Skelett und Muskulatur des Kopfes und Prothorax vonOchterus marginatus Latreille

The Leg Sensilla of Insects from Different Habitats-Comparison of Strictly Aquatic and Riparian Bugs (Corixidae, Ochteridae, Gelastocoridae: Nepomorpha: Insecta: Heteroptera)

The aim of this study was to analyze morphological types and arrangement of the leg sensilla of Corixidae, Ochteridae and Gelastocoridae, in relation to their various habitats. The leg sensilla of four species of Corixidae, six of Gelastocoridae and two of Ochteridae were studied. Eight main types of sensilla with six subtypes of sensilla trichodea and four subtypes of sensilla chaetica were found and described. The greatest variability was observed among mechanoreceptive sensilla. The study showed differences in the shape of the legs between strictly aquatic and terrestrial taxa. It is the first attempt to describe leg sensilla among nepomorphan taxa.

Phylogeny and historical biogeography of the water boatmen (Insecta: Hemiptera: Heteroptera: Nepomorpha: Corixoidea)

The water boatmen of Corixoidea, a group of aquatic bugs with more than 600 extant species, is one of the largest superfamilies of Nepomorpha. Contrary to the other nepomorphan lineages, the Corixoidea are most diverse in the Laurasian remnant Holarctic region. To explicitly test whether the present-day Holarctic distribution of diverse corixids is associated with the arising of the Laurasian landmass that was separated from Gondwana, we investigated the phylogeny, divergence times and historical biogeography of Corixoidea based on morphological and molecular characters sampled from 122 taxa representing all families, subfamilies, tribes and approximately 54 % of the genera. Our results were largely congruent with the phylogenetic relationships within the established nepomorphan phylogenetic context. The fossil calibrated chronogram, diversification analysis and ancestral ranges reconstruction indicated that Corixoidea began to diversify in Gondwana in the late Triassic approximately at 224 Ma and the arising of the most diverse subfamily Corixinae in Corixidae in the Holarctic region was largely congruent with the time of separation of Laurasia from Gondwana. The large-scale expansion of the temperate and cold zones on the northward-moving Laurasian landmass after the breakup of the Pangea provided new aquatic niches and ecological opportunities for promoting rapid diversification for the Holarctic corixid lineage.

The mouthparts of the Aradidae (Insecta: Hemiptera: Heteroptera)

The flat bugs, Aradidae, have exceptionally long piercing-sucking stylets coiled up at rest in the anterior part of the head. Previous studies suggested that the majority of aradids can be divided into two groups by the direction of stylet coiling, clockwise or anticlockwise. Detailed reconstruction of the head skeleton and musculature from series of polished sections, examined in SEM, of epon-embedded specimens of three species has shown that these groups represent two disparate modifications of the head groundplan. In Aradus betulae (L.), the stylet coil is accommodated inside the greatly enlarged anteclypeus within an expansible membranous diverticulum of its epipharyngeal cuticle. In contrast, in Isodermus planus Erichson and Carventus brachypterus Kormilev, the coil lies freely underneath the anteclypeus between the extended maxillary lobes (in I. planus fused with the extended gular lobe). The intraclypeal coils occur in the subfamilies Aradinae, Calisiinae, and Chinamyersiinae and the subclypeal coils in Isoderminae, Carventinae, Mezirinae, Aneurinae, Prosympiestinae, and possibly in the closely related family Termitaphididae. Each method of stylet coiling is associated with a suite of divergently specialized structural traits, suggesting that the two groups have independently evolved from ancestors endowed with regular stylets. Functional mechanics of the coiled stylet bundles are discussed.

Three New Species of Velvety Shore Bugs (Hemiptera: Heteroptera: Ochteroidea) From Mid-Cretaceous Kachin Amber Shed Light on the Evolution of Rostrum Length in Ochteroidea

Two new genera of velvety shore bugs, Arcochterus Zhang, Ren and Yao gen. nov. and Parvochterus Zhang, Ren and Yao gen. nov. are described, with three new species between them—Arcochterus fuscus Zhang, Ren and Yao sp. nov., Parvochterus reticulatus Ren and Yao sp. nov., and P. lanceolarus Zhang, Ren and Yao sp. nov. Based on the combination of fossil and extant taxa, a cladistic analysis is conducted to confirm the phylogenetic position of these species and allows reconstruction of the inter-genus relationships within the superfamily Ochteroidea. Major conclusions of the phylogenetic analysis: (1) these new species and Grimaldinia pronotalis belong to Ochteridae; (2) Ochteroidea is a monophyletic group, Ochteridae and Gelastocoridae are sister group and monophyletic, respectively. (3) The ancestral character state reconstruction (ACSR) shows that the length of the rostrum has occurred in at least three independent transitions during the evolution of the superfamily Ochteroidea.

