A new Cinygmula McDunnough, 1933 species with distinct imaginal frontal fold from eastern Chinese Himalaya (Ephemeroptera: Heptageniidae).

In the family Heptageniidae (Ephemeroptera), Cinygmula hutchinsoni (Traver, 1939) from central Asia is the only species known to possess pointed claws and a distinct frontal fold. Here, a second similar species with the same combination of characters is described. Cinygmula longissima sp. nov. is found in the eastern Himalaya of China, shows stouter imaginal penes, darker wingbases, and narrower nymphal gills than the previous one. This discovery indicates that this species of Heptageniidae are not limited to central Asia but live in high-altitude alpine habitats.

The Exact Morphology of the Species Ephemera pieli Navás, 1934 from Eastern China (Ephemeroptera: Ephemeridae).

The original description and outline figure of the mayfly Ephemera pieli Navás, 1934, were based on male subimagoes, and its morphology and taxonomic status have not been confirmed since then. However, recently collected materials from eastern China, including all stages of this mayfly, reveal several unique characteristics that indicate E. pieli is a valid species in the subgenus Ephemera (Ephemera). These characteristics include forewings with numerous dark dots, hindwings or hind wingpads with one or two distinct median dots, penes covered mostly by the subgenital plate, and the apex of the penis bluntly extended. A neotype is designated.

Report of intersex individuals from a southeastern Chinese Choroterpes facialis (Gillies, 1951) population (Ephemeroptera: Leptophlebiidae).

Previously there were only three cases of mayfly gynandromorphism reported from Asia, occurring in the families Baetidae and Heptageniidae. Here, we report two intersex individuals of Choroterpes facialis (Gillies, 1951) (Ephemeroptera: Leptophlebiidae) from southeastern China. They have similar external morphologies (each having two different eyes, two shortened penes, and female sternum IX) but with one being predominately male and the other being predominately female (one with eggs in the abdomen, but the other apparently with sperm). We believe this to be the first report of a feminized male individual. This phenomenon implies their intersexuality is caused by some similar reasons, such as temperature or parasitism. Remarkably, two intersex specimens found among 1,736 normal individuals shows that gynandromorphism does occur rarely, and only six normal males in the sampling suggest the species C. facialis is partially parthenogenetic at least.

The imaginal and nymphal morphology of Gilliesia pulchra Zhou, 2004 and its contribution to understanding generic phylogeny (Ephemeroptera: Leptophlebiidae).

The nymphs of the leptophlebiid mayfly Gilliesia pulchra Zhou, 2004 have not been reported before, which inhibits deeper understanding of the taxonomy and phylogenetic position of this species and its genus. In 2022, we reared nymphs from southwestern China to the adult stage. All stages are described and photographed here. Nymphs of this species have single deeply-forked gills, somewhat elongated maxillary palpi and two setal tufts on the lingua. Its imaginal characteristics, including wings and penes, are quite similar to G. hindustanica (Gillies, 1951), the type species of the genus. Comparatively, the third species of the genus, G. ratchaburiensis Boonsoong & Sartori, 2015, seems less similar, both in adults and nymphs. Generally, features of G. pulchra nymphs link the two genera Gilliesia Peters & Edmunds, 1970 and Habrophlebiodes Ulmer, 1919 together, while features of the nymphs of G. ratchaburiensis bridge the genera Gilliesia and Dipterophlebiodes Demoulin, 1954.

A preliminary review of Isonychia Eaton, 1871 from Chinese mainland with a re-description of I.kiangsinensis Hsu, 1936 (Insecta, Ephemeroptera, Isonychiidae).

Previously, seven species of the genus Isonychia Eaton, 1871 were reported in China, but they have never been systematically reviewed. After examining our collections from the Chinese mainland, six species and one additional subspecies have been recognized, compared, and photographed. Among them, I.kiangsinensis is redescribed in all stages and a neotype is designated. Its males have triangular penes and nymphs have three dark pigments on each gill. A synonym of I.guixiensisWu et al., 1992 (I.sinensisWu et al., 1992) is confirmed. The males of this species have nearly cylindrical penes and clear abdominal markings. Finally, two species and one subspecies are recorded for the first time in China: I.ussuricasibiricaTiunova et al., 2004, I.ussuricaussurica Bajkova, 1970 and I.vshivkovaevshivkovaeTiunova et al., 2004. Together with the I.ignota (Walker, 1853), I.sexpetalaTiunova et al., 2004, I.formosana (Ulmer, 1912) and possible I.japonica (Ulmer, 1920), they show the rich diversity of the genus Isonychia in China.

