Evolution of satDNAs on holocentric chromosomes: insights from hemipteran insects of the genus Mahanarva

Satellite DNAs (satDNAs) constitute one of the main components of eukaryote genomes and are involved in chromosomal organization and diversification. Although largely studied, little information was gathered about their evolution on holocentric species, i.e., diffuse centromeres, which, due to differences in repeat organization, could result in different evolutionary patterns. Here, we combined bioinformatics and cytogenetic approaches to evaluate the evolution of the satellitomes in Mahanarva holocentric insects. In two species, de novo identification revealed a high number of satDNAs, 110 and 113, with an extreme monomer length range of 18-4228 bp. The overall abundance of satDNAs was observed to be 6.67% in M. quadripunctata and 1.98% in M. spectabilis, with different abundances for the shared satDNAs. Chromosomal mapping of the most abundant repeats of M. quadripunctata and M. spectabilis on other Mahanarva reinforced the dynamic nature of satDNAs. Variable patterns of chromosomal distribution for the satDNAs were noticed, with the occurrence of clusters on distinct numbers of chromosomes and at different positions and the occurrence of scattered signals or nonclustered satDNAs. Altogether, our data demonstrated the high dynamism of satDNAs in Mahanarva with the involvement of this genomic fraction in chromosome diversification of the genus. The general characteristics and patterns of evolution of satDNAs are similar to those observed on monocentric chromosomes, suggesting that the differential organization of genome compartments observed on holocentric chromosomes compared with monocentric chromosomes does not have a large impact on the evolution of satDNAs. Analysis of the satellitomes of other holocentric species in a comparative manner will shed light on this issue.

Comparative analysis of mitochondrial genomes of Nirvanini and Evacanthini (Hemiptera: Cicadellidae) reveals an explicit evolutionary relationship

Mitogenomes of five leafhopper species, Chudania hellerina and Concaveplana rufolineata in Nirvanini, Carinata rufipenna, Evacanthus danmainus and E. heimianus representing Evacanthini, were sequenced. The lengths of these five mitogenomes range from 15,044 (C. hellerina) to 15,680 bp (E. heimianus). All five mitogenomes exhibit similar base composition, gene size and codon usage of protein-coding genes. All 22 tRNA genes have typical cloverleaf secondary structures, except for trnS1 (AGN) which appears to lack the dihydrouridine arm. The two included Nirvanini species employ the anticodon TCT instead of the commonly used GCT in trnS1 (AGN). Genes nad2, atp8 and nad6 were highly variable while cox1 and cob showed the lowest nucleotide diversity. Phylogenetic analyses of two concatenated nucleotide datasets, incorporating the newly sequenced taxa and other available membracoid mitogenomes, recovered each included leafhopper subfamily as monophyletic with evacanthine tribes Nirvanini and Evacanthini forming monophyletic sister clades. A relationship among Evacanthinae, Cicadellinae and Typhlocybinae received moderate branch support.

Ultrastructure of spermatozoa in three cicada species from China (Hemiptera, Cicadomorpha, Cicadidae)

The ultrastructure of mature spermatozoa of three cicada species, Subpsaltriayangi, Kareniacaelatata, and Platypleurakaempferi, was investigated using epifluorescence and transmission electron microscopies. This is the first investigation of the sperm ultrastructure of species in the subfamily Tibicininae and the tribe Sinosenini, represented by S.yangi and K.caelatata, respectively. The three species all produce two or three types of spermatozoa with various lengths, viz., polymegaly. The centriolar adjunct of spermatozoa in S.yangi shows a granular substructure, which is different from that of other cicada species, suggesting that spermatozoa in Tibicininae may have their own characteristics in comparison with other cicadas. The centriolar adjunct of spermatozoa of K.caelatata displays characteristics similar to that of the Cicadinae. Combined with other morphological characters, it is reasonable to remove K.caelatata and its allies (i.e., Sinosenini) from Cicadettinae to Cicadinae. The study of sperm ultrastructure, particularly in the species of Tibicininae and Sinosenini, expands the spermatological research of Cicadidae and provides more information for phylogenetic analysis of Cicadidae.

Re-description of the sperm morphology of Dalbulus maidis (Hemiptera: Cicadellidae: Deltocephalinae)

The corn leafhopper, Dalbulus maidis, which is one of the most important vectors of maize diseases, had the morphology of its spermatozoa described more than 40 years ago. However, the description is imprecise, requiring certain rectifications. Hence, we re-describe the sperm morphology of this species using light microscopy and transmission electron microscopy. Their spermatozoa measured from 118.1 to 128.5 μm in length, this value being about three times smaller than what was previously described. The head region is formed by a small acrosome and the nucleus. The acrosome is paracrystalline and has the bifurcated base that is docked in two cavities on one side of the anterior region of the nucleus. The nucleus, which is linear and thin, measured from 19.3 to 22.9 μm in length, and exhibited homogeneously compact chromatin. In cross-section, it has a thumbtack shape, except in the anterior and posterior regions, where it is oval. The flagellum consists of an axoneme with 9 + 9 + 2 microtubules, two similar mitochondrial derivatives, two accessory bodies each associated with a small sub-ellipsoidal structure, and a 'center-flagellar material'. In all the spermatozoa observed, the final portion of the flagellum was branched into four filaments. Some of these morphological features are now being re-described, while others have been observed for the first time in the Cicadellidae family, as the center-flagellar material.

