Research

Comparative Morphology of Female Genitalic Region in Insectia

The main research focus is the comparative morphology and evolution of the female postabdomen in insects. This most posterior part of the body includes the female genitalic region (bearing the ovipositor, if such a structure is present) and the postgenital abdomen (with, e.g., the cerci). Both the exoskeletal elements and the musculature are examined.

The female genitalic region is represented by the ventral sides of abdominal segments 7–9. It includes three major pairs of processes that form the ovipositor (gonapophyses and gonoplacs; or “valves”) and a number of sclerites with their mutual articulations. Internally the exoskeleton forms various apodemes, strengthening ridges, and pouch-like structures; the gonoducts, spermatheca, and accessory glands open in this area; and a complex musculature is also present. This highly complex body region shows much structural diversity across and within insect “orders”, but is still conservative enough to allow for homologising most components. This makes the female genitalic region a phylogenetically very informative character system. The postgenital abdomen is comprised of segments 10 and 11; characters of interest for phylogenetic work come, for instance, from the various small sclerites around the bases of the cerci and from the equipment with rectal and cercal muscles.

The morphological work on the postabdomen eventually aims at establishing a fully resolved homology scheme for sclerotisations, muscles, and cuticular form-giving elements (such as processes and apodemes; see illustration below). This will allow for the use of this character system in phylogenetic studies, concerning both inter-ordinal insect relationships as well as relationships within many orders. On this basis conclusions can then be drawn on evolutionary aspects of reproduction and egg deposition.

K.-D. Klass studied the female genitalic region in a variety of insect taxa. The first study treated the Dictyoptera (Klass 1998, Zoologischer Anzeiger). Important results were that the spermatheca is an element of the 8th abdominal segment, and the “laterosternal shelf” is a lobe on the hind margin of the 7th segment and thus a potential homologue of the “languette” lobe in Zygentoma.

The Dermaptera were studied in the second and third contributions (Klass 2001, Zoological Journal of the Linnean Society; Klass 2003, Entomologische Abhandlungen); the focus was on the epizoic genus Hemimerus and on 9 species of “basal” dermapterans (from Karschiellidae, Diplatyidae, and Pygidicranidae), respectively. These studies showed that in “basal” dermapterans an almost complete ovipositor is present, and that the morphology of the female genitalia is extremely diverse among the various genera.

The exoskeleton of the female genitalia of the newly discovered Mantophasmatodea was described in Klass et al. 2003, Entomologische Abhandlungen.

In 2008 a major paper on the female genitalic region in those Odonata that bear a plesiomorphic ovipositor was published (Zygoptera, Epiophlebiidae, and Aeshnidae; Klass 2008, Arthropod Systematics & Phylogeny). One striking result was the presence of a bipartite gonangulum in all of these Odonata – with the sole exception of Epiophlebia.

In 2009 a study of the exoskeleton (including gonoducts) in 5 species of Embioptera followed (Klass & Ulbricht 2009, Organisms, Diversity & Evolution).

Among the more recent studies, one treats a selection of “higher” Dermaptera (Schneider & Klass 2012, Zoologischer Anzeiger), including evidence of parallel evolution of (ovo)viviparity in different Spongiphoridae. The strongly depress earwig Apachyus is currently under study (Kaidel & Klass), as is the polyphagid cockroach Ergaula (Casper & Klass). A study of the female genitalic region in a petalurid dragonfly has been published (Matushkina & Klass 2011, International Journal of Odonatology), and another on 15 species of libellulid dragonflies is almost completed (Casper & Klass).

Another recent focus is on female genitalia in primarily apterygote insects: Zygentoma and Archaeognatha (Klass & Matushkina). This work is fundamentally important for providing sound outgroup comparison for Pterygota and thus to reach well-founded conclusions on the evolution of the female genitalia in this megadiverse group (comprising 99% of insect species). In a publication on the archaeognathan Petrobiellus(Klass & Matushkina 2012, Arthropod Structure & Development) the function of an external egg transportation tract was hypothesised.

