Defence behaviours of the praying mantis Tenodera aridifolia in response to looming objects

Defence responses to approaching objects were observed in the mantis Tenodera aridifolia. The mantis showed three kinds of behaviour, fixation, evasion and cryptic reaction. The cryptic reaction consisted of rapid retraction of the forelegs under the prothorax or rapid extending of the forelegs in the forward direction. Obstructing the mantis’ sight decreased its response rates, suggesting that the visual stimuli generated by an approaching object elicited the cryptic reaction. The response rate of the cryptic reactions was highest for objects that approached on a direct collision course. Deviation in a horizontal direction from the direct collision course resulted in a reduced response. The response rate of the cryptic reaction increased as the approaching velocity of the object increased, and the rate decreased as the object ceased its approach at a greater distance from the mantis. These results suggest that the function of the observed cryptic reactions is defence against impending collisions. The possible role of the looming-sensitive neuron in the cryptic reaction is also discussed.     

Investigating saccade programming in the praying mantis Tenodera aridifolia using distracter interference paradigms

To investigate the saccadic system in the mantis, I applied distracter interference paradigms. These involved presenting the mantis with a fixation target and one or several distracters supposed to affect saccades towards the target. When a single target was presented, a medium-sized target located in its lower visual field elicited higher rates of saccade response. This preference for target size and position was also observed when a target and a distracter were presented simultaneously. That is, the mantis chose and fixated the target rather than a distracter that was much smaller or larger than the target, or was located above the target. Furthermore, the mantis' preference was not affected by increasing the number of distracters. However, the presence of the distracter decreased the occurrence rate of saccade and increased the response time to saccade. I conclude that distracter interference paradigms are an effective way of investigating the visual processing underlying saccade generation in the mantis. Possible mechanisms of saccade generation in the mantis are discussed.     

Coordinated movements of the head and body during orienting behaviour in the praying mantis Tenodera aridifolia

The visual orienting behaviour towards prey in the free-moving mantis was investigated with a high-speed camera. The orienting behaviour consisted of head, prothorax, and abdomen rotations. Coordinated movements of these body parts in the horizontal plane were analysed frame-by-frame. Rotations of these body parts were initiated with no or slight (≤40 ms) differences in timing. The initiation timing of prothorax-abdomen rotation was affected by its initial angle before the onset of orienting. There were positive correlations in amplitude among head-prothorax, prothorax-abdomen, and abdomen rotations. The ratio of these rotations to total gaze rotation was affected by the initial prothorax-abdomen angle before the onset of orienting. Our data suggest that coordinated movements of the head, prothorax, and abdomen during orienting are ballistic events and are pre-determined according to visual and proprioceptive information before the onset of orienting.     

Predatory behavior of the praying mantis,Tenodera aridifolia I. Effect of prey size on prey recognition

Predatory behavior and effect of prey size of the praying mantis,Tenodera aridifolia, was investigated using three-dimensional prey models. Parameters of prey such as width, length, shape (length/width), area (width×length) and volume were investigated for effects on Watch and Attack responses. Regression analyses suggest that volume is the most important variable in prey recognition. This behavioral trait is considered adaptive, since prey volume is the most reliable measurement for the energy content of the prey.     

Saccadic tracking of a light grey target in the mantis,Tenodera aridifolia

I presented a horizontally moving square on a computer display to the mantis, Tenodera aridifolia, and examined the effects of target brightness and velocity, and background brightness on its tracking behavior. The mantis tracked a light grey square with more saccadic head movements than a black square, although these squares moved on a homogeneous background. The amplitude of saccades was larger when the light grey square moved at a lower velocity. The background brightness had little effect on the type (smooth or saccadic) of tracking behavior. These results suggest that the saccadic tracking of light grey objects on a homogeneous background may not be caused by low contrast, i.e., the difficulty in discriminating the object from the background. The possible biological significance of saccadic tracking on a homogenous background is discussed.     

Responses to non-locomotive prey models by the praying mantis,Tenodera angustipennis Saussure

Adult females of the praying mantisTenodera angustipennis were presented with computer-generated images, and the attractiveness of “non-locomotive” prey models was examined. Mantises fixated and struck the “body and leg” model (consisting of an immobile black square on a white background with 2 black lines oscillating randomly at its sides) more frequently than the “leg” model (only oscillating lines) or the “body” model (static square only). This indicates that the model consisting of a static object and moving lines effectively elicits mantis strike behavior, although it is “non-locomotive.”     

