The Mechanism of Dual Responsiveness in Muscle Fibers of the Grasshopper Romalea microptera

Dually innervated Romalea muscle fibers which respond differently to stimulation of their fast and slow axons are excited by intracellularly applied depolarizing stimuli. The responses, though spike-like in appearance, are graded in amplitude depending upon the strength of the stimuli and do not exceed about 30 mv. in height. In other respects, however, these graded responses possess properties that are characteristic of electrically excitable activity: vanishingly brief latency; refractoriness; a post-spike undershoot. They are blocked by hyperpolarizing the fiber membrane; respond repetitively to prolonged depolarization, and are subject to depolarizing inactivation. As graded activity, these responses propagate decrementally. The fast and slow axons of the dually responsive muscle fibers initiate respectively large and small postsynaptic potentials (p.s.p.'s) in the muscle fiber. These responses possess properties that characterize electrically inexcitable depolarizing activity. They are augmented by hyperpolarization and diminished by depolarization. Their latency is independent of the membrane potential. They have no refractory period, thus being capable of summation. The fast p.s.p. evokes a considerable or maximal electrically excitable response. The combination, which resembles a spike, leads to a twitch-like contraction of the muscle fiber. The individual slow p.s.p.'s elicit no or only little electrically excitable responses, and they evoke slower smaller contractile responses. The functional aspects of dual responsiveness and the several aspects of the theoretical importance of the gradedly responsive, electrically excitable component are discussed.     

Organisation of wing cuticle in Locusta migratoria linnaeus,Tropidacris cristata linnaeus and Romalea microptera beauvais (Orthoptera : Acrididae)

The composite fibrous architectures of the wing cuticles of Locusta migratoria, Tropidacris (= Eutropidacris) cristata and Romalea microptera (Orthoptera : Acrididae) have been established. The wing cuticle in all the 3 species consists of: (i) an exocuticle, which is either pigmented or birefringent, and which under an electron microscope shows constantly helicoidal architecture of chitin microfibrils; (ii) endocuticle, which shows alternately birefringent and isotropic layers when sectioned transversely across the wing veins; these layers show helicoidal and unidirectional architecture, respectively of chitin microfibrils under the electron microscope. In transverse section, the chitin microfibrils appear as clear rods (2.8 nm in diameter) in a darkly stained matrix. However, in the hinge called the “claval furrow”, these microfibrils are considerably larger, being 25 nm in diameter. This presumably gives sufficient hardness to the claval hinge, which is the most vulnerable area for wear and tear during flight. The pore canals follow the parabolic pattern of microfibrils in the helicoidal layer, but remain straight in the unidirectional layers. The thickness of wing cuticle increases up to about 10–12 days, the time at which the acridids most probably attain the optimum flight ability. It is suggested that changes in the wing cuticle are related to increased wing beat frequency and speed of flight with age, and may help in resisting the simultaneous increase in the bending and twisting forces on the wing.     

Sex-based divergence in head shape and diet in the Eastern lubber grasshopper (Romalea microptera)

Biologists are becoming increasingly aware of sex-based differences in ecologically important traits (locomotor performance, feeding morphology, thermoregulatory behavior). Yet, the overwhelming majority of these studies have been performed on vertebrates, despite often striking examples of sexual size dimorphism among the insects. Here, I tested whether adult male and female Eastern lubber grasshoppers differ in size/shape and feeding ecology. The morphological data clearly showed sex-based differences in several aspects of head and body size, with females being significantly larger in all aspects. Moreover, the sexes also differed in two aspects of size-adjusted morphology: head width and pronotum width, with females having relatively wider heads and thoraxes than males. Multiple regression analysis indicated that width of consumed foliage was positively related to pronotum width and foliage thickness was positively related to pronotum width, head width, and size-adjusted head width. Females consumed wider and thicker foliage (primarily smooth cord grass, Spartina alterniflora) than males, which most frequently consumed the narrow-leafed forb hemp sesbania (Sesbania macrocarpa). Therefore, the sex-based differences in size and shape in this grasshopper are correlated with differences in consumed foliage shape.     

