Resource allocation and time budgeting in adults of the cockroach,Periplaneta americana: The interaction of behaviour and metabolic reserves

Activity (to food, water and shelter) and resource allocation (mass budget, and size of various body components) were examined in populations of adult Periplaneta americana subjected to periods of starvation or sugar feeding. Following 13 days of starvation, roaches ate 5 times their normal daily ration and feeding required about 20 days to return to pre-starvation levels. When sucrose was substituted for the usual dog-food diet for 13 days, there was also a large increase in feeding initially. When the dog food was re-established, however, there was very little feeding for about one week. Although reproduction was markedly curtailed by starvation, females fed sucrose continued reproducing for at least 59 days. The results suggested that the roaches were mainly energy limited. Although the consumption of roaches was strongly affected by reserve depletion, eating was a small component of the time budget, and overall activity was relatively unchanged by starvation or sugar-feeding. There was a slight decrease in activity during starvation, but the circadian pattern remained unchanged. Females carrying oöthecae were highly active and were apparently attracted to food (even though they ate little). Thus the activity of the population was dominated by circadian rhythmicity and the reproductive cycle.     

Antennal motor system of the cockroach, <Emphasis Type="Italic">Periplaneta americana</Emphasis>

The organization of the antennal muscles, nerves, and motor neurons has been investigated in the cockroach, Periplaneta americana. Antennal movements have been observed by video analysis, muscle actions have been determined by dissection and direct mechanical testing, and the motor neurons innervating each muscle have been defined with a recently developed selective backfill method. A model of the antennomotor system of Periplaneta has thus been established and compared with that of crickets. Five muscles located within the head capsule insert on the most proximal antennal segment, the scape. By their action, they allow the scape to move in essentially any direction within the dorsoventral and anteroposterior planes. An additional pair of muscles, one dorsal and one ventral, are found within the scape. They insert on the pedicel and move the pedicel in the dorsal-ventral plane. These seven muscles are controlled by at least 17 motor neurons with somata located in the deutocerebrum. By their action, these motor neurons enable cockroaches to move the long flagellum of each antenna through a wide range of positions in the frontal space, medio-laterally, and also allow depression toward the substrate and elevation well above the level of the head. The antennal motor neurons have been classified into five morphological types based on soma and axon location. Each morphological type has been correlated with a particular pattern of muscle innervation and control. The neurites of all motor neurons are located along the medial aspect of the dorsal lobe of the deutocerebrum. This research was supported by grant nos. IBN 96-04629 and 04-22883 from the National Science Foundation.     

Analysis of Extensive [FeFe] Hydrogenase Gene Diversity Within the Gut Microbiota of Insects Representing Five Families of Dictyoptera

We have designed and utilized degenerate primers in the phylogenetic analysis of [FeFe] hydrogenase gene diversity in the gut ecosystems of roaches and lower termites. H₂ is an important free intermediate in the breakdown of wood by termite gut microbial communities, reaching concentrations in some species exceeding those measured for any other biological system. The primers designed target with specificity the largest group of enzymatic H domain proteins previously identified in a termite gut metagenome. “Family 3” hydrogenase sequences were amplified from the guts of lower termites, Incisitermes minor, Zootermopsis nevadensis, and Reticulitermes hesperus, and two roaches, Cryptocercus punctulatus and Periplaneta americana. Subsequent analyses revealed that all termite and Cryptocercus sequences were phylogenetically distinct from non-termite-associated hydrogenases available from public databases. The abundance of unique sequence operational taxonomic units (as many as 21 from each species) underscores the previously demonstrated physiological importance of H₂ to the gut ecosystems of these wood-feeding insects. The diversity of sequences observed might be reflective of multiple niches that the enzymes have been evolved to accommodate. Sequences cloned from Cryptocercus and the lower termite samples, all of which are wood feeding insects, clustered closely with one another in phylogenetic analyses to the exclusion of alleles from P. americana, an omnivorous cockroach, also cloned during this study. We present primers targeting a family of termite gut [FeFe] hydrogenases and provide results that are consistent with a pivotal role for hydrogen in the termite gut ecosystem and point toward unique evolutionary adaptations to the gut ecosystem.     

