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, B^M, present in 12.9% of the males and two small telocentrics, B^T and B^t, present in 8.2% and 3.5% of the males, respectively. The B^M element is mitotically stable, while the B^T and B^t 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 B^M, B^T, and B^t 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 B^t-chromosomes were regularly missing the smallest pair of A-chromosomes, suggesting that the B^t element induces non-disjunction of a pair of A-chromosomes and, possibly, that the B^t-chromosome is derived from the missing A-chromosome.Portions of this study were submitted by R. T. Stephens in partial fulfillment of the requirements for the degree of Master of Arts, Department of Biology, State University College, New Paltz, New York.     

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 (X_h) and one euchromatic X (X_e). 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 X_e+X_h 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 (X_h vs. X_e) 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 X_e 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).     

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.     

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.     

Leaf wilting alters a plant species ranking by the grasshopper Melanoplus differentialis

Abstract. 1. Field observations of the feeding behaviour of the polyphagous grasshopper Melanoplus differentialis suggest that plant quality can override plant species as a determinant of choice. When offered binary choices in laboratory tests between leaves of two host plant species, Helianthus annuus and Ambrosia trifida , in all combinations of wilted and turgid, grasshoppers prefer A. trifida in all test conditions, except when it is turgid and H.annuus is wilted. In this case, the preference switches to H.annuus
2. Preliminary evidence suggests that chemical factors are responsible for the alteration in preference.     

Metabolites of insecticidal chromenes from the migratory grasshopper Melanoplus sanguinipes

Three insecticidal acetylchromenes, including encecalin, and precocene II were topically administered to adults of the migratory grasshopper Melanoplus sanguinipes. Metabolites formed and excreted via the frass were identified by gas chromatography-mass spectrometry (GC-MS) and by direct comparison with reference compounds obtained by partial synthesis or from plant sources. Of the 12 metabolites found, six compounds were new natural products. Their tentative structure elucidation is described based on MS analysis. The biological importance of the elucidated chromene metabolism in M. sanguinipes is discussed for the excretion and detoxification of potentially hazardous compounds.     

Heritability and physiological correlates of migratory tendency in the grasshopper Melanoplus sanguinipes

Abstract. Durations of tethered flights by the North American migratory grasshopper Melanoplus sanguinipes Fabricius are bimodally distributed: most individuals either will not fly, or else will fly for many hours. This observation suggests a simple measure (the ‘one‐hour rule’) for distinguishing migrants from non‐migrants. This measure is repeatable (repeatability = 0.6–0.7). Using laboratory‐reared offspring of grasshoppers from an Arizona population of mixed migratory tendency, a breeding experiment was conducted to determine the heritability of migratory tendency and possible correlated responses to selection on migratory behaviour. When migratory tendency is considered as a threshold trait, the heritability of liability is in the range 0.5–0.6. Most families in the breeding experiment had at least some migrants among their offspring; selection on migratory incidence had a correlated effect on the durations of flights by these individuals. The magnitude of thoracic lipid reserves showed a modest correlated response to selection on migratory behaviour. Thoracic and abdominal lipid reserves in identified migrants are reduced by flight, indicating that lipid is mobilized and consumed during flight in this species.     

Mobilization of lipid and carbohydrate reserves in the migratory grasshopper Melanoplus sanguinipes

Abstract. The North American migratory grasshopper Melanoplus sanguinipes Fabricius (Orthoptera: Acrididae) exhibits heritable variation in predisposition to make long-duration flights, and performance of long-duration flight enhances reproductive output. As a first step in understanding the physiological basis of these phenomena, we examined the mobilization of lipid and carbohydrate reserves during flight and in response to injection of extracts of the corpora cardiaca. Extract of conspecific corpora cardiaca elevates the concentration of haemolymph lipid. Both synthetic locust adipokinetic hormone I (AKH I) and synthetic Locusta migratoria AKH II raise the concentration of lipid in the haemolymph. However, although AKH I is more active than AKH II in locusts, dose-response curves for the two peptides are similar in M.sanguinipes. Neither extract of conspecific corpora cardiaca nor locust AKH I affects haemolymph carbohydrate in this species. Haemolymph carbohydrate and total glycogen reserves are Diminished by tethered flight; in contrast, haemolymph lipid is elevated by flight. Grasshoppers identified as presumptive migrants or non-migrants do not differ significantly in body composition. Total lipid reserves did not decrease measurably after extended flight, even though total reserves of carbohydrate do not appear to be sufficient to maintain the durations of flight performed.     

