Prothoracic Legs Research Articles

Functional morphology and development of tibial organs in the legs I, II and III of the bushcricketEphippiger ephippiger (Insecta, Ensifera)

The anatomy of the complex tibial organs in the pro-, meso- and metathoracic legs of adults and larvae of the bushcricketEphippiger ephippiger is described comparatively. The subgenual organ and the intermediate organ are differentiated in the same way in legs I, II and III; the anatomy of the crista acustica and the tracheal morphology are significantly different. The final number of scolopidia in the tibial organ of each leg is present at the time of hatching. In the subgenual organ, the number of scolopidia is the same in all legs; in the intermediate organ, and especially in the crista acustica, the number of scolopidia decreases from leg I to legs II and III. In the first larval instar, the morphology of the tibia, the course of the trachea and the anatomy of accessory structures are developed in the same way in each leg. The specific differentiations forming the auditory receptor organ in leg I, such as the acoustic trachea, the tympana and tympanal cavities, develop step by step in subsequent instars. The auditory threshold recorded from the tympanal nerve in the prothoracic leg of adults is remarkably lower than in the meso- and metathoracic legs. Morphometrical analyses of structures that are suggested to play a role in stimulus transduction on scolopidia of the crista acustica reveal significant differences in the three legs.

Enhanced calling song syllable period discrimination during one-eared phonotaxis by the female cricket (Acheta domesticus)

1. In an arena, female Acheta domesticus, which walked directly to a standard model calling song (CS) in a pretest, displayed angular deviations and complete 360° circling following unilateral occlusion of the posterior and anterior tympana. Following removal of the occlusion, the crickets once again oriented directly to the sound source (Fig. 1). Following unilateral removal of the tibia of a prothoracic leg just distal to the ear, crickets oriented directly to a standard CS. Unilateral leg amputation just proximal to the ear caused angular deviations and circling which was similar to that following occlusion of an ear (Fig. 2). 2. Thresholds of auditory interneurons increased dramatically (to greater than 85 dB) following occlusion of the ear which provides excitatory input to these neurons. Removal of the occlusion restored responsiveness (Fig. 3). 3. The mean number of complete turns by a cricket with one ear occluded is greatest in response to syllable periods that are most attractive and thus can be used as a measurement of the relative attractiveness of the CS presented (Figs. 4, 5). Females that did not significantly discriminate between different syllable periods before unilateral occlusion of an ear, discriminated between CS syllable periods by their degree of circling following occlusion.

GABA and glutamate-like immunoreactivity in processes presynaptic to afferents from hair plates on the proximal joints of the locust leg

Hair plate afferents from coxal group 1 on the meso- and prothoracic legs of the locust were backfilled with cobalt salts or HRP for light and electron microscopy. The distribution of the terminal branches of the afferents is described from wholemount preparations and from 150 microns thick slices through the ganglion. Identified branches from the slices were sectioned for electron microscopy and examined for the presence of input and output synapses. Both were found in close proximity on small-diameter varicose branches in all parts of the arborization. Immunocytochemistry using antibodies against GABA and glutamate was used to try to identify putative transmitters in processes presynaptic to the afferents. Ninety-three percent of processes presynaptic to the hair plate afferents were clearly immunoreactive for GABA and only 7% appeared unlabelled. Most neuronal processes in the vicinity of afferent terminals were also immunoreactive for GABA, but a small number of glutamate-immunoreactive processes were found in intimate contact with afferents and one of these was demonstrated to be presynaptic. Processes postsynaptic to the afferents were of small diameter (mean = 0.28 micron) and were not found to be immunoreactive for GABA.

Hearing in a primitive ensiferan: the auditory system of Cyphoderris monstrosa (Orthoptera: Haglidae)