Parasitism and decreased response to sex pheromones in malePeriplaneta americana (Dictyoptera: Blattidae)

Parasites are known to alter the behavior of their hosts, but little is known about their effects on responses to sexual stimuli. Periplaneta americanainfected with the acanthocephalan Moniliformis moniliformiswere compared to uninfected animals in their behavioral and electroantennogram responses to a synthetic P. americanapheromone component, periplanone-B, and a pheromone mimic, bornyl acetate. In a t-maze there was no significant difference between infected animals' responses to periplanone-B and a random binomial distribution; the responses of uninfected animals were significantly nonrandom. The electroan-tennogram responses of infected and uninfected animals to bornyl acetate or periplanone-B did not differ significantly, however, indicating that the alteration probably does not occur at the peripheral level but at a central nervous system level.     

Cellular and molecular basis of decision‐making

People think they are in control of their own decisions: what to eat or drink, whom to marry or pick a fight with, where to live, what to buy. Behavioural economists and neurophysiologists have long studied decision‐making behaviours. However, these behaviours have only recently been studied through the light of molecular genetics. Here, we review recent research in mice, Drosophila melanogaster and Caenorhabditis elegans, that analyses the molecular and cellular mechanisms underlying decision‐making. These studies interrogate decision‐making about food, sexual behaviour, aggression or foraging strategies, and add molecular and cell biology understanding onto the consilience of brain and decision.     

Histochemical demonstration of GABA-like immunoreactivity in cobalt labeled neuron individuals in the insect olfactory pathway

Summary Individual olfactory neurons in the antennal lobes of Periplaneta americana were investigated for their morphological and neurochemical properties by means of intracellular cobalt injection and indirect peroxidase-antiperoxidase immunohistochemistry. GABA-like immunoreactivity was demonstrated in many local interneurons but not in uniglomerular projection neurons.     

Could Species Segregation be a Consequence of Aggregation Processes? Example of Periplaneta americana (L.) and P. fuliginosa (Serville)

Our aim was to show how interindividual interactions, based on specific recognition signals that induce aggregation, can lead to the emergence of a segregation pattern between species. Groups including two cockroach species, Periplaneta americana (L.) (P.a.) and Periplaneta fuliginosa (Serville) (Dictyoptera: Blattidae) (P.f.) were tested. Behavioural choice tests between two resting sites demonstrated aggregation behaviour in the two species. Aggregation in both species is based on chemical cues. Periplaneta fuliginosa has a higher aggregation level than P.a. and responds only to its conspecific odour. Periplaneta americana is attracted by the odour of both species presented alone. In the presence of the odours of both species, P.f. selects its own odour, but P.a. neither selects its own odour, nor aggregates under these conditions. This could mean that the perceived chemical signals impair the aggregation process. In mixed groups including larvae of these two species, segregation between species occurs. We assumed that the first species that happened to form an aggregate on one of the resting sites induced the other species to occupy the remaining site. The emergence of a segregation pattern between the two species could be a consequence of the aggregation processes.     

First molecular genetic evidence for automictic parthenogenesis in cockroaches

Parthenogenesis is an asexual mode of reproduction that plays an important role in the evolution of sex, sociality, and reproduction strategies in insects. Some species of cockroach exhibit thelytoky, a type of parthenogenesis in which female offspring are produced without fertilization. However, the cytological and genetic mecha? nisms of parthenogenesis in cockroaches are not well understood. Here we provide the first molecular genetic evidence that cockroaches can reproduce through automixis. Using the American cockroach Periplaneta aniericana, we performed microsatellite analysis to investigate the genetic relationship between parthenogenetically produced nymphs and the parent virgin females, and found that all parthenogenetic offspring were homozygous for autosomal microsatellite markers, whereas the female parents were heterozygous. In addition, flow cytometry analysis revealed that the parthenogenetic offspring were diploid. Taken together, our results demonstrate that P. americana exhibits automixis-type thelytoky, in which diploidy is restored by gamete duplication or terminal fusion. These findings highlight the unique reproduction strategies of cockroaches, which are more varied than was previously recognized.     

Localization of CRF immunoreactivity in the central nervous system of three vertebrate and one insect species

Summary By use of a specific antiserum against synthetic ovine corticotropin-releasing factor (CRF) in the peroxidase-antiperoxidase (PAP) immunocytochemical procedure (Vandesande and Dierickx 1976), CRF-like antigenic determinants were demonstrated in the central nervous system of a human fetus, the Wistar rat, the frog Rana ridibunda, and the American cockroach Periplaneta americana. The immunoreactive CRF-producing cells occur mainly in the nucleus paraventricularis of the rat, while in Rana ridibunda these cells occur in the nucleus praeopticus. Immunoreactive CRF-containing fibres were also visualized. Very clear CRF-immunoreactive products were observed in the brain as well as the corpora cardiaca (CC) and corpora allata (CA) of the cockroach Periplaneta americana. ACTH-immunoreactivity was also demonstrated in the brain-CC-CA complex of this insect. Double immunohistochemical staining (Vandesande 1983) also revealed that both the CRFand ACTH-like substances occur in different neurosecretory neurons and nerve fibres. These results suggest that the antigenic determinants of CRF are very similar in vertebrates and insects bespeaking their very long evolutionary history.     

