Venom of a parasitoid wasp induces prolonged grooming in the cockroach

The Cocoon of the Developing Emerald Jewel Wasp (Ampulex compressa) Resists Cannibalistic Predation of the Zombified Host

INTRODUCTION

To reproduce, the parasitoid emerald jewel wasp (Ampulex compressa) envenomates an American cockroach (Periplaneta americana) and barricades it in a hole with an egg on the host's leg. The larval wasp feeds externally before entering the host and consuming internal organs before forming a cocoon inside the host carcass.

METHODS

The vulnerability of jewel wasp larvae to predation by juvenile cockroaches was investigated, and data were recorded with time-lapse videography.

RESULTS

Cockroaches were found to be predators of parasitized hosts. When parasitized cockroaches were exposed to hungry cockroaches on days 0-8 of development, the developing larva was killed. Eggs were dislodged or consumed, larvae on the leg were eaten, and larvae inside the host were eaten along with the host. On day 9, 80% of the wasp larvae were killed and eaten along with the host. Conversely, on day 10, 90% of the larvae survived. On developmental day 11 or later, the wasp larva always survived, although the host carcass was consumed. Survival depended entirely on whether the cocoon had been completed.

CONCLUSION

The results highlight the vulnerability of larvae to predation and suggest the cocoon defends from insect mandibles. This may explain the unusual feeding behavior of the jewel wasp larvae, which eat the host with remarkable speed, tapping into the host respiratory system in the process, and consuming vital organs early, in contrast to many other parasitoids. Results are discussed in relation to larval wasp behavior, evolution, and development, and potential predators are considered.

Sublethal biochemical, behavioral, and physiological toxicity of extremely low dose of bendiocarb insecticide in Periplaneta americana (Blattodea: Blattidae)

Insecticides are dedicated to impair the insect organisms, but also have an impact on other, non-target organisms, including humans. In this way, they became important risk factor for disturbance of physiological homeostasis and can be involved in the development of diseases or in deterioration of existing conditions. The influence of sublethal doses of various insecticides on vertebrates' and invertebrates' organisms has been previously observed. In this paper, we have evaluated the impact of exposure to extremely low dose of neurotoxin, bendiocarb (0.1 nM), a commonly used carbamate insecticide on a model organism in neurobiology-Periplaneta americana. The assessment was performed on all levels of animal organism from molecular (oxidative stress parameters: phosphorylation level of proteins, cAMP level, protein kinase A and C levels, and octopamine) to physiological (heart beat and gas exchange tests) and behavioral (motor skills assay, grooming test). Exposure to such a low level of bendiocarb did not cause direct paralysis of insects, but changed their grooming behavior, decreased heart rate, and increased gas exchange. We also observed the increased parameters of oxidative stress as well as stressogenic response to 0.1 nM bendiocarb exposure. Exposure to a trace amount of bendiocarb also increased sensitivity to effective doses of the same insecticide, thus acts as preconditioning. These results force us to reconsider the possible risk from frequent/continuous exposure to traces of pesticide residues in the environment to human health.

Parasitoid wasp venom re-programs host behavior through downmodulation of brain central complex activity and motor output

The parasitoid wasp Ampulex compressa hunts down its host, the American cockroach (Periplaneta americana), and envenomates its brain to make it a behaviorally compliant food supply for its offspring. The primary target of the wasp sting is a locomotory command center called the central complex (CX). In the present study, we employ, for the first time, chronic recordings of patterned cockroach CX activity in real time as the brain is infused with wasp venom. CX envenomation is followed by sequential changes in the pattern of neuronal firing that can be divided into three distinct temporal phases during the 2 h interval after venom injection: (1) reduction in neuronal activity for roughly 10 min immediately after venom injection; (2) rebound of activity lasting up to 25 min; (3) reduction of ongoing activity for up to 2 h. Long-term reduction of CX activity after venom injection is accompanied by decreased activity of both descending interneurons projecting to thoracic locomotory circuitry (DINs) and motor output. Thus, in this study, we provide a plausible chain of events starting in the CX that leads to decreased host locomotion following brain envenomation. We propose that these events account for the onset and maintenance of the prolonged hypokinetic state observed in stung cockroaches.

Parasitoid wasp venom manipulates host innate behavior via subtype-specific dopamine receptor activation

The subjugation strategy employed by the jewel wasp is unique in that it manipulates the behavior of its host, the American cockroach, rather than inducing outright paralysis. Upon envenomation directly into the central complex (CX), a command center in the brain for motor behavior, the stung cockroach initially engages in intense grooming behavior, then falls into a lethargic sleep-like state referred to as hypokinesia. Behavioral changes evoked by the sting are due at least in part to the presence of the neurotransmitter dopamine in the venom. In insects, dopamine receptors are classified as two families, the D1-like and the D2-like receptors. However, specific roles played by dopamine receptor subtypes in venom-induced behavioral manipulation by the jewel wasp remain largely unknown. In the present study, we used a pharmacological approach to investigate roles of D1-like and D2-like receptors in behaviors exhibited by stung cockroaches, focusing on grooming. Specifically, we assessed behavioral outcomes of focal CX injections of dopamine receptor agonists and antagonists. Both specific and non-specific compounds were used. Our results strongly implicate D1-like dopamine receptors in venom-induced grooming. Regarding induction of hypokinesia, our findings demonstrate that dopamine signaling is necessary for induction of long-lasting hypokinesia caused by brain envenomation.

Highlighted Article: Subtype-specific dopamine receptors are involved in the manipulation of host behavior by the parasitoid jewel wasp.

Insect Body Defence Reactions against Bee Venom: Do Adipokinetic Hormones Play a Role?

