Descending control of turning behavior in the cockroach, Blaberus discoidalis

Legged locomotion has evolved as the most effective form of movement through unpredictable and tortuous environments. Upon encountering an obstacle, an animal must evaluate the object with its sense organs then use the information it acquires to direct appropriate transitional behaviors, such as turning. Previous studies using genetic and surgical lesions implicate the central body complex (CBC) in control of such transitional behaviors of various insects. In this study, lesions of the CBC and surrounding brain regions were used to examine the effects of damage on turning in free-moving and tethered cockroaches. Lesions were performed either as sagittal incisions or by inserting small pieces of foil into regions of the brain. Locomotor behaviors of intact and lesioned animals were compared using high speed video and kinematic analysis. The lesions locations were determined through histological methods. Sagittal lesions to the CBC often result in continuous or incorrect turns. Foil lesions in the CBC also increase the probability that individuals will show turning deficits. The location and degree of the lesion had a strong effect on the animal’s ability to turn. These data strongly suggest that the CBC mediates the effects of head sense organs that produce changes in the direction of walking.     

Control of obstacle climbing in the cockroach, Blaberus discoidalis. I. Kinematics

An advantage of legged locomotion is the ability to climb over obstacles. We studied deathhead cockroaches as they climbed over plastic blocks in order to characterize the leg movements associated with climbing. Movements were recorded as animals surmounted 5.5-mm or 11-mm obstacles. The smaller obstacles were scaled with little change in running movements. The higher obstacles required altered gaits, leg positions and body posture. The most frequent sequence used was to first tilt the front of the body upward in a rearing stage, and then elevate the center of mass to the level of the top of the block. A horizontal running posture was re-assumed in a leveling-off stage. The action of the middle legs was redirected by rotations of the leg at the thoracal-coxal and the trochanteral-femoral joints. The subsequent extension movements of the coxal-trochanteral and femoral-tibial joints were within the range seen during horizontal running. The structure of proximal leg joints allows for flexibility in leg use by generating subtle, but effective changes in the direction of leg movement. This architecture, along with the resulting re-direction of movements, provides a range of strategies for both animals and walking machines.     

In vitro superoxide activity in the haemolymph of the West Indian leaf cockroach,Blaberus discoidalis

The respiratory burst is an NADPH oxidase-driven reduction of molecular oxygen to superoxide, which can occur in phagocytic cells as part of an antimicrobial defence, and is well documented among the vertebrates. This paper describes a process resembling the respiratory burst, which occurs in the haemolymph and haemocytes of the cockroach, Blaberus discoidalis. The in vitro reduction of nitroblue tetrazolium by superoxide to formazan was measured spectrophotometrically in B. discoidalis haemolymph in response to various immune elicitors. Nitroblue tetrazolium reduction was partly impeded in the presence of superoxide dismutase, a specific antioxidant which converts superoxide to hydrogen peroxide, as well as by chemicals known to inhibit the respiratory burst in vertebrates (trifluoperazine, diphenylene iodonium, and N-ethylmaleimide). This suggests the generation of superoxide anions by haemolymph as part of an immune response. Furthermore, formazan staining of elicitor-treated haemocytes was observed microscopically, with less intense staining in the presence of superoxide dismutase. Finally, respiratory burst inhibitors and superoxide dismutase enhanced the growth of E. coli incubated in whole haemolymph, implying a role for haemolymph-derived superoxide in antibacterial defence.     

A neuromechanical simulation of insect walking and transition to turning of the cockroach Blaberus discoidalis

A neuromechanical simulation of the cockroach Blaberus discoidalis was developed to explore changes in locomotion when the animal transitions from walking straight to turning. The simulation was based upon the biological data taken from three sources. Neural circuitry was adapted from the extensive literature primarily obtained from the studies of neural connections within thoracic ganglia of stick insect and adapted to cockroach. The 3D joint kinematic data on straight, forward walking for cockroach were taken from a paper that describes these movements in all joints simultaneously as the cockroach walked on an oiled-plate tether (Bender et al. in PloS one 5(10):1–15, 2010b). Joint kinematics for turning were only available for some leg joints (Mu and Ritzmann in J Comp Physiol A Neuroethol Sens Neural Behav Physiol 191(11):1037–54, 2005) and thus had to be obtained using the methods that were applied for straight walking by Bender et al. (PloS one 5(10):1–15, 2010b). Once walking, inside turning, and outside turning were characterized, phase and amplitude changes for each joint of each leg were quantified. Apparent reflex reversals and joint activity changes were used to modify sensory coupling pathways between the CPG at each joint of the simulation. Oiled-plate experiments in simulation produced tarsus trajectories in stance similar to those seen in the animal. Simulations including forces that would be experienced if the insect was walking freely (i.e., weight support and friction) again produced similar results. These data were not considered during the design of the simulation, suggesting that the simulation captures some key underlying the principles of walking, turning, and transitioning in the cockroach. In addition, since the nervous system was modeled with realistic neuron models, biologically plausible reflex reversals are simulated, motivating future neurobiological research.     

