Destruction in vivo de neurones ocellaires chez la Blatte, Periplaneta americana

Cobalt chloride has on the ocellus of the cockroach Periplaneta americana, the same destroying effect as a thermocauterisation or electrocoagulation. When an iontophoretic diffusion of cobalt chloride is done without any current from the ocelli, the second-order ocellar neurons are destroyed yet no modification is observed in the vital functions of the cockroach. Cobalt chloride iontophoresis could be used to destroy ocellar neurons only if these ocellar neurons are not going to be immediately replaced. Experiments show that the ocellar neuron killed is replaced after apolysis, but if the substitute neuron is destroyed in its turn, the destruction is definitive. These results suggest two methods of destruction for second-order ocellar neurons: one for larvae and one for adult cockroaches.     

Etude ultrastructurale des corpora cardiaca et de quelques formations annexes chez Locusta migratoria L.

Résumé Les corpora cardiaca de l'adulte de Locusta migratoria sont formés de deux régions bien individualisées ce qui nous a permis de reconnaître la sécrétion propre des différents types de neurosécrétion. Dans la région nerveuse, nous distinguons par la taille des grains trois types de neurosécrétion dense classique et un quatrième type d'aspect clair. Dans la région »propre« non nerveuse, les cellules ont des caractères nettement endocriniens et sont mélangées à un seul type d'axones neurosécréteurs.

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Ultrastructural study of the corpora cardiaca and affiliated structures in Locusta migratoria L.

Summary The corpora cardiaca of adult Locusta migratoria consist of two well separated areas, a fact which permits the differentiation between intrinsic and extrinsic neurosecretory material. In the neural area three types of electron dense classical neurosecretory granules, and a fourth more lucent type can be distinguished according to size. In the non-neural glandular area typical endocrine cells mingle with only one type of neurosecretory axons.

     

Sorptionsmessungen an den beiden Schabenarten Periplaneta americana und Blaberus trapezoideus

The absorption rate of adult males of the two cockroaches Periplaneta americana and Blaberus trapezoideus has been investigated by weight measurements and a tracer method.Both species loose weight in 26°C and 33%, 53%, 78%, and 98% relative humidity, and they finally die after a weight loss of 25 to 35%. Even in a high air humidity there is always a certain loss of weight. This weight loss masks the small absorption rate—shown by tracer methods—which increases disproportionally with rising humidity. The absorption represents probably a passive transport because narcotized animals show the same rate of absorption as normal insects. Also, there is a reduction of the absorption rate during exposure time. The water exchange between the animal and its atmosphere is therefore likely to lead to an equilibrium between the radioactive atmosphere and the unlabelled body water.Absorption occurs over the whole body surface. The amount absorbed via the posterior wing and the anus has no ecological significance. P. americana shows a higher cuticular permeability than B. trapezoideus.     

Nutrition de quelques myxomycetes en cultures pures et associees et leurs proprietes antibiotiques

Sans résumé     

Behavioural responses to female sex pheromone components in Periplaneta americana

Female American cockroaches, Periplaneta americana, release two sex pheromones, periplanone-A and periplanone-B, each of which is perceived by a specialized receptor type on the male antennae. This study investigates whether male behavioural responses to both components may differ qualitatively or quantitatively. Running, upwind orientation and wing-raising were evoked by stimulation with either component. The intensity of running increased with stimulus concentration in much the same way for both substances. However, the relative effectiveness of periplanone-A was 30 times lower in behavioural assays than in the electroantennogram. Behavioural responses to periplanone-B declined faster and were more easily adapted by repeated stimulation than those to periplanone-A. It is hypothesized that periplanone-B is responsible for long distance attraction while periplanone-A influences male behaviour near the female.     