First finding of a dual-meaning X wave for phloem and xylem fluid ingestion: Characterization of Scaphoideus titanus (Hemiptera: Cicadellidae) EPG waveforms

The leafhopper Scaphoideus titanus (Hemiptera: Cicadomorpha: Cicadellidae), an invasive deltocephaline species introduced into Europe from North America, is the vector of the most important phytoplasma disease in European viticulture, flavescence dorée. In this first electropenetrography (EPG) study of S. titanus, we characterized its feeding waveforms and defined their biological meanings. Four typical waveform phases (pathway, X wave, sustained ingestion, and interruption) and four families within those phases (A, B, C, and N) were characterized using DC EPG technology. We proposed biological meanings for these waveforms based on excreta pH-ingestion correlations, presence of X waves, and comparison with previous AC, DC, and AC-DC EPG waveforms conducted on Cicadomorpha. We observed that sustained (i.e., >10min) ingestion by a deltocephaline leafhopper can occur from both xylem and phloem vascular cells. Waveform C2x represented ingestion of xylem fluid, and two waveforms represented behaviors when stylets were inserted into phloem sieve elements: C2p variant 1 (C2p-1), which may represent salivation (perhaps simultaneous with ingestion), and C2p variant 2 (C2p-2), which represented active ingestion. Furthermore, we found that the EPG-recorded X wave has a dual meaning by occurring prior to sustained ingestion from either phloem or xylem. This X wave was very similar in appearance to the model X wave of sharpshooters, an entirely different leafhopper subfamily, Cicadellinae. All cicadellines are obligate xylem-ingesters. Such a "dual-meaning X wave" will provide insights into how the feeding tactics of S. titanus relate to other sheath-feeding hemipterans, and will provide support for future research to clarify the role of this leafhopper as a vector of plant pathogens.

Mixed xylem and phloem sap ingestion in sheath-feeders as normal dietary behavior: Evidence from the leafhopper Scaphoideus titanus

In phytophagous piercing-sucking insects, salivary sheath-feeding species are often described as xylem- or phloem-sap feeding specialists. Because these two food sources have very different characteristics, two feeding tactics are often associated with this supposed specialization. Studying the feeding behavior of insects provides substantial information on their biology, ecology, and evolution. Furthermore, study of feeding behavior is of primary importance to elucidate the transmission ability of insects that act as vectors of plant pathogens. In this study, we compared the durations of ingestion performed in xylem versus phloem by a leafhopper species, Scaphoideus titanus Ball, 1932. This was done by characterizing and statistically analyzing electrical signals recorded using the electropenetrography technique, derived from the feeding behaviors of males and females. We identified three groups of S. titanus based on their feeding behavior: 1) a group that reached the phloem quickly and probed for a longer time in phloem tissue than the other groups, 2) a group that reached the xylem quickly and probed for a longer time in xylem tissue than the other groups, and 3) a group where individuals did not ingest much sap. In addition, the numbers and durations of waveforms representing ingestion of xylem and phloem saps differed significantly depending on the sex of the leafhopper, indicating that the two sexes exhibit different feeding behaviors. Males had longer phloem ingestion events than did females, which indicates that males are greater phloem feeders than females. These differences are discussed, specifically in relation to hypotheses about evolution of sap feeding and phytoplasma transmission from plant to plant.

Bambusimukaria, a new bamboo-feeding leafhopper genus from China, with description of one new species (Hemiptera, Cicadellidae, Deltocephalinae, Mukariini)

A new genus and species, Bambusimukariaquinquepunctatagen. & sp. n., feeding on bamboo in Guizhou and Fujian, China, are described and illustrated. The characters of crown, frontoclypeus, forewing venations and male genitalia place the new genus in the tribe Mukariini.

Comparative cytogenetics of Auchenorrhyncha (Hemiptera, Homoptera): a review

A comprehensive review of cytogenetic features is provided for the large hemipteran suborder Auchenorrhyncha, which currently contains approximately 42,000 valid species. This review is based on the analysis of 819 species, 483 genera, and 31 families representing all presently recognized Auchenorrhyncha superfamilies, e.i. Cicadoidea (cicadas), Cercopoidea (spittle bugs), Membracoidea (leafhoppers and treehoppers), Myerslopioidea (ground-dwelling leafhoppers), and Fulgoroidea (planthoppers). History and present status of chromosome studies are described, as well as the structure of chromosomes, chromosome counts, trends and mechanisms of evolution of karyotypes and sex determining systems, their variation at different taxonomic levels and most characteristic (modal) states, occurrence of parthenogenesis, polyploidy, B-chromosomes and chromosome rearrangements, and methods used for cytogenetic analysis of Auchenorrhyncha.