An allometric analysis of oxygen consumption rate and cardiovascular function in the cockroach, Blaberus discoidalis.

The interrelationship of metabolic rate and cardiovascular function has been well documented in vertebrates through allometric analyses. However, similar studies are lacking in insects. Unlike vertebrates, the cardiovascular system of insects does not play a significant role in oxygen transport. A comparison of the interrelationship in insects and vertebrates might provide insight into the nature of the connection between metabolic rate and the cardiovascular system. Oxygen consumption, heart rate and heart dimensions were measured in the nymphs of the cockroach Blaberus discoidalis over a mass range of 0.03-5 g. Oxygen consumption rate scaled with an exponent of 0.83. The relationship between heart rate and body mass scaled negatively, however, it did not appear to be linear. Using measurements of heart widths, abdominal length and heart rate, stroke volume and cardiac output were estimated. Cardiac output appeared to scale linearly with an exponent of 0.85, which was not significantly different from the exponent observed for the rate of oxygen consumption. Thus, the observed similarity between the exponents for oxygen consumption rate and cardiac output in vertebrates also appears to be present in insects.     

Effect of lysozyme on the lectin-mediated phagocytosis of Bacillus cereus by haemocytes of the cockroach, Blaberus discoidalis

Lysozyme-like activity has been demonstrated in both cell-free haemolymph and, more abundantly, in haemocyte-lysate supernatants of Blaberus discoidalis. This activity was non-inducible, but heat-stable, with a maximum activity at pH 6.2. When B. cereus was pre-incubated in a concentration of chicken egg-white lysozyme equivalent to the concentration of lysozyme-like activity in cell-free haemolymph, the phagocytosis of B. cereus opsonized with GlcNAc-specific lectins, i.e. BDL2, WGA and HPA, was significantly reduced by up to 50%, while phagocytosis of B. cereus opsonized with mannose-specific lectins, such as BDL1 and Con A, was significantly increased. Pre-incubation of B. cereus in a higher concentration of lysozyme resulted in a smaller, shorter lived increase in the phagocytic rate of bacteria opsonized with these mannose-specific lectins. The action of lysozyme on the peptidoglycan in the cell wall of B. cereus probably resulted in a reduction in the number of binding sites for the GlcNAc-specific lectins, and, therefore, reduced the phagocytic rate of BDL2, HPA and WGA-opsonized B. cereus. Concomitantly, the breakdown of peptidoglycan probably exposed mannose-containing polysaccharides, previously embedded in the peptidoglycan layer, resulting in an increase in the phagocytic rate of the BDL1- and Con A-opsonized B. cereus. These results are discussed in relation to the immune-potential of B. discoidalis.     

Control of climbing behavior in the cockroach, Blaberus discoidalis. II. Motor activities associated with joint movement

Deathhead cockroaches employ characteristic postural strategies for surmounting barriers. These include rotation of middle legs to re-direct leg extension and drive the animal upward. However, during climbing the excursions of the joints that play major roles in leg extension are not significantly altered from those seen during running movements. To determine if the motor activity associated with these actions is also unchanged, we examined the electromyogram activity produced by the slow trochanteral extensor and slow tibial extensor motor neurons as deathhead cockroaches climbed over obstacles of two different heights. As they climbed, activity in the slow trochanteral extensor produced a lower extension velocity of the coxal-trochanteral joint than the same frequency of slow trochanteral extensor activity produces during horizontal running. Moreover, the pattern of activity within specific leg cycles was altered. During running, the slow trochanteral extensor generates a high-frequency burst prior to foot set-down. This activity declines through the remainder of the stance phase. During climbing, motor neuron frequency no longer decreased after foot set-down, suggesting that reflex adjustments were made. This conclusion was further supported by the observation that front leg amputees generated even stronger slow trochanteral extensor activity in the middle leg during climbing movements.     