Morphology of the Antennal Sensilla of Notonectoidea and Comparison of Evolutionary Changes in Sensilla Types and Distribution in Infraorder Nepomorpha (Insecta: Heteroptera)

Simple Summary

Antennal sensilla are important sensory organs for insects. According to their morphological structures, they respond to different chemical or mechanical stimuli. The antennae of the studied families of water insects (Notonectidae, Pleidae and Helotrephidae) are short and concealed under the head, leaving a small amount of space for the existence of sensory structures. Nevertheless, six main types of sensilla have been discovered on the surfaces of these antennae. The morphological types described in this study were further compared with other studies on the antennal sensilla of water bugs (Nepomorpha) in order to compare their evolutionary changes within the group.

Abstract

This article introduces the results of a study of three families of Nepomorpha and is the last part of a series of studies that sums up our work on the morphologies of the antennal sensory structures in this taxon. The morphologies and distribution of the sensilla in the families Notonectidae, Pleidae and Helotrephidae were studied under a scanning electron microscope. Six main types (sensilla trichodea, chaetica, campaniformia, basiconica, ampullacea and coeloconica) and ten subtypes (five subtypes of sensilla trichodea and five subtypes of sensilla basiconica) were described. The results were compared with other studies on the antennal sensilla of Nepomorpha in order to assess evolutionary changes within the infraorder. With the use of cladistics analysis, the monophyly of the families Nepidae, Micronectidae, Corixidae and Gelastocoridae was supported. On the other hand, the occurrence of some clades forming superfamilies was weakly supported by bootstrap analysis. These results, supported by presence of the numerous autapomorphies, suggest that antennal sensilla evolved within inner groups.

The variability of antennal sensilla in Naucoridae (Heteroptera: Nepomorpha)

The morphology and distribution of sensilla on the surface of the antennae of the naucorids' species were studied via scanning electron microscopy. Eleven types of sensilla were identified regarding specific sensory modalities, based on their cuticular morphology. Cuticle morphology identifies five types of sensilla trichodea, four types of sensilla basiconica, one type of sensillum coeloconicum and sensillum ampullaceum. Three new types of mechanosensitive sensilla were found. Moreover, the morphological diversity between the antennae allowed the distinction of ten different antennal types that correspond to different sensillar sets. The sensilla found in Naucoridae share similarities with the sensilla of other nepomorphan taxa, as well as of terrestrial insects. However, no sensillar synapomorphy was found between Naucoridae and Aphelocheiridae.

Comparative Study of Antennal Sensilla of Corixidae and Micronectidae (Hemiptera: Heteroptera: Nepomorpha: Corixoidea)

The goal of this study was to analyze the types and distributional patterns of sensilla in Corixoidea, which is part of the approach to the phylogeny study of Nepomorpha, based on the morphological characters of sensilla. This paper presents the results of the study, with the use of a scanning electron microscope (SEM), on the antennae of species from the families Corixidae and Micronectidae. The antennal sensilla of eleven species from Corixidae and two species from Micronectidae were studied. Five main types of sensilla with several subtypes of sensilla trichodea were found and described. The study has shown that the family Corixidae has a strong uniformity when it comes to antennal sensilla (similar patterns of sensilla trichodea and basiconica), and a similarity to the types and distributions of sensilla in two species of the family Micronectidae. However, significant differences between the families were also discovered (differences in sensilla presence on the first and second antennomeres, lack of sensilla coeloconica on the third antennomere in Micronectidae), which leads to a supportive conclusion of the systematic position of Micronectidae as a family.