Pharmacology of octopamine-, dopamine-, and 5-hydroxytryptamine-stimulated cyclic amp accumulation in the corpus cardiacum of the american cockroach,Periplaneta americana L

A variety of potential receptor agonists were incubated with isolated corpora cardiaca from the American cockroach Periplaneta americana to determine their effects on cyclic AMP production in this gland. Octopamine, dopamine, and 5-hydroxytryptamine elevated cyclic AMP levels in a dose-dependent manner with estimated K_a values of 15.8, 1.7, and 1.1 m?M, respectively, and their stimulation was found to be additive. Several vertebrate receptor antagonists were tested against the three amines and a preliminary pharmacological profile developed.     

Comparative actions of the neuropeptides leucopyrokinin and periplanetin CCI on the visceral muscle systems of the cockroaches Leucophaea maderae and Periplaneta americana

1. The effects of two structurally-related peptides, leucopyrokinin (LPK) and periplanetin CC-I (CCI), on contractile activities of visceral muscle systems were compared in the two cockroaches from which these peptides were originally isolated.2. LPK elicited consistent proctolin-like responses on the hindgut, foregut, oviduct and heart of the Madeira cockroach, Leucophaea maderae, with increases in both amplitude and frequency of contraction. CCI, on the other hand, elicited a mostly tonic response on these tissues.3. For the American cockroach, Periplaneta americana, the responses elicited by LPK and CCI were tonic in nature.4. With the exception of the response of the L. maderae hindgut and heart to LPK, threshold levels for either LPK or CCI on all other tissues of both roaches were considerably higher (10–100 times greater) than those for proctolin on the same tissues.5. The maximum response to any concentration of LPK or CCI on the foregut and oviduct of L. maderae and that on the foregut and hindgut of P. americana never reached more than 60% of the maximum contraction achieved with proctolin.     

Rezeptorrauschen und Informationskapazität der Sehzellen vonCalliphora erythrocephala undPeriplaneta americana

Zusammenfassung Die mittlere, effektive Rauschamplitude des Belichtungspotentials wird im Soma der Sehzellen vonCalliphora erythrocephala undPeriplaneta americana in Abhängigkeit von der Lichtintensität gemessen. Sie nimmt mit ansteigender Intensität ab. Für eine Intensitätsspanne von 11000 beträgt sie fürCalliphora erythrocephala 0,440,26 mV und fürPeriplaneta americana 0,670,16 mV. Die Amplitudenverteilung des Rauschens ist gaußförmig. Der Einfluß auf die Informationskapazität (bit/sec) wird für verschiedene Kontrastverteilungen diskutiert; die Informationskapazität ist bei geringen mittleren Lichtintensitäten im Soma der Sehzellen vonCalliphora erythrocephala gering, d.h. bei geringen Beleuchtungsstärken werden Kontraste aus der Umwelt nur schlecht übertragen. In den Axonen der Sehzellen 1–6 wird jedoch durch die präsynaptische Summation der Belichtungspotentiale die Übertragung von Kontrasten gerade bei geringen Beleuchtungsstärken erheblich verbessert (Abb. 5). Die Informationskapazitäten im Soma der Sehzellen vonCalliphora erythrocephala undPeriplaneta americana werden verglichen; die Leistung der Sehzellen bei der Übertragung von Kontrasten vor allem bei geringen Beleuchtungsstärken ist beiPeriplaneta americana erheblich schlechter als beiCalliphora erythrocephala.

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Inherent noise and information capacity in the visual cells ofCalliphora erythrocephala andPeriplaneta americana

Summary When the receptor potential from the soma of the visual cells ofCalliphora erythrocephala andPeriplaneta americana is measured we distinguish the r.m.s. voltage of the noise in dependence on the stimulus light intensity. The r.m.s. voltage of the noise decreases with increasing light intensity. The values for an intensity range of 11000 are 0.440.26 mV forCalliphora erythrocephala and 0.670.16 mV forPeriplaneta americana. The amplitude of the inherent receptor noise has a Gaussian Distribution. The influence on the information capacity of the visual cell is discussed for different contrast distributions as stimulus pattern. The information capacity is decreased at low mean light intensities inCalliphora erythrocephala visual-cell somata, i.e. environmental contrasts are transmitted only weakly at low illuminations. In the axons of visual cells 1–6, however, the transmission of contrasts especially at low illumination intensities is considerably improved by the presynaptie summation of receptor potentials (Fig. 5). The information capacities in the visual cell somata ofCalliphora erythrocephala andPeriplaneta americana are compared; the efficiency of visual cells during the transmission of contrasts, especially at low illumination intensities, is far worse inPeriplaneta than inCalliphora.

