakefront Superfund site. Mean abundance was similar and mean biomass of Ephemeridae was slightly less in 2012 than in 2002, most likely due to the occurrence ofE. simulansin 2012, a smaller species not collected in 2002. In 2012, mean ephemerid abundance and biomass outside the Superfund site was significantly higher than inside the Superfund site. Biomass was higher in clay, clay with sand, and sand with clay substrates than in fine sand, coarse sand, or wood debris substrates. Substrate in the Superfund site was predominantly wood debris. Future monitoring of ephemerid populations in Chequamegon Bay, and particularly in the Superfund site as clean up begins, would be valuable to establish long-term population trends for these two species and potentially shed light on the habitat requirements ofE. simulans, an understudied species in the Great Lakes. [ABSTRACT FROM AUTHOR]

An antifogging function surface with simple structure and suitable for large-area production was found inspired by Ephemera pictiventris McLachlan compound eyes. The compound eyes structure, antifogging properties and mechanism were studied by anti-fog test, dyeing test and scanning electron microscopy, and so forth. Then, 3D model of the sample was established, and the antifogging mechanism was explained by the Cassie model. Results showed that the compound eyes are composed of hundreds of micron size ommatidia arranged in curved array form, and this structure shows excellent antifogging function. This research may provide new ideas for design of simple structure and micron size antifogging function surface. This work is also expected to be applied to antifogging function surface of astronaut helmets and medical endoscopes, and so forth. [ABSTRACT FROM AUTHOR]

The horned Australian burrowing mayfly genus Jappa Harker ( Leptophlebiidae) is revised based on adult and larval material collected throughout Australia. Five named species [ J. campbelli Bae & Finlay, J. edmundsi Skedros & Polhemus, J. furcifera ( Eaton), J. serrata Skedros & Polhemus and J. strigata (Eaton 1871) (= J. bicornis Ulmer 1916; = J. kutera Harker 1954, syn. n.)] are recognised, and two new species [ J. harkerae n. sp. and J. suteri n. sp.] are described. Descriptions, diagnoses, line-drawings and images of key characters, distributional information, taxonomic remarks and keys to adults and larvae are provided. The species Jappa tristis Harker 1954 is transferred to the genus Tillyardophlebia Dean. [ABSTRACT FROM AUTHOR]

Both the library and the museum communities have developed conceptual models for the information they produce about the collections they hold: FRBR (Functional Requirements for Bibliographic Records) and CIDOC CRM (Conceptual Reference Model). But neither proves perfectly adequate when it comes to some specific types of rare and unique materials: manuscripts, hand-press resources, annotated copies of printed books, art prints, and ephemera and clippings files. However, a combination of these two models, named FRBROO, solves the problem. The article examines in detail how each of these types of resources is modeled according to FRBROO. [ABSTRACT FROM AUTHOR]

Abstract: Field-collected populations of mayflies, Ephemera orientalis were tested for susceptibility to 10 different insecticides using a direct-contact mortality bioassay. Ephemera orientalis subimagoes were susceptible to the insecticides chlorpyrifos, fenitrothion and chlorfenapyr with LD50 values of 69.7, 78.8 and 81.9μg/♀, and adults had LD50 values of 71.9, 78.8 and 85.4μg/♀, respectively. Susceptibility ratios (SRs) of subimagoes and adults of E. orientalis to the 10 insecticides were 1.0 to1.2 folds. The mayflies showed higher susceptibility to organophosphates than to pyrethroids. The SRs of Anopheles sinensis to E. orientalis were 514 to 1438 folds higher for organophosphates (LD50 values of 0.05 to 0.23μg/♀) and 62 to 1155 folds higher for pyrethroids (LD50 values of 0.13 to 2.41μg/♀). The SRs of Culex pipiens to E. orientalis were 606 to 3595 folds higher for organophosphates with LD50 values of 0.02–0.17μg/♀ and 81 to 1365 folds higher for pyrethroids with LD50 values of 0.11–1.83μg/♀. These results indicate that the use of ineffective insecticides will result in unsatisfactory control against field populations of the subimagoes and adults of E. orientalis. [Copyright &y& Elsevier]