Chromosomal divergence and evolutionary inferences in Pentatomomorpha infraorder (Hemiptera, Heteroptera) based on the chromosomal location of ribosomal genes

With the objective of assisting in the understanding of the chromosome evolution of Pentatomomorpha and in the quest to understand how the genome organizes/reorganizes for the chromosomal position of the 45S rDNA in this infraorder, we analyzed 15 species (it has being 12 never studied before by FISH) of Pentatomomorpha with the probe of 18S rDNA. The mapping of the 45S gene in the Coreidae family demonstrated that the species presented markings on the autosomes, with the exception of Acanthocephala parensis and Leptoglossus gonagra that showed markers on m-chromosomes. Most species of the Pentatomidae family showed marking in the autosomes, except for two species that had 45S rDNA on X sex chromosome (Odmalea sp. and Graphosoma lineatum) and two that showed marking on the X and Y sex chromosomes. Species of the Pyrrhocoridae family showed 18S rDNA markers in autosomes, X chromosome as well as in Neo X. The Largidae and Scutelleridae families were represented by only one species that showed marking on the X sex chromosome and on a pair of autosomes, respectively. Based on this, we characterized the arrangement of 45S DNAr in the chromosomes of 12 new species of Heteroptera and discussed the main evolutionary events related to the genomic reorganization of these species during the events of chromosome and karyotype evolution in Pentatomomorpha infraorder.

Phylogeny and diversification of the true water bugs (Insecta: Hemiptera: Heteroptera: Nepomorpha)

Climate fluctuations and tectonic reconfigurations associated with environmental changes play large roles in determining patterns of adaptation and diversification, but studies documenting how such drivers have shaped the evolutionary history and diversification dynamics of limnic organisms during the Mesozoic are scarce. Members of the heteropteran infraorder Nepomorpha, or aquatic bugs, are ideal for testing the effects of these determinants on their diversification pulses because most species are confined to aquatic environments during their entire life. The group has a relatively mature taxonomy and is well represented in the fossil record. We investigated the evolution of Nepomorpha based on phylogenetic analyses of morphological and molecular characters sampled from 115 taxa representing all 13 families and approximately 40% of recognized genera. Our results were largely congruent with the phylogenetic relationships inferred from morphology. A divergence dating analysis indicated that Nepomorpha began to diversify in the late Permian (approximately 263 Ma), and diversification analyses suggested that palaeoecological opportunities probably promoted lineage diversification in this group.

Long-branch attraction and the phylogeny of true water bugs (Hemiptera: Nepomorpha) as estimated from mitochondrial genomes

BACKGROUND

Most previous studies of morphological and molecular data have consistently supported the monophyly of the true water bugs (Hemiptera: Nepomorpha). An exception is a recent study by Hua et al. (BMC Evol Biol 9: 134, 2009) based on nine nepomorphan mitochondrial genomes. In the analysis of Hua et al. (BMC Evol Biol 9: 134, 2009), the water bugs in the group Pleoidea formed the sister group to a clade that consisted of Nepomorpha (the remaining true water bugs) + Leptopodomorpha (shore bugs) + Cimicomorpha (assassin bugs and relatives) + Pentatomomorpha (stink bugs and relatives), thereby suggesting that fully aquatic hemipterans evolved independently at least twice. Based on these results, Hua et al. (BMC Evol Biol 9: 134, 2009) elevated the Pleoidea to a new infraorder, the Plemorpha.

RESULTS

Our reanalysis suggests that the lack of support for the monophyly of the true water bugs (including Pleoidea) by Hua et al. (BMC Evol Biol 9: 134, 2009) likely resulted from inadequate taxon sampling. In particular, long-branch attraction (LBA) between the distant outgroup taxa and Pleoidea, as well as LBA among taxa in the ingroup, made Nepomorpha appear to be polyphyletic. We used three complementary strategies to test and alleviate the effects of LBA: (1) the removal of distant outgroups from the analysis; (2) the addition of closely related outgroups; and (3) the addition of a mitochondrial genome from a second family of Pleoidea. We also performed likelihood-ratio tests to examine the support for monophyly of Nepomorpha with different combinations of taxa included in the analysis. Furthermore, we found that specimens of Helotrephes sp. were misidentified as Paraplea frontalis (Fieber, 1844) by Hua et al. (BMC Evol Biol 9: 134, 2009).

CONCLUSIONS

All analyses that included the addition of more taxa significantly and consistently supported the placement of Pleoidea within the Nepomorpha (i.e., supported the monophyly of the traditional true water bugs). Our analyses further support a close relationship between Notonectoidea and Pleoidea within Nepomorpha, and the superfamilies Nepoidea, Ochteroidea, Naucoroidea, and Pleoidea are resolved as monophyletic in all trees with strong support. Our results also confirmed that monophyly of Nepomorpha clearly is not refuted by the mitochondrial genome data.