A new Neoleptophlebia Kluge, 1997 species from eastern China (Ephemeroptera: Leptophlebiidae).

The genus Neoleptophlebia Kluge, 1997 includes five Asian species. Three of them were reported from northeastern Asia and two were found from Chinese Taiwan Island, leaving a huge geographic gap on the Chinese mainland. Here we find a new one, which is named N. uncinata Zhou sp. nov., from Nanjing municipality, eastern China. Via field collecting and indoor rearing, all life stages were obtained, and its nymphs are found living in small creeks (with a width less than 1 m) and shallow waters (with a depth less than 30 cm). Diagnostically, the imago of this new species has larger lateral penial appendages than its congeners, and its nymph has subequal broadened segments II and III of maxillary and labial palpi. Biogeographically, this species bridges two northern and southern groups of the genus.

A contribution to knowledge of Procloeon Bengtsson, 1915 from the Chinese mainland (Ephemeroptera: Baetidae) with description of a new species.

The mayflies of the genus Procloeon Bengtsson, 1915 are common insects in China. However, partially because of its complicated taxonomic history and numerous species, this genus has never been revised locally in China. Here, we review all reported and related species from the Chinese mainland and confirmed three species of Procloeon occurred namely, Procloeon pennulatum (Eaton, 1870) (= Centroptilum henanensis Zhou et al., 1997, syn. n.) distributed in northern China, P. chinensis (She et al., 1995) (comb. nov.) from southern China and P. strumiferum sp. n. found in eastern China. The imagoes of the new species lack a costal projection of the hindwings but the gills IV of the nymphs have double lamellae. In contrast, both the former species have costal process in the hindwings and double lamellae of gills IVI. The three species can all be differentiated by imaginal genitalia and nymphal color. This revision clarifies all historical species in the genus Procloeon and Centroptilum from the Chinese mainland and provides a base for further research.

A detailed comparison of two species in the genus Potamanthus Pictet, 1843 from China (Ephemeroptera, Potamanthidae).

Photographs and details of structures of two Potamanthus species, P.huoshanensis Wu, 1987 and P.luteus (Linnaeus, 1767), are presented for the first time. Here, based upon Chinese specimens of those species, all external structures are illustrated digitally and compared. The results and photos clearly show that the adults of the two species are different in wing color and genitalia shape, and that their nymphs have different mandibular tusks and forelegs. Specifically, P.luteus has a more colorful body and wings, longer penes and nymphal mandibular tusks but shorter foretarsi than those of P.huoshanensis. This comparison not only confirms the differences between these two similar species, but also supports the updated generic delineations of Potamanthus and Potamanthodes.

Systematics of Potamanthodes nanchangi Hsu, 1936 (Ephemeroptera: Potamanthidae).

The enigmatic mayfly Potamanthodes nanchangi Hsu, 1936 was briefly described based on a male. Currently, this species has an unclear taxonomic position and no supporting type specimen, consequently its recognition, differentiation and classification is vague. In this study, by using fresh specimens from type locality in Jiangxi province at central China, this species is redescribed, photographed, and a neotype is designated. This species evidently belongs to the genus Potamanthodes Ulmer, 1920 by its short mandibular tusks (shorter than head), presence of setae row on forefemora of nymphs, slender and deeply bifurcated V-shaped penes, common base of MP2 and CuA of forewings. Significant morphological characters defining this species are relatively long penial tips, greatly bent R1 of hindwings and small compound eyes of the males, large mandibular tusks and long forelegs of the nymphs. Therefore, the P. nanchangi is indeed a valid and apomorphic species in the genus Potamanthodes.

The genus Rhoenanthus Eaton, 1881 in China with the redescription of R. hunanensis You amp; Gui, 1995 (Ephemeroptera: Potamanthidae).