In this study, we investigated the life history of Ephemera orientalis, a common lowland burrowing mayfly which resides in temperate East Asia and often causes a serious nuisance to people due to mass emergence from the Han River in Seoul, Korea. Larvae were sampled monthly (every two weeks during the emergence period) from April 2006 to June 2007 using a Surber sampler (50 × 50 cm, mesh 0.25 mm, two replicates). The mean density of E. orientalis was found to be 105.88±42.14 indiv/m2 during the study period. On the basis of the larval body size distribution and emergence time, we concluded that E. orientalis has a univoltine life cycle with two distinct cohort groups, S1-group emerging in May-June and S2-group in August-September. The estimated annual production of the larvae was 1350.84 mg DW/m2; the mean biomass was 325.17 mg DW/m2; the annual production to mean biomass ratio (P/B) was 4.15. Mean water temperature during the study period was 15.02±6.84°C. The accumulated degree days for the S1- and S2-groups were 2565.07 and 2,621.69 degree days, respectively. This study shows that the Han River population of E. orientalis lacks the fast growing cohort (F-group) in May-August, and demonstrates a relatively higher secondary production than that of other stream mayflies (e.g. Gapyeong stream population of E. orientalis). [ABSTRACT FROM AUTHOR]

The genus Ephemera Linnaeus, the type genus of the family Ephemeridae and the order Ephemeroptera, began to be studied as early as in the nineteenth century, but the East Asian species of Ephemera remained poorly understood. In this paper, 16 Ephemera species from tropical Southeast Asia are reviewed and descriptions of new or poorly known species and life stages, synonyms, reference sources, type information, taxonomic remarks, a male adult key to the species, and a tabulated checklist of the species are provided. Ephemera mccaffertyi sp. n. from Malaysia is described. Ephemera hainanensis Zhang, Gui & You, E. rufomaculata Zhou & Zheng, and E. spilosa Navás are redescribed. The larval stage of E. hainanensis and E. spilosa are described. Ephemera innotata Navás, E. javana Navás, E. longiventris Navás, and E. quadrigutata Lestage are assigned as nomina dubia. As a result of this study, four species from Vietnam, four species from Myanmar, two species from Thailand, one new species from Malaysia, and three species from Taiwan have been identified as members of the genus Ephemera. [ABSTRACT FROM AUTHOR]

The larval stage of Tortopus is redescribed based on three species: T. puella from North America, the only species of the genus previously known from larva, and the larvae of T. obscuripennis and T. sarae from South America described here. Generic characters of the larva include: relatively large finger-like gill near base of maxilla, inner margin of mandibular tusks with a subdistal tubercle, straight or weakly convex frontal ridge present between antennae, reduced unilamellated gill on abdominal segment I. Additionally the male imagines of both Neotropical species are described for the first time, and T. obscuripennis is recorded from Bolivia. Diagnoses, SEM photographs, and illustrations are given for the new stages described and for the identification of the three Tortopus species known as larvae. [ABSTRACT FROM AUTHOR]