The previous contributions include extensive homology discussions and comparisons throughout Insecta. Important topics concern, e.g., the morphological composition of the subgenital plates in the various orders and the shift of the gonopore from segment VII to segment VIII. The gonangulum sclerite (a multiarticulated sclerite functionally important for the coordination of gonapophyseal movements) and its phylogenetic evidence was discussed in a paper of its own (Klass et al. 2012, Arthropod Structure & Development). The comparative morphology of the postgenital abdomen was extensively discussed in the contributions on Hemimerus and Odonata, including the homology and morphological interpretation of the muscles moving the cerci and neighbouring sclerites.

Contributors from SNSD: Klass, Casper, Schneider, Kaidel, Schröter
External collaborators: Nataly Matushkina (National University of Kiev, Ukraine)

Comparative Morphology of male genitalia in insecta

Some early publications were dedicated to Dictyoptera: One covered the cockroaches and mantids (Klass 1997, Bonner Zoologische Monographien), whose members have highly complicated asymmetrical male genitalia. This was followed by two papers on the strongly simplified organs in termites (Mastotermes: Klass 2000, Zoologischer Anzeiger; Stolotermes: Klass et al. 2000: Acta Zoologica), which also treat many other parts of the abdomen.

A more recent contribution on male genitalia in the phasmatodean (stick insect) Oxyartes (Helm et al. 2011, Zoologischer Anzeiger) is especially meaningful, as it yields the first detailed description of these organs in a member of this order and indicates a great value of male genitalic morphology for taxonomic and phylogenetic work in stick insects.

Currently ongoing studies refer to Odonata (dragon- and damselflies), where a sample of 6 species from various families has been studied (Endler & Klass); to Dermaptera, where a few representatives from different subgroups are under study (Scheide & Klass); to Mantodea, where 5 species from quite closely related genera were examined in order to explore this character system for its use in phylogenetic work at a lower systematic rank (Erkeling & Klass); and to Archaeognatha, for which comparative work on a selection of 5 distantly related species is almost completed (Matushkina & Klass).

The work on male genitalia aims at a better understanding of the evolution of these structures in insects, at an improved use of their characters in the reconstruction of phylogenetic relationships between and within insect orders, and at an improved use in taxonomic work. In combination with the studies on the female genitalia, the data will, on a longer term, allow for analysing the divergent evolution of homonomous structures in the two sexes, will provide a multitude of evidence on the evolution of reproduction in insects, and will also strongly improve the basis for studies on genitalia-based sexual selection and on the mutual fitting of male and female genitalia in copulation, and thus for a much closer testing of the role of this in insect evolution and speciation.

Morphology and Phylogeny of Dictyoptera 

Dictyoptera includes the Mantodea (praying mantises) and Blattodea (cockroaches, with the termites as a subgroup), with altogether close to 10.000 known species. It is a focal research taxon in the Section Coleoptera. Early works treated the male and female genitalia (see above), overall abdominal morphology (a cockroach and a mantid in Klass 1999, Deutsche Entomologische Zeitschrift; Mastotermes in Klass 2000, Zoologischer Anzeiger), and the proventriculus (part of the foregut; Klass 1998, Zoologischer Anzeiger).

More recent studies refer to the tentorium and anterior part of the head capsule (Klass & Eulitz 2007, Zoologischer Anzeiger); to the transition region between the tibia and tarsus on the legs, with special reference to its function and a small sclerite present in this area (Klass et al. 2009, Insect Systematics & Evolution); and to the hypopharynx, a tongue-like organ in the center of the mouthparts (Buder & Klass 2012, Zoologischer Anzeiger).