1. Insects of the family Haglidae are relicts of primitive Ensifera. Members of this group display acoustic behaviour in the typical ensiferan pattern, with males producing stereotyped acoustic signals by tegminal stridulation. They are closely related to the major groups of acoustic Ensifera, but their auditory system has not been previously studied. I present here a description of the morphology, and physiology of the peripheral auditory system of Cyphoderris monstrosa. 2. The tympana of C. monstrosa are similar to those of Tettigoniidae, but less well-differentiated from normal leg cuticle. The acoustic trachea is well-developed, but does not form a single, continuous tube in the leg proximal to the tympana. The organization of the auditory organ is similar to the Tettigoniidae, with the tibial organ comprising the subgenual organ, intermediate organ, and crista acustica. Projections of the tibial organ sensory cells to the prothoracic ganglion are also typical of acoustic Orthoptera. The meso- and metathoracic legs possess tibial organs similar to that of the prothoracic leg, although lacking tympana and well-developed acoustic tracheae. Central projections of the mesothoracic tibial organ are similar to those of the prothoracic. 3. Auditory whole nerve responses are not tuned to the frequency of the species calling song. Auditory best frequency (BF) is 2 kHz; calling song frequency is 12 kHz. Threshold intensity levels at BF are typical for insect hearing organs (35–45 dB SPL). The response of the auditory organ is not strongly directional at the calling song frequency. Occlusion of the acoustic trachea has no effect on the sensitivity, tuning, or directionality of the auditory system. Occlusion of either of the tympana alone also has no effect on auditory responses, but occlusion of both tympana leads to a marked decrease in sensitivity. Tuning is not affected. The tibial organ of the mesothoracic leg is sensitive to airborne sound at low frequencies (BF = 1 kHz) with thresholds comparable to the ear. 4. The auditory system of C. monstrosa is a pressure receiver, adapted to low frequency sensitivity. This low frequency tuning, in contrast to the calling song frequency, suggests an auditory system adapted to another function in addition to intraspecific communication.

Etude Experimentale Des Modalites De Communication Dans Le Comportement Sexuel De Calliphora Vomitoria (Diptera, Calliphoridae). 2. Role De La Tete Du Partenaire Sexuel

This paper analyzes the consequences of modifications of the head of the sexual partner on the initiation and behavioural processing of the courtship of the male Calliphora vomitoria. Experiments were made with male and female specimen without head, with an inverted head, or a head of the other sex. Courtship was quantitatively evaluated with respect to the latency time of the first contact the male made with the female, the duration of courtship and of the main acts performed, the frequency of these acts as well as the sequences in which they occurred, and the number of copulations. The results show that the structure of the male's courtship varies according to anatomical characteristics of the head of the partner. It seems that first, from a short distance, visual features of the head and especially of the inter-ocular space (which anatomically differs between the sexes) direct the male; they are of more importance than the integrated structure of the anterioposterior axis of the insect. After contact is made the male collects, on the basis of the visual information received, tactile and chemical information, mainly by drumming the head and specifically the interocular space with its prothoracic legs. Courtship was most severely disrupted to females with inverted heads; second to it came that to female decoys with male heads. On the basis of the results obtained the experiments can be arranged on a gliding scale from perverted to normal courtship. Several different courtship sequences can be effectuated with the activities available in the repertoire. Lack of signals from a decoy seem to be less of a handicap than false signals. The data suggest that for the organisation of normal courtship a certain coherence has to exist among the sensory stimuli, their order of appearance signalling the female's body. An internal image of the female seems to be compared with the pattern of stimulation received by the male.

Genetic analysis of extra sex combs in the hybrids between Drosophila subobscura and D. madeirensis

Drosophila subobscura and D. madeirensis are closely related species, the first distributed over a large area and the latter restricted to the island of Madeira. These species can hybridize in laboratory conditions, yielding fertile females and sterile males. Hybrid offspring show several phenotypic anomalies, including sex combs on the second and third pairs of legs in males. The extra sex comb trait is a homeotic transformation of the mesothoracic and metathoracic legs into prothoracic legs. This anomaly is observed almost exclusively in F1 males with D.madeirensis mothers. Analysis of backcross males shows that D.subobscura and D.madeirensis have diverged at a minimum of four autosomal loci affecting the extra sex comb anomaly. In addition, some incompatibility involving the X chromosome and/or a maternal effect is also implicated.

Reorganization of persistent motoneurons in a metamorphosing insect (Tenebrio molitor L., coleoptera)

The present analysis outlines how the shape of motoneurons which persist through metamorphosis in the beetle Tenebrio molitor is regulated by cellular interactions. This study focused on the structural changes of prothoracic leg motoneurons. The fate of these neurons is described in normal metamorphic development, so as to provide a basis for experimental analysis. In a first experiment the prothoracic leg imaginal discs or part of these were extirpated in the prepupa or early pupa. In a second experiment the leg imaginal discs were rotated by 180 degrees in early larval instars of Tenebrio; the procedure caused a threefold leg anlage. Thereafter, the treated individuals continued to develop. In both experiments the effect of the operation on the structure of the dendritic trees of the persisting motoneurons was analyzed at the imaginal stage. In the first experiment the dendritic tree of the motoneurons is locally deleted. In the second experiment the branching index (quantitative description of dendritic arborization pattern) of the dendritic tree of the persisting motoneurons increased. Both experiments provided evidence that the shape of persistent leg motoneurons is stabilized and even regulated by cellular interactions during metamorphosis. Evidence is presented that sensory neurons are effective both in stabilization and regulation of the shape of persistent motoneurons.