Mechanisms of pheromone inactivation in the gut of Periplaneta americana

The sex attractant of the cockroach, Periplaneta americana, has been shown in earlier work to be largely inactivated by dissected midgut from males and from mated females. It is only slightly inactivated by the midgut from virgin females. In this paper, the sex pheromone inactivating system is further studied and shown to be active in late instar larvae of both sexes. In the male this pheromone inactivation is inhibited by piperonyl butoxide, a microsomal oxidase inhibitor. This compound appears to act on the midgut tissue directly. In the mated female, piperonyl butoxide has little effect. When the pheromone inactivating capacity is partitioned into soluble and tissue components, it appears that the soluble component is most active in the male, whereas the tissue component is most active in the female. Evidence from heat inactivation, trichloracetic acid precipitation, and the use of soy bean trypsin inhibitor, as well as the time course of the reaction, suggest that the factor or factors inactivating pheromone are proteins, probably enzymes. Evidence that at least part of the pheromone inactivating capacity is due to microsomal oxidases is considered. It is also observed that both pheromone and piperonyl butoxide absorb to membranes.     

Haemolymph lipase activity in the American cockroach, Periplaneta americana

The haemolymph of the cockroach, Periplaneta americana, has been shown to possess pronounced lipolytic activity. The enzyme may be considered a ‘true’ lipase because of its ability to hydrolyse long chain fatty acid glycerides. The enzyme exhibits dual optima at pH 4·9 and 7·0 and is inhibited by fluoride ion. Lipase activity in the intact cockroach is unaffected by the corpus cardiacum hypolipemic factor; however, prolonged periods of starvation result in a significant decline in enzyme activity.     

One trial learning in the American cockroach, Periplaneta americana

A new and simple method of training intact cockroaches was designed. (1) Cockroaches were maintained before and during the experiment with a high motivation to look for sugar. They were kept in a chamber with water and yeast extract ad libitum but without any sugar. (2) Cockroaches were individually trained to associate two artificial scent signals, i.e. menthol and vanilla, with sugar and salt solutions. Discriminatory learning performance was measured by testing the scent preference before and after training. Care was taken to exclude other than olfactory cues in the discriminatory paradigm. (3) Cockroaches exhibited a spontaneous initial preference for vanilla over menthol. This preference could be modified by training. The insect showed fast learning and long retention. One training trial was enough to reverse the initial preference with a significant retention after 7 days. Reversal of trained preference was accomplished by retraining. (4) The method provides an opportunity to study sensory performance and memory consolidation in cockroaches.     

Corpus allatum regulation during the metamorphosis of Periplaneta americana: Axon pathways

The anatomy of the retrocerebral complex was studied after supravital staining with methylene blue, and axonal tracts within the corpora allata (CA) were traced after applying the CoCl₂ technique together with Timm's sulfide-silver enhancement. Cobalt chloride fills of the nerves to and from the CA revealed two major sources of innervation: the brain and the subesophageal ganglion. Three cell clusters in the brain contribute axons that reach each nervus corporis allati I (NCA I) and, apparently, pass to or beyond the CA. These are: a cluster of 8 to 12 cells in the contralateral pars lateralis, a cluster of 16 to 20 cells in the ipsilateral pars lateralis, and a cluster of 50 to 60 cells in the contralateral pars intercerebralis. PAF-stained sections of other brains revealed a corresponding number of PAF-positive cells in these same regions. The medial and lateral neurons arborize in the neuropile adjacent to the pars intercerebralis, and may associate there. The lateral group also arborizes extensively in the neuropile surrounding the pedunculus of the mushroom body. At least four cell bodies located antero-ventrad in the subesophageal ganglion send axons to the CA via each nervus corporis allati II (NCA II).To determine possible inhibitory pathways to the CA, the NCA I, NCA II, and postallatal nerves of last instar larvae were severed; either singly, or in combination. Additional experiments were performed on last instar larvae to substantiate that superlarvae were a direct result of an enhanced or sustained juvenile hormone titre. These experiments included: implanting two or more CA, extirpating one CA, or applying 100 μg of Altosid topically onto allatectomized larvae. The experiments indicated that only NCA I is an inhibitory pathway and that superlarvae were a direct consequence of CA activation. NCA II does not seem to provide the CA with an essential excitatory innervation; when it and NCA I are severed a supernumerary apolysis will still result. Some of the cells in the brain stainable by the CoCl₂ method are most probably identical to those that are PAF-positive. These cells may inhibit the CA in last instar larvae via neurosecretomotor junctions.     