Several papers aimed at reconstructing phylogenetic relationships in Dictyoptera. A first study used 175 morphological characters, mostly from the male genitalia (Klass & Meier 2006, Entomologische Abhandlungen). Two others were conducted with cooperation partners, one combining molecular and morphological data (Ware et al. 2008, Systematic Entomology), and one being purely based on molecular data (Djernaes et al. 2012, Systematic Entomology). This work allowed for outlining a few principal lineages of Dictyoptera, while the relationships among these have remained fairly unclear. Phylogenetic work on the Dictyoptera is ongoing.

The discovery of a small cockroach, Saltoblattella montistabularis, that possesses long hindlegs adapted to jumping is especially noteworthy (Bohn et al. 2010, Arthropod Systematics & Phylogeny). This animal from Table Mountain in Cape Town was officially awarded a place among the 10 most striking organisms newly described in 2010. The genus Cryptocercus, which most likely is the sister group of the termites, has been another focal taxon. This includes research on the diversity of this genus in the Appalachian Mountains (USA; Nalepa et al. 2001, Annals of the Entomological Society of America) and a discussion of Cryptocercus being the preferred model taxon for early evolution in termites (Klass et al. 2008, Molecular Phylogenetics & Evolution).

Contributors from SNSD: Klass, Buder, Eulitz, Barton, Erkeling
External collaborators: Marie Djernaes (The Natural History Museum, UK); Jessica Ware (Rutgers University, USA), Mike D. Picker (University of Cape Town, South Africa), Horst Bohn (Zoological State Collections Munich, Germany), Christine Nalepa (North Carolina State University)

Morphology, Species Diversity, and Phylogeny of Mantophasmatodea (Heel-Walkers)

The wingless Mantophasmatodea were discovered in 2001. Their formal description (Klass et al. 2002, Science) was based on a male from Tanzania and a female from Namibia, which had been found in museum collections (London resp. Berlin) and represented two different species. As Mantophasmatodea were found to lack the sets of apomorphies that characterise the various other insect orders, and as the evidence on the sister-group relationship of this taxon was conflicting, Klass et al. (2002) classified it as an insect order of its own. Since then, mantophasmatodeans were frequently collected in the wild both in South Africa and Namibia. They are 1,2–3,5 cm long and feed on other arthropods, which they catch using their spinose fore- and midlegs. The placement of the group in Pterygota-Neoptera is clear, but otherwise its phylogenetic relationships have remained ambiguous (Klass 2009, Proceedings of the Arthropodan Embryological Society of Japan) – though Grylloblattodea is a good candidate to be the sister group.

Meanwhile, altogether 19 extant species of Mantophasmatodea have been described from South Africa, Namibia, and Tanzania, and the existence of a few additional ones is shown by molecular studies. These have been classified into several families and genera. In both South Africa and Namibia there is a distinct pattern of vicariance-based endemism, with different regions harbouring their own species.

In Klass et al. 2003, Entomologische Abhandlungen, the morphology of some body parts was studied more closely, especially the male and female postabdomen (including the genitalia), which is the major source of characters useful in the distinction of species. In the male, there are differences in the presence and shape of several genitalic sclerites and lobes; in the structure of the vomeroid (a sclerotised projection above the genitalia), in the shape of abdominal tergite 10, and in the shape and some structural details of the cerci. The females show differences in the shape and sclerotisation of the subgenital plate, in the shape of the internal bulb of the spermatheca, in the vaginal sclerotisations, and in the setation of the region between the two gonapophyses IX.

While the general colouration varies much among specimens of the same species and even population, groups of species differ with regard to the distribution of dark patches over the compound eye (“striped type” versus “mosaic type”) and the spatial relationship between cuticular setae and pigment spots in the epidermis (“strict correlation type” versus “loose correlation type”) (Klass et al. 2003; see also Eberhard et al. 2011, Organisms, Diversity & Evolution).

Another publication from our team (Damgaard et al. 2008, Molecular Systematics & Evolution) provided the so far most extensive molecular-based study on the internal phylogenetic relationships in Mantophasmatodea, analysing the mitochondrial genes COI and 16S rDNA for 97 specimens from 15 mantophasmatodean species (with a strong focus on South African ones). 

