Defense mechanisms against herbivory in Picea: sequence evolution and expression regulation of gene family members in the phenylpropanoid pathway

Background

The insect order Neuroptera encompasses more than 5,700 described species. To date, only three neuropteran mitochondrial genomes have been fully and one partly sequenced. Current knowledge on neuropteran mitochondrial genomes is limited, and new data are strongly required. In the present work, the mitochondrial genome of the ascalaphid owlfly Libelloides macaronius is described and compared with the known neuropterid mitochondrial genomes: Megaloptera, Neuroptera and Raphidioptera. These analyses are further extended to other endopterygotan orders.

Results

The mitochondrial genome of L. macaronius is a circular molecule 15,890 bp long. It includes the entire set of 37 genes usually present in animal mitochondrial genomes. The gene order of this newly sequenced genome is unique among Neuroptera and differs from the ancestral type of insects in the translocation of trnC. The L. macaronius genome shows the lowest A+T content (74.50%) among known neuropterid genomes. Protein-coding genes possess the typical mitochondrial start codons, except for cox1, which has an unusual ACG. Comparisons among endopterygotan mitochondrial genomes showed that A+T content and AT/GC-skews exhibit a broad range of variation among 84 analyzed taxa. Comparative analyses showed that neuropterid mitochondrial protein-coding genes experienced complex evolutionary histories, involving features ranging from codon usage to rate of substitution, that make them potential markers for population genetics/phylogenetics studies at different taxonomic ranks. The 22 tRNAs show variable substitution patterns in Neuropterida, with higher sequence conservation in genes located on the α strand. Inferred secondary structures for neuropterid rrnS and rrnL genes largely agree with those known for other insects. For the first time, a model is provided for domain I of an insect rrnL. The control region in Neuropterida, as in other insects, is fast-evolving genomic region, characterized by AT-rich motifs.

Conclusions

The new genome shares many features with known neuropteran genomes but differs in its low A+T content. Comparative analysis of neuropterid mitochondrial genes showed that they experienced distinct evolutionary patterns. Both tRNA families and ribosomal RNAs show composite substitution pathways. The neuropterid mitochondrial genome is characterized by a complex evolutionary history.     

PETRIFIED NEUROPTERID FOLIAGE FROM A MIDDLE PENNSYLVANIAN COAL BALL

Petrified specimens of pteridosperm foliage assignable to Reticulopteris muensteri (Eichwald) Gothan and Neuropteris rarinervis Bunbury were found in a Middle Pennsylvanian age coal ball from central Iowa. The presumed close affinity of these two foliage taxa is supported by various anatomical similarities including hydathode-like vein terminations and non-papillate lower epidermises with high stomatal density. Comparison of the foliar anatomy of these neuropterids to that of the xeromorphic taxa Alethopteris sullivanti (Lesquereux) Schimper and A. lesquereuxi Wagner show striking differences which suggest that these neuropterid and alethopterid taxa were adapted to markedly different habitats.     

Variations of foraging tactics in a water bug,Diplonychus indicus

The predatory behaviour ofDiplonychus indicus Venk. & Rao (Heteroptera: Belostomatidae), a tropical water bug, appeared to be highly versatile. Male adultD. indicus alternated from active foraging to ambushing during the same observation. The predatory movements described here were divided into 7 different categories. Five include ambushing and no active search: simple capture, strike, lunge and strikes following a preliminary vertical or horizontal orientation. Two include active search: dive and swimming bout. Success rates of capture varied with predatory movement category and with predatorprey distance. Attempts including lunges had the highest success rate. Attempts including short lunges, small vertical or horizontal turns or short dives were less likely to be successful than attempts including relatively longer lunges, larger vertical or horizontal turns or longer dives.     