Predatory behavior of the praying mantis,Tenodera aridifolia II. Combined effect of prey size and predator size on the prey recognition

Predatory behavior of the praying mantis,Tenodera aridifolia, as a function of the combined effect of its size and the size of the prey was investigated by using prey models. Behavioral responses were almost identical through the nymphal development in the predator. As the mantis grew, it attacked larger prey models, suggesting that it recognizes the prey's size in accordance with its own body size. Regression analyses demonstrate that the ratio of the prey's volume to the cube and the square of the predator's length is a more important parameter for prey recognition than are the one-dimensional parameters of the prey's and the predator's sizes.     

Responses to computer-generated visual stimuli by the male praying mantis, Sphodromantis lineola (Burmeister)

We tested male mantis' responses to square, computer-generated visual stimuli of various sizes to determine the stimulus parameters that affect their striking behaviour. Males in a high-hunger group displayed a sharp preference for solid black 12×12-degree squares moving linearly against a white background, especially when the squares moved downward (versus horizontally). Males in a low-hunger group visually tracked but, with rare exception, did not strike at any linearly moving squares. In contrast, when solid black squares moved erratically around visual field centre, males struck regularly at them irrespective of hunger level, even when the squares were as large as 47×47 degrees. Males also recognized black-and-white Julesz-patterned square stimuli moving against a similarly patterned background, indicating that they recognized the synchronous movement of a group of stimulus elements as a single moving object. Finally, we compared allometric and life history data between male and females S. lineola to elucidate the possible reasons for the differences between male response patterns and previously published data on females. These comparisons suggest that males employ a different behavioural strategy than do females when faced with large, erratically moving visual stimuli.     

Responses of descending neurons to looming stimuli in the praying mantis <Emphasis Type="Italic">Tenodera aridifolia</Emphasis>

Responses to visual stimuli of some neurons that descend the nerve cord from the brain were recorded extracellularly in the mantis Tenodera aridifolia. Most of the recorded neurons showed their largest responses to looming stimuli that simulated a black circle approaching towards the mantis. The neurons showed a transient excitatory response to a gradually darkening or receding circle. The neurons showed sustained excitation to the linearly expanding stimuli, but the spike frequency decreased rapidly. The responses of the neurons were affected by both the diameter and the speed of looming stimuli. Faster or smaller looming stimuli elicited a higher peak frequency. These responses were observed in both recordings from the connective between suboesophageal and prothoracic ganglia and the connective between prothoracic and mesothoracic ganglia. There was a one-to-one correspondence of spike firing between these two recordings with a fixed delay. The neurons had the receptive field on ipsilateral side to its axon at the cervical connective. These results suggest that there is a looming-sensitive descending neuron, with an axon projecting over prothoracic ganglion, in the mantis nervous system.     

Purification and characterization of a serine protease with fibrinolytic activity from Tenodera sinensis (praying mantis)

Mantis egg fibrolase (MEF) was purified from the egg cases of Tenodera sinensis using ammonium sulfate fractionation, gel filtration on Bio-Gel P-60 and affinity chromatography on DEAE Affi-Gel blue gel. The protease was assessed homogeneous by SDS-polyacrylamide gel electrophoresis and has a molecular mass of 31500 Da. An isoelectric point of 6.1 was determined by isoelectric focusing. Amino acid sequencing of the N-terminal region established a primary structure composed of Ala-Asp-Val-Val-Gln-Gly-Asp-Ala-Pro-Ser. MEF readily digested the Aalpha- and Bbeta-chains of fibrinogen and more slowly the gamma-chain. The nonspecific action of the enzyme results in extensive hydrolysis of fibrinogen and fibrin releasing a variety of fibrinopeptide. The enzyme is inactivated by Cu2+ and Zn2+ and inhibited by PMSF and chymostatin, yet elastinal, aprotinin, TLCK, TPCK, EDTA, EGTA, cysteine, beta-mercaptoethanol, iodoacetate, E64, benzamidine and soybean trypsin inhibitor do not affect activity. Antiplasmin was not sensitive to MEF but antithrombin III inhibited the enzymatic activity of MEF. Among chromogenic protease substrates, the most sensitive to MEF hydrolysis was benzoyl-Phe-Val-Arg-p-nitroanilide with maximal activity at pH 7.0 and 30 degrees C. MEF preferentially cleaved the oxidized B-chain of insulin between Leu15 and Tyr16. D-Dimer concentrations increased on incubation of cross-linked fibrin with MEF, indicating the enzyme has a strong fibrinolytic activity.     