Some further publications from our group cover selected morphological structures of Mantophasmatodea. The tentorium was described in a paper otherwise focused on Dictyoptera (Klass & Eulitz 2007, Zoologischer Anzeiger). For the antennae, which in Mantophasmatodea show a unique structure, the exoskeletal fine structure was studied, including the sensilla equipment and the tiny pouches present apically on two distiflagellomeres (Drilling & Klass 2010, Zoologischer Anzeiger). The ontogeny of antennae in nymphs of Mantophasmatodea was the focus of another contribution (Hockman et al. 2009, Arthropod Structure & Development). The unique dorsal projections on the tarsus have been studied in a large sample including most mantophasmatodean species (Buder & Klass in press, Deutsche Entomologische Zeitschrift); the projections were found to bear campaniform sensilla, and a hypothesis was given for the function of the projections.

 Previous studies have already provided a crude picture of the systematic structuring of Mantophasmatodea in South Africa. Currently it is planned to use this as a basis for studying mantophasmatodean diversity at a much finer scale, analysing morphology and DNA sequences (nuclear and mitochondrial) between species and between populations, with a special focus on the situation along borders between neighbouring species.

Contributors from SNSD: Klass, Buder, Drilling, Hell
External collaborators: Mike Picker (University of Cape Town, South Africa), Jakob Damgaard (University of Copenhagen, Denmark), Ryuichiro Machida (University of Tsukuba, Japan), Koji Tojo (Shinshu University, Japan), Monika Eberhard (Humboldt University Berlin, Germany) 

Taxonomy of Coleoptera-Byrrhidae

Byrrhidae includes ca 450 described species worldwide, most of which are associated with mosses. We study the taxonomy of this beetle family with a focus on the species of the Himalaya Mountains (mainly Nepal). This region is of particular interest, as it comprises a multitude of different habitats, is vastly unexplored with regard to its beetle fauna, and moreover lies at the border between the Palaearctic and Oriental zoogeographical regions. Byrrhidae occur at altitudes from 2500 to over 5000 m, which encompass several zones of vegetation up to the nival one. As often found in high-elevation & low-dispersal taxa, several genera of Byrrhidae form groups of species that are endemic to particular mountain ranges. So far 51 Byrrhidae species have become known from Nepal; 46 of these are mountain endemics – belonging to the genera Morychus, Chrysosimplocaria, Himalayoligus, Simplocaria, and Curimopsis – and 39 were described by O. Jäger and his external collaborators. Published papers deal with new species of the genera Chrysosimplocaria (Jäger 1997, Reichenbachia; Jäger 1998, Reichenbachia; Jäger 2000, Reichenbachia), Byrrhus (Jäger 2002, Reichenbachia), and Morychus (Jäger & Pütz 2009 in “Biodiversität und Naturausstattung im Himalaya”) or provide an overview of the Byrrhidae of Nepal (Jäger & Pütz 2003 in “Biodiversität und Naturausstattung im Himalaya”).

In 2009 taxonomic work on the Byrrhidae of New Zealand was begun, based on specimens assembled during an 8-weeks collecting trip as well as museum material (mainly from the New Zealand Arthropod Collection in Auckland). First results have already shown that together with the southern part of Australia, New Zealand harbours some 25% of the world Byrrhidae fauna, with many species still undescribed.

A critical taxonomic overview of the Byrrhidae of the Palaearctic region was contributed by Jäger & Pütz 2003 in “Catalogue of Palaearctic Coleoptera vol. 3”. 