Quantitative Analysis of the Deltoid and Rotator Cuff Muscles in Humans and Great Apes

The shoulder is one of the anatomic regions differentiating orthograde primates (gibbons, orangutans, gorillas, chimpanzees, bonobos, and humans) from the rest of the pronograde primates. Orthograde primates are characterized by a dorsal position of the scapula and a more lateral orientation of the glenoid cavity. This anatomic pattern, together with adaptations in related osteological structures and muscles, serves to facilitate the elevation of the upper extremity in the scapular plane. We quantified the proportions of the muscles comprising the principal functional and stabilizing components of the glenohumeral joint —deltoid, subscapularis, supraspinatus, infraspinatus, and teres minor— in 3 species of orthograde primates: Pongo pygmaeus, Pan troglodytes, and Homo sapiens. Our objective was to determine whether quantifiable differences in these muscles relate to the functional requirements of the types of locomotion used by these 3 species: suspension/vertical climbing, knuckle-walking, and bipedalism. We observed a close similarity between the proportional mass of these muscles in Homo sapiens and Pongo pygmaeus, whereas Pan troglodytes displayed a unique anatomic pattern, particularly in the subscapularis, which may be due to differences in how the glenohumeral joint is stabilized in a great ape knuckle-walker. Our findings may help explain the high incidence of subacromial impingement syndrome in humans.     

A comparison of models explaining muscle activation patterns for isometric contractions

One of the main problems in motor-control research is the muscle load sharing problem, which originates from the fact that the number of muscles spanning a joint exceeds the number of degrees of freedom of the joint. As a consequence, many different possibilities exist for the activation of muscles in order to produce a desired joint torque. Several models describing muscle activation have been hypothesized over the last few decades to solve this problem. This study presents theoretical analyses of the various models and compares the predictions of these models with new data on muscle activation patterns for isometric contractions in various directions. None of the existing models fitted the experimental data in all aspects. The best fit was obtained by models based on minimization of the squared sum of muscle forces (∑ _m φ² _m , which is almost equivalent to the Moore-Penrose pseudo-inverse solution), muscle stress σ (∑ _m σ _m ²) or muscle activation α (∑ _m α _m ²). Since muscle activation patterns are different for isometric contractions and for movements, it could well be that other models or optimization criteria are better suited to describe muscle activation patterns for movements. The results of our simulations demonstrate that the predicted muscle activation patterns do not depend critically on the parameters in the model. This may explain why muscle activation patterns are highly stereotyped for all subjects irrespective of differences between subjects in many neuro-anatomical aspects, such as, for example, in the physiological cross-sectional area of muscle. Received: 24 September 1998 / Accepted in revised form: 1 March 1999     

The larval head of Raphidia (Raphidioptera, Insecta) and its phylogenetic significance

External and internal head structures of larval representatives of Raphidiidae are described. The obtained data were compared to characters of other neuropterid larvae and to larval characters of representatives of other endopterygote lineages. Characters potentially relevant for phylogenetic reconstruction are listed and discussed. The larvae of Raphidioptera differ distinctly from other neuropterid larvae in their morphology. They are mainly characterised by autapomorphic and plesiomorphic character states and few features indicate systematic affinities with other groups. Endopterygote groundplan features maintained in Raphidioptera are the complete tentorium, the free labrum, the full set of labral muscles, the presence of four extrinsic antennal muscles, the three-segmented labial palpi, the presence of a full set of extrinsic maxillary and labial muscles, the presence of a salivarium, and possibly the high number of stemmata. Apomorphies likely correlated with predaceous habits are the long gula, the protracted maxillae, the longitudinal arrangement of extrinsic maxillary muscles, and the elongated prepharyngeal tube. Highly unusual, potentially autapomorphic features are the presence of a dorsal ligament of the tentorium and paired gland-like structures below the pharynx. A prognathous or very slightly inclined head and slender mandibles without mola are features shared by larvae of all orders of Neuropterida. The parallel-sided head is a potential synapomorphy of Raphidioptera and Megaloptera. A fully prognathous head with anteriorly shifted posterior tentorial grooves and the presence of a parietal ridge and a distinct neck region are features shared with Corydalidae. Characters of the larval head are not sufficient for a reliable placement of Raphidioptera.     