Morphology and Phylogenetic Position of Two New Gregarine Species (Apicomplexa: Eugregarinorida) Parasitizing the Lubber Grasshopper Taeniopoda centurio (Drury, 1770) (Insecta: Orthoptera: Romaleidae) in Mexico

Eugregarines are understudied apicomplexan parasites of invertebrates inhabiting marine, freshwater, and terrestrial environments. Most currently known terrestrial eugregarines have been described parasitizing the gut from less than 1% of total insect diversity, with a high likelihood that the remaining insect species are infected. Eugregarine diversity in orthopterans (grasshoppers, locusts, katydids, and crickets) is still little known. We carried out a survey of the eugregarines parasitizing the Mexican lubber grasshopper, Taeniopoda centurio, an endemic species to the northwest of Mexico. We described two new eugregarine species from the gut of the host: Amoebogregarina taeniopoda n. sp. and Quadruspinospora mexicana n. sp. Both species are morphologically dissimilar in their life‐cycle stages. Our SSU rDNA phylogenetic analysis showed that both species are phylogenetically distant to each other, even though they parasitize the same host. Amoebogregarina taeniopoda n. sp. clustered within the clade Gregarinoidea, being closely related to Amoebogregarina nigra from the grasshopper Melanoplus differentialis. Quadruspinospora mexicana n. sp. clustered within the clade Actinocephaloidea and grouped with Prismatospora evansi, a parasite from dragonfly naiads. Amoebogregarina taeniopoda n. sp. and Q. mexicana n. sp. represent the first record of eugregarines found to infect a species of the family Romaleidae.     

Divergent egg physiologies in two closely related grasshopper species: Taeniopoda eques versus Romalea microptera (Orthoptera: Romaleidae)

We compared egg survivorship and egg development time at different soil moistures for two closely related grasshopper species from divergent habitats: marsh-inhabiting Romalea microptera (Beauvois) versus desert-inhabiting Taeniopoda eques (Burmeister). These two species can interbreed and produce viable offspring. In nature, both species have a similar 8-9 mo subterranean egg stage, but their soil environments differ dramatically in water content. We predicted that the eggs of the two species would exhibit differential survivorship and development times under different moisture levels. Our laboratory results show that the eggs of both species survived a wide range of soil moistures (≈ 0.5 to 90%), maintained for 3 mo. However, the eggs of the marsh grasshopper, R. microptera, better tolerated the highest soil moistures (95 and 100%), whereas the eggs of the desert species, T. eques, better tolerated the lowest soil moistures (0.0 and 0.1%). Sixty-five percent of marsh-inhabiting R. microptera eggs, but no desert T. eques eggs, survived 3 mo submersion under water. In contrast, 49% of desert T. eques eggs, but only 3.5% of R. microptera eggs, survived after being laid into oven-dried sand and then maintained with no additional water until hatch. In the laboratory at 26 °C, the two species differed significantly in the mean length of the oviposition-to-hatch interval: 176 d for R. microptera versus 237 d for T. eques. These divergent traits presumably benefit these insects in their divergent habitats. Our results suggest the evolution of physiological divergence that is consistent with adaptations to local environments.     

Grasshopper (Orthoptera: Acridoidea) species diversity in the Pampas, Argentina

Abstract.  A study was conducted to describe the major features of geographical and temporal variation in the diversity of grassland grasshopper species (Orthoptera: Acridoidea) in different sites of the Pampas, Argentina. Species richness and relative abundance were assessed at 12 sites in eastern La Pampa and western Buenos Aires provinces, from 1994 through 1999. Mean species richness at the regional level was 10, and 34 grasshopper species were collected throughout of the study. Comparison with grasshopper species diversity from the Great Plains of North America is discussed. An evaluation of the proportions of species in each of the three distribution groups (broad, intermediate and narrow) revealed that, over all sites, broadly distributed species made up 14.7% of species composition and intermediately and narrowly distributed species made up 26.5% and 58.8%, respectively. The three top-ranked species in the studied sites were Dichroplus elongatus , D. pratensis and Staurorhectus longicornis . Results showed that, contrary to what was expected, one of the widely distributed species in the region (i.e. Baeacris punctulatus ) does not always constitute one of the most abundant species. Finally, the loss of one of the historically most common species in the Pampas, D. maculipennis , is also discussed.     