Bees originally developed their stinging apparatus and venom against members of their own species from other hives or against predatory insects. Nevertheless, the biological and biochemical response of arthropods to bee venom is not well studied. Thus, in this study, the physiological responses of a model insect species (American cockroach, Periplaneta americana) to honeybee venom were investigated. Bee venom toxins elicited severe stress (LD₅₀ = 1.063 uL venom) resulting in a significant increase in adipokinetic hormones (AKHs) in the cockroach central nervous system and haemolymph. Venom treatment induced a large destruction of muscle cell ultrastructure, especially myofibrils and sarcomeres. Interestingly, co-application of venom with cockroach Peram-CAH-II AKH eliminated this effect. Envenomation modulated the levels of carbohydrates, lipids, and proteins in the haemolymph and the activity of digestive amylases, lipases, and proteases in the midgut. Bee venom significantly reduced vitellogenin levels in females. Dopamine and glutathione (GSH and GSSG) insignificantly increased after venom treatment. However, dopamine levels significantly increased after Peram-CAH-II application and after co-application with bee venom, while GSH and GSSG levels immediately increased after co-application. The results suggest a general reaction of the cockroach body to bee venom and at least a partial involvement of AKHs.

Modulation of octopaminergic and cholinergic pathways induced by Caatinga tree Manilkara rufula chemical compounds in Nauphoeta cinerea cockroaches

The entomotoxic potential of Manilkara rufula crude extract (CEMR) and its aqueous (AFMR) and methanolic (MFMR) fractions were evaluated against Nauphoeta cinerea cockroaches. The results point out to a direct modulation of octopaminergic and cholinergic pathways in insect nervous system. CEMR induced an anti-acetylcholinesterase (AChE) effect in cockroach brain homogenates. CEMR significantly decreased the cockroach heart rate in semi-isolated heart preparations. CEMR also caused a broad disturbance in the insect behavior by reducing the exploratory activity. The decreased antennae and leg grooming activities, by different doses of CEMR, mimicked those of phentolamine activity, a selective octopaminergic receptor antagonist. The lethargy induced by CEMR was accompanied by neuromuscular failure and by a decrease of sensilla spontaneous neural compound action potentials (SNCAP) firing in in vivo and ex vivo cockroach muscle-nerve preparations, respectively. AFMR was more effective in promoting neuromuscular paralysis than its methanolic counterpart, in the same dose. These data validate the entomotoxic activity of M. rufula. The phentolamine-like modulation induced in cockroaches is the result of a potential direct inhibition of octopaminergic receptors, combined to an anti-AChE activity. In addition, the modulation of CEMR on octopaminergic and cholinergic pathways is probably the result of a synergism between AFMR and MFMR chemical compounds. Further phytochemical investigation followed by a bio-guiding protocol will improve the molecular aspects of M. rufula pharmacology and toxicology to insects.

Entomotoxic Activity of Prasiola crispa (Antarctic Algae) in Nauphoeta cinerea Cockroaches: Identification of Main Steroidal Compounds

Prasiola crispa is a macroscopic green algae found in abundance in Antarctica ice free areas. Prasiola crispan-hexaneextract (HPC) induced insecticidal activity in Nauphoeta cinerea cockroaches after 24 h of exposure. The chemical analysis of HPC revealed the presence of the followingphytosterols: β-sitosterol, campesterol and stigmasterol. The incubation of cockroach semi-isolated heart preparations with HPC caused a significant negative chronotropic activity in the heartbeats. HPC affected the insect neuromuscular function by inducing a complete inhibition of the cockroach leg-muscle twitch tension. When the isolated phytosterols were injected at in vivo cockroach neuromuscular preparations, there was a progressive inhibition of muscle twitches on the following order of potency: β-sitosterol > campesterol > stigmasterol. HPC also provoked significant behavioral alterations, characterized by the increase or decrease of cockroach grooming activity, depending on the dose assayed. Altogether, the results presented here corroborate the insecticide potential of Prasiola crispa Antarctic algae. They also revealed the presence of phytosterols and the involvement of these steroidal compounds in the entomotoxic activity of the algae, potentially by modulating octopaminergic-cholinergic pathways. Further phytochemical-combined bioguided analysis of the HPC will unveil novel bioactive compounds that might be an accessory to the insecticide activity of the algae.

Neurotoxic effects of sublethal concentrations of cyanobacterial extract containing anatoxin-a(s) on Nauphoeta cinerea cockroaches

The detection of cyanotoxins, such as the anatoxin-a(s), is essential to ensure the biological safety of water environments. Here, we propose the use of Nauphoeta cinerea cockroaches as an alternative biological model for the biomonitoring of the activity of anatoxin-a(s) in aquatic systems. In order to validate our proposed model, we compared the effects of a cyanobacterial extract containing anatoxin-a(s) (CECA) with those of the organophosphate trichlorfon (Tn) on biochemical and physiological parameters of the nervous system of Nauphoeta cinerea cockroaches. In brain homogenates from cockroaches, CECA (5 and 50 μg/g) inhibited acetylcholinesterase (AChE) activity by 53 ± 2% and 51 ± 7%, respectively, while Tn (5 and 50 μg/g) inhibited AChE activity by 35 ± 4% and 80 ± 9%, respectively (p < 0.05; n = 6). Moreover, CECA at concentrations of 5, 25, and 50 µg/g decreased the locomotor activity of the cockroaches, diminishing the distance travelled and increasing the frequency and duration of immobile episodes similarly to Tn (0.3 μg/g) (p < 0.05, n = 40, respectively). CECA (5, 25 and 50 μg/g) induced an increase in the leg grooming behavior, but not in the movement of antennae, similarly to the effect of Tn (0.3 μg/g). In addition, both CECA (50 µg/200 μl) and Tn (0.3 µg/200 μl) induced a negative chronotropism in the insect heart (37 ± 1 and 47 ± 8 beats/min in 30 min, respectively) (n = 9, p > 0.05). Finally, CECA (50 µg/g), Tn (0.3 µg/g) and neostigmine (50 µg/g) caused significant neuromuscular failure, as indicated by the monitoring of the in vivo neuromuscular function of the cockroaches, during 100 min (n = 6, p < 0.05, respectively). In conclusion, sublethal doses of CECA provoked entomotoxicity. The Tn-like effects of CECA on Nauphoeta cinerea cockroaches encompass both the central and peripheral nervous systems in our insect model. The inhibitory activity of CECA on AChE boosts a cascade of signaling events involving octopaminergic/dopaminergic neurotransmission. Therefore, this study indicates that this insect model could potentially be used as a powerful, practical, and inexpensive tool to understand the impacts of eutrophication and for orientating decontamination processes.

