Grasshopper Melanoplus Femurrubrum Research Articles

Life history traits associated with body size covary along a latitudinal gradient in a generalist grasshopper

Animal body size often varies systematically along latitudinal gradients, where individuals are either larger or smaller with varying season length. This study examines ecotypic responses by the generalist grasshopper Melanoplus femurrubrum (Orthoptera: Acrididae) in body size and covarying, physiologically based life history traits along a latitudinal gradient with respect to seasonality and energetics. The latitudinal compensation hypothesis predicts that smaller body size occurs in colder sites when populations must compensate for time constraints due to short seasons. Shorter season length requires faster developmental and growth rates to complete life cycles in one season. Using a common garden experimental design under laboratory conditions, we examined how grasshopper body size, consumption, developmental time, growth rate and metabolism varied among populations collected along an extended latitudinal gradient. When reared at the same temperature in the lab, individuals from northern populations were smaller, developed more rapidly, and showed higher growth rates, as expected for adaptations to shorter and generally cooler growing seasons. Temperature-dependent, whole organism metabolic rate scaled positively with body size and was lower at northern sites, but mass-specific standard metabolic rate did not differ among sites. Total food consumption varied positively with body size, but northern populations exhibited a higher mass-specific consumption rate. Overall, compensatory life history responses corresponded with key predictions of the latitudinal compensation hypothesis in response to season length.

Astral microtubules physically redistribute cortical actin filaments to the incipient contractile ring

Prior to cell cleavage, cytokinetic proteins are recruited into the nascent actomyosin contractile ring, paving the way for formation of a functional cleavage furrow. Interactions between spindle microtubules and the cell cortex may play a critical role in this recruitment, since microtubules have been shown to affect distribution and activation of cytokinetic proteins within the cortex. However, direct evidence for physical interaction between microtubules and the cortex has been lacking. Here, we probed the physical connection between astral microtubules and cortical actin filaments, by micromanipulating the fluorescently tagged cytoskeleton in living spermatocytes of the grasshopper Melanoplus femurrubrum. When microtubules were tugged with a microneedle, they in turn pulled on cortical actin filaments, interrupting the filaments' journey toward the equator. Further displacement of the actin dragged the cell membrane inward, demonstrating that the cortical actin network physically linked spindle microtubules to the cell membrane. Regional disruption of the connection by breaking spindle microtubules prevented actin accumulation in a segment of the ring, which locally inhibited furrowing. We propose a model in which dynamic astral microtubules physically redistribute cortical actin into the incipient contractile ring.

Grasshopper Injury to Potato: Consumption, Effect on Photosynthesis, and Economic Injury Level

Generalist grasshopper species feed at agricultural field edges, often triggering management practices because of defoliation injury. Few controlled studies in agroecosystems, however, have quantified grasshopper consumption or plant photosynthetic response to feeding. Consequently, we examined if injury caused by the red‐legged grasshopper Melanoplus femurrubrum (DeGeer), would influence the gas exchange parameters on the remaining tissue. We conducted this examination on three potato (Solanum tuberosum L.) cultivars (Norkotah, Atlantic, and Frito‐Lay proprietary) and at three times during potato growth (all post flowering). With injury rates of about 10 to 25%, we observed no significant change in photosynthetic rates on the remaining leaf tissue in any cultivar or in any of the three experiments. Additionally, we measured potato canopy area and, in the laboratory, placed individual M. femurrubrum on premeasured potato leaflets. Individual grasshoppers consumed a mean of 4.4 cm2 d−1 of leaf area. Early in the season when potato plant leaf area indices (LAIs) are less than about 4.5, grasshoppers have the potential to significantly reduce yield. When potato canopies reach LAIs of 5.0, however, which in Nebraska typically occurs in July when grasshopper numbers also increase, grasshopper densities are rarely high enough to justify treatment.

Herbivory on invasive exotic plants and their non-invasive relatives

The Enemy Release Hypothesis links exotic plant success to escape from enemies such as herbivores and pathogens. Recent work has shown that exotic plants that more fully escape herbivores and pathogens are more likely to become highly invasive, compared to plants with higher enemy loads in their novel ranges. We predicted that highly invasive plants from the Asteraceae and the Brassicaceae would be less acceptable, in laboratory no-choice feeding trials, to the generalist herbivore the American grasshopper, Schistocerca americana. We also compared herbivory on invasive and non-invasive plants from the genus Centaurea in no-choice feeding trials using the red-legged grasshopper Melanoplus femurrubrum and in a common garden in the field. In accordance with our predictions, highly invasive plants were fed on less by grasshoppers in the laboratory. They also received less damage in the field, suggesting that they contain feeding deterrents that render them less acceptable to generalist herbivores than non-invasive plants.