Unipolar orientation stability of the sex univalent in the grasshopper (Melanoplus sanguinipes)

The behavior of the X chromosome in living Melanoplus sanguinipes primary spermatocytes was examined utilizing phase contrast microscopy and micromanipulation. During early prometaphase I, the X univalent establishes a unipolar orientation which is normally stable. In 28 cells, the X chromosome did not reorient once during a total of 122 h of observation. Though normally stable, the X chromosome can be induced to reorient by micromanipulation. An anomalous increase in X reorientation was observed in one testicular preparation. Stable unipolar orientation is an intrinsic characteristic of the X chromosome and was not displayed by two small autosomal univalents discovered in one cell. The two autosomal univalents, resulting from asynapsis or desynapsis, oscillated back and forth within the spindle, averaging 26.0 and 17.6 min respectively between reorientation events. The behavior of the M. sanguinipes X chromosome reveals an orientation stability mechanism that does not involve tension created by forces from opposing kinetochoric spindle fibers.     

Hydroxylation of n-alkanes to secondary alcohols and their esterification in the grasshopper Melanoplus sanguinipes

Labeled n-alkanes administered to the grasshopper $\text{Melanoplus}$$\text{sanguinipes}$ are hydroxylated at or near the middle of the carbon chain. The secondary alcohols formed are then esterified. Chain length specificity is evident in both the hydroxylation of n-alkanes and the esterification of secondary alcohols, with the shorter chain C₂₃, C₂₁, C₁₉, and C₂₅ compounds converted to secondary alcohol wax esters more readily than the longer chain C₂₇, C₂₉, and C₃₁ compounds. Secondary alcohols and ketones are not reduced to alkanes.     

Effects of tissue extracts on oviduct contraction in the migratory grasshopper,Melanoplus sanguinipes

The isolated oviduct of the migratory grasshopper, Melanoplus sanguinipes, shows a myogenic, rhythmic pattern of contraction. The pattern of contraction can be modified by treatment with hemolymph or extracts from a variety of tissues from animals of differing age, sex, and mated status. Extracts of oviducts and ventral nerve cord (VNC), as well as hemolymph, from both virgin and mated females were almost always stimulating, though their effect on frequency, amplitude and/or tonus varied. In contrast, whereas extracts of spermatheca and brain from mated females were stimulating, extracts of these tissues from virgin females inhibited contraction. All male material tested (long hyaline tubules (LHT), the male accessory gland complex less the LHT, testes, brain, VNC and hemolymph) stimulated oviduct contraction in a dose-dependent manner, usually enhancing at least two of frequency, amplitude and tonus. However, oviposition-stimulating protein, a purified product of the LHT, provoked only an increase in frequency when applied to the oviduct. LHT extract modulated the effects of virgin female tissue extracts, always in a stimulatory manner.     

Long hyaline gland discharge and multiple spermatophore formation by the male grasshopper, Melanoplus sanguinipes

ABSTRACT. Discharge from the male accessory reproductive gland (ARG) by the male grasshopper, Melanoplus sanguinipes (Fabr.), has been studied by assay of a characterized product, a glycoprotein LHPI, and the rate of formation of spermatophores. LHPI is an exclusive long hyaline gland (a prominent ARG tubule type) product whose discharge is symmetrical from the bilaterally paired glands. LHPI forms 65% of a viscous secretion that is discharged concomitantly with the spermatophores. Though low ARG reserves in 5-day-old males limit both the number of spermatophores formed and LHPI discharged in copulations ≤6 h, this appears to be the result of shorter copulations. The number of spermarophores formed in 1 h was not impaired by general depletion of ARG protein (by repeated copulations) or by selective depletion of long hyaline gland protein (by unilateral and bilateral long hyaline gland removal), though these manipulations reduced LHPI discharge by 22%, 44% and 100%, respectively. However, 56% of spermatophores formed by males with the long hyaline gland bilaterally ablated failed to uncoil properly. These results indicate LHPI and/or other long hyaline gland proteins may act as lubricants. Unlike spermatophore formation and LHPI discharge, which increased steadily up to 90–120 min then levelled off, transfer of radiolabelled male ejaculate to the spermatheca was very variable. In 90 min copulations, only 1% of the total radioactivity (representing c. 5 μg protein) lost from the ARG complex was transferred to the spermatheca. The importance of male-derived protein in vitellogenesis is discussed.     

Increased juvenile hormone levels after long-duration flight in the grasshopper, Melanoplus sanguinipes

Although, in many insects, migration imposes a cost in terms of timing or amount of reproduction, in the migratory grasshopper Melanoplus sanguinipes performance of long-duration flight to voluntary cessation or exhaustion accelerates the onset of first reproduction and enhances reproductive success over the entire lifetime of the insect. Since juvenile hormone (JH) is involved in the control of reproduction in most species, we examined JH titer after long flight using a chiral selective radioimmunoassay. JH levels increased on days 5 and 8 in animals flown to exhaustion on day 4 but not in 1-h or non-flier controls. No difference was seen in the diel pattern of JH titer, but hemolymph samples were taken between 5 and 7 h after lights on. Treatment of grasshoppers with JH-III mimicked the effect of long-duration flight in the induction of early reproduction. The increased JH titer induced by performance of long-duration flight is thus at least one component of flight-enhanced reproduction. To test the possibility that post-flight JH titer increases are caused by adipokinetic hormone (AKH) released during long flights, a series of injections of physiological doses of Lom-AKH I were given to unflown animals to simulate AKH release during long flight. This treatment had no effect on JH titers. Thus, although AKH is released during flight and controls lipid mobilization, it is not the factor responsible for increased JH titers after long-duration flight.     