Molecular cross-talk in a unique parasitoid manipulation strategy

Envenomation of cockroach cerebral ganglia by the parasitoid Jewel wasp, Ampulex compressa, induces specific, long-lasting behavioural changes. We hypothesized that this prolonged action results from venom-induced changes in brain neurochemistry. Here, we address this issue by first identifying molecular targets of the venom, i.e., proteins to which venom components bind and interact with to mediate altered behaviour. Our results show that venom components bind to synaptic proteins and likely interfere with both pre- and postsynaptic processes. Since behavioural changes induced by the sting are long-lasting and reversible, we hypothesized further that long-term effects of the venom must be mediated by up or down regulation of cerebral ganglia proteins. We therefore characterize changes in cerebral ganglia protein abundance of stung cockroaches at different time points after the sting by quantitative mass spectrometry. Our findings indicate that numerous proteins are differentially expressed in cerebral ganglia of stung cockroaches, many of which are involved in signal transduction, such as the Rho GTPase pathway, which is implicated in synaptic plasticity. Altogether, our data suggest that the Jewel wasp commandeers cockroach behaviour through molecular cross-talk between venom components and molecular targets in the cockroach central nervous system, leading to broad-based alteration of synaptic efficacy and behavioural changes that promote successful development of wasp progeny.

Parasitoid Jewel Wasp Mounts Multipronged Neurochemical Attack to Hijack a Host Brain

The parasitoid emerald jewel wasp Ampulex compressa induces a compliant state of hypokinesia in its host, the American cockroach Periplaneta americana through direct envenomation of the central nervous system (CNS). To elucidate the biochemical strategy underlying venom-induced hypokinesia, we subjected the venom apparatus and milked venom to RNAseq and proteomics analyses to construct a comprehensive "venome," consisting of 264 proteins. Abundant in the venome are enzymes endogenous to the host brain, including M13 family metalloproteases, phospholipases, adenosine deaminase, hyaluronidase, and neuropeptide precursors. The amphipathic, alpha-helical ampulexins are among the most abundant venom components. Also prominent are members of the Toll/NF-κB signaling pathway, including proteases Persephone, Snake, Easter, and the Toll receptor ligand Spätzle. We find evidence that venom components are processed following envenomation. The acidic (pH∼4) venom contains unprocessed neuropeptide tachykinin and corazonin precursors and is conspicuously devoid of the corresponding processed, biologically active peptides. Neutralization of venom leads to appearance of mature tachykinin and corazonin, suggesting that the wasp employs precursors as a prolonged time-release strategy within the host brain post-envenomation. Injection of fully processed tachykinin into host cephalic ganglia elicits short-term hypokinesia. Ion channel modifiers and cytolytic toxins are absent in A. compressa venom, which appears to hijack control of the host brain by introducing a "storm" of its own neurochemicals. Our findings deepen understanding of the chemical warfare underlying host-parasitoid interactions and in particular neuromodulatory mechanisms that enable manipulation of host behavior to suit the nutritional needs of opportunistic parasitoid progeny.

Entomotoxic activity of Rhinella icterica (Spix, 1824) toad skin secretion in Nauphoeta cinerea cockroaches: An octopamine-like modulation

Rhinella icterica is a poisonous toad whose toxic secretion has never been studied against entomotoxic potential. Sublethal doses of Rhinella icterica toxic secretion (RITS) were assayed in Nauphoeta cinerea cockroaches, in order to understand the physiological and behavioral parameters, over the insect central and peripheral nervous system. RITS (10 μg/g) injections, induced behavioral impairment as evidenced by a significant decrease (38 ± 14%) in the distance traveled (p < .05), followed by an increase (90 ± 6%) of immobile episodes (p < .001, n = 28, respectively). In cockroaches semi-isolated heart preparations, RITS (16 μg/200 μl) induced a significant irreversible dose-dependent negative chronotropism, reaching ~40% decrease in heart rate in 20 min incubation. In in vivo cockroach neuromuscular preparations, RITS (20, 50 and 100 μg/g of animal weight) induced a time-dependent inhibition of twitch tension that was complete for 20 μg/g, in 120 min recordings. RITS (10 μg/g) also induced a significant increase in the insect leg grooming activity (128 ± 10%, n = 29, p < .01), but not in the antennae counterparts. The RITS increase in leg grooming activity was prevented in 90% by the pretreatment of cockroaches with phentolamine (0.1 μg/g). The electrophysiological recordings of spontaneous neural compound action potentials showed that RITS (20 μg/g) induced a significant increase in the number of events, as well as in the rise time and duration of the potentials. In conclusion, RITS showed to be entomotoxic, being the neuromuscular failure and cardiotoxic activity considered the main deleterious effects. The disturbance of the cockroaches' behavior together with the electrophysiological alterations, may unveil the presence of some toxic components present in the poison with inherent biotechnological potentials.

Neuroparasitology of Parasite-Insect Associations

Insect behavior can be manipulated by parasites, and in many cases, such manipulation involves the central and peripheral nervous system. Neuroparasitology is an emerging branch of biology that deals with parasites that can control the nervous system of their host. The diversity of parasites that can manipulate insect behavior ranges from viruses to macroscopic worms and also includes other insects that have evolved to become parasites (notably, parasitic wasps). It is remarkable that the precise manipulation observed does not require direct entry into the insect brain and can even occur when the parasite is outside the body. We suggest that a spatial view of manipulation provides a holistic approach to examining such interactions. Integration across approaches from natural history to advanced imaging techniques, omics, and experiments will provide new vistas in neuroparasitology. We also suggest that for researchers interested in the proximate mechanisms of insect behaviors, studies of parasites that have evolved to control such behavior is of significant value.