Comparative morphology of cheliceral muscles using high-resolution X-ray microcomputed-tomography in palpimanoid spiders (Araneae,Palpimanoidea)

Spiders are important predators in terrestrial ecosystems, yet we know very little about the principal feeding structures of spiders, the chelicerae, which are functionally equivalent to “jaws” or “mandibles” and are an extremely important aspect of spider biology. In particular, members of Palpimanoidea have evolved highly unusual cheliceral morphologies and functions, including high-speed, ballistic movements in mecysmaucheniid spiders, the fastest arachnid movements known thus far, and the elongated, highly maneuverable chelicerae of archaeids that use an attack-at-a-distance strategy. Here, using micro-Computed-Tomography scanning techniques, we perform a comparative study to examine cheliceral muscle morphology in six different spider specimens representing five palpimanoid families. We provide a hypothesis for homology in palpimanoid cheliceral muscles and then compare and contrast these findings with previous studies on other non-palpimanoid spiders. We document and discuss two sets of cheliceral muscles in palpimanoids that have not been previously observed in other spiders or which may represent a position shift compared to other spiders. In the palpimanoids, Palpimanus sp., Huttonia sp., and Colopea sp. showed similar cheliceral muscle anatomy. In Eriauchenius ranavalona, which has highly maneuverable chelicerae, some of the muscles have a more horizontal orientation, and there is a greater degree of cheliceral muscle divergence. In Zearchaea sp. and Aotearoa magna, some muscles have also shifted to a more horizontal orientation, and in Zearchaea sp., a species with a ballistic, high-speed predatory strike, there is a loss of cheliceral muscles. This research is a first step toward understanding cheliceral form and function across spiders.     

A mitochondrial genome phylogeny of the Neuropterida (lace-wings, alderflies and snakeflies) and their relationship to the other holometabolous insect orders

We present a mitochondrial (mt) genome phylogeny inferring relationships within Neuropterida (lacewings, alderflies and camel flies) and between Neuropterida and other holometabolous insect orders. Whole mt genomes were sequenced for Sialis hamata (Megaloptera: Sialidae), Ditaxis latistyla (Neuroptera: Mantispidae), Mongoloraphidia harmandi (Raphidioptera: Raphidiidae), Macrogyrus oblongus (Coleoptera: Gyrinidae), Rhopaea magnicornis (Coleoptera: Scarabaeidae), and Mordella atrata (Coleoptera: Mordellidae) and compared against representatives of other holometabolous orders in phylogenetic analyses. Additionally, we test the sensitivity of phylogenetic inferences to four analytical approaches: inclusion vs. exclusion of RNA genes, manual vs. algorithmic alignments, arbitrary vs. algorithmic approaches to excluding variable gene regions and how each approach interacts with phylogenetic inference methods (parsimony vs. Bayesian inference). Of these factors, phylogenetic inference method had the most influence on interordinal relationships. Bayesian analyses inferred topologies largely congruent with morphologically‐based hypotheses of neuropterid relationships, a monophyletic Neuropterida whose sister group is Coleoptera. In contrast, parsimony analyses failed to support a monophyletic Neuropterida as Raphidioptera was the sister group of the entire Holometabola excluding Hymenoptera, and Neuroptera + Megaloptera is the sister group of Diptera, a relationship which has not previously been proposed based on either molecular or morphological data sets. These differences between analytical methods are due to the high among site rate heterogeneity found in insect mt genomes which is properly modelled by Bayesian methods but results in artifactual relationships under parsimony. Properly analysed, the mt genomic data set presented here is among the first molecular data to support traditional, morphology‐based interpretations of relationships between the three neuropterid orders and their grouping with Coleoptera.     