The potamanthid mayfly genus Rhoenanthus Eaton, which was not investigated systematically before in China, is revised herein. Six species in the subgenus Potamanthindus are recognized. Among them, R. sapa, R. obscurus and R. coreanus are new records for this country, and the presence in China of the species R. magnificus and R. hunanensis is confirmed, the nymphal stage of the latter species being described for the first time. Phylogenetically and evolutionarily, R. sapa, which has shorter maxillary and labial palpi, foretibiae and less setaceous mouthparts and forelegs, is close to the plesiomorphic genus Potamanthus. At the same time, R. youi, R. obscurus and R. coreanus, which have larger tusks and spines, longer and more setaceous foretibiae, maxillary and labial palpi, are somewhat similar to the other subgenus Rhoenanthus (Rhoenanthus). The Chinese Rhoenanthus (Potamanthindus) species indicate that the genus Rhoenanthus is closer to Anthopotamus rather than Potamanthus, both of them bearing elongated mandibular tusks.

Two new species of the genus Notacanthurus from China (Ephemeroptera: Heptageniidae, Ecdyonurinae).

Previously, only three of seven species in the Asian genus Notacanthurus were reported both nymphs and imagoes, and no Chinese species was found. Here two new species collected from China, which are named as Notacanthurus maculatus sp. n. and N. lamellosus sp. n. respectively, are described and pictured in detail. The nymph of N. maculatus sp. n. has following combined characters: posterior margin of sternum IX straight, claws with two subapical denticles, and gills V-VI with arrow-like accessory lobes. The male imago has unspecialized anterior margin of head and Electrogena-like penis lobes. The second species N. lamellosus sp. n. is more distinguishable. Its nymph has pale dots on head, median dorsal ridges on abdominal terga I-IX, claws with five subapical denticles, and dorsal lamellae of gills II-IV divided into two portions. Anterior margin of male imago is not protruding either, forewings have less pigmented crossveins between Sc and R1, and penis lobes have apical and ventral sclerites. A key to all known nymphs of the genus is provided.

The imaginal and detailed nymphal characters of Cincticostella fusca (Kang amp; Yang, 1995) (Ephemeroptera: Ephemerellidae).

Among the 17 known species of the genus Cincticostella, only five of them have been reported as both nymphs and imagoes, which does not include the Chinese species C. fusca Kang et Yang (1995). Here the nymphs are redescribed and reared imagoes are reported for the first time, based on material collected from southeastern China. Morphologically, the nymph is unique because of its large body size, expanded genae, pale median stripe on the anterior of the head, and dark tarsi. The male imago can be differentiated from congeners by its large body size, pigmented forewings, and the mesothoracic scutellum having a pair of membranous lamellae. More importantly, its penes are distinct, being fused for most of their length and having complex ventral projections. Adults emerge in early spring (March to April).

Redescription of Parafronurus youi and generic affinities (Ephemeroptera, Heptageniidae, Ecdyonurinae).

The detailed morphology and phylogenetic positon of Parafronurus youi Zhou Braasch, 2003 have not been discussed especially so far. In this study, we re-describe and illustrate all stages in more detail. Compared to other genera in the subfamily Ecdyonurinae, the nymph of P. youi is characterized by rounded supracoxal spurs, rounded rectangular head capsule, dense setae on dorsal side of labrum, simple proximal and distal dentisetae, primarily swimming setae of caudal filaments. Upon the latter two characters, this genus seems closer to Asian Rhithrogeniella Ulmer, 1939.

De novo transcriptome of the mayfly Cloeon viridulum and transcriptional signatures of Prometabola.

Mayflies (Ephemeroptera) display many primitive characters and a unique type of metamorphosis (Prometabola). However, information on the genomes and transcriptomes of this insect group is limited. The RNA sequencing study presented here generated the first de novo transcriptome assembly of Cloeon viridulum (Ephemeroptera: Baetidae), and compared gene expression signatures among the young larva (YL), mature larva (ML), subimago (SI), and imago (IM) stages of this mayfly. The transcriptome, based on 88 Gb of sequence data, comprised a set of 81,185 high quality transcripts. The number of differentially expressed genes (DEGs) in YL vs. ML, ML vs. SI, and SI vs. IM, was 4,825, 1,584, and 1,278, respectively, according to the reads per kilobase of transcript per million mapped reads analysis, assuming a false discovery rate <0.05 and a fold change >2. Gene enrichment analysis revealed that these DEGs were enriched in the "chitin metabolic process", "germ cell development", "steroid hormone biosynthesis", and "cutin, suberine, and wax biosynthesis" pathways. Finally, the expression pattern of a selected group of candidate signature genes for Prometabola, including vestigial, methoprene-tolerant, wingless, and broad-complex were confirmed by quantitative real time-PCR analysis. The Q-PCR analysis of larval, subimaginal, and imaginal stages of C. viridulum suggests that the development of mayflies more closely resembles hemimetamorphosis than holometamorphosis.