Circadian rhythmicity in the nervous system of the cockroach, Periplaneta americana

Diurnal rhythmicity of nervous activity in Periplaneta americana was investigated, using acetylcholine (ACh) content, acetylcholinesterase (AChE) and spontaneous electrical activities as indices. AChE and electrical activities were maximum at 0 hr and minimum at 12 hr, while ACh showed an opposite rhythm. Central nervous system extract from cockroaches at 12 hr elevated the electrical activity while 0 hr-extract exerted inhibition. Lower concentrations of ACh had an elevatory influence while higher concentrations inhibited the electrical activity. A hypothesis is proposed, suggesting synthetic and releasing phases of ACh in a regular diurnal cycle, to explain the results obtained.     

Transport of bacterial end products from the colon of Periplaneta americana

The possible contribution of fermentation products produced by the anaerobic bacterial hindgut flora of Periplaneta americana was examined with respect to the physiology of the host. The microbial flora of the ileum and colon produced readily detectable quantities of short chain acids in vivo. Experiments where [¹⁴C] acids were injected into the hindgut indicated these products were transported out through the gut wall in vitro and in vivo. Other data underscore the importance of considering the metabolic capabilities of the gut microflora when using dyes as controls in studies on insect gut function.     

Isolation of proctolin,a myotropic peptide,from Periplaneta americana

The isolation of a myotropic substance, proctolin, associated with the innervation of the viscera of the cockroach, Periplaneta americana, is reported. Proctolin, previously described as a neurotransmitter or neurohormone, is a small basic peptide with an estimated molecular weight of 500 to 700. The proctodeal (hindgut) muscles of P. americana contract at threshold levels of about 0·5 ng/ml, equivalent to about 10⁻⁹ M proctolin. Approximately 180 μg proctolin were isolated from 125 kg of whole cockroaches. The isolated peptide was homogeneous on paper and thin-layer chromatography and on high-voltage paper electrophoresis at pH 3·5 and 6·4.     

Etude comparee des lipides et de la fixation passive du calcium dans les racines et les fractions subcellulaires du Lupinus luteus et de la Vicia faba

In both lupin and broad bean, the root lipids contain paraffins, triglycerides, diglycerides, free fatty acids and polar lipids (phospholipids and galactolipids). The polar lipids and the triglycerides are the more abundant classes. The root galactolipids are mono- and di-galactosyldiglycerides; two steryl glycosides are also present. The phospholipids in both species are: phosphatidylinositol, phosphatidylcholine, phosphatidylglycerol, phosphatidylserine, phosphatidylethanolamine, diphosphatidylglycerol and phosphatidic acid. This last phospholipid represents 8·3% of total lipid phosphorus in Lupinus against 2·3% in Vicia. The other acidic phospholipids represent 30·4% in Lupinus against 20·9% in Vicia. The lipids of Lupinus are rich in linolenic acid whereas those found in Vicia are richer in linoleic acid. The various subcellular fractions prepared from the roots of both species have an homogeneous lipid composition, reflecting exactly that of entire cells. The calcium passive fixation capacity in microsomes and mitochondria of Lupinus roots is more important than that in the same organelles of Vicia faba roots. Thus a relationship is suggested between the amount of phospholipids in membranes and the passive fixation of calcium.     

Serotonin in the central nervous system of the cockroach, Periplaneta americana

Studies on serotonin in the insect nervous system has long been neglected, although serotonin is a putative neurotransmitter. During the course of this study the serotonin content was found to be significantly higher than that found in mammalian midbrain. Parachlorophenylalanine was found to inhibit the first step of the biosynthetic pathway by inhibiting tryptophan-hydroxylase enzyme and leading to alterations in the concentrations of metabolites such as 5-hydroxy tryptophan, 5-hydroxy indole acetic acid and tryptophan. Using a dose of 15 μg/g the inhibitory effect was not long lasting and recovery was observed to restore the normal levels. Higher trytophan levels were observed after a certain period of P-chlorophenylalanine treatment because there was a block in the biosynthetic path and tryptophan could not be utilized for 5-HT synthesis. A negative correlation between brain tryptophan and protein content was observed in both the cases of P-chlorophenylalanine and reserpine treatments.     