Grasshopper （Orthoptera： Acrididae） biodiversity and grassland ecosystems

Interesting results may arise by combining studies on the structure and function of ecosystems with that of biodiversity for certain species. Grasshopper biodiversity is the result of the evolution of grassland ecosystems; however, it also impacts on the structure and the function of those ecosystems. We consider there to be a close relationship between the health of grassland ecosystems and grasshopper biodiversity. The main problems involved in this relationship are likely to include： （i） grasshopper biodiversity and its spatial pattern; （ii） the effect of grasshopper biodiversity on the ecological processes of grassland ecosystems; （iii） the biodiversity threshold of grasshopper population explosions; （iv） the relationship between grasshopper biodiversity and the natural and human factors that affect grassland ecosystems; and （v） grasshopper biodiversity and the health of grassland ecosystems. The solutions to these problems may provide sound bases for controlling disasters caused by grasshoppers and managing grassland ecosystems in the west of China. In this paper, we introduced two concepts for grasshopper biodiversity, that is, ＂spatial pattern＂ and ＂biodiversity threshold＂. It is helpful to understand the action of the spatial pattern of grasshopper biodiversity on the ecological processes of grassland ecosystems and the effect of this spatial pattern on the health of those ecosystems, owing to the fact that, in the west of China, grasslands are vast and grasshoppers are widely distributed. Moreover, we inferred that the change in the level of component richness at each type of grasshopper biodiversity can make an impact on grassland ecosystems, and therefore, there is likely to be a threshold to grasshopper biodiversity for the stability and the sustainability of those ecosystems.     

Males vs. female meiotic prophase in a grasshopper,Arcyptera microptera (Orthoptera: Acridiae)

Female and male first meiotic prophase are analyzed in the grasshopper Arcyptera microptera with special reference to the heteropycnotic chromatin. Differences in the behaviour of the megameric and X-chromosomes, in nuclear size and in the response to C-banding treatment are described. The evidence for a distinctive meiotic prophase in both sexes is compared with results obtained in other species of grasshoppers by other authors using more advanced stages. The discussion centers around the role of the diffuse stage and the differential behaviour of the X-chromosome in the two sexes.     

宽翅曲背蝗受精囊形态与超微结构观察

[目的]明确宽翅曲背蝗Pararcyptera microptera meridionalis雌虫受精囊的形态、组织结构与超微结构,为更好地认识昆虫受精囊的功能提供依据.[方法]本研究以宽翅曲背蝗已交配雌成虫为实验材料,利用光学显微镜和透射电子显微镜观察其受精囊的形态、组织结构和超微结构.[结果]宽翅曲背蝗受精囊由一个端囊和一条长的受精囊管组成,端囊用于储存精子.端囊和受精囊管有相似的组织学结构,由外到内依次为肌肉层、基膜、上皮层及表皮内膜.上皮层含上皮细胞、腺细胞和导管细胞3种细胞类型.腺细胞具有一个被有微绒毛的细胞外腔.腺细胞的分泌物经细胞外腔通过分泌导管进入到受精囊腔.分泌导管由导管细胞形成.[结论]在宽翅曲背蝗受精囊的端囊和受精囊管上,内膜和腺细胞的细胞外腔结构均存在差异,由此推测,端囊和受精囊管的功能存在一定差异.上皮细胞的超微结构特点显示上皮细胞具有支持、分泌和吸收的功能.     