Leg kinematics and muscle activity during treadmill running in the cockroach, Blaberus discoidalis: II. Fast running

We have combined kinematic and electromyogram (EMG) analysis of running Blaberus discoidalis to examine how middle and hind leg kinematics vary with running speed and how the fast depressor coxa (Df) and fast extensor tibia (FETi) motor neurons affect kinematic parameters. In the range 2.5–10 Hz, B. discoidalis increases step frequency by altering the joint velocity and by reducing the time required for the transition from flexion to extension. For both Df and FETi the timing of recruitment coincides with the maximal frequency seen for the respective slow motor neurons. Df is first recruited at the beginning of coxa-femur (CF) extension. FETi is recruited in the latter half of femur-tibia (FT) extension during stance. Single muscle potentials produced by these fast motor neurons do not have pronounced effects on joint angular velocity during running. The transition from CF flexion to extension was abbreviated in those cycles with a Df potential occurring during the transition. One effect of Df activity during running may be to phase shift the beginning of joint extension so that the transition is sharpened. FETi is associated with greater FT extension at higher running speeds and may be necessary to overcome high joint torques at extended FT joint angles. Accepted: 24 May 1997     

Biogenesis of mitochondria: neuroendocrine effects on the development of respiratory functions in fat body mitochondria of the cockroach, Blaberus discoidalis

Fat body mitochondria from male Blaberus discoidalis cockroaches underwent a hormone-independent respiratory development during the first 5 days of adult life followed by a neurohormone-dependent development during the next 5 days. Increases of two- to threefold were shown for oxygen uptake and for succinate-cytochrome c reductase and cytochrome c oxidase activities during this period. Also, an increased capacity for respiratory control by ADP was evident. No further respiratory changes occurred between 10 and 30 days of adult age. Respiratory enzyme activities and respiratory control failed to develop beyond the 5 day level after disruption of neurosecretory functions by extirpation of the corpora cardiaca. Conversely, daily administration of corpora cardiaca extracts stimulated precocious 10 day levels of respiration by 5 days of adult age. Uncoupling with 2,4-DNP indicated electron transport as the rate-limiting process of respiratory activity. Total incorporation of ¹⁴Camino acids into fat body mitochondria increased twofold during the first 5 days of adult life. This level of amino acid incorporation was maintained thereafter and corpora cardiaca removal had no effect. The fat body of Blaberus appears useful for studies on the hormonal regulation of mitochondrial development in higher eucaryotic animals.     

Efficacy of oral sulfadimethoxine against two gregarine parasites,Protomagalhaensia granulosae and Gregarina cubensis (Apicomplexa: Eugregarinida), infecting the Death's Head cockroach,Blaberus discoidalis

Gregarines are common parasites of insects in culture, but no effective chemotherapeutic or prophylactic control protocol has been demonstrated. Sulfadimethoxine was administered in 5- and 7-day treatments to Death's Head cockroaches (Blaberus discoidalis) infected with Gregarina cubensis and Protomagalhaensia granulosae to test the efficacy of this sulfonamide against gregarine infection. Sulfadimethoxine significantly reduced the mean intensity of both G. cubensis and P. granulosae. Sulfadimethoxine treatment reduced gregarine intensity by 80% to 85% but had no significant effect on gametocyst production, suggesting that sulfonamide toxicity is directed primarily at sporozoites, trophozoites, and perhaps young gamonts. The possible use of sulfadimethoxine to produce gregarine-free insect cultures and the potential utility of gregarines as target organisms for screening pharmacologically active compounds for use against other intestinal apicomplexans are discussed.     

Indolamines and onset of vitellogenesis in the imaginal molt-decapitated cockroach Blaberus craniifer Burm.

1. The effects of 5-hydroxytryptamine, 5-hydroxyindoleacetic acid and N-acetyl-5-hydroxytryptamine on oocytes of Blaberus craniifer, in which vitellogenesis was prevented by imaginal molt decapitation, were investigated. 2. Sites binding anti-egg-protein antibodies were detected in the periphery of basal oocytes of treated females, with individual variability. 3. In this ovoviviparous cockroach, the onset of vitellogenesis may thus not be triggered solely by juvenile hormone, and indolamines may play a role in the uptake of haemolymphatic proteins by oocytes.     