Although degree-days can be used to determine when insect emergence begins, peak swarming events in species that exhibit extended emergence periods are difficult to estimate. With the aid of logistic regression, we estimated the probability of adult mayfly swarms (≥50 individuals/m2), occurring on any given night in western Lake Erie, using meteorological data. We sampled adult Hexagenia Walsh, 1863 from 2130 (sunset) to 2300 on 18 dates in 2000 (2 June – 18 July), with the largest numbers retrieved between 13 June and 2 July. Water temperature (20 °C) was the cue to the onset of swarming (subimagos). Highest mean (±SE) density of all Hexagenia adults (subimagos and imagos) was 24 740 ± 8 757 individuals/m2. Overall, 10-fold more imagos (mostly females) than subimagos were attracted to lights. Of the factors examined (air and water temperature, Julian day, dew point, heat index, humidity, moon phase, wind chill, wind direction, wind speed), onshore wind speed (0–9.2 km/h) on calendar dates for which the water temperature exceeded 20 °C was the most significant factor to account for total adult swarms. Eighty-three percent of the 18 swarming events observed in 2000 were correctly predicted. Validity of the model was confirmed with data collected in 2002, during which 5 of 6 swarming events were correctly predicted from the logistic model. Wind promotes adult aggregation at the land–water interface, the effect of which facilitates mating success and predator swamping. [ABSTRACT FROM AUTHOR]

In a second-order montane stream of the Hanjiang River basin, Leptophlebia sp. and Ephemera sp. appeared to develop two generations per year, and there was little overlap with the two generations in either species. Leptophlebia sp. pupated in autumn and winter, while Ephemera sp. did so in summer and winter. Annual production of Leptophlebia sp., estimated by the size-frequency method, was 7.23 g (dry weight)/m². The annual production of Ephemera sp. was 14.45 g/m². The principal food type and major contributor to this production in both mayflies was amorphous detritus (59.2%), while diatoms contributed 36.4% to the production. [ABSTRACT FROM AUTHOR]

The article discusses the study on the emergence cues of a mayfly in a high-altitude stream ecosystem. The study authors compared the spatial variation in timing of emergence among populations in multiple streams of the drainage basin during two different years. They also designed experiments to manipulate water temperature and stream flow which enabled them to decouple the potential causal mechanisms that explain early emergence of mayfly in low-flow years. The results of the study imply that large-scale climate changes involving warming and stream dying could cause significant shifts in the timing of mayfly metamorphosis.

The article discusses the study on the possible link between burrowing mayfly recruitment and periods of intermittent stratification for the years 1997-2002. In order to predict stratification, a simple model was developed using surface temperature, wind speed and water column data from 2003. It was then used to observe episodes of stratification in past years for which water column data are unavailable. The results of the study suggest that even relatively brief periods of stratification can result in loss of larval mayfly recruitment through the effects of hypoxia.

We conducted a reciprocal transfer of nymphs of the burrowing mayfly Hexagenia limbata between two rivers harboring populations of this insect that differed in their cadmium (Cd) concentrations. We measured Cd uptake and loss rates simultaneously in the held at several levels of biological organization: in the gut and body of whole nymphs as well as in three subcellular fractions. The most marked changes in Cd concentrations occurred in the insect's gut, where Cd was largely associated with heat-stable proteins, a fraction that includes the metal-binding protein metallothionein. Because most of the Cd that entered nymphs was detoxified in this manner, we would not expect it to have direct toxic effects; however, it would be readily transferred to higher trophic levels. Our data on subcellular partitioning suggest that there is a fast-exchanging pool of Cd bound to heat-stable proteins such as metallothionein and a slow-exchanging pool bound to either or both of the remaining fractions (heat-denatured proteins; remainder, which includes exoskeleton and granules). Nymphs of H. limbata responded rapidly to changes in bioavailable Cd, which suggests that they would be useful for monitoring changes in ambient Cd for weeks or months in the field. A one-compartment model successfully explained the changes we observed in nymph Cd values. Furthermore, values of the modal constant for Cd loss were close to those reported for Hexagenia rigida in the laboratory, which suggests that accumulation patterns observed in the laboratory can be representative of those measured in nature. [ABSTRACT FROM AUTHOR]