Individual Size Variation and Population Stability in a Seasonal Environment: A Discrete‐Time Model and Its Calibration Using Grasshoppers

Much recent literature is concerned with how variation among individuals (e.g., variability in their traits and fates) translates into higher-level (i.e., population and community) dynamics. Although several theoretical frameworks have been devised to deal with the effects of individual variation on population dynamics, there are very few reports of empirically based estimates of the sign and magnitude of these effects. Here we describe an analytical model for size-dependent, seasonal life cycles and evaluate the effect of individual size variation on population dynamics and stability. We demonstrate that the effect of size variation on the population net reproductive rate varies in both magnitude and sign, depending on season length. We calibrate our model with field data on size- and density-dependent growth and survival of the generalist grasshopper Melanoplus femurrubrum. Under deterministic dynamics (fixed season length), size variation impairs population stability, given naturally occurring densities. However, in the stochastic case, where season length exhibits yearly fluctuations, size variation reduces the variance in population growth rates, thus enhancing stability. This occurs because the effect of size variation on net reproductive rate is dependent on season length. We discuss several limitations of the current model and outline possible routes for future model development.

Nickel hyperaccumulation as an elemental defense of Streptanthus polygaloides (Brassicaceae): influence of herbivore feeding mode

No study of a single nickel (Ni) hyperaccumulator species has investigated the impact of hyperaccumulation on herbivores representing a variety of feeding modes. Streptanthus polygaloides plants were grown on high- or low-Ni soils and a series of no-choice and choice feeding experiments was conducted using eight arthropod herbivores. Herbivores used were two leaf-chewing folivores (the grasshopper Melanoplus femurrubrum and the lepidopteran Evergestis rimosalis), a dipteran rhizovore (the cabbage maggot Delia radicum), a xylem-feeder (the spittlebug Philaenus spumarius), two phloem-feeders (the aphid, Lipaphis erysimi and the spidermite Trialeurodes vaporariorum) and two cell-disruptors (the bug Lygus lineolaris and the whitefly Tetranychus urticae). Hyperaccumulated Ni significantly decreased survival of the leaf-chewers and rhizovore, and significantly reduced population growth of the whitefly cell-disruptor. However, vascular tissue-feeding insects were unaffected by hyperaccumulated Ni, as was the bug cell-disruptor. We conclude that Ni can defend against tissue-chewing herbivores but is ineffective against vascular tissue-feeding herbivores. The effects of Ni on cell-disruptors varies, as a result of either variation of insect Ni sensitivity or the location of Ni in S. polygaloides cells and tissues.

TRANSMISSION OF A GENETICALLY ENGINEERED RHIZOBACTERIUM BY GRASSHOPPERS IN THE LABORATORY AND FIELD

Root-colonizing bacteria have little inherent dispersal ability. However, we have shown previously that they routinely move into plant stems, sometimes at high densities, and might therefore be acquired and transmitted by foliage-feeding insects. Here we describe laboratory and field experiments on the transmission of a genetically engineered strain of the root-colonizing bacterium Pseudomonas chlororaphis (formerly aureofaciens) by a common herbivorous insect, the red-legged grasshopper Melanoplus femurrubrum. In laboratory and field microcosms, the engineered P. chlororaphis were applied to corn seeds at planting and allowed to colonize the developing roots and to invade the aerial tissues naturally. Adult M. femurrubrum that later fed on the foliage of these plants became infested with the bacteria. The bacteria were harbored throughout the digestive tracts and elsewhere in the exposed grasshoppers and could be recovered from their frass. Grasshoppers carried the bacteria for ≥1 wk after removal from the source of inoculum and could transmit the bacteria to new plants. In the laboratory, the likelihood of transmission declined as the proportion of grasshoppers remaining infested decreased through time. Transmission was less predictable in the field. Transport by insects may make naturally occurring soil bacteria more mobile than previously thought and could make the containment of engineered strains unlikely. However, at least in this system, microbial movement through plants and insects in the field was accurately predicted by laboratory studies, which therefore remain useful in basic research in microbial ecology, and in risk assessment.