Variations of Predatory Tactics of a Water Bug during Development

At all developmental stages, Diplonychus indicus Venk. & Rao (Heteroptera: Belostomatidae) bugs make predatory attempts and catch prey both from ambush and while foraging actively. The distribution of predatory movements between these two foraging modes does not vary significantly during development, although a bug generally performs more predatory attempts from ambush than during active search. Both modes were subdivided and six different predatory movement types were recorded. These different predatory types are not all performed at the same frequency at all developmental stages. The proportion of predatory attempts including a preliminary lunge decreases with age whereas the proportion of simple predatory attempts (strike) increases with age. There is a significant effect of developmental stage and of predatory mode on capture success. General capture success rate increases with age and success rates vary with predatory type. Capture success of predatory attempts made while swimming is always lower than capture success of simple predatory attempts (strike). These rates do not vary during development. On the contrary, success rates for the predatory types dive and lunge increase with developmental stage. For some predatory categories, capture success varies with predator-prey distance. The data then suggest that the bugs are undershooting.     

The Roles of Monoarticular and Biarticular Muscles of the Lower Limbs in Terrestrial Locomotion

Specific features of the functioning of mono- and biarticular muscles were studied using a multijoint movement (a high jump) as an example. The powers of the knee and ankle joint extensors are insufficient for a strong and quick movement such as a high jump. Biarticular muscles (m. rectus femoris) transfer forces/powers from one joint to another, thereby compensating for the physiological shortcoming of monoarticular muscles, that is, a decrease in the tractive force with increasing contraction rate. In a high jump, a power of 300 W may be transferred from the hip to the knee joint via the m. rectus femoris; 230 W, from the knee to the hip joint via the hamstring muscle; 210 W, from the knee joint to the ankle via the m. gastrocnemius; and 15 W, from the metatarsophalangeal joint to the ankle via the mm. flexors.     

Araneophagic behavior of Gardena brevicollis Stål (Heteroptera: Reduviidae): Foraging on pre‐dispersal spiderlings in the spider's web

Araneophagic behavior of an Emesinae assassin bug, Gardena brevicollis Stål (Hemiptera: Reduviidae) was observed in the field. The bug invaded a web of Acusilas coccineus Simon (Araneae: Araneidae) spiderlings and hunted five juvenile spiders. The bug showed stalking tactics to prey on spiders, whereas luring tactics, which have been reported in other Emesinae bugs, were not observed. To the best of my knowledge, the present study is the first report of araneophagy in the genus Gardena and the first report of araneophagic behavior in East Asian assassin bugs.     

Nonspiking pathways antagonize the resistance reflex in the thoraco-coxal joint of stick insects

In the stick insect (Carausius morosus) imposed forward and backward movements of the coxa of the middle leg induce resistance reflexes in the retractor or protractor coxae muscles, depending on the direction of movement. The hairs of the ventral coxal hairplate (cxHPv) function as the primary transducer of the retractor part of the underlying feedback loop: bending of the hairs of the cxHPv during an imposed forward movement of the coxa leads to a reflex activation of the retractor motoneurones, whereas releasing of the hairs causes an inhibition of these motoneurones. Local nonspiking interneurones were investigated, which transmit information from the cxHPv onto the retractor motoneurones: 1) they are depolarized during bending of the hair sensilla of the cxHPv and 2) they decrease the activities of retractor motoneurones. In addition, four of the interneurones drive a protractor motoneurone, when they are depolarized. As bending stimuli at the cxHPv (mimicking an imposed forward movement of the leg) induce reflex activation of the retractor motoneurones and reflex inhibition of the protractor motoneurones, the physiology of the recorded interneurones appears to antagonize the resistance reflex in the thoraco-coxal joint. The results indicate that these nonspiking interneurones take part in the shaping of the reflex response and that furthermore these interneurones are involved in the organization of the motor output to the two antagonistic sets of motoneurones. The possible role of these interneurones might be the adjustment of the gain and of the time constant in the thoraco-coxal feedback loop.     