Dopamine regulates termite soldier differentiation through trophallactic behaviours

Caste polyphenism in social insects is regulated by social interactions among colony members. Trophallaxis is one of the most frequently observed interactions, but no studies have been conducted identifying the intrinsic factors involved in this behaviour and caste differentiation. Dopamine (DA) has multiple roles in the modulation of behaviours and physiology, and it produces species-specific behaviours in animals. Here, to verify the role of DA in termite soldier differentiation, we focused on the first soldier in an incipient colony of Zootermopsis nevadensis, which always differentiates from the oldest 3rd instar (No. 1 larva) via a presoldier. First, brain DA levels of the No. 1 larva at day 3 after its appearance were significantly higher than day 0. Second, DA synthesis gene expression levels were extraordinarily high in the No. 1 larva at day 0-1 after appearance. Finally, injection of a DA receptor antagonist into the No. 1 larva resulted in the inhibition of presoldier differentiation. Behavioural observations of the antagonist or control-injected larvae suggested that brain DA and signalling activity regulate the frequencies of trophallaxis from reproductives and presoldier differentiation. Because trophallaxis is a social behaviour frequently observed in natural conditions, the role of DA should be investigated in other social insects with frequent trophallactic and allogrooming behaviour.

Venom and Dufour's glands of the emerald cockroach wasp Ampulex compressa (Insecta, Hymenoptera, Sphecidae): structural and biochemical aspects

The digger wasp species Ampulex compressa produces its venom in two branched gland tubules. They terminate in a short common duct, which is bifurcated at its proximal end. One leg is linked with the venom reservoir, the other one extends to the ductus venatus. Each venom gland tubule possesses, over its entire length, a cuticle-lined central duct. Around this duct densely packed class 3 gland units each composed of a secretory cell and a canal cell are arranged. The position of their nuclei was demonstrated by DAPI staining. The brush border of the secretory cells surrounds the coiled end-apparatus. Venom is stored in a bladder like reservoir, which is surrounded by a thin reticulated layer of muscle fibres. The reservoir as a whole is lined with class 3 gland units. The tubiform Dufour's gland has a length of about 350 μm (∅ 125 μm) only and is surrounded by a network of pronounced striated muscle fibres. The glandular epithelium is mono-layered belonging to the class 1 type of insect epidermal glands. The gland cells are characterized by conspicuous lipid vesicles. Secretion of material via the gland cuticle into the gland lumen is apparent. Analysis of the polypeptide composition demonstrated that the free gland tubules and the venom reservoir contain numerous proteins ranging from 3.4 to 200 kDa. The polypeptide composition of the Dufour's gland is completely different and contains no lectin-binding glycoproteins, whereas a dominant component of the venom droplets is a glycoprotein of about 80 kDa. Comparison of the venom reservoir contents with the polypeptide pattern of venom droplets revealed that all of the major proteinaceous constituents are secreted. The secreted venom contains exclusively proteins present in the soluble contents of the venom gland. The most abundant compound class in the Dufour's gland consisted of n-alkanes followed by monomethyl-branched alkanes and alkadienes. Heptacosane was the most abundant n-alkane. Furthermore, a single volatile compound, 2-methylpentan-3-one, was identified in various concentrations in the lipid extract of the Dufour's gland.

Two dopamine receptors play different roles in phase change of the migratory locust

The migratory locust, Locusta migratoria, shows remarkable phenotypic plasticity at behavioral, physiological, and morphological levels in response to fluctuation in population density. Our previous studies demonstrated that dopamine (DA) and the genes in the dopamine metabolic pathway mediate phase change in Locusta. However, the functions of different dopamine receptors in modulating locust phase change have not been fully explored. In the present study, DA concentration in the brain increased during crowding and decreased during isolation. The expression level of dopamine receptor 1 (Dop1) increased from 1 to 4 h of crowding, but remained unchanged during isolation. Injection of Dop1 agonist SKF38393 into the brains of solitary locusts promoted gregarization, induced conspecific attraction-response and increased locomotion. RNAi knockdown of Dop1 and injection of antagonist SCH23390 in gregarious locusts induced solitary behavior, promoted the shift to repulsion-response and reduced locomotion. By contrast, the expression level of dopamine receptor 2 (Dop2) gradually increased during isolation, but remained stable during crowding. During the isolation of gregarious locusts, injection of Dop2 antagonist S(–)-sulpiride or RNAi knockdown of Dop2 inhibited solitarization, maintained conspecific attraction-response and increased locomotion; by comparison, the isolated controls displayed conspecific repulsion-response and weaker motility. Activation of Dop2 in solitary locusts through injection of agonist, R(-)-TNPA, did not affect their behavioral state. Thus, DA-Dop1 signaling in the brain of Locusta induced the gregariousness, whereas DA-Dop2 signaling mediated the solitariness. Our study demonstrated that Dop1 and Dop2 modulated locust phase change in two different directions. Further investigation of Locusta Dop1 and Dop2 functions in modulating phase change will improve our understanding of the molecular mechanism underlying phenotypic plasticity in locusts.

The role of the cerebral ganglia in the venom-induced behavioral manipulation of cockroaches stung by the parasitoid jewel wasp

The jewel wasp stings cockroaches and injects venom into their cerebral ganglia, namely the subesophageal ganglion (SOG) and supraesophageal ganglion (SupOG). The venom induces a long-term hypokinetic state, during which the stung cockroach shows little or no spontaneous walking. It was shown that venom injection to the SOG reduces neuronal activity, thereby suggesting a similar effect of venom injection in the SupOG. Paradoxically, SupOG-ablated cockroaches show increased spontaneous walking in comparison with control. Yet most of the venom in the SupOG of cockroaches is primarily concentrated in and around the central complex (CX). Thus the venom could chiefly decrease activity in the CX to contribute to the hypokinetic state. Our first aim was to resolve this discrepancy by using a combination of behavioral and neuropharmacological tools. Our results show that the CX is necessary for the initiation of spontaneous walking, and that focal injection of procaine to the CX is sufficient to induce the decrease in spontaneous walking. Furthermore, it was shown that artificial venom injection to the SOG decreases walking. Hence our second aim was to test the interactions between the SupOG and SOG in the venom-induced behavioral manipulation. We show that, in the absence of the inhibitory control of the SupOG on walking initiation, injection of venom in the SOG alone by the wasp is sufficient to induce the hypokinetic state. To summarize, we show that venom injection to either the SOG or the CX of the SupOG is, by itself, sufficient to decrease walking.