Transmission of a Genetically Engineered Rhizobacterium by Grasshoppers in the Laboratory and Field

Root-colonizing bacteria have little inherent dispersal ability. However, we have shown previously that they routinely move into plant stems, sometimes at high densities, and might therefore be acquired and transmitted by foliage-feeding insects. Here we describe laboratory and field experiments on the transmission of a genetically engineered strain of the root-colonizing bacterium Pseudomonas chlororaphis (formerly aureofaciens) by a common herbivorous insect, the red-legged grasshopper Melanoplus femurrubrum. In laboratory and field microcosms, the engineered P. chlororaphis were applied to corn seeds at planting and allowed to colonize the developing roots and to invade the aerial tissues naturally. Adult M. femurrubrum that later fed on the foliage of these plants became infested with the bacteria. The bacteria were harbored throughout the digestive tracts and elsewhere in the exposed grasshoppers and could be recovered from their frass. Grasshoppers carried the bacteria for ≥1 wk after removal from the source of inoculum and could transmit the bacteria to new plants. In the laboratory, the likelihood of transmission declined as the proportion of grasshoppers remaining infested decreased through time. Transmission was less predictable in the field. Transport by insects may make naturally occurring soil bacteria more mobile than previously thought and could make the containment of engineered strains unlikely. However, at least in this system, microbial movement through plants and insects in the field was accurately predicted by laboratory studies, which therefore remain useful in basic research in microbial ecology, and in risk assessment.

Comparison of Sampling Techniques for Grasshoppers (Orthoptera: Acrididae) in Soybean

A 2-yr study was conducted for evaluating sampling techniques for the grasshoppers Melanoplus femurrubrum (De Geer) and M. differentialis (Thomas) in soybean. Objectives were to establish a technique for obtaining absolute estimates of density and to evaluate the potential for calibrating the sweep net (relative density estimates) for absolute density estimates. Assessments of absolute density were made at night by using a cage-bag method. Sweep samples were collected during both day and night. Night sweeping was more effective than day sweeping for capturing grasshoppers. Regression results of relative on absolute estimates for nymphs indicated that both day and night sweeps adequately reflected population change. In contrast, similar analyses for adults indicated sufficient fidelity for night sweeps only. Day or night, fidelity of sweeps was better for M. femurrubrum than for M. differentialis . Regression coefficients were significantly different between nymphs and adults, but not between species. Therefore, combined-species regression models were formulated for nymphs (day and night) and for adults (night). Satisfactory fidelity of species-specific and combined-species day (nymphs) and night (nymphs and adults) models warrants the use of these models for calibration. Despite both day and night sweeps being biased in estimating age-class structure for nymphs, nymphal models are useful for management.

Structural patterns in the corpora pedunculata of orthoptera: a reduced silver analysis.

The calyx region and pedunculus of the corpora pedunculata ("mushroom bodies") were studied comparatively in reduced silver preparations of the brain from 16 species of Orthoptera representing four families (Acrididae, Gryllidae, Tettigoniidae, and Gryllacrididae). In the acridid grasshopper Melanoplus femurrubrum (de Geer), on which emphasis was placed, the concave primary calyx is bilayered and exhibits a special central zone. Globuli cell axons occur within both layers. The bulbous accessory calyx is unlayered and sends anterior extensions beneath the primary calyx. The main input tracts into primary and accessory calyx, respectively, are the tractus olfactorio-globularis and tritocerebral tract. The pedunculus consists of one barrel with three major fiber columns, of which two originate in the primary calyx and one in the accessory calyx. Its fibers display a coaxial arrangement, superimposed on the tripartite organization. Structural conditions in other acridids are similar. In the other families the calyx region similarly includes a bilayered primary calyx and unlayered accessory calyx. The latter, variable in form, is closely associated with the base of the primary calyx in tettigoniids and gryllacridids. The calyces receive the same major tracts as in acridids. The pedunculus is coaxially organized. These features are theorized to have originated as follows. In the progenitors of Orthoptera the corpora pedunculata included two mutually equivalent, bilayered calyces and a "double-barreled" pedunculus. The orthopteran primary calyx arose through coalescence of these calyces. Concomitantly, the two peduncular barrels fused into one. The accessory calyx originated at the base of the primary calyx, from the class of globuli cell axons of the latter's external layer. Probably this occurred in response to increased functional importance to tritocerebral input.

