The cercal receptor system of the praying mantid,Archimantis brunneriana Sauss.

Summary The cerci of the praying mantid, Archimantis brunneriana Sauss., are paired segmented sensory organs located at the tip of the abdomen. Basally the cercal segments are slightly flattened dorso-ventrally and are fused to such a degree that it is difficult to distinguish them. Distally the segments become progressively more flattened laterally and their boundaries become more obvious.Two types of sensilla are present on the cerci, trichoid sensilla and filiform sensilla. Trichoid hairs are longest on the medial side of the cerci and toward the cercal base. On the proximal cercal segments they are grouped toward the middle of each segment while they are more uniformly distributed on the distal segments. Filiform sensilla are found at the distal end of each segment except the last and are most abundant on the middle segments of the cercus. Both the number of cercal segments and the number of sensilla are variable. Trichoid hairs are highly variable in appearance from short and stout to long and thin. They arise from a raised base, have a fluted shaft, and some have a pore at the tip. They are innervated by from one to five dendrites, one of which is always considerably larger than the others. Some of the dendrites continue out into the shaft of the hair.Filiform hairs have fluted shafts and are mounted in a flexible membrane within a cuticular ring in a depression. They are innervated by a single large sensory neuron, the dendrite of which passes across a flattened area on the inner wall of the lumen of the hair. The dendritic sheath forms the lining of the ecdysial canal and is therefore firmly attached to the hair. The dendrite is attached to the sheath by desmosomes distally and is penetrated by projections of the sheath more proximally. A fibrous cap surrounds the dendrite and may hold it in place relative to the hair.The cercal receptor system of Archimantis is compared to those of cockroaches and crickets.     

Transneuronal uptake of horseradish peroxidase in the central nervous system of dipterous insects

Summary Horseradish peroxidase (HRP) applied to lesioned neurons in the retina and thoracic ganglia of the flies Musca, Calliphora and Drosophila labeled axon terminals, dendrites and perikarya of the severed neurons after anterograde or retrograde passage. In addition, HRP reaction product secondarily labeled intact neurons that are contiguous with injured nerve cells. In many cases labeling of optic lobe neurons remote from primarily filled ones was also seen (here called tertiary labeling). HRP labeling was extensive and both primarily and transneuronally filled neurons could be resolved in almost as much detail as Golgi-impregnated or cobalt-silver-labeled cells. Electron microscopy showed that in both primarily and secondarily filled neurons, reaction product was distributed diffusely in the cytoplasm.Transneuronal uptake of HRP was specific to certain types of neurons in the brain and thus displayed certain pathways. The pathways resolved by transneuronal labeling with HRP extend from the optic lobes to the thoracic ganglia and include visual neurons previously identified electrophysiologically and anatomically.Transneuronal HRP uptake, although believed to occur in vivo, could not be shown to be dependent on synaptic activity. Three other heme peptides tested were taken up by injured neurons, but showed no transneuronal labeling: lactoperoxidase, cytochrome c, and microperoxidase.     

Mitotic waves and embryonic pattern formation: No correlation inCallosobruchus (Coleoptera)

Summary In early insect embryogenesis, mitosis (which is not accompanied by cell division) often starts at one or both egg poles and spreads like a wave over the egg. Relationships between these waves and those processes which coordinate spatial cell differentiation have been proposed. One possibility is that the egg region which has a slower mitotic rate may become temporally advanced in differentiation because of its longer interphase periods, so that the egg becomes polarized (Agrell 1962). Alternatively, the mitotic waves might reflect the position of different determined states (Kauffman 1973). We investigated the mitotic waves inCallosobruchus eggs, treated to produce 20% partially reversed segment sequences (double abdomens). In normal eggs, mitotic waves move predominantly from anterior to posterior whereas in treated eggs, the reversed posterior to anterior orientation was predominant. Despite this, we concluded that mitotic waves do not reflect processes involved in the specification of segment position because the reversal of mitotic waves was more than twice as frequent as the reversal of segment sequence and because they occurred in various control experiments in which there was no reversal of segment sequence.     