Embryonic development and evolutionary origin of the orthopteran auditory organs

Two different types of ears characterize the order of Orthopteran insects. The auditory organs of grasshoppers and locusts (Caelifera) are located in the first abdominal segment, those of bushcrickets and crickets (Ensifera) are found in the tibiae of the prothoracic legs. Using neuron-specific antibody labelling, we describe the ontogenetic origin of these two types of auditory organs, use comparative developmental studies to identify their segmental homologs, and on the basis of homology postulate their evolutionary origin. In grasshoppers the auditory receptors develop by epithelial invagination of the body wall ectoderm in the first abdominal segment. Subsequently, at least a part of the receptor cells undergo active migration and project their out-growing axons onto the next anterior intersegmental nerve. During this time the receptor cells and their axons express the cell-cell adhesion molecule, Fasciclin I. Similar cellular and molecular differentiation processes in neighboring segments give rise to serially homologous sensory organs, the pleural chordotonal organs in the pregenital abdominal segments, and the wing-hinge chordotonal organs in the thoracic segments. In more primitive earless grasshoppers pleural chordotonal organs are found in place of auditory organs in the first abdominal segment. In bushcrickets the auditory receptors develop in association with the prothoracic subgenual organ from a common developmental precursor. The auditory receptor neurons in these insects are homologous to identified mechanoreceptors in the meso- and metathoracic legs. The established intra- and interspecies homologies provide insight into the evolution of the auditory organs of Orthopterans.

Mating behavior in seaweed flies (Coelopa frigida)

Video recordings were used to obtain a detailed description of the mating behavior of seaweed flies. The roles of wings, antennae, and legs were inferred from ablation and masking experiments. There is no apparent interaction between flies over a distance of more than 1–2 cm. After mounting the prothoracic legs of the male are located in the region of the female's antennae and interactions between these structures appear to facilitate successful mating. There follows either a female rejection response or a voluntary dismount by the male, or mating proceeds to insemination. When triplets of one female and two males were observed, larger males often displaced small males and were themselves less frequently displaced. The observed opportunities for female choice, male choice, and male-male competition are discussed in the light of previous reports of differential male mating success and of assortative mating with respect to size and genotypes.

Neural control of leg movements in a metamorphic insect: persistence of larval leg motor neurons to innervate the adult legs of Manduca sexta.

During metamorphosis of the hawkmoth Manduca sexta, the larval thoracic legs along with their associated sensory organs and muscles degenerate and new adult legs develop. The larval legs are small and relatively simple structures capable of lateral extension and medial flexion allowing them to grasp the substrate as the caterpillar crawls along. By contrast, the adult legs are used for walking with an alternating gait. They are much larger than the larval legs and articulate such that they are capable of movement in several directions. This change in form and function is accompanied by a reorganization of the neural circuits controlling leg movements. In a previous report (Kent and Levine: J. Comp. Neurol. 271:559-576, '88) we described motor neurons innervating the larval prothoracic legs, and here we describe motor neurons innervating the prothoracic legs of the adult. Using a combination of cobalt staining methods and the persistent fluorescent dye Fluoro-Gold, we have found that some, if not all, larval leg motor neurons are retained and innervate the new adult leg muscles. Moreover, we have been able to discover the fate of individual larval leg motor neurons by marking a single larval neuron with Fluoro-Gold and using a second fluorescent dye to double label the same neuron in the adult. Our results suggest that specific larval leg motor neurons innervate corresponding muscles in the adult stage, although their apparent function is significantly different. In addition, the motor neurons undergo significant remodeling of their dendritic branching patterns during metamorphosis, alterations which doubtless contribute to their new roles in adult behavior.

Expression of the Sex combs reduced protein in Drosophila larvae

We have generated a monoclonal antibody that binds specifically to the protein product of the homeotic Sex combs reduced ( Scr) gene of Drosophila, and have mapped the patterns of Scr expression in late third instar larvae. Virtually the entire prothoracic leg imaginal disc expresses the gene, although the levels of expression vary in different disc regions. This heterogeneity does not reflect the compartmental domains defined by engrailed gene expression. Expression is also observed in the cells of the humeral and labial discs, and there is a small patch of Scr-expressing cells in the antenna disc. The gene is expressed in adepithelial cells of the three thoracic leg discs, but not in the wing or haltere discs. In the central nervous system, Scr expression is confined to a narrow band of cells in the subesophageal region of the ventral ganglion. The results are discussed with respect to the known genetic requirements for Scr + function.

