Penetration mechanics of elongated female and male genitalia of earwigs.

We unveiled the penile penetration mechanics of two earwig species, Echinosoma horridum, whose intromittent organ, termed virga, is extraordinarily long, and E. denticulatum, whose virga is conversely short. We characterised configuration, geometry, material and bending stiffness for both virga and spermatheca. The short virga of E. denticulatum has a material gradient with the stiffer base, whereas the long virga of E. horridum and the spermathecae of both species are homogeneously sclerotised. The long virga of E. horridum has a lower bending stiffness than the spermatheca. The virga of E. denticulatum is overall less flexible than the spermatheca. We compared our results to a previous study on the penetration mechanics of elongated beetle genitalia. Based on the comparison, we hypothesised that the lower stiffness of the male intromittent organ comparing to the corresponding female structure is a universal prerequisite for the penetration mechanics of the elongated intromittent organ in insects.

Egg structure of five antarctoperlarian stoneflies (Insecta: Plecoptera, Antarctoperlaria).

The egg structures of five antarctoperlarian species - Stenoperla prasina of Eustheniidae; Austroperla cyrene of Austroperlidae; and Zelandobius truncus, Megaleptoperla grandis, and Acroperla trivacuata of Gripopterygidae, were examined in detail, and the groundplan of the egg structure was considered within the representative lineages of Antarctoperlaria and Plecoptera. The flattened egg shape and the circular arrangement of micropyles along the equator are regarded as potential autapomorphies for not only Eustheniidae but also for Eusthenioidea. Austroperlidae has eggs with thin, less-sclerotized chorion, a gelatinous layer on the surface, and micropyles roughly and randomly arranged along the equator. A significant ultrastructural difference between the attachment disc in Gripopterygidae and the anchor plate of arctoperlarian Systellognatha suggests that these structures were independently derived. The thin less-sclerotized chorion represents a groundplan feature in Plecoptera, along with micropyles arranged in a circle, including those circularly arranged along the equator of the egg. On the other hand, in contrast to previous understanding, the sclerotized hard chorion is regarded as a derived feature, having been independently acquired in each of Eustheniidae and Gripopterygidae of Antarctoperlaria and Systellognatha of Arctoperlaria.

Pest and natural enemy: how the fat bodies of both the southern armyworm Spodoptera eridania and the predator Ceraeochrysa claveri react to azadirachtin exposure.

The effects of biopesticides on insects can be demonstrated by morphological and ultrastructural tools in ecotoxicological analysis. Azadirachtin-based products are widely used as biopesticides, affecting numerous insect populations. Through morphological biomarkers, this study aimed to characterize the fat bodies of both the southern armyworm Spodoptera eridania and the predator Ceraeochrysa claveri after chronic exposure to azadirachtin. Larvae of S. eridania and C. claveri were fed with fresh purple lettuce leaves (Lactuca sativa) and egg clusters of Diatraea saccharalis treated with azadirachtin solution of 6 mg active ingredient (a.i.)/L and 18 mg a.i./L for 7 days, respectively. The biological data showed a significant reduction in survival and body mass in S. eridania and cytotoxic effects in the parietal and perivisceral fat bodies in both species. Ultrastructural cell damage was observed in the trophocytes of both species such as dilated cisternae of the rough endoplasmic reticulum and swollen mitochondria. Trophocytes of S. eridania and C. claveri of the parietal and perivisceral layers responded to those injuries by different cytoprotective and detoxification means such as an increase in the amount of cytoplasmic granules containing calcium, expression of heat shock protein (HSP)70/HSP90, and development of the smooth endoplasmic reticulum. Despite all the different means of cytoprotection and detoxification, they were not sufficient to recover from all the cellular damages. Azadirachtin exhibited an excellent performance for the control of S. eridania and a moderate selectivity for the predator C. claveri, which presents better biological and cytoprotective responses to chronic exposure to azadirachtin.

Morphogenesis of serial abdominal outgrowths during development of the viviparous dermapteran, Arixenia esau (Insecta, Dermaptera).

The embryos and first instar larvae of the epizoic earwig, Arixenia esau, develop sequentially in two different compartments of the female reproductive system, that is ovarian follicles and the lateral oviducts (the uterus). Here we show that the second (intrauterine) phase of development consists of three physiologically disparate stages: early embryos (before dorsal closure, surrounded by an egg envelope), late embryos (after dorsal closure, surrounded by an egg envelope) and the first instar larvae (after "hatching" from an egg envelope). Early and late embryos float in the fluid filling the uterus, whereas the first instar larvae develop attached to the uterus wall. Our analyses revealed also that in Arixenia serial multilobed outgrowths develop on dorso-lateral aspects of all abdominal segments. At the onset of the third developmental stage and after liberation from an egg envelope, these outgrowths (or more precisely their lobes) adhere to the epithelium lining the uterus, forming a series of small contact sites, where the mother and embryo tissues are separated only by a thin, presumably permeable, embryonic cuticle. We suggest that all these contact sites collectively constitute a dispersed placenta-like organ involved in the nourishment of the embryo.