Undercondensation and localized euchromatinization of the x chromosome in the grasshopper Melanoplus femur-rubrum.

In most animals, including grasshoppers, the X chromosome is heterochromatic (heteropycnotic) during prophase I and metaphase I of spermatogenesis. This report describes one grasshopper male in which at these states some of the X chromosomes contained an euchromatic (E) segment. In grasshoppers, the heteropycnotic state of the X is apparently established prior to the formation of the cysts. The spermatocytes containing the E segments, however, did not comprise whole cysts. It was concluded, therefore, that the E segments resulted from a localized euchromatinization rather than a failure to become heteropycnotic. The cytology of this male was unusual in two other respects. In most of the spermatocytes the chromosomes were longer and thinner than those of other males. In addition, in some of the cells undergoing meiosis, the cytoplasm failed to divide during both meiotic divisions and the resulting spermatids failed to differentiate into sperm. Because in this species both the presence of Xs with E segments and undercondensation are very rare and both involve condensation, it is likely that they are in some way related. Evidence for and against the possibility that the E segments were genetically active and that this activity led to the arrest of some of the spermatids is discussed.

Localized euchromatinization of the X chromosome during spermatogenesis in the grasshopper Melanoplus femur-rubrum

In grasshoppers, as well as in most other animals, the X chromosome is heteropycnotic (heterochromatic) during prophase I and metaphase I of spermatogenesis. During the same stages, in some of the cells of three Melanoplus femur-rubrum males (out of several hundred males examined) part of the X appeared euchromatic (E). In one male, the E segment was observed in 90% of the cells of a single cyst in which all the cells lacked one of the smallest autosomes. In another cyst of the same follicle all the cells contained one additional small autosome, and none of the Xs exhibited an E segment. The size of the E segment suggested that it resulted from the failure of part of the X to become heteropycnotic prior to the formation of the cyst. In the other two males, many of the cells contained chromosome fragments and translocations. In many cells in which the X exhibited an E segment, however, there was no evidence of chromosome breakage. The E segments were sometimes terminal and sometimes interstitial in the same cyst. This variation suggested that they resulted from the euchromatinization of part of the X immediately prior to prophase I of meiosis. Because fragmentation and the presence of Xs with an E segment were each very rare, it was concluded that they were in some way causally related. It was also concluded that in this species the heterochromatinization of the X is not controlled by a single inactivation center.

Asymmetrically heteropycnotic X chromosomes in the grasshopper Melanoplus femur-rubrum

In short-horned grasshoppers the X chromosome is negatively heteropycnotic in at least some of the spermatogonia but is positively heteropycnotic (heterochromatic) during prophase I of spermatogenesis. In tetraploid (4n) spermatocytes in prophase I the two Xs present have so far been reported always to be heterochromatic and unpaired. In several males of the grasshopper Melanoplus femur-rubrum (Acrididae), however, some of the 4n primary spermatocytes contained one heterochromatic X (Xh) and one euchromatic X (Xe). This asymmetry of heteropycnosis (AH) was first observed in grasshoppers by M.J.D. White who observed it, however, only in 4n spermatogonia in which one X was negatively heteropycnotic and the other was isopycnotic (euchromatic). In M. femur-rubrum the AH involved both positive and negative heteropycnosis. In some of the 4n cells both Xs were heterochromatic and these cells were usually present in small groups but sometimes comprised whole cysts. The 4n cells with Xe+Xh always comprised several whole cysts in a follicle or whole follicles. The origin of the two cell types may be explained by assuming that heteropycnosis originated prior to the origin of the cysts, that when, as a result of polyploidization, two Xs were present in a 4n cell only one became heteropycnotic, and that the state of the X (Xh vs. Xe) usually persisted into meiosis. The 4n primary spermatocytes exhibiting AH divided regularly during the first meiotic division but following telophase I they usually failed to undergo cytokinesis and to enter the second meiotic division. The available evidence suggests that the arrest of these cells is the result of the genetic activity of the Xe in those stages in which the X is usually heterochromatic and genetically inactive. The relationship between AH and facultative heterochromatinization is discussed and it is concluded that the present observations put into question the validity of previous models attempting to explain facultative heterochromatinization (including that of the X in the mammalian female).