Anatomy of the Ventral Eversible Gland of Fall Armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae), Larvae1

The ventral eversible gland (VEG) of the fifth instar fall armyworm, Spodoptera frugiperda (J. E. Smith), is described and illustrated. The orifice of the VEG is a transverse slit anterior to the prothoracic legs. An increase in hemocoelic pressure everts the VEG, and the action of six pairs of retractor muscles inverts it. The VEG consists of two functionally different regions-a noneversible glandular sac lined with secretory cells, and an eversible cuticular tube which, when everted, forms a visible, external papilla. Eversion is pleurecbolic, occurring by movement of the sides of the cuticular tube rather than the apex, in response to hemocoelic pressure. A secondary glandular region occurs on the ventral surface of the everted cuticular tube. Neither the function of the VEG nor the chemical composition of its secretion is known.

Time course of the Houseflies' landing response

The landing response of stationary flying houseflies Musca domestica has been recorded on video tape. The leg movements were quantitatively evaluated. It could be demonstrated that: 1) only the first two pairs of legs are involved in the reaction (Fig. 1). Prothoracic tarsi are lifted beyond the head, mesothoracic tarsi are lowered and moved sidewards (Fig. 2a and b). 2) the movement of the tarsal tips is mainly due to an opening of one single joint per leg, i.e. the femurtibia joint of the prothoracic leg (Fig. 2c), and the coxa-femur joint of the mesothoracic leg. 3) the landing reaction is a fixed action pattern which does not seem to require further sensory input once it is released (Fig. 4d). 4) the landing responses to a light-off stimulus and to expanding patterns with different angular velocities are indistinguishable (compare Fig. 3a-c with Fig. 2a-c). The only parameter that is obviously dependent on the stimulus conditions, is the latency of the reaction (Fig. 4a-c).

Functional morphology of burrowing in the mayflies Hexagenia limbata and Pentagenia vittigera

A video system, consisting of a high-resolution, infrared-sensitive, surveillance television camera, time-date generator, video recorder and high-resolution monitor, was developed for naturalistic observation of the subaquatic activities of larval mayflies. Exemplars were isolated from light, sound and mechanical disturbance, and their burrowing behaviour was recorded for subsequent slow-motion analysis. Larvae of silt-inhabiting Hexagenia limbata were observed to be ploughers that displaced and compacted soft substrate in the excavation of an open tunnel. The head and prothoracic legs had the principal roles in substrate displacement, while the mesothoracic and metathoracic legs drove the body forward. Five stereotyped burrowing cycles were distinguished, although one, termed the Alternate Undercut because of the motions of the prothoracic legs, predominated. Larvae of clay-inhabiting Pentagenia vittigera were observed to chisel and gouge out compacted substrates, also creating an open burrow. Their mandibular tusks were used to dislodge substrate, while the prothoracic legs displaced loosened substrate and widened the opening. The body was driven forward either by strong abdominal flexions or by activity of the mesothoracic and metathoracic legs. Four burrowing cycles were distinguished, two of which, the Tusk Gouge and the Chisel and Sweep, predominated. Differences in proportion and armature of the head and appendages correlated with the different substrate types excavated.

Interaction between the leg and surrounding thorax in the beetle

Interactions between the insect leg and surrounding thoracic epidermis were studied in the beetle, Tenebrio, by grafting the entire larval prothoracic leg into the metathoracic leg site in various orientations. Control grafts simply heal, but A/P reversed grafts lead to regeneration of supernumerary legs of host orientation in A and P positions. M/L reversed grafts also give supernumeraries, again with host orientation but in M (or MP) and L (or LA) positions. The differences in structure between adult prothoracic and metathoracic legs allow the origin of these supernumeraries to be analysed at coxa and tarsus level. The A/P supernumeraries are consistent and complementary in structure, of host origin on the host side and graft origin on the graft side, and with the borders in apparently constant midmedial and midlateral positions. The M/L supernumeraries, however, are variable and often non-complementary in structure. The results of the A/P and M/L reversals are similar to those found at a more distal level in Tenebrio legs and the legs of several hemimetabolous insects, suggesting that the arrangement of positional values and A and P compartments extends from the epidermis of the leg onto the surrounding thorax. The results of a 180 degrees rotation of the entire leg, however, differ from those found at a more distal level in that the grafted leg rarely derotated and two (or occasionally one or three) supernumeraries are formed in a wide variety of positions, some with constant and others with variable orientation. These results are not readily explained by current models of insect leg formation and regeneration.