A new species of the genus Teloganopsis with setaceous mouthparts and forelegs from southern China (Ephemeroptera, Ephemerellidae).

The nymph and reared male and female of a new ephemerellid species, which was collected from southern China and named Teloganopsis setosa Zhou, sp. n., are described. The nymph is unique because of its long and dense setae on labrum, mandibles, maxillae, labium, and forelegs as well as the elongated segments II of labial palpi and expanded paraglossae. The male can be differentiated from close relatives by its larger penis lobes with dorsolateral projections, and the more pigmented tergum IV and caudal filaments. The nymph described in this paper represents a new adaptive and ecological type in the family Ephemerellidae.

The nymph, habitat, and status of Eatonigenia in China (Ephemeroptera: Ephemeridae).

The nymphs of a new species of Eatonigenia have more modified labrum and smaller foreclaws than congeners, and the males have a more reddish-brown colored body, cerci, genitalia and more sclerotized projections of gonopores. These characters indicate a new species which is named E. zhangi sp. nov. The nymphs live in fine sandy/muddy substrates of large rivers.

The nymph and imago of Chinese mayfly Siphlonurus davidi (Navás, 1932).

The imagos and nymphs of Siphlonurus davidi (Navás, 1932) are described for the first time. The adult has colourful wings and cross veins, the MP is forked asymmetrically at its base, a long cubital area is present with more intercalaries, and it has a relatively simpler penis and larger hindwings compared to its congeners. The venation and genitalia show that it is a plesiomorphic species in the genus. A key to the Asian species of Siphlonurus with coloured wings is provided in conclusion.

The complete mitochondrial genome of Paegniodes cupulatus (Ephemeroptera: Heptageniidae).

The complete mitochondrial genome of Paegniodes cupulatus (Ephemeroptera: Heptageniidae), which is sequenced for the first time here, is 15,715 bp in length, containing 13 protein-coding genes, 2 rRNAs, 22 tRNAs and a control region. The overall base composition of the genome is 33.1% for T, 20.7% for C, 32.5% for A and 13.7% for G, with an AT bias of 65.6%.

The phylogeny of Ephemeroptera in Pterygota revealed by the mitochondrial genome of Siphluriscus chinensis (Hexapoda: Insecta).

The mayfly species Siphluriscus chinensis (Siphluriscidae) has valuable structures useful for phylogeny reconstruction, given its putative basal position within the Ephemeroptera. Here its nearly complete mitochondrial genome is sequenced. We built phylogenetic trees through multiple analytical strategies with some other insect mitogenomes. Structurally, the obtained mitochondrial genome of S. chinensis is 16,616 bp in length,(1) containing 37 genes and an extra trnK-like (trnK2 (AAA)) gene. The 12 PCGs start with typical ATN codons, except the nad1 gene which starts with an unnormalized TTG. Like other known mayfly mitogenomes, the strand bias has negative AT-skew and negative GC-skew. Phylogenetically, our topologies suggest that Odonata is the basally diverged clade in Pterygota; Ephemeroptera is the sister group of the Neoptera; and S. chinensis is indeed the most basal mayfly branch.

A new species of Thraulus from Nanjing (eastern China) with single first gill (Insecta: Ephemeroptera: Leptophlebiidae).

Thraulus femoratus sp. nov., a new species found in eastern China, is described from imagos, subimagos, nymphs, and eggs. The nymphs are unique in the genus as well as in the Thraulus group because of their single lanceolate gills 1. The imagos can be differentiated from those of related species by the following combination of characters: slightly robust hindwing with a bluntly rounded costal projection that is situated over half the distance from wing base to apex, darkly pigmented basal portion of hindwing, and subapical dark band on hind femur. Subimagos resemble the imagos in color pattern. Eggs have eight pairs of long threads on the polar portion and slight ridges on the surface. The reduced gills 1 in combination with entirely fringed gills 2-7 represent a new evolutionary lineage and ecological type in the Thraulus group, but provide limited information regarding phylogenetic relationships.