High densities of leaf‐tiers in open habitats are explained by host plant architecture

1. Crown architecture remains one of the least studied plant traits that influence plant–herbivore interactions. The hypotheses that dense crown architecture of mountain birches from open habitats favours leaf‐tying caterpillars through bottom‐up and/or top‐down effects associated with high leaf connectivity were tested. 2. Population densities of leaf‐tying herbivores in open (industrial barren and seashore) habitats were three times as high as in the shaded (forest) habitats. An experimental increase in leaf density by branch binding did not affect foliar consumption by free‐living herbivores but increased consumption by leaf‐tiers. 3. The specific leaf weight was lower in shaded habitats and in bound branches, but branch binding did not influence either the foliar concentrations of carbon and nitrogen or the pupal weight of the most abundant leaf‐tier, Carpatolechia proximella Hbn. (Lepidoptera: Gelechiidae). 4. Caterpillars of C. proximella build several shelters during their lifetime and spend a considerable amount of time outside the shelter, where they excrete most of their faeces. In bound branches, caterpillars built new shelters more frequently than in control branches, and consumed less foliar biomass per shelter. 5. Mortality from parasitoids in bound branches was half that in the control, presumably because the complex environment disrupted parasitoid searching behaviour and/or because of lower damage to leaves from which the shelters were built. 6. It is concluded that the crown architecture associated with high leaf connectivity decreases mortality risks from natural enemies both outside and inside the shelter. Compact and dense crowns of host plants may at least partly explain high population densities of leaf‐tiers in open habitats.     

Improved PC1/3 production through recombinant expression in insect cells and larvae

Protein convertase 1/3 is a serine endoproteinase present in the regulated secretory pathway of endocrine and neuroendocrine cells. It is responsible for the processing of numerous prohormones and proneuropeptides into their biologically active moieties, often following cleavage at pairs of basic residues. The determination of its three-dimensional structure, as well as the understanding of its enzymatic properties, would greatly benefit from the production and availability of large amounts of recombinant enzyme. We report herein improvements in the production of PC1/3 by expressing recombinant mutated forms in both insect cells (Spodoptera frugiperda, Sf9 cells) and larvae (Trichoplusia ni commonly referred to as cabbage looper). On one hand, we deleted the last 135 COOH-terminal residues of mPC1/3 and, on the other hand, we replaced the signal peptide of mPC1/3 by the viral glycoprotein gp67 signal peptide. These modifications were shown to improve markedly (up to 125%) the secretion into the Sf9 cells medium and the amount of enzymatic activity recovered when compared to the original vector. Moreover, intracoelemic injection of the vectors into insect larvae led to the production and purification of enzymatically active enzyme at a level of 30 microg/larva in the case of mPC1/3 and to the production of a high amount of another enzymatically active convertase, PC7. The optimal viral titer for infection of larvae was determined to be 10(6)pfu/ml. Taking into account the purification protocol combined with the ease and efficiency of using larvae, it should now be possible to meet the needs for biochemical and structural studies.     

Sperm structure and spermiogenesis in Coletinia sp. (Nicoletiidae, Zygentoma, Insecta) with a comparative analysis of sperm structure in Zygentoma

The spermatozoon of Coletinia sp. has a bilayered acrosome, a short nucleus (4 microm) and a relatively short sperm tail with two mitochondrial derivatives. The chromatin is uniformly dense except for several electron-lucid channels or strands which permeate the nucleus and which originate in the spermatid as invaginations of the nuclear envelope. The invaginations occur mostly or exclusively along two meridians of the spermatid that are also characterized by the presence of a longitudinal rod of medium electron density. The two rods (designated as 'mid-spermatid rods') evidently are instrumental in the formation of the electron-lucid channels. The significance of this elaborate system of intranuclear channels is not understood. The sperm tail has a 9 + 9 + 2 axoneme with each of the nine microtubular doublets accompanied by an accessory microtubule; scant intertubular material can also be distinguished. Hence, the tail axoneme resembles that of many pterygote insects. Each of the two mitochondrial derivatives contains a crystalline inclusion that has periodically spaced layers going in different directions on either side of the midline. Two synapomorphic traits appear to be shared by Ateluridae and Nicoletiidae, namely the invaginations of the nuclear membrane along two meridians of the nucleus and the shape of the crystalline inclusions of the mitochondrial derivatives. Four species from the family Lepismatidae were also examined as to their sperm ultrastructure. Three of them, Allacrotelsa kraepelini, Ctenolepisma longicaudata and Ctenolepisma sp., were found to be very similar to the two previously examined lepismatids, Thermobia domestica and Lepisma saccharina. On the other hand, spermatozoa of Tricholepisma aurea were aggregated in small groups rather than pairwise joined as seen in the other lepismatids. Sperm characters are also used to reconstruct a phylogenetic hypothesis which suggests a close relationship between Ateluridae and Nicoletiidae.