MAINTENANCE OF A "PARASITIC" B CHROMOSOME IN THE GRASSHOPPER MELANOPLUS FEMUR-RUBRUM

About 10-15% of the males and females of the grasshopper Melanoplus femur-rubrum collected near Rochester, New York, possessed a supernumerary B chromosome. The frequency of the B chromosome remained fairly constant during the years 1971-1974. The B chromosome was shown previously to be transmitted at a rate of about 0.5 and 0.8 by 1B males and females, respectively. This study was designed to determine the forces preventing the B chromosome from increasing in frequency due to the high rate of transmission by the females. Eighty inseminated females collected in the wild were analyzed cytologically together with their embryos (10-20 per female). Ten of the 80 females had a B chromosome, and they transmitted it at a rate of about 0.75. Among the 983 embryos analyzed, 0.141 had one B, 0.007 had two, and the mean number of B chromosomes per embryo was 0.155. The frequency of the B chromosome in the sperm pool (0.061) was consistent with a 0.5 rate of transmission. Individuals with two B chromosomes apparently have low viability, because about six were expected, but none was found among 851 adult males and females examined. The data suggest that the viability of the 1B individuals was only about 0.86 that of the OB individuals. There was no evidence that the B chromosome increased the fecundity of either the 1B males or females. It was concluded, therefore, that the B chromosome reduced the fitness of all the individuals carrying it and was thus "parasitic," and that it was maintained in the population only because of its high transmission rate. The maintenance of other B chromosomes with high transmission rates is reviewed.

Meiosis in the grasshopper. 3. Chiasma frequencies in females after elevated temperature.

The effect of high temperature on chiasma formation during oogenesis has been studied in the grasshopper Melanoplus femur-rubrum. Prolonged heat treatment (40° C.) during mid-prophase of meiosis causes a reduction in the mean chiasma frequency per cell. Only those bivalents in which more than one chiasma occurs are affected by the heat. The pattern of chiasma frequency response to heat is similar to that which occurs in males of the same species.

Accumulation of B-chromosomes by preferential segregation in females of the grasshopper Melanoplus femur-rubrum.

In a population of Melanoplus femur-rubrum 13.9% of the males and 9.1% of the females sampled possessed a metacentric B chromosome (B). In crosses of females with one B (1 B females) and 0 B males 0.82 ± 0.05 of the offspring received the B. The value expected from Mendelian segregation is 0.5. In crosses of 1 B males and 0 B females the frequency of offspring receiving the B was 0.53 ± 0.02. The B is heterochromatic during prophase I of spermatogenesis but is euchromatic during prophase I of oogenesis. The observation that in 1 B females only one B was present in metaphase I of oogenesis suggested strongly that the high rate of transmission of the B by the females resulted from preferential segregation of the B into the secondary oocyte. The maintenance of the B in the species in discussed.

Meiosis in the grasshopper. II. The preleptotene spiral stage during oogenesis and spermatogenesis in Melanoplus femur-rubrum.

Chromosome behaviour occurring from premeiotic DNA synthesis to leptotene of meiosis is described for both males (spermatogenesis) and females (oogenesis) in the grasshopper Melanoplus femur-rubrum. These events include a period of chromosome spiralization and contraction following premeiotic DNA synthesis and prior to leptotene. The diploid complement of chromosomes becomes visible in both sexes. No pairing between homologous chromosomes or chiasmata are observed in either sex. The results suggest that synapsis and crossing over must occur following preleptotene spiralization during spermatogenesis and oogenesis in this grasshopper.

The B-chromosome system of the grasshopper Melanoplus femur-rubrum.

In a sample of 85 males of the grasshopper Melanoplus femur-rubrum, three different supernumerary chromosomes (B-chromosomes) were observed: a medium-sized metacentric, BM, present in 12.9% of the males and two small telocentrics, BT and Bt, present in 8.2% and 3.5% of the males, respectively. The BM element is mitotically stable, while the BT and Bt elements are mitotically unstable, exhibiting numerical variation among testicular follicles. The mean number of B's per male (testis) is 1.00, 1.62, and 1.38 for the BM, BT, and Bt elements, respectively. A study of chiasma frequency among A-chromosomes revealed that there are no significant differences among the zero B and various B classes either for chiasma frequency or for the variation in chiasma frequency between individuals. There was, however, evidence for a higher within-individual variation in B-containing males when these were pooled. Cells with two Bt-chromosomes were regularly missing the smallest pair of A-chromosomes, suggesting that the Bt element induces non-disjunction of a pair of A-chromosomes and, possibly, that the Bt-chromosome is derived from the missing A-chromosome.