The species of the genus Isonychia Eaton, 1871 (Isonychiidae) of East Palaearctic are revised. Two subgenera, Isonychia s.s. and Prionoides Kondratieff et Voshell, 1983, are represented in the Palaearctic. New species and subspecies of Isonychia s.s. are described: I. sexpetala sp. nov., I. ussurica sibirica subsp, nov., I. concoloria sp. nov., I. crassiuscula sp. nov., and I. vshivkovae sp. nov. with subspecies I. vshivkovae vshivkovae and I. vshivkovae sinitshenkovae subsp. nov. A new species group japonica, with three species (I. crassiuscula, I. vshivkovae, and I. japonica), is recognized on the basis of adult and larval characteristics. The name Isonychia hainanensis She et You, 1988 is synonymized with Isonychia ignota (Walker, 1853) syn. nov. [ABSTRACT FROM AUTHOR]

The mature larva of a new species, Neoephemera projecta sp. n.,from China is described in detail. It represents a new country record of thegenus for China. The discovery shows that the genus Neoephemera McDunnoughhas a more extensive Holarctic distribution than previously known. Ecologicalvicariance instead of geographic isolation is therefore favoured as presumedcause of the origin of the three neoephemerid genera. [ABSTRACT FROM AUTHOR]

Three State of the Lakes Ecosystem Conferences have been held since 1996 to encourage the development of Great Lakes indicators of ecosystem health for use in reporting on progress in restoring and maintaining the chemical, physical and biological integrity of the Great Lakes ecosystem. Here we report on the development of an indicator based on burrowing mayflies , Hexagenia (Ephemeroptera: Ephemeridae), using production and biomass as the indicator metrics. Burrowing mayflies were selected because they (1) were historically abundant in unpolluted, soft-bottomed mesotrophic habitats throughout the Great Lakes, (2) are intolerant of and were extirpated by pollution in most of those habitats during the 1940s to1950s, (3) have shown the ability to recover in one of those habitats following pollution abatement, (4) are ecologically important as bioturbators of lakebed sediments and as trophic integrators that link detrital energy resources directly to fishes that feed preferentially on them, and (5) have highly visible mating flights, which carry the message directly to an informed public that the source water body is healthy. In addition, their annual production can be estimated from their mean annual biomass by the sizefrequency method. Productivity and biomass can also could be estimated with a 'cohort-direct' method, using the biomass of mature nymphs collected in May or early June from the cohort that is about to emerge as subimagos in late June or early July. Although both the size-frequency and cohort-direct methods provide reliable estimates of productivity and biomass, the latter method greatly reduces sample collection and processing effort and thus makes it feasible to use Hexagenia as an indicator of ecosystem health in surveys requiring the collection of large numbers of samples. [ABSTRACT FROM AUTHOR]

The phylogenetic relationship of Ephemeridae (Insect: Ephemeroptera) remains hotly debated using mitochondrial (mt) genomes. All previously reported mt genomes of Ephemeridae belong to the genus Ephemera . This study provides the first complete mt genome sequence from the genus Hexagenia with an analysis of the mitogenome of Hexagenia rigida Mc Dunnough, 1924 (Ephemeroptera: Ephemeridae) and providing new information to discuss the phylogenetic relationships within Ephemeroptera. The complete mt genome of H. rigida was a circular molecule of 16,159 bp in length, containing 37 genes (2 rRNA genes, 13 protein-coding genes, 22 tRNA genes), which showed the typical mt gene arrangement of insects. The AT content of the whole genome was 70.0% and the length of the control region was 1091 bp. All protein-coding genes used ATN as the start codon, and most PCGs used TAA/TAG as the stop codons excluding COI, COII, ND5 and Cyt b that used T as the stop codon. BI and ML phylogenetic trees constructed from 27 species of 13 families showed that Ephemeridae is a sister clade to the clade Polymitarcyidae., Competing Interests: The authors declare no conflict of interest., (© 2022 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.)

The article focuses on a study on recolonization of burrowing mayflies, Hexagenia spp. western Lake Erie during the 1990s. It is noted that logistic models, ranging in carrying capacity from 600 to 2000 nymphs/m2 were used to predict the time to full recovery of the mayfly population. The study predicts full recovery between years 1998 and 2000 for mayfly population in western Lake Erie.