Modulation of dopaminergic neurotransmission induced by sublethal doses of the organophosphate trichlorfon in cockroaches

Organophosphate (OP) insecticides have been used indiscriminately, based on their high dissipation rates and low residual levels in the environment. Despite the toxicity of OPs to beneficial insects is principally devoted to the acetylcholinesterase (AChE) inhibition, the physiological mechanisms underlying this activity remain poorly understood. Here we showed the pharmacological pathways that might be involved in severe alterations in the insect locomotion and grooming behaviors following sublethal administration of the OP Trichlorfon (Tn) (0.25, 0.5 and 1 µM) in Phoetalia pallida. Tn inhibited the acetylcholinesterase activity (46±6, 38±3 and 24±6 nmol NADPH/min/mg protein, n=3, p<0.05), respectively. Tn (1 µM) also increased the walking maintenance of animals (46±5 s; n=27; p<0.05). Tn caused a high increase in the time spent for this behavior (344±18 s/30 min, 388±18 s/30 min and 228±12 s/30 min, n=29-30, p<0.05, respectively). The previous treatment of the animals with different cholinergic modulators showed that pirenzepine>atropine>oxotremorine>d-tubocurarine>tropicamide>methoctramine induced a decrease on Tn (0.5 µM)-induced grooming increase, respectively in order of potency. Metoclopramide (0.4 µM), a DA-D2 selective inhibitor decreased the Tn-induced grooming activity (158±12 s/30 min; n=29; p<0.05). Nevertheless, the effect of the selective DA-D1 receptor blocker SCH 23390 (1.85 µM) on the Tn (0.5 µM)-induced grooming increase was significative and more intense than that of metoclopramide (54±6 s/30 min; n=30; p<0.05). Taken together the results suggest that a cross-talking between cholinergic M1/M3 and dopaminergic D1 receptors at the insect nervous system may play a role in the OP-mediated behavioral alterations.

Grooming behavior in American cockroach is affected by novelty and odor

The main features of grooming behavior are amazingly similar among arthropods and land vertebrates and serve the same needs. A particular pattern of cleaning movements in cockroaches shows cephalo-caudal progression. Grooming sequences become longer after adaptation to the new setting. Novelty related changes in grooming are recognized as a form of displacement behavior. Statistical analysis of behavior revealed that antennal grooming in American cockroach, Periplaneta americana L., was significantly enhanced in the presence of odor.

Grooming Behavior as a Mechanism of Insect Disease Defense

Grooming is a well-recognized, multipurpose, behavior in arthropods and vertebrates. In this paper, we review the literature to highlight the physical function, neurophysiological mechanisms, and role that grooming plays in insect defense against pathogenic infection. The intricate relationships between the physical, neurological and immunological mechanisms of grooming are discussed to illustrate the importance of this behavior when examining the ecology of insect-pathogen interactions.

Parasitoid wasp virulence: A window into fly immunity

In nature, larvae of the fruit fly Drosophila melanogaster are commonly infected by parasitoid wasps. Following infection, flies mount an immune response termed cellular encapsulation in which fly immune cells form a multilayered capsule that covers and kills the wasp egg. Parasitoids have thus evolved virulence factors to suppress cellular encapsulation. To uncover the molecular mechanisms underlying the antiwasp response, we and others have begun identifying and functionally characterizing these virulence factors. Our recent work on the Drosophila parasitoid Ganaspis sp.1 has demonstrated that a virulence factor encoding a SERCA-type calcium pump plays an important role in Ganaspis sp.1 virulence. This venom SERCA antagonizes fly immune cell calcium signaling and thereby prevents the activation of the encapsulation response. In this way, the study of wasp virulence factors has revealed a novel aspect of fly immunity, namely a role for calcium signaling in fly immune cell activation, which is conserved with human immunity, again illustrating the marked conservation between fly and mammalian immune responses. Our findings demonstrate that the cellular encapsulation response can serve as a model of immune cell function and can also provide valuable insight into basic cell biological processes.

What can parasitoid wasps teach us about decision-making in insects?

Millions of years of co-evolution have driven parasites to display very complex and exquisite strategies to manipulate the behaviour of their hosts. However, although parasite-induced behavioural manipulation is a widespread phenomenon, the underlying neuronal mechanisms are only now beginning to be deciphered. Here, we review recent advancements in the study of the mechanisms by which parasitoid wasps use chemical warfare to manipulate the behaviour of their insect hosts. We focus on a particular case study in which a parasitoid wasp (the jewel wasp Ampulex compressa) performs a delicate brain surgery on its prey (the American cockroach Periplaneta americana) to take away its motivation to initiate locomotion. Following a brief background account of parasitoid wasps that manipulate host behaviour, we survey specific aspects of the unique effects of the A. compressa venom on the regulation of spontaneous and evoked behaviour in the cockroach host.

Investigating candidate neuromodulatory systems underlying parasitic manipulation: concepts, limitations and prospects

Studies addressing the functional basis of parasitic manipulation suggest that alteration of the neuromodulatory system is a common feature of manipulated hosts. Screening of the neuromodulatory system has so far been carried out by performing ethopharmacological analysis, biochemical quantification of neurotransmitters and neuromodulators, and/or immunocytochemistry. Here, we review the advantages and limitations of such approaches through the analysis of case studies. We further address whether the analysis of candidate neuromodulatory systems fits the current view of manipulation as being multidimensional. The benefits in combining ethopharmacology with more recent molecular tools to investigate candidate neuromodulatory pathways is also emphasized. We conclude by discussing the value of a multidisciplinary study of parasitic manipulation, combining evolutionary (parasite transmission), behavioural (syndrome of manipulation) and neuroimmunological approaches.

Conserved role of dopamine in the modulation of behavior

Dopamine is an ancient signaling molecule. It is responsible for maintaining the adaptability of behavioral outputs and is found across taxa. The following is a summary of the role of dopamine and the mechanisms of its function and dysfunction. We discuss our recent findings on dopaminergic control of behaviors in C. elegans and discuss its potential implications for work in the fields of C. elegans and Parkinson research.