Corpus al latum regulation of copulatory behaviour in the male grasshopper, Melanoplus sanguinipes

Abstract The relationship between corpus allatum (CA) regulation of copulatory behaviour and the CA's influence on the development of the accessory reproductive glands was studied in the male grasshopper, Melanoplus sanguinipes (Fabr.). Allatectomy slowed the development of copulatory behaviour; ≤80% of control males 7 days and older mated with females, but allatectomized males did not show comparable levels of copulation until day 19. In a 3 h observation period, the time taken for 50% of males to initiate copulation was c. 60 min for allatectomized males and only c. 10 min for controls. At the age when 50% of males copulated, the accessory glands of allatectomized males were less developed than those of controls; the accessory gland weight was 65%, soluble protein was 72% and reserves of long hyaline protein I were 40% those of controls. Treatment with Juvenile Hormone III on day 2 stimulated accumulation of long hyaline protein I in 9-day-old allatectomized males to the level found in untreated 19-day-old allactec-tomized males, but did not elicit heightened copulation. No positive feedback from the accessory glands appeared necessary to elicit copulation since vasectomy, ablation of the accessory glands or isolation of the terminal abdominal ganglion by ventral nerve cord transection did not inhibit copulatory behaviour in 7-day-old males. Because allatectomy inhibited copulatory behaviour in 7-day-old males in which the accessory glands were removed but not in 19-day-old males without accessory glands, the increased tendency of older allatectomized males to mate with females was not due to release of inhibition caused by continued growth of the accessory reproductive glands.     

Intranuclear and cytoplasmic annulate lamellae in grasshopper spermatocytes (Genus Melanoplus)

Intranuclear and cytoplasmic annulate lamellae were studied in grasshopper spermatocytes (Melanoplus) with the electron microscope. Although cytoplasmic annulate lamellae were observed in all three species examined, intranuclear annulate lamellae were found in only one species. The intranuclear annulate lamellae encompass certain nuclear material adjacent to the nuclear envelope forming a vesicle that is extruded into the spermatocyte cytoplasm. In this same species, cytoplasmic annulate lamellae are seen contiguous with granular masses of varying size. These structures were noted as being morphologically indistinguishable from the "yolk nuclei" of dragonfly oocytes (Kessel and Beams, 1969; Kessel, 1973).     

Structure of the accessory reproductive glands of the male migratory grasshopper,Melanoplus sanguinipes

The accessory reproductive glands of Melanoplus sanguinipes comprise two bilateral masses of 16 tubules each, distinguishable in sexually mature insects as four white, ten short hyaline, one long hyaline, and a seminal vesicle. Over most of its length, the wall of each tubule consists of a simple glandular epithelium resting on a basal lamina, surrounded by a thin layer of circular muscle. However, near the junction with the ejaculatory duct, the wall of each tubule has a much thickened circular muscle layer and squamous or cuboidal epithelium, the region serving to regulate movement of secretion into the ejaculatory duct. Interdigitation of adjacent epithelial cells is common, and several kinds of specialized junctions occur. In the glandular region, all epithelial cells appear the same and may be flattened, cuboidal, or columnar depending on the tubule type. Except for those of the seminal vesicle, the glandular epithelial cells share ultrastructural features typical of cells engaged in the synthesis of protein for export. Despite these general similarities, in most instances subtle differences occur in the cellular ultrastructure of the epithelia of each tubule and in the appearance of their luminal secretions, suggesting that the tubules are functionally specialized.     

Changes in learning ability and mechanism during development of grasshopper nymphs, Melanoplus bivittatus

Abstract. In an experimental arena, Melanoplus bivittatus (Say) (Orthoptera: Acrididae) nymphs of four stadia were observed to determine whether they learn to associate food with positional or light-related cues. Nymphs were observed for 4 h in the arena containing one yellow box and one green box, then they were trained by placing food in the green box overnight. Following training, the responses of nymphs to green and yellow boxes were observed for a second 4 h period.
Before training, nymphs of all stadia visited the yellow box more frequently than the green box. Training did not affect the behaviour of second-stadium nymphs, but training increased the relative frequency of visits to the green box by third, fourth and fifth instars. Effects of training on duration of visits to boxes were not evident. Investigations of the mechanism of learning showed that positional cues were used by third-stadium nymphs, but that fourth and fifth instars responded to light-related cues. The progression from no learning in second instars, through use of positional cues by third instars, to use of light-related cues by fourth and fifth instars is probably associated with the greater mobility, greater food consumption, and more varied diet of older nymphs.