Phylogenetic signals from Nepomorpha (Insecta: Hemiptera: Heteroptera) mouthparts: stylets bundle, sense organs, and labial segments

The present study is a cladistic analysis of morphological characters focusing on the file of the mandible, the apices of the maxillae, the rupturing device on the maxillae, the internal structures of the mouthparts, and the external morphology of the labial segments as well as the distribution of labial sensilla in true water bugs (Hemiptera: Heteroptera, infraorder Nepomorpha). The study is based on data referring to sixty-two species representing all nepomorphan families (Heteroptera), together with one outgroup species representing the infraorders Gerromorpha (Mesoveliidae). The morphological data matrix consists of forty-eight characters. The present hypothesis supports the monophyly of the Nepomorpha and the monophyly of all families. The new modification in the systematic classification has been proposed: ((Nepidae + Belostomatidae), (Diaprepocoridae + Corixidae + Micronectidae), (Ochteridae + Gelastocoridae), Aphelocheiridae, Potamocoridae, Naucoridae, Notonectidae, and (Pleidae + Helotrephidae)).

Deliberations on the external morphology and modification of the labial segments in the Nepomorpha (Heteroptera: Insecta) with notes on the phylogenetic characteristics

The present study provides new data concerning the external morphology of the labial segments of 46 species from nine Nepomorpha families using the scanning electron microscope. The labial segments are described in detail and images of their structures are presented for the systematic groups. Subsequent segments of the labium (I, II, III, and IV) are shaped similarly in all investigated taxa but carry individual characters in some (sub-)families. Five morphologically distinct forms of the apical plate and five intercalary sclerites have been identified. Additionally, three types of the articulation on the dorsal side between the third and second segments are interpreted as the new characters. The presence of the midventral condyle on the distal edge of the first segment and the third segment has been reanalyzed. New position of the midventral condyle on the proximal edge of the fourth labial segment has been distinguished in several groups. The new set of characters has been estimated from the plesiomorphic taxa of the Nepoidea (Nepidae and Belostomatidae) and subsequently through the more advanced taxa in the relation to the outgroup (Gerromorpha). The evaluation of these characters has revealed twenty-seven new apomorphies for the labium in the Nepomorpha.

Comparative analysis and systematic mapping of the labial sensilla in the Nepomorpha (Heteroptera: Insecta)

The present study provides new data concerning the morphology and distribution of the labial sensilla of 55 species of 12 nepomorphan families (Heteroptera: Nepomorpha) using the scanning electron microscope. On the labial tip, three morphologically distinct types of chemosensilla have been identified: two types of papillae sensilla and one type of peg-in-pit sensilla. Twenty-one morphologically distinct types of the mechanosensilla as well as two types of the trichoid sensilla (contact-chemoreceptive sensillum) have been identified on all labial segments in representatives of subfamilies. In Nepomorpha, morphological ground plan of the labial sensory structures is represented by an apical sensory field with 10–13 pairs of papillae sensilla and the peg-in-pit ones placed more laterally; numerous trichoid sensilla are placed on the IV segment; the chaetica sensilla are present and placed in groups or rows distributed along the labium near the labial groove on the dorsal side, and also several chaetica sensilla are unevenly scattered on the surface of that segment; the cupola and peg sensilla are numerous and evenly scattered on the fourth labial segment; the prioprerecptive sensilla, one pair is positioned on the dorsal side and on the fourth segment of the labium. The new apomorphical characters have been established for the labial sensilla in the Nepomorpha.

The cephalic morphology of the Gondwanan key taxon Hackeriella (Coleorrhyncha, Hemiptera)

External and internal head structures of Coleorrhyncha, a key-taxon within the Hemiptera, are described in detail and documented using modern techniques. The main focus is on Hackeriella veitchi, but two additional representatives of the Gondwanan relict group were also examined, and also head structures of Enicocephalidae, a member of a potentially basal heteropteran lineage. Features were compared to those documented in literature for the Sternorrhyncha, Auchenorrhyncha, and Heteroptera. Coleorrhyncha are characterized by highly modified head structures and correspondingly an entire series of autapomorphies, such as for instance a strongly flattened head capsule with fenestrations. However, they also display features that are likely plesiomorphic compared to members of other hemipteran groups. These include the almost complete tentorium and the lack of the gula. The sistergroup relationship between Coleorrhyncha and Heteroptera is well supported by cephalic features. Potential synapomorphies are the presence of a distinct mandibular sulcus, the reduced number of antennomeres, the absence of clasping organs in the labial groove, coiled accessory salivary ducts, the presence of a small cervical muscle M1a (M. pronotopostoccipitalis medialis), the presence of a second mandibular promotor M14 (M. zygomaticus mandibulae), the presence of M28 (M. verticopharyngalis), and M30 (M. frontobuccalis posterior).