Elevational gradient of Hemiptera (Heteroptera, Auchenorrhyncha) on a tropical mountain in Papua New Guinea

Malaise trap sampling of Hemiptera (Heteroptera; Auchenorrhyncha) was conducted at 500 m intervals along an elevational gradient from 200 m to 3,700 m on the east slope of Mount Wilhelm, Madang Province, Papua New Guinea. Hemiptera had a decrease in morphospecies richness and overall abundance with increasing elevation, however, the Heteroptera did not exhibit either pattern. A few species were relatively abundant at each elevation, whereas the majority of species were represented by ≤5 specimens. Morphospecies richness of Auchenorrhyncha, Cicadomorpha, Fulgoromorpha, Cicadellidae, Cixiidae, and Derbidae also decreased with increasing elevation but abundance decline was not significant due to the large number of specimens captured at 200 m relative to those captured at higher elevations. The percentage of Cicadomorpha specimens decreased with increasing elevation relative to that of the Fulgoromorpha which increased with increasing elevation. Environmental factors that may influence patterns of species richness along the elevational gradient are discussed.

On cicadas of Hyalessa maculaticollis complex (Hemiptera, Cicadidae) of China

The genus Hyalessa China is reviewed based on the discovery of male of the type species H. ronshana China as well as the description of one new species (H. batangensis sp. n.). The species formerly included in the genus Sonata Lee are removed to Hyalessa as new combinations. Intraspecific variations of H. maculaticollis are enumerated based on materials collected from various locations from China. The identity of Sonata and the systematic placement of Hyalessa are discussed. A key to all species of Hyalessa is provided.

First karyotype data on the family Myerslopiidae (Hemiptera, Auchenorrhyncha, Cicadomorpha)

In the first cytogenetic study of the recently proposed family Myerslopiidae the male karyotype of Mapucheachilensis (Nielson, 1996) was analyzed using conventional chromosome staining, AgNOR- and C-bandings, and fluorescence in situ hybridization (FISH) with 18S rDNA and (TTAGG) n telomeric probes. A karyotype of 2n = 16 + XY, NOR on a medium-sized pair of autosomes, subterminal location of C-heterochromatin, and presence of (TTAGG) n telomeric sequence were determined. Additionally, the male internal reproductive system was studied.

The Auchenorrhyncha fauna of peat bogs in the Austrian part of the Bohemian Forest (Insecta, Hemiptera)

The first overview on the Auchenorrhyncha fauna of peat bogs of the Austrian Bohemian Forest is presented. Seven oligotrophic peat bog sites were studied in 2011 by suction sampler (“G-Vac”) and 93 Auchenorrhyncha species (with 7465 adult specimens) were recorded. Eleven species (about 18 % of the individuals) are tyrphobiontic or tyrphophilous. The relative species abundance plot is not very steep; the six most abundant species represent 50 % of the individuals. The most common species is Conomelus anceps (17 % of the individuals). Compared to the whole Austrian Auchenorrhyncha fauna, the fauna of peat bogs comprises distinctly more univoltine species and more species hibernating in nymphal stage. Densities of adult Auchenorrhyncha in peat bogs are low in spring (about 10–60 individuals per m²) and high in July, with up to 180 (±50) individuals per m². Disturbed peat bogs have higher species numbers and higher Auchenorrhyncha densities in total, but lower numbers and densities in peat bog specialists.

Two new species of the bamboo-feeding leafhopper genus Abrus Dai & Zhang (Hemiptera, Cicadellidae, Deltocephalinae) from China

Two new species of the bamboo-feeding genus Abrus Dai & Zhang, 2002, Abrus xishuiensis sp. n. and Abrus langshanensis sp. n., are described and illustrated from Guizhou and Hunan, South China. A checklist and a key to 13 known species are given.

First record of the leafhopper genus Sweta Viraktamath & Dietrich (Hemiptera, Cicadellidae,Typhlocybinae) from China, with description of one new species feeding on bamboo

Sweta bambusanasp. n. (Hemiptera: Cicadellidae: Typhlocybinae: Dikraneurini), a new bamboo-feeding species, is described and illustrated from Guizhou and Guangdong of China. This represents the first record of the genus Sweta Viraktamath& Dietrich from China and the second known species of the genus. The new taxon extends the range of the genus Sweta, previously known only from northeast India and Thailand, considerably eastwards. A key for separation of the species of Sweta is given.