Social interactions influence dopamine and octopamine homeostasis in the brain of the ant Formica japonica

In ants, including Formica japonica, trophallaxis and grooming are typical social behaviors shared among nestmates. After depriving ants of either food or nestmates and then providing them with either food or nestmates, a behavioral change in type and frequency of social interactions was observed. We hypothesized that starvation and isolation affected levels of brain biogenic amines including dopamine (DA) and octopamine (OA) - neuromediators modifying various insect behaviors - and tested the relationship between brain biogenic amines and social behaviors of stressed ants. Ants starved for 7 days contained lower brain DA levels and they did not perform trophallaxis toward nestmates. Feeding starved ants sucrose solution re-established trophallaxis but not brain DA levels. The performance of trophallaxis induced recovery of brain DA content to the level of untreated ants. Ants that were isolated for 2 days displayed markedly increased OA levels, which following nestmate interactions, returned to levels similar to those of control (non-isolated) ants and ants isolated for 1 h. We conclude that: (1) starvation reduced brain DA level but had no significant effect on brain OA (trophallaxis recovered the brain DA levels), and (2) isolation increased brain OA level but had no effect on brain DA (trophallaxis and grooming events recovered the brain OA levels). We suggest that social interactions with nestmates influenced brain biogenic amine homeostasis in stressed F. japonica.

Structure, chemical composition and putative function of the postpharyngeal gland of the emerald cockroach wasp, Ampulex compressa (Hymenoptera, Ampulicidae)

The postpharyngeal gland (PPG) plays a major role in the social integration of ant colonies. It had been thought to be restricted to ants but was recently also described for a solitary wasp, the European beewolf (Philanthus triangulum). This finding posed the question whether the gland has evolved independently in the two taxa or has been inherited from a common ancestor and is hence homologous. The latter alternative would be supported if a PPG was found in more basal taxa. Therefore, we examined a species at the base of the Apoidea, the solitary ampulicid wasp Ampulex compressa, for the existence of a PPG. Both sexes of this species possess a cephalic gland that branches off the posterior part of the pharynx, is lined by a cuticular intima and surrounded by a monolayered epithelium with the epithelial cells bearing long hairs. Most of these morphological characteristics conform to those of the PPG of ants and beewolves. Chemical analysis of the gland content revealed that it contains mainly hydrocarbons and that there is a congruence of the pattern of hydrocarbons in the gland, on the cuticle, and in the hemolymph, as has also been reported for both ants and beewolves. Based on these morphological and chemical results we propose that the newly described cephalic gland is a PPG and discuss its possible function in A. compressa. The present study supports the view of a homologous origin of the PPG in the aculeate Hymenoptera.

Modulation of motor behavior by dopamine and the D1-like dopamine receptor AmDOP2 in the honey bee

Determining the specific molecular pathways through which dopamine affects behavior has been complicated by the presence of multiple dopamine receptor subtypes that couple to different second messenger pathways. The observation of freely moving adult bees in an arena was used to investigate the role of dopamine signaling in regulating the behavior of the honey bee. Dopamine or the dopamine receptor antagonist flupenthixol was injected into the hemolymph of worker honey bees. Significant differences between treated and control bees were seen for all behaviors (walking, stopped, upside down, grooming, flying and fanning), and behavioral shifts were dependent on drug dosage and time after injection. To examine the role of dopamine signaling through a specific dopamine receptor in the brain, RNA interference was used to reduce expression levels of a D1-like receptor, AmDOP2. Injection of Amdop2 dsRNA into the mushroom bodies reduced the levels of Amdop2 mRNA and produced significant changes in the amount of time honey bees spent performing specific behaviors with reductions in time spent walking offset by increases in grooming or time spent stopped. Taken together these results establish that dopamine plays an important role in regulating motor behavior of the honey bee.

Manipulation of host behavior by parasitic insects and insect parasites

Parasites often alter the behavior of their hosts in ways that are ultimately beneficial to the parasite or its offspring. Although the alteration of host behavior by parasites is a widespread phenomenon, the underlying neuronal mechanisms are only beginning to be understood. Here, we focus on recent advances in the study of behavioral manipulation via modulation of the host central nervous system. We elaborate on a few case studies, in which recently published data provide explanations for the neuronal basis of parasite-induced alteration of host behavior. Among these, we describe how a worm may influence the nervous system of its cricket host and manipulate the cricket into committing suicide by jumping into water. We then focus on Ampulex compressa, which uses an Alien-like strategy for the sake of its offspring. Unlike most venomous hunters, this wasp injects venom directly into specific cerebral regions of its cockroach prey. As a result of the sting, the cockroach remains alive but immobile, but not paralyzed, and serves to nourish the developing wasp larva.

Neurobiology: venom of wasps and initiation of movements

The ability to initiate movements can be impaired in some brain injuries even though motor actions proceed normally once they are begun. The effects of venom that wasps use in preying upon cockroaches could provide insights into this problem.

Octopamine partially restores walking in hypokinetic cockroaches stung by the parasitoid waspAmpulex compressa

When stung by the parasitoid wasp Ampulex compressa, cockroaches Periplaneta americana enter a hypokinetic state that is characterized by little, if any, spontaneous locomotor activity. In the present study we investigate the effect of an octopamine receptor agonist and an antagonist on the locomotor behavior of stung and control cockroaches. We show that in cockroaches stung by a wasp the octopamine receptor agonist chlordimeform induces a significant increase in spontaneous walking. In good agreement, in control individuals an octopamine receptor antagonist significantly reduces walking activity. Adipokinetic hormone I (AKH-I) promotes spontaneous walking in controls but does not do so in stung individuals, which suggests that the venom effect is most probably not mediated by AKH-I. Dopamine receptor agonists or antagonists had no significant effect on the spontaneous walking of stung or control cockroaches, respectively. The effect of the octopamine receptor agonist was maximal when injected into the brain, suggesting that the wasp venom interferes with octopaminergic modulation of walking initiation in central structures of the cockroach brain.