Fate of glucose in haemolymph of the American cockroach, Periplaneta americana

The rate of removal of high concentrations of glucose (10 μg/μl haemolymph) from haemolymph of adult male cockroaches, Periplaneta americana, was studied in normal and ligated insects. More than 50% of the injected glucose is removed from the haemolymph of normal insects within 20 min of injection. A period of rapid trehalose synthesis occurs during the initial 10 min following injection of glucose into the haemocoele, and this is succeeded by a period of glycogen synthesis. The results are discussed in terms of earlier observations on ‘stress-induced hypertrehalosemia’ and the possible involvement of a glycogenic agent.     

Les sensilles de l'antenne chez quelques blattes et en particulier chez Blaberus craniifer (Burm.)

Résumé Les organes sensoriels du scape et du pédicelle sont essentiellement propriocepteurs. Le fouet est très riche en chimiorécepteurs (plus de 100000) mais chez Periplaneta et Blatta, on observe un net dimorphisme sexuel qui n'existe pas chez Blaberus. La relation entre un tel dimorphisme et la perception des phéromones sexuelles est discutée. L'ultrastructure des trois principaux types de sensilles est décrite: Ce sont des grandes soies gustatives et mécanoréceptrices, des petites soies olfactives à paroi mince et percée de pores et de tubules qui sont innervées par un ou deux neurones, des petites soies olfactives à paroi épaisse et striée qui contiennent toujours quatre neurones. L'étude électrophysiologique préliminaire confirme les résultats ci dessus en ce qui concerne le rôle des sensilles: La phéromone grégaire peut être perçue au niveau de certaines petites soies olfactives striées.

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The antennal sensilla of some cockroaches with special reference to Blaberus craniifer (Burm.)

Summary The antennae of cockroaches were studied with both scanning and transmission electron microscope. The sense organs of the scape and pedicel are essentially proprioceptors. The chemoreceptors are very numerous on the flagellum (more than 100000) but in the case of Periplaneta and Blatta, a significant sexuel dimorphism is noticed. Such a dimorphism does not exist in Blaberus and its relation with the perception of the sexual attractants is discussed. Three principal sense organs of Blaberus are described: big thick walled hairs with gustatory and mechanoreceptive function; thin walled olfactory hairs with pore-tubules innervated by one or two neurons; thick walled grooved hairs with four neurons and olfactory function. Special attention was given to the secretory aspect of the accessory cells in the olfactory sensilla. A preliminary electrophysiological investigation confirms the above mentioned functional interpretations. The gregarious pheromone seems to be perceived by some little thick walled grooved hairs.

     

Functional analysis of Scr during embryonic and post-embryonic development in the cockroach, Periplaneta americana

The cockroach, Periplaneta americana represents a basal insect lineage that undergoes the ancestral hemimetabolous mode of development. Here, we examine the embryonic and post-embryonic functions of the hox gene Scr in Periplaneta as a way of better understanding the roles of this gene in the evolution of insect body plans. During embryogenesis, Scr function is strictly limited to the head with no role in the prothorax. This indicates that the ancestral embryonic function of Scr was likely restricted to the head, and that the posterior expansion of expression in the T1 legs may have preceded any apparent gain of function during evolution. In addition, Scr plays a pivotal role in the formation of the dorsal ridge, a structure that separates the head and thorax in all insects. This is evidenced by the presence of a supernumerary segment that occurs between the labial and T1 segments of RNAiScr first nymphs and is attributed to an alteration in engrailed (en) expression. The fact that similar Scr phenotypes are observed in Tribolium but not in Drosophila or Oncopeltus reveals the presence of lineage-specific variation in the genetic architecture that controls the formation of the dorsal ridge. In direct contrast to the embryonic roles, Scr has no function in the head region during post-embryogenesis in Periplaneta, and instead, strictly acts to provide identity to the T1 segment. Furthermore, the strongest Periplaneta RNAiScr phenotypes develop ectopic wing-like tissue that originates from the posterior region of the prothoracic segment. This finding provides a novel insight into the current debate on the morphological origin of insect wings.