Activation of human arm muscles during flexion/extension and supination/pronation tasks: A theory on muscle coordination

Generally the number of muscles acting across a joint exceeds the number of degrees of freedom available to the joint. This redundancy raises a problem regarding the ratio in which these muscles are activated during a particular motor task. In this paper we present a theory to explain the activation patterns of muscles used during voluntary and reflex induced contractions. The basic assumptions underlying the theory are that 1) coordination of muscles is based on synergistic muscle activities, 2) the synergisms involved satisfy certain transformations of muscle spindle signals to muscle activation signals and 3) muscle spindle output is proportional to the ratio of muscle stretch and muscle length in lengthening muscles, and is zero in shortening muscles. The theory is used to predict the recruitment threshold of motor units in six arm muscles during voluntary isometric contractions. All theoretical predictions are in reasonable agreement with the experimentally observed behavior of a large population of motor units within each muscle. However, within a single muscle sometimes motor-unit populations have been found to have different types of recruitment behavior. This deviating behavior is discussed in the light of the theory presented here.     

Electromyographic evaluation of masseter and anterior temporalis muscles in rest position of edentulous patients with temporomandibular disorders, before and after using complete dentures with sliding plates

Objectives: This study was performed with the purpose of investigating electromyographic (EMG) activity of the anterior temporalis and masseter muscles in edentulous individuals with temporomandibular disorder (TMD), before and after using sliding plates on complete dentures in the mandibular rest position. Background: Edentulous patients may present TMD, which is characterised by pain in temporomandibular joints, masticatory and neck muscles, uncoordinated and limited mandible movements, joint sounds and an altered occlusal relationship. It is imperative to offer treatment in order to re‐establish stomatognathic system structures before submitting the individual to any definitive restorative treatment. Materials and methods: The patients were edentulous for at least 10 years. EMG recordings were made before the insertion of the dentures (0 months) and also after using the sliding plates at the fourth month, 9th month and 12th month, using computerised electromyography K6‐I/ EMG Light Channel Surface. EMG evaluations of the muscles were performed under the following clinical conditions: rest position with dentures (R1), rest position without dentures (R2), rest position with dentures post‐activity (chewing) (R3), rest position without dentures post‐activity (chewing) (R4). Results: All patients obtained remission of muscular fatigue and reduced pain in stomatognathic system structures. Temporalis muscle showed significant increase in EMG activity compared with initial values (p < 0.01). Masseter muscles showed significantly lower mean values (p < 0.01) compared with initial values. Conclusion: The sliding plates allowed the process of neuromuscular deprogramming, contributing to muscular balance of the masticatory system, and are therefore indicated to be used before the fabrication of definitive complete dentures in patients with TMD.     

Development of the musculature in the limpet Patella (Mollusca, Patellogastropoda)

 Whole-mount technique using fluorescent-labelled phalloidin for actin staining and confocal laser scanning microscopy as well as semi-thin serial sectioning, scanning and transmission electron microscopy were applied to investigate the ontogeny of the various muscular systems during larval development in the limpets Patella vulgata L. and P. caerulea L. In contrast to earlier studies, which described a single or two larval shell muscles, the pretorsional trochophore-like larva shows no less than four different muscle systems, namely the asymmetrical main head/foot larval retractor muscle, an accessory larval retractor with distinct insertion area, a circular prototroch/velar system, and a plexus-like pedal muscle system. In both Patella species only posttorsional larvae are able to retract into the shell and to close the aperture by means of the operculum. Shortly after torsion the two adult shell muscles originate independently in lateral positions, starting with two fine muscle fibres which insert at the operculum and laterally at the shell. During late larval development the main larval retractor and the accessory larval retractor become reduced and the velar muscle system is shed. In contrast, the paired adult shell muscles and the pedal muscle plexus increase in volume, and a new mantle musculature, the tentacular muscle system, and the buccal musculature arise. Because the adult shell muscles are entirely independent from the various larval muscular systems, several current hypotheses on the ontogeny and phylogeny of the early gastropod muscle system have to be reconsidered. Received: 23 June 1998 / Accepted: 25 November 1998     