Structure-activity relationships on hyperglycemia by representatives of the adipokinetic/hyperglycemic hormone family in Blaberus discoidalis cockroaches

Summary Several members of the adipokinetic/hyperglycemic neurohormone family from several different invertebrate species have been prepared by solid-phase peptide synthesis and assayed by a modified in vivo hyperglycemic bioassay in Blaberus discoidalis cockroaches. The hypertrehalosemic hormone (HrTH) is the endogenous hypertrehalosemic factor for B. discoidalis and was the most potent peptide in the assay. The more divergent the sequence of a family member from Blaberus HrTH, the less potent was the bioanalog. Manduca adipokinetic hormone is the most divergent peptide of the family and was totally inactive in the bioassay. Locusta adipokinetic hormone I had reduced maximum activity in the assay, which suggests that Ser⁵ is an important residue for the transduction of the hyperglycemic response. The direct relation between bioanalog similarity to Blaberus HrTH sequence and potency suggests that the hormone and target cell receptor for HrTH have evolved to maintain an optimal fit.Abbreviations AKH adipokinetic hormone - HrGH hyperglycemic hormone - HrTH hypertrehalosemic hormone - RPCH red pigmentconcentrating hormone - CAH cardioacceleratory hormone. Hormone abbreviations are according to the convention of Gäde and Raina (1989) except that the genus names are not abbreviated     

Characterization of novel glycolipids from the giant cockroach (Blaberus colosseus)

A novel class of glycolipids, assigned the trivial name blaberosides, was isolated from whole head tissues of the giant cockroach (Blaberus colosseus). The class consists of two closely related families, blaberoside I and blaberoside II, each containing species differing by 26 atomic mass units. The structure of these gentiobiose-based glycoglycerolipids was elucidated by chromatographic behavior, nuclear magnetic resonance spectroscopy, mass spectrometry, and analysis of chemical degradation products and derivatives. Species in the blaberoside I family have been identified as 2-O-[6'-O-(6"-O-3-hydroxy-11-eicosenoyl-beta-D-glucopyranosyl)-bet a-D- glucopyranosyl]-3-(hexadecyloxy)-1-(3-hydroxy-11-eicosenoyl)-1,2-p ropanediol (blaberoside Ia) and 2-O-[6'-O-(6"-O-3-hydroxy-11-eicosenoyl-beta-D-glucopyranosyl)-bet a- D-glucopyranosyl]-3-(6-octadeceloxy)-1-(3-hydroxy-11-eicosenoyl )-1,2- propanediol (blaberoside Ib). Two smaller homologs of the blaberoside II family were discerned to be 2-O-[6'-O-(6"-O-3-hydroxy-11- eicosenoyl-beta-D-glucopyranosyl)-beta-D-glucopyranosyl]-3-(hex ade cyloxy)- 1,2-propanediol (blaberoside IIa), and 2-O-[6'-O-(6"-O-3-hydroxy-11-eicosenoyl-beta-D- glucopyranosyl)-beta-D-glucopyranosyl]-3-(4-octadeceloxy)-1,2-prop anediol (blaberoside IIb). These compounds are unique because they are animal origin glyceroglycolipids with a highly flexible gentiobiose backbone, and a beta-linkage of the carbohydrate to the glycerol ether at the 2 position rather than the usual 1 position.     

The deutocerebrum of the cockroach Blaberus craniifer burm. Spatial organization of the sensory glomeruli

The objective of this work is to describe the glomerular organization of the deutocerebrum in Blaberus craniifer and to test the hypothesis that the glomeruli are identifiable. The problem is studied using the techniques of analytical geometry, i.e., by measuring the location of the glomeruli in cartesian coordinate systems. Computerized geometrical and statistical techniques are described for the three-dimensional reconstruction and quantitative study of these brain structures. The invariance of the glomerular organization, and consequently the identifiability of the glomeruli, is based on three criteria: (1) the number of glomeruli per hemideutocerebrum (hDTC) is a constant (109); (2) the position of the glomeruli is symmetrical in the two sides of one individual and identical in the same side of two individuals, except for small local variations, (3) the dimensions of two positionally homologous glomeruli are statistically equal in the same and in different individuals, except for a macroglomerulus which is found only in the male. The causes of variability, from experimental and biological origin, are discussed and quantitatively evaluated. The interindividual biological variability, not ascribable to differences in size between brains, expressed as a 95% interval, is estimated to be 27 μm for the location of glomeruli and 12 μm for the diameter of glomeruli.