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Die Experimente wurden mit Sachmitteln durchgeführt, die Herrn Prof. Dr. Dr. h. c. H. Autrum von der Deutschen Forschungsgemeinschaft zur Verfügung gestellt wurden.     

Protease-mediated prophenoloxidase activation in the haemolymph of American cockroach Periplaneta americana

Prophenoloxidase has been successfully obtained from the haemolymph of the cockroach Periplaneta americana using cane sugar saline solution. The proenzyme was activated by various exogenously added proteases such as chymotrypsin, trypsin, subtilisin and thermolysin. Thermolysin was found to be the greatest activator, followed by chymotrypsin and subtilisin. Chymotrypsin activation showed a lag period when compared with the other proteases tested, indicating that activation by chymotrypsin followed an indirect path, whereas, subtilisin and thermolysin activated the proenzyme directly.Exogenously added protease inhibitor showed inhibition towards protease-mediated prophenoloxidase activation. Benzamidine inhibited chymotrypsin and trypsin activation, whereas soybean trypsin inhibitor inhibited trypsin. In situ inhibitor isolated from the haemocytes of Periplaneta americana inhibited the prophenoloxidase activation and showed evidence for the presence of a built-in inhibition system for the release of the components of the prophenoloxidase activating system of P. americana. Electrophoretic localization of activated phenoloxidase showed two bands, suggesting the dimeric condition of high mol. wt prophenoloxidase.     

Pheromone-stimulated locomotory and orientation responses in the American cockroach

Males of Periplaneta americana respond to the sex pheromone secreted by females with increased locomotion and positive chemo-orientation. Both sexes orient toward aggregation pheromone without an increase in locomotion. Immediately following removal of one antenna males exhibit ‘circus’ movements, but after 2 days orient toward pheromones; a bi-modal mechanism of chemo-orientation is proposed. Cockroaches turn away from air currents, but orient toward air currents carrying sex or aggregation pheromone, suggesting the possibility of up-wind orientation. Antennae deflect upward and outward when pheromone is first perceived; the head then moves toward the pheromone source. Following removal of one antenna, the pattern of head and antennal movement changes in a manner which enhances the sweeping of the intact antenna.     

The shadow response of the cockroach periplaneta americana

We show that the “escape response” (running) of the cockroach Periplaneta americana is interrupted when the insect runs through a shadow. Shadows were cast by holding an opaque plastic sheet so that the cockroach ran beneath it. In control experiments, a similarly positioned clear plastic sheet was ineffective. Removal of the shadow stimulus allowed running to continue. The likelihood that cockroaches would resume running after removal of the shadow stimulus decreased with the time they were allowed to remain in shadow.     

Evolution of nubbin function in hemimetabolous and holometabolous insect appendages

Insects display a whole spectrum of morphological diversity, which is especially noticeable in the organization of their appendages. A recent study in a hemipteran, Oncopeltus fasciatus (milkweed bug), showed that nubbin (nub) affects antenna morphogenesis, labial patterning, the length of the femoral segment in legs, and the formation of a limbless abdomen. To further determine the role of this gene in the evolution of insect morphology, we analyzed its functions in two additional hemimetabolous species, Acheta domesticus (house cricket) and Periplaneta americana (cockroach), and re-examined its role in Drosophila melanogaster (fruit fly). While both Acheta and Periplaneta nub-RNAi first nymphs develop crooked antennae, no visible changes are observed in the morphologies of their mouthparts and abdomen. Instead, the main effect is seen in legs. The joint between the tibia and first tarsomere (Ta-1) is lost in Acheta, which in turn, causes a fusion of these two segments and creates a chimeric nub-RNAi tibia–tarsus that retains a tibial identity in its proximal half and acquires a Ta-1 identity in its distal half. Similarly, our re-analysis of nub function in Drosophila reveals that legs lack all true joints and the fly tibia also exhibits a fused tibia and tarsus. Finally, we observe a similar phenotype in Periplaneta except that it encompasses different joints (coxa–trochanter and femur–tibia), and in this species we also show that nub expression in the legs is regulated by Notch signaling, as had previously been reported in flies and spiders. Overall, we propose that nub acts downstream of Notch on the distal part of insect leg segments to promote their development and growth, which in turn is required for joint formation. Our data represent the first functional evidence defining a role for nub in leg segmentation and highlight the varying degrees of its involvement in this process across insects.     