Contributors from SNSD: Jäger
External collaborators: A. Pütz

Morphology of Coleoptera-Chrysomelinae (Leaf Beetles)

In the leaf beetle subfamily Chrysomelinae two character systems were studied comparatively in a sample of ca. 40 species, and the phylogenetic implications of the results are discussed:

(1) The region between the mesocoxae, which mainly consists of a double-walled infolding that in different chrysomelines either has or lacks a perforation. The presence of a perforation represents a remarkable condition, as for its evolutionary origin external surfaces of the cuticle had to be connected (Klass et al. 2011, Zoologischer Anzeiger).

(2) The metendosternite (a complicated apodeme originating from in between the metacoxae) and the ventral part of the abdomen immediately behind it (Hübler & Klass submitted).

Contributors from SNSD: Hübler, Klass

Axonomy and Phylogeny of Coleoptera-Ciidae

The Ciidae are small to minute members of the Cucujiformia-Tenebrionoidea, which live in polyporous fungi. About 600 species are known worldwide, but the true number of species is surely much higher. Members of our team contribute phylogenetic, taxonomic, and eco-faunistic work on these beetles.

In 2008 a molecular-based phylogenetic analysis has been published that used DNA sequences from 18S, COI, and COII for a sample of 20 ciid species and many cucujiform outgroup taxa (Buder et al. 2008, Arthropod Systematics & Phylogeny). This analysis showed that the genus Cis (to which numerous species are assigned) is grossly polyphyletic, and it provided good support for a few clades within the Ciidae. However, the overall resolution was low and results quite inconsistent among different analytical methods applied (maximum parsimony, maximum likelihood, MrBayes, and direct optimisation).

Many Ciidae show sexual dimorphism, with males having pronotal and/or frontoclypeal projections and a ventro-abdominal gland. A new species from South Africa, Cis pickerifound near Ceres (described in Lopes-Andrade et al. 2009, Zootaxa), additionally showed dimorphic males with projections developed to a very different extent.

The Ciidae fauna of northern Iran (mainly Alburz Mountains) is currently studied including taxonomic, faunistic, and ecological aspects (Rezaei). This region is of particular interest because it harbours many relictual species. The project additionally considers some other mycophagous tenebrionoid groups, such as Mycetophagidae and Tetratomidae.

Contributors from SNSD: Buder, Rezaei, de Oliveira, Klass, Hundsdoerfer
External collaborators: Cristiano Lopes-Andrade (University of Vicosa, Brasil) 

Gland Morphology of Coleoptera-Erotylidae (Pleasing Fungus Beetles)

The Erotylidae (including the former Languriidae) comprise ca 3500 described, small to medium-sized species of often colourful cucujiform beetles that are either phytophagous or live on tree fungus. Our studies focus on the ectodermal glands of these beetles.
There is a maximum set of 6 pairs of compound glands in Erotylidae, but most species only possess some of these. The occurrence of the glands in a sample of ca 35 erotylids was studied mainly by SEM, serching for the external pores (Drilling & Klass in press, Annales de la Société Entomologique de France); a phylogenetic evaluation of the results was based on phylogenetic hypotheses previously published by other authors. 
Morphology at the cellular level was studied (SEM and TEM) in one exemplary species, Tritoma bipustulata, for the compound glands that open in the anterior and posterior corners of the pronotum (Drilling et al. 2010, Organisms, Diversity & Evolution). These consist of a long common duct bearing numerous gland units, each comprising two cells (secretory cell and canal cell); all parts of the gland bear a cuticular intima. This study revealed some structural components that have not been found previously in such glands of Coleoptera. One example is a cuticular strand filling the lumen of the canal cell. In the same species the chemical composition of the secretion of the pronotal gland was examined (Drilling & Dettner 2010, Chemoecology).

Contributors from SNSD: Drilling, Klass
External collaborators: Konrad Dettner (University of Bayreuth, Germany)

Evolutionary Biology and Taxonomy of Stream Dwelling Coleoptera-Elmidae

The predominantly aquatic family Elmidae (riffle beetles) has a global distribution. Most representatives are “True Water Beetles” and occur only in lotic waters due to their microplastron-based respiration. Many elmids are highly sensitive to water pollution and are therefore very useful bioindicators.