Visual stimuli that elicit appetitive behaviors in three morphologically distinct species of praying mantis

We assessed the differences in appetitive responses to visual stimuli by three species of praying mantis (Insecta: Mantodea), Tenodera aridifolia sinensis, Mantis religiosa, and Cilnia humeralis. Tethered, adult females watched computer generated stimuli (erratically moving disks or linearly moving rectangles) that varied along predetermined parameters. Three responses were scored: tracking, approaching, and striking. Threshold stimulus size (diameter) for tracking and striking at disks ranged from 3.5 deg (C. humeralis) to 7.8 deg (M. religiosa), and from 3.3 deg (C. humeralis) to 11.7 deg (M. religiosa), respectively. Unlike the other species which struck at disks as large as 44 deg, T. a. sinensis displayed a preference for 14 deg disks. Disks moving at 143 deg/s were preferred by all species. M. religiosa exhibited the most approaching behavior, and with T. a. sinensis distinguished between rectangular stimuli moving parallel versus perpendicular to their long axes. C. humeralis did not make this distinction. Stimulus sizes that elicited the target behaviors were not related to mantis size. However, differences in compound eye morphology may be related to species differences: C. humeralis’ eyes are farthest apart, and it has an apparently narrower binocular visual field which may affect retinal inputs to movement-sensitive visual interneurons.     

Head grooming behaviour in the praying mantis

Mantis head grooming is a rhythmic behaviour pattern involving co-ordinated movements of head and foreleg. The probability of grooming is influenced by releaser concentration, while the number of cycles/episode is influenced by concentration and amount of releaser. Within a grooming episode (usually 4 to 6 cycles) successive cycles are longer in duration; this is primarily caused by an increase in the actual head cleaning phase, although all three phases increase in duration. The phase cleaning the femur brush is most sensitive to feedback effects from releaser substances. It is concluded that head grooming is a programmed, i.e. centrally organized, movement pattern responsive to peripheral feedback. First approximations to the model-equations and model-hypotheses are presented.     

Responses to worm-like-wriggling models by the praying mantis: effects of amount of motion on prey recognition

Adult females of the mantis, Tenodera angustipennis, were presented with a wriggling model, consisting of six circular spots positioned in a row horizontally and adjacently. During presentation, this model wriggled like a worm by moving some spots. When the motion of the model was small (the number of moving spots ≤2), the mantis sometimes stalked the model with peering movements but seldom struck it. When the motion was large (the number of moving spots ≥3), the mantis frequently fixated, rapidly approached, and struck the model. These results suggest that the mantis changes its approach behavior depending on the amount of prey motion. Disappearance of some terminal spots at the stationary end hardly affected the rates of fixation, peering, and strike. The model that wriggled at each end elicited lower rates of fixation and strike than the model that wriggled at one end. These results suggest that the mantis responds to only the fastest moving part of the wriggling model when the motion of the model is large. Electronic Publication     

Visual stimuli that elicit visual tracking, approaching and striking behavior from an unusual praying mantis, Euchomenella macrops (Insecta: Mantodea)

In comparison to other similarly sized mantis species examined in previous studies, Euchomenella macrops has a significantly smaller head, shorter foreleg tibia, but longer prothorax which have been interpreted as specializations for the capture of smaller, slower prey. We tested this conjecture by assessing the rates at which computer generated stimuli elicit visual tracking, approaching, and striking behaviors by adult females. When presented with black disks moving erratically against a white background, strike rate rose progressively as disks enlarged up to 44 deg (visual angle) if the disks moved rapidly (e.g., 143 deg/s); at slower speeds (113, 127 deg/s), smaller disks (<27 deg) were preferred. When black moved linearly from the visual periphery to visual field center (at 73 or 143 deg/s) and then stopped, E. macrops struck consistently at disks as small as 5 deg after movement ceased. E. macrops also struck at higher rates in response to 23 deg erratically moving (subjective) red (versus subjective blue or green) disks that were luminance matched to a grey background although they tracked all colors at equally high rates. Unlike some other species, E. macrops did not strike at higher rates in response to elongated rectangular stimuli moving parallel (versus perpendicular) to their long axis, although the former elicited higher rates of approaching. An analysis of tracking behavior revealed that virtually all tracking movements were a result of head (versus) prothorax rotation.     

Parvalbumin-expressing interneurons linearly transform cortical responses to visual stimuli

The response of cortical neurons to a sensory stimulus is shaped by the network in which they are embedded. Here we establish a role of parvalbumin (PV)-expressing cells, a large class of inhibitory neurons that target the soma and perisomatic compartments of pyramidal cells, in controlling cortical responses. By bidirectionally manipulating PV cell activity in visual cortex we show that these neurons strongly modulate layer 2/3 pyramidal cell spiking responses to visual stimuli while only modestly affecting their tuning properties. PV cells' impact on pyramidal cells is captured by a linear transformation, both additive and multiplicative, with a threshold. These results indicate that PV cells are ideally suited to modulate cortical gain and establish a causal relationship between a select neuron type and specific computations performed by the cortex during sensory processing.