Evolution of developmental strategies in parasitic hymenoptera

Parasitoid wasps have evolved a wide spectrum of developmental interactions with hosts. In this review we synthesize and interpret results from the phylogenetic, ecological, physiological, and molecular literature to identify factors that have influenced the evolution of parasitoid developmental strategies. We first discuss the origins and radiation of the parasitoid lifestyle in the Hymenoptera. We then summarize how parasitoid developmental strategies are affected by ecological interactions and assess the inventory of physiological and molecular traits parasitoids use to successfully exploit hosts. Last, we discuss how certain parasitoid virulence genes have evolved and how these changes potentially affect parasitoid-host interactions. The combination of phylogenetic data with comparative and functional genomics offers new avenues for understanding the evolution of biological diversity in this group of insects.

Parasitoid wasp uses a venom cocktail injected into the brain to manipulate the behavior and metabolism of its cockroach prey

Unlike other venomous predators, the parasitoid wasp Ampulex compressa incapacitates its prey, the cockroach Periplaneta americana, to provide a fresh food supply for its offspring. We first established that the wasp larval development, from egg laying to pupation, lasts about 8 days during which the cockroach must remain alive but immobile. To this end, the wasp injects a cocktail of neurotoxins to manipulate the behavior of the cockroach. The cocktail is injected directly into the head ganglia using biosensors located on the stinger. The head sting induces first 30 min of intense grooming followed by hypokinesia during which the cockroach is unable to generate an escape response. In addition, stung cockroaches survive longer, lose less water, and consume less oxygen. Dopamine contained in the venom appears to be responsible for inducing grooming behavior. For the hypokinesia, our hypothesis is that the injected venom affects neurons located in the head ganglia, which send descending tonic input to bioaminergic neurons. These, in turn, control the thoracic premotor circuitry for locomotion. We show that the activity of identified octopaminergic neurons from the thoracic ganglia is altered in stung animals. The alteration in the octopaminergic neurons' activity could be one of the mechanisms by which the venom modulates the escape circuit in the cockroach's central nervous system and metabolism in the peripheral system.

Parasitoid wasp affects metabolism of cockroach host to favor food preservation for its offspring

Unlike predators, which immediately consume their prey, parasitoid wasps incapacitate their prey to provide a food supply for their offspring. We have examined the effects of the venom of the parasitoid wasp Ampulex compressa on the metabolism of its cockroach prey. This wasp stings into the brain of the cockroach causing hypokinesia. We first established that larval development, from egg laying to pupation, lasts about 8 days. During this period, the metabolism of the stung cockroach slows down, as measured by a decrease in oxygen consumption. Similar decreases in oxygen consumption occurred after pharmacologically induced paralysis or after removing descending input from the head ganglia by severing the neck connectives. However, neither of these two groups of cockroaches survived more than six days, while 90% of stung cockroaches survived at least this long. In addition, cockroaches with severed neck connectives lost significantly more body mass, mainly due to dehydration. Hence, the sting of A. compressa not only renders the cockroach prey helplessly submissive, but also changes its metabolism to sustain more nutrients for the developing larva. This metabolic manipulation is subtler than the complete removal of descending input from the head ganglia, since it leaves some physiological processes, such as water retention, intact.

Wasp venom injected into the prey's brain modulates thoracic identified monoaminergic neurons

The wasp Ampulex compressa injects a cocktail of neurotoxins into the brain of its cockroach prey to induce an enduring change in the execution of locomotory behaviors. Our hypothesis is that the venom injected into the brain indirectly alters the activity of monoaminergic neurons, thus changing the levels of monoamines that tune the central synapses of locomotory circuits. The purpose of the present investigation was to establish whether the venom alters the descending control, from the brain, of octopaminergic neurons in the thorax. This question was approached by recording the activity of specific identified octopaminergic neurons after removing the input from the brain or after a wasp sting into the brain. We show that the activity of these neurons is altered in stung and "brainless" animals. The spontaneous firing rate of these neurons in stung and brainless animals is approximately 20% that in control animals. Furthermore, we show that an identified octopamine neuron responds more weakly both to sensory stimuli and to direct injection of current in all treated groups. The alteration in the activity of octopamine neurons is likely to be part of the mechanism by which the wasp induces a change in the behavioral state of its prey and also affects its metabolism by reducing the potent glycolytic activator fructose 2,6-bisphosphate in leg muscle. To our knowledge, this is the first direct evidence of a change in electrical activity of specific monoaminergic neurons that can be so closely associated with a venom-induced change in behavioral state of a prey animal.

Insights into age-related locomotor declines from studies of insects

Locomotor deficits frequently accompany aging in animals. These deficits are often caused by degeneration in the nervous and musculoskeletal systems. Insects are an excellent model for age-related behavior studies because they are short-lived and have a reduced nervous system with fewer cells than vertebrates. Furthermore, they are highly mobile and display a complex set of locomotor behaviors. This review presents research that has examined age-related locomotor deficits in insects and discusses the value of these studies to understand aging processes in all animals.

Wasp manipulates cockroach behavior by injecting venom cocktail into prey central nervous system

The parasitoid wasp Ampulex compressa induces behavioral changes in the cockroach prey by injecting venom into its central nervous system. In contrast to most other venomous predators, the wasp's sting does not induce paralysis. Rather, the two consecutive stings in the thoracic and head ganglia induce three stereotypic behavioral effects. The prey behavior is manipulated in a way beneficial to the wasp and its offspring by providing a living meal for its newborn larva. The first sting in the thorax causes a transient front leg paralysis lasting a few minutes. This paralysis prevents the cockroach from fighting with its front legs, thereby facilitating the second sting in the head. A postsynaptic block of central synaptic transmission mediates this leg paralysis. Following the head sting, dopamine identified in the venom induces 30 minutes of intense grooming that appears to prevent the cockroach from straying until the last and third behavioral effect of hypokinesia commences. In this lethargic state that lasts about three weeks, the cockroach does not respond to various stimuli nor does it initiates movement. However, other specific behaviors of the prey are unaffected. We propose that the venom represses the activity of head ganglia neurons thereby removing the descending excitatory drive to specific thoracic neurons.