Ultrastructural study of cholecystokinin-like immunoreactivity in endocrine cells of the insect midgut

Summary Electron-microscopic immunocytochemistry for the demonstration of CCK-like material in basal endocrine cells of the midgut of Aeschna cyanea, Locusta migratoria, Carausius morosus and Periplaneta americana was performed by use of the peroxidase-antiperoxidase procedure and the colloidal gold method. Immunoreactive cells appeared scattered among digestive and regenerative cells of the epithelium. Immunoreactivity was specifically detected over round to oval electron-dense granules whose size appeared rather different from species to species. Thus, the average size of 30% (d30) of the largest granules ranged from 312 nm in Periplaneta americana to 159 nm in Carausius morosus with intermediate values in Aeschna cyanea (d30=195 nm) and Locusta migratoria (d30=225 nm).     

Blattabacteria,the endosymbionts of cockroaches,have small genome sizes and high genome copy numbers

Blattabacteria are intracellular endosymbionts of cockroaches and primitive termites that belong to the class Flavobacteria and live only in specialized cells in the abdominal fat body of their hosts. In the present study we determined genome sizes as well as genome copy numbers for the endosymbionts of three cockroach species, Blattella germanica, Periplaneta americana and Blatta orientalis. The sole presence of blattabacteria in the fat body was demonstrated by rRNA‐targeting techniques. The genome sizes of the three blattabacteria were determined by pulsed field gel electrophoresis. The resulting total genome sizes for the three symbionts were all approximately 650 ± 15 kb. Comparison of the genome sizes with those of free‐living Bacteroidetes shows extended reduction, as occurs in other obligatory insect endosymbionts. Genome copy numbers were determined based on cell counts and determination of DNA amounts via quantitative PCR. Values between 10.2 and 18.3 and between 323 and 353 were found for the symbionts of P. americana and B. orientalis respectively. Polyploidy in intracellular bacteria may play a significant role in the genome reduction process.     

Orientation to sex pheromone in the American cockroach: Analysis of chemo-orientation mechanisms

Male Periplaneta americana were photographed in a 2.4 m diameter arena containing a female sex pheromone source in the centre. Orientation pathways were digitized and analysed with regard to chemo-orientation mechanisms employed. Indirect components of chemo-orientation include arrestment near the pheromone source owing to an increase in turning rate and decrease in rate of locomotion, and zig-zag motor patterns that facilitate localization of the source. Most males were successful in locating the source if they moved to within 30 cm. Direct components of chemo-orientation include looping and relatively sharp correcting turns.No significant differences in orientation were observed between intact and unilaterally-antennectomized males, except that correcting turns close to the pheromone source were significantly less precise in males with one antenna. These results indicate that males with two antennae have an advantage over males with one antenna in being able to employ simultaneous information processing close to the pheromone source. Males with crossed antennae were unable to locate the pheromone source, suggesting that the fixed position of their antennae interfered with sensory information input.     

Gross and fine structure of the antennal circulatory organ in cockroaches (Blattodea,Insecta)

The antennal circulatory organ of Periplaneta americana and Blaberus craniifer was investigated by light and electron microscopy. This organ consists of two pulsatile ampullae located near the antennal base which are interconnected by a large transverse muscle and associated blood vessels which run into the antennae. Diastole is caused simultaneously in both ampullae by the transverse muscle. Systole is produced passively by the elasticity of the wall of the ampullae and minute accessory tendons. Both elastic structures contain fine unbanded extracellular filaments. The antennal vessels possess two distinct regions: a proximal convoluted region lying within the hemocoel of the head and a narrower distal region running through the antenna and opening near the antennal apex. The length of the proximal portion increases markedly during ontogeny in correlation with the growing antenna. Its wall consists of a high-prismatic epithelium ensheathed by a thick layer of collagen fibrils. The structure of the wall cells is comparable to that found in some salt transporting epithelia: it shows a polar organization with basal infoldings, a large number of mitochondria, and typical arrangement of the junctions or mitochondrial-scalariform junctional complexes. The possible physiological function of this epithelium in ionic or osmoregulation of the hemolymph entering the antenna is discussed. The wall of the distal vessel region consists of a flat single-layered epithelium and seems to be specialized only for delivery of hemolymph to antennae. The structure and function of the antennal heart in cockroaches is compared to that found in other insects.