Multiple host use by the egg parasitoid Trissolcus basalis (Wollaston) in a soybean agricultural system: biological control and environmental implications

1 Species of bugs (Hemiptera: Pentatomidae and other families) that are parasitized by the egg parasitoid Trissolcus basalis (Wollaston) (Hymenoptera: Scelionidae) in the soybean agricultural system on the Darling Downs in south-eastern Queensland, Australia, are reported. The degree to which eggs of each bug species are used by T. basalis is quantified, which allows assessment of the role of these alternative host species in the biological control of the green vegetable bug Nezara viridula (L.). 2 Egg masses of nine species of pentatomid bugs and one unidentified bug species were collected. Parasitism rates of egg masses of all species averaged 50–70% but were significantly lower for the more important pest species, including the green vegetable bug, than for some of the agriculturally less important species. 3 Trissolcus basalis emerged from nearly all species collected and was the major parasitoid to emerge from most species. A number of native species were parasitized heavily by T. basalis and parasitism of such species may enhance biological control of the green vegetable bug, but may also pose environmental concerns. Parasitism of predatory bugs by T. basalis may have a negative impact on the biological control of other pests, especially lepidopterous pests. 4 Although the impact of T. basalis on native and predatory host species was not directly quantified, these host species remain abundant and therefore do not appear to be affected adversely by such high rates of parasitism.     

Influence of Host Pheromone on Egg Parasitism by Scelionid Wasps: Comparison of Phoretic and Nonphoretic Parasitoids

The kairomonal activity of the attractant pheromone for the spined soldier bug, Podisus maculiventris (Hemiptera: Pentatomidae), was investigated by exposing fresh pentatomid egg masses in field traps with or without synthetic pheromone. Predominantly two parasitoids were recovered from exposed eggs of P. maculiventris and Euschistus obscurus: Telenomus podisi Ashmead (a generalist pentatomid egg parasitoid) and Telenomus calvus Johnson (a phoretic specialist on Podisus eggs) (Hymenoptera: Scelionidae). The incidences of T. podisi from P. maculiventris and E. obscurus eggs placed in pheromone-baited and nonbaited traps were not significantly different, suggesting that this oophagous wasp does not use the spined soldier bug attractant pheromone as a kairomone. However, T. calvus was reared almost exclusively from egg masses of P. maculiventris placed inside pheromone-baited traps. These results suggest that T. calvus females orient to volatile chemicals emitted by spined soldier bug males as a searching strategy to find areas likely to contain host eggs, in addition to the previously discovered strategy of using the pheromone to guide their phoretic behavior. The data also indicate that T. calvus can distinguish between the egg masses of these pentatomid hosts at close range.     

Biological control of soybean stink bugs by inoculative releases of Trissolcus basalis

Field studies of inoculative releases of Trissolcus basalis (Wollaston) (Hymenoptera: Scelionidae) in early-maturing soybean, used as a trap crop, were conducted during four consecutive seasons to evaluate the parasitoid's potential as an IPM tactic for use against stink bug (Pentatomidae) species. Fifteen thousand adults of the parasitoid were released per hectare in the trap crop when the first stink bugs were detected in the experimental area. The stink bug population density was reduced by an average of 54% in the trap crop and by 58% in the main crop. The inoculative releases produced a reduction and delay in the stink bug population peak, mainly represented by Nezara viridula (L.), Piezodorus guildinii (Westwood) and Euschistus heros (Fabr.), which were held below economic threshold levels during the most critical stages of stink bug attack on soybean (pod and seed fill, R3–R6). As a result, seed quality was better in areas where T. basalis was released, demonstrating the efficacy of inoculative releases of this egg-parasitoid which could be an important component of the soybean IPM program in Brazil.