Channel-forming activity in the venom of the cockroach-hunting wasp, Ampulex compressa

The parasitoid solitary wasp Ampulex compressa uses the cockroach Periplaneta americana as a food supply for its larvae. To subdue its prey, the wasp injects a venom cocktail into the brain of the cockroach. We investigated channel activity of A. compressa venom by collecting venom and incorporating it into a planar lipid bilayer. The venom, reconstituted into the bilayer, showed ion channel activity, forming a fast-fluctuating channel with a small conductance of 20+/-0.1pS, with no voltage sensitivity. These channels were not observed when the venom was digested with proteases before application to the bilayer, but were not affected by exposure to protease after their incorporation into the bilayer, indicating that the active venom component is a peptide. The channels were found to be cation selective with similar selectivity for the monovalent cations K(+), Li(+) and Na(+), but showed high selectivity against anions (Cl(-)) and divalent cations (Ca(2+) and Mg(2+)). This study is the first demonstration and biophysical characterization of channel activity in the venom of A. compressa. The possible functional significance of this channel activity is discussed in light of the unusual nature of the effects of this wasp venom on the behavior of its prey.

Wasp parasitoid disruption of host development: implications for new biologically based strategies for insect control

Wasp parasitoids use a variety of methods to commandeer their insect hosts in order to create an environment that will support and promote their own development, usually to the detriment of the host insect. Parasitized insects typically undergo developmental arrest and die sometime after the parasitoid has become independent of its host. Parasitoids can deactivate their host's immune system and effect changes in host hormone titers and behavior. Often, host tissues or organs become refractory to stimulation by tropic hormones. Here we present an overview of the manipulative capabilities of wasp-injected calyx fluid containing polydnaviruses and venom, as well as the parasitoid larva and the teratocytes that originate from the serosal membrane that surrounds the developing embryo of the parasitoid. Possibilities for using regulatory molecules produced by the parasitoid or its products that would be potentially useful in developing new, environmentally safe insect control agents are discussed.

Direct injection of venom by a predatory wasp into cockroach brain

In this article, we provide direct evidence for injection of venom by a wasp into the central nervous system of its cockroach prey. Venomous predators use neurotoxins that generally act at the neuromuscular junction, resulting in different types of prey paralysis. The sting of the parasitoid wasp Ampulex compressa is unusual, as it induces grooming behavior, followed by a long-term lethargic state of its insect prey, thus ultimately providing a living meal for the newborn wasp larvae. These behavioral modifications are induced only when a sting is inflicted into the head. These unique effects of the wasp venom on prey behavior suggest that the venom targets the insect's central nervous system. The mechanism by which behavior modifying compounds in the venom transverse the blood-brain barrier to induce these central and long-lasting effects has been the subject of debate. In this article, we demonstrate that the wasp stings directly into the target ganglia in the head of its prey. To prove this assertion, we produced "hot" wasps by injecting them with (14)C radiolabeled amino acids and used a combination of liquid scintillation and light microscopy autoradiography to trace radiolabeled venom in the prey. To our knowledge, this is the first direct evidence documenting targeted delivery of venom by a predator into the brain of its prey.

Wasp venom blocks central cholinergic synapses to induce transient paralysis in cockroach prey

The parasitoid wasp Ampulex compressa induces a set of unique behavioral effects upon stinging its prey, the cockroach. It stings into the first thoracic segment inducing 2 to 3 min of transient flaccid paralysis of the front legs. This facilitates a second sting in the cockroach's head that induces 30 min of excessive grooming followed by a 2 to 5-week long lethargic state. In the present study, we examine the immediate effect of the first sting, which is a transient paralysis of the front legs. Using radiolabeled wasps, we demonstrate that the wasp injects its venom directly into the cockroach's first thoracic ganglion. The artificial injection of milked venom into a thoracic ganglion abolishes spontaneous and evoked responses of the motoneurons associated with leg movements. To investigate the physiological mechanism of action of the venom, we injected venom into the last abdominal ganglion of the cockroach, which houses a well-characterized cholinergic synapse. Injected venom abolishes both sensory-evoked and agonist-evoked postsynaptic potentials recorded in the postsynaptic neuron for 2 to 3 min without affecting action potential propagation. Thus, the venom blocking effect has a postsynaptic component that follows the same time course as the transient paralysis induced by the thoracic sting. Finally, injection of a nicotinic antagonist in the front thoracic ganglion induces paralysis of the front legs. We conclude that the transient paralytic effect of the thoracic sting can be mainly accounted for by the presence of a venom active component that induces a postsynaptic block of central cholinergic synaptic transmission.

Digger wasp versus cricket: mechanisms underlying the total paralysis caused by the predator's venom

The data presented here describe neurophysiological experiments addressing the question of cellular mechanisms underlying the total paralysis of locomotor behavior in crickets occurring after being stung by females of the digger wasp species Liris niger. The Liris venom effects have been studied by both in vivo recordings from identified neurons of the well-described giant fiber pathway and in vitro recordings from cultured neurons isolated from the terminal ganglion of crickets. The total paralysis of the prey is characterized by a general block of action potential generation as well as by a block of synaptic transmission. Intracellular recordings from neurons in intact ganglia under single electrode voltage-clamp conditions, as well as whole-cell patch-clamp recordings from cultured cricket neurons consistently show that the block of action potential generation by the Liris venom is due to a block of voltage-gated sodium inward currents in neurons of the stung ganglia. Furthermore, our data provide evidence that the Liris venom also blocks calcium currents in identified neurosecretory neurons. On the other hand, outward currents are not affected by the Liris venom. The in vitro recordings suggest that the Liris venom contains active venom components, which, at least for the observed block of inward currents, do not require a metabolic modification. Because venom application does not affect the ACh-induced EPSPs in giant interneurons, the Liris venom does not seem to influence the postsynaptic ACh receptors. The possible pre- and postsynaptic sites of venom action and the functional consequences on synaptic transmission within the giant fiber system are discussed.