Systematics and evolution of Heteroptera: 25 years of progress

Heteroptera, or true bugs, are part of the most successful radiation of nonholometabolous insects. Twenty-five years after the first review on the influence of cladistics on systematic research in Heteroptera, we summarize progress, problems, and future directions in the field. The few hypotheses on infraordinal relationships conflict on crucial points. Understanding relationships within Gerromorpha, Nepomorpha, Leptopodomorpha, Cimicomorpha, and Pentatomomorpha is improving, but progress within Enicocephalomorpha and Dipsocoromorpha is lagging behind. Nonetheless, the classifications of several superfamily-level taxa within the Pentatomomorpha, such as Aradoidea, Coreoidea, and Pyrrhocoroidea, are still unaffected by cladistic studies. Progress in comparative morphology is slow and drastically impedes our understanding of the evolution of major clades. Molecular systematics has dramatically contributed to accelerating the generation and testing of hypotheses. Given the fascinating natural history of true bugs and their status as model organisms for evolutionary studies, integration of cladistic analyses in a broader biogeographic and evolutionary context deserves increased attention.

Phylogenetic analysis of the true water bugs (Insecta: Hemiptera: Heteroptera: Nepomorpha): evidence from mitochondrial genomes

BACKGROUND

The true water bugs are grouped in infraorder Nepomorpha (Insecta: Hemiptera: Heteroptera) and are of great economic importance. The phylogenetic relationships within Nepomorpha and the taxonomic hierarchies of Pleoidea and Aphelocheiroidea are uncertain. Most of the previous studies were based on morphological characters without algorithmic assessment. In the latest study, the molecular markers employed in phylogenetic analyses were partial sequences of 16S rDNA and 18S rDNA with a total length about 1 kb. Up to now, no mitochondrial genome of the true water bugs has been sequenced, which is one of the largest data sets that could be compared across animal taxa. In this study we analyzed the unresolved problems in Nepomorpha using evidence from mitochondrial genomes.

RESULTS

Nine mitochondrial genomes of Nepomorpha and five of other hemipterans were sequenced. These mitochondrial genomes contain the commonly found 37 genes without gene rearrangements. Based on the nucleotide sequences of mt-genomes, Pleoidea is not a member of the Nepomorpha and Aphelocheiroidea should be grouped back into Naucoroidea. Phylogenetic relationships among the superfamilies of Nepomorpha were resolved robustly.

CONCLUSION

The mt-genome is an effective data source for resolving intraordinal phylogenetic problems at the superfamily level within Heteroptera. The mitochondrial genomes of the true water bugs are typical insect mt-genomes. Based on the nucleotide sequences of the mt-genomes, we propose the Pleoidea to be a separate heteropteran infraorder. The infraorder Nepomorpha consists of five superfamilies with the relationships (Corixoidea + ((Naucoroidea + Notonectoidea) + (Ochteroidea + Nepoidea))).

Wing-locking mechanisms in aquatic Heteroptera

This account provides a detailed morphological and ultrastructural study of wing-locking mechanisms (LM) in some aquatic Heteroptera. Scanning and transmission electron microscopy were used to describe the functional significance of macro- and microstructures holding wings tightly against the body at rest and those involved in functional diptery in flight. There are two types of LM holding the forewings (hemelytra) at rest: 1) wing-to-wing LM, and 2) wing-to-body LM. The first type includes the brush-to-brush LM, the clavus-clavus clamp and the clavus-clavus locking ridge. The second type includes devices locking the hemelytra to the body: the subcostal border of the hemelytra to the lateral border of mesepimeron, the knob-and-socket locking mechanism of the hemelytra, and the clavus-locking mechanism to the scutellum groove. The hindwing is locked by a pair of microtrichial fields situated on the hindwing-articulated pad at the basal area of the hindwing and on the thoracic pad in the vicinity of the wing articulation. Morphological and ultrastructural data suggest that different LM are parts of one mechanism holding wings to the body at rest. An additional locking mechanism, connecting the hemelytra with the hindwing, is the only LM providing functional diptery in flight.