A main focus has been the Philippine archipelago, from where several species of the genera Ancyronyx and Prionosolus(Freitag 2008, Koleopterologische Rundschau) have been described in course of the AQUA Palawana program (aquapalawana.nhm-wien.ac.at).

Recent works focus on the larval taxonomy, systematics and phylogeny of Ancyronyx (Freitag & Balke 2011, Zookeys; Freitag 2012, Zootaxa). All its representatives have extremely long legs and strong claws as an adaptation to their habitats. This is partly accompanied by an eye-catching cross-like elytral colour pattern reminiscent of spiders. Furthermore, the genus shows a remarkable distribution pattern (one species in the Nearctic region, all other species from the Oriental region).

The medium-term project goal is the taxonomic revision of the genus Ancyronyx (with inclusion of extensive samples of undescribed material) combined with a study of the phylogenetic relationships among Ancyronyx species and the position of the genus within Elmidae. This altogether aims at reconstructing the evolutionary history of Ancyronyx and related genera in space and time and at tracing shifts of habitat and life history. Methods of molecular genetics (mitochondrial and nuclear gene fragments) as well as classical morphological methods are being used in this project.

Contributors from SNSD: Freitag
External collaborators: Manfred Jaech (Natural History Museum Vienna, Austria), Michael Balke  (Zoological State Collections Munich, Germany)

Faunistic Studies on Coleoptera in the Eastern Part of Germany

The faunistic studies are mostly focused on selected habitats, which are inventorised by repeated collecting over several years, using a number of specialised techniques. Focal taxa are the aquatic Hydrophilidae, Hydraenidae (Polyphaga), and Dytiscoidea (Adephaga). However, inventories are often done together with specialists of other beetle families (external collaborators), whereby a more complete coverage of the beetle fauna of the selected areas is reached. Projects completed during the last decade refer to the “Elbhangbäche am Schönfelder Hochland” near Dresden (Jäger 2004, Entomologische Nachrichten und Berichte; aquatic beetles only), the “Binnensalzstelle Sülten”  (Mecklenburg-Vorpommern; Schmidt et al. 2004, Archiv der Freunde der Naturgeschichte in Mecklenburg), the “Conventer Niederung”  (Mecklenburg-Vorpommern; Schmidt et al. 2007, Archiv der Freunde der Naturgeschichte in Mecklenburg), the “Goldgruben- und Tiergartenteiche bei Schönborn und Linz” near Meißen (Saxony; Jäger & Reike 2012, Sächsische Entomologische Zeitschrift) as well as the Oberlausitz region (eastern Saxony; Klausnitzer et al. 2009, Entomologische Nachrichten und Berichte). Ongoing projects provide inventories of the forest fens of the “Ivendorfer Forst” near Rostock (Mecklenburg-Vorpommern; project at an early stage), of the “Kleinraschützer Heide” near Großenhain (Saxony; Jäger et al., manuscript almost completed), a former military training area, and to the “Sächsische Schweiz” (Jäger & Zinke, manuscript almost completed; only aquatic beetles).

In addition, sporadic collecting by members of the section occasionally leads to the discovery of species very rare in, or new to Saxony. Such opportunities are used for small publications where also various interesting aspects of the beetle species or genus in question are reviewed. Examples are publications on Ptinella aptera (Ptiliidae; Klass et al. 2004, Entomologische Nachrichten und Berichte), Soronia punctatissima (Nitidulidae; Buder et al. 2006, Entomologische Nachrichten und Berichte), Platydema violacea (Tenebrionidae; Grossmann & Klass 2007, Entomologische Nachrichten und Berichte), and Lixus subtilis (Curculionidae; Drilling & Klass 2006, Entomologische Nachrichten und Berichte).

Contributors from SNSD: Jäger, Klass, Buder, Grossmann, Drilling
External collaborators: numerous specialists of beetle taxonomy and faunistics