Physiology and tonotopic organization of auditory receptors in the cricket Gryllus bimaculatus DeGeer.

Physiological recordings were obtained from identified receptors in the tympanal organ of Gryllus bimaculatus. By immersing the prothoracic leg in Ringer solution and removing the anterior tympanic membrane the auditory receptors were exposed without significantly altering the frequency response of the auditory organ (Fig. 1). Each receptor was tuned to a specific sound frequency. For sound frequencies below this characteristic frequency the roll-off in sensitivity decreased from 20-30 dB/octave to 10-15 dB/octave as the characteristic frequency of receptors increased from 3-11 kHz (Fig. 4A). For each individual receptor the slope, dynamic range and maximum spike response were similar for different sound frequencies (Fig. 9A). The receptors were tonotopically organized with the characteristic frequency of the receptors increasing from the proximal to the distal end of the array (Figs. 5, 6). Several receptors had characteristic frequencies of 5 kHz. These receptors were divided into two groups on the basis of their maximum spike response produced in response to pure tones of increasing intensity (Fig. 7). Independent of the tuning of the receptor no two-tone inhibition was observed in the periphery, thus confirming that such interactions are a property of central integration.

A comparison of shock avoidance learning in headless cockroaches in leg-lifting and lowering task

Headless cockroaches were trained either to lift or to lower the prothoracic leg to avoid electric shocks. The learning process in both cases was very distinct. However, the learning performance in the lifting was better than in the lowering task. The reason for this poorer learning in the lowering task is due to the unconditioned leg raising movement of the animals to electric shocks. This unconditioned response affects the acquisition of the conditioned lowering response. Therefore, the lowering task becomes more difficult. Furthermore, headless cockroaches avoid shocks in the lifting task by escape learning, whereas they avoid shocks in the lowering task by true avoidance learning. Injection of 30 μl of Ringer's solution has no significant effect on the learning process in the lifting task. In the lowering task, however, Ringer's solution impairs the learning ability considerably. Crude extract of corpora cardiaca strongly inhibits the learning of both tasks.

The musculature of the prothoracic legs and its innervation inHierodula membranacea(Mantidea)

The musculature of the fore limbs and the innervation pattern of the muscles in the praying mantidHierodula membranacea(Burm.) are described. There are three antagonistic pairs of muscles (promotors-remotors, abductors-adductors, anterior rotator-posterior rotators) operating the prothoracic-coxal joint around three different axes. At the coxo-trochanteral, femoro-tibial and tibio-tarsal joints there are flexor and extensor muscles, but at the tarsal-pretarsal joint only flexors are present. The trochanteral extensor is a complex muscle, with both parallel-fibred and pennate parts. The trochanteral-femoral joint is operated by a single muscle, the femoral reductor. There are six pairs of prothoracic nerves, the first of which innervates the musculature of the neck and pro-mesothoracic joints. The other five nerves are all concerned with the innervation of the muscles and sense organs of the prothoracic legs. Some of the motor neuron somata in the prothorathic ganglion have been identified by using the cobalt chloride backstaining technique. The leg musculature, its innervation pattern and the location of the motor neuron somata are compared with those of other orthopteroid insects.

Avoidance and escape components of leg position learning in the prothoracic and mesothoracic ganglia of the cockroach, P. americana

Prothoracic and mesothoracic legs of headless cockroaches with only a ventral nerve cord were trained to lift their legs when shock occurred. The prothoracic leg showed both avoidance learning (a decrease over time in the frequency of leg extension) and escape learning (a decrease in extension duration following shock receipt). The mesothoracic leg showed avoidance learning as fast and as well as the prothoracic leg but was unable to support escape learning. Furthermore, the avoidance component of prothoracic learning showed longer-term retention of several hours whereas the escape component showed only shorter-term retention which did not last 15 minutes.

TheUbx syndrome ofDrosophila: the prothoracic transformation (ppx) is independent ofbx, bxd andpbx.

If, early in development, theUbx + gene is removed by mitotic recombination from cells of the meso-and metathoracic leg primordia, theseUbx - cells develop as in the posterior prothoracic leg. We show that this transformation, termedpostprothorax, is a discrete genetic function that is independent of other homeotic transformations such asbx, pbx orbxd, which also result from the inactivation of theUbx gene.