Excretion in the mother's body: modifications of the larval excretory system in the viviparous dermapteran, Arixenia esau.

The vast majority of Dermaptera are free-living and oviparous, i.e., females lay eggs within which embryonic development occurs until the larva hatches. In contrast, in the epizoic dermapteran Arixenia esau, eggs are retained within mother's body and the embryos and first instar larvae develop inside her reproductive system. Such a reproductive strategy poses many physiological challenges for a mother, one of which is the removal of metabolic waste generated by the developing offspring. Here, we examine how the Arixenia females cope with this challenge by analyzing features of the developing larval excretory system. Our comparative analyses of the early and late first instar larvae revealed characteristic modifications in the cellular architecture of the Malpighian tubules, indicating that these organs are functional. The results of the electron probe microanalyses suggest additionally that the larval Malpighian tubules are mainly involved in maintaining ion homeostasis. We also found that the lumen of the larval alimentary track is occluded by a cellular diaphragm at the midgut-hindgut junction and that cells of the diaphragm accumulate metabolic compounds. Such an organization of the larval gut apparently prevents fouling of the mother's organism with the offspring metabolic waste and therefore can be regarded as an adaptation for viviparity.

The legs of "spider associated" parasitic primary larvae of Mantispa aphavexelte (Mantispidae, Neuroptera) - Attachment devices and phylogenetic implications.

The legs of the primary larva of Mantispa aphavexelte, parasite in egg sacks of spiders, were examined using scanning electron microscopy (SEM), histology and confocal laser scanning microscopy (CLSM). The leg morphology is described in detail, including intrinsic muscles. Functional adaptations of the leg attachment devices are discussed, especially regarding the material composition. For example, a sole-like flexible ventral tarsal surface containing resilin is combined with sclerotized pseudo-claws. This likely enables the larvae to cope with surface structures on the spider's body, with substrates on the ground, and also with various structural elements in the spider's nest. The leg morphology is evaluated with respect to phylogenetic affinities. A trumpet-shaped, elongated empodium has likely evolved early in the evolution of Neuroptera and may consequently belong to the groundplan of a large subgroup of the order. It characterizes most groups of the hemerobiform lineage and is also present in the myrmeleontiform Psychopsidae. The presence of a tarsal protrusion resembling a pretarsus confirms the monophyletic origin of Mantispoidea. A single fixed tooth and a specific surface structure are potential autapomorphies of Mantispidae. A distal tibial subunit partly separated from the main part of the leg segment is an apomorphy only described for larvae of M. aphavexelte.

Versatility of Turing patterns potentiates rapid evolution in tarsal attachment microstructures of stick and leaf insects (Phasmatodea).

In its evolution, the diverse group of stick and leaf insects (Phasmatodea) has undergone a rapid radiation. These insects evolved specialized structures to adhere to different surfaces typical for their specific ecological environments. The cuticle of their tarsal attachment pads (euplantulae) is known to possess a high diversity of attachment microstructures (AMS) which are suggested to reflect ecological specializations of different groups within phasmids. However, the origin of these microstructures and their developmental background remain largely unknown. Here, based on the detailed scanning electron microscopy study of pad surfaces, we present a theoretical approach to mathematically model an outstanding diversity of phasmid AMS using the reaction-diffusion model by Alan Turing. In general, this model explains pattern formation in nature. For the first time, we were able to identify eight principal patterns and simulate the transitions among these. In addition, intermediate transitional patterns were predicted by the model. The ease of transformation suggests a high adaptability of the microstructures that might explain the rapid evolution of pad characters. We additionally discuss the functional morphology of the different microstructures and their assumed advantages in the context of the ecological background of species.

The structure and ultrastructure of the egg capsules of stoneflies of the genus Isoperla (Insecta, Plecoptera, Perlodidae).

The egg capsules of five systellognathan stoneflies species representing the genus Isoperla (Plecoptera, Perlodidae) have been investigated using light and electron microscopes (SEM and TEM). We consider the structural modifications of egg coverings (egg capsules, eggshells) like: a shape of a capsule, presence of structures fixing an egg to the substratum under water, intrachorionic aeropylar system facilitating gas exchange as a factor adapting an egg/embryo to the environment. The structures protecting eggs against desiccation during a female flight before oviposition into water as well as against the dangers of external mechanical injury caused by turbulences in rapid water currents of mountain streams are described and discussed. The ground plan of the egg capsule in arctoperlarian stoneflies is also discussed.