Pharmacological Activation of Stridulation in the Grasshopper Chorthippus albomarginatus (Orthoptera: Gomphocerinae)

Calling and courtship stridulatory behavior of Chorthippus albomarginatus was induced by injections of acetylcholine agonists into the protocerebrum. Pharmacologically induced stridulation, in many parameters, was quite similar to the natural behavior. However, the order of the courtship element alternation was different from that of the natural song. In some cases the pharmacologically induced stridulation included only one or two courtship elements. Based on the exclusive stimulation of a particular element of courtship songs and similarity of its movement pattern with the calling song, both patterns of Ch. albomarginatus stridulation appear to be homologous. The results obtained on this species confirm the idea of a hierarchic organization of the central nervous control of stridulation in gomphocerine grasshoppers and indicate participation of certain protocerebrum structures in this control.     

Hematopoiesis in Hematopoietic Organ in Euprepocnemis shirakii (Orthoptera, Insecta)

ABSTRACT The present study was undertaken to investigate the hematopoiesis of the hematopoietic organ found in orthopteran Euprepocnemis shirakii under both light and transmission electron microscopy. It was shown that the hemocyte differentiation of E. shirakii was distinct from features compared to patterns previously reported in other insect species: Their prohemocytes, plasmatocytes, granulocytes I, granulocytes II and spherulocytes were all derived from the hematopoietic stem cells surrounded by reticular cells. This pattern of hematopoiesis was also first observed in the Orthoptera. Thus, findings of this study strongly suggested that the patterns of hematopoiesis in insects differed, among groups, showing the need of an extensive investigation in order to correctly comprehend the patterns of hemocyte differentiation in insects in accordance with first order, and then systematically important taxa.     

Developmental response to a seasonal time constraint: the effects of photoperiod on reproduction in the grasshopper Romalea microptera

Abstract.  1. Some organisms respond adaptively to seasonal time constraints by altering development time to life-history transitions (e.g. metamorphosis, oviposition). Such life-history changes may have costs (e.g. reduced fecundity, mass, offspring quality).
2. The hypothesis that a northern population of the grasshopper Romalea microptera (Beauvois) would show adaptive plasticity in oviposition timing in response to seasonal time constraints was tested by manipulating photoperiod to simulate the middle of the active season (Long photoperiod), the end of the active season (Short photoperiod), and seasonal change (photoperiod Declining from long to short). Females received either high or low food rations. Short or Declining photoperiod were predicted to induce early oviposition with costs of reduced egg number, post-oviposition mass, or egg size, particularly in low-food females.
3. Effects of food ration and photoperiod, but not interaction, were significant in failure time analysis of age at oviposition. mancova on age at oviposition, egg number, and post-oviposition mass yielded similar effects. The multivariate effect of photoperiod resulted primarily from reduced time to oviposition in Short or Declining photoperiod. No costs in egg number or post-oviposition mass were associated with this photoperiod-induced reduction in time to oviposition. The multivariate effect of food ration resulted mainly from lower egg number with low food. Food ration affected egg size, but photoperiod and interaction did not. In all cases, Short and Declining photoperiod produced similar effects.
4. In its northern range, R. microptera accelerates reproduction in response to seasonal constraints, a response that may be adaptive. How R. microptera avoids costs associated with this reduced pre-oviposition period remains unknown.     

吉林省蝗虫一新种（直翅目：丝角蝗科）

1987年7～8月,作者在吉林省西部草原进行调查时采到的蝗虫,经鉴定整理,发现雏蝗属一新种,现报导如下。模式标本保存在东北师范大学生物系动物标本室。     

小翅负蝗雌性的记述

首次记述了小翅负蝗Atractomorpha micropennaZheng,1992的雌性。     

Development of the accessory glands in the genital tract of female Teleogryllus commodus WALKER (Insecta, Orthoptera)

The development of the female accessory glands in Teleogryllus commodus was studied by detailed morphometric and stereological analyses. In addition, a microsurgical method was developed to quantify the gland secretion. The morphometric results yield evidence that the glands are subject to a significant growth during peak differentiation, starting immediately after the adult moult. The gland growth is exclusively caused by a hypertrophy of single gland cells with respective volume gains between 400 and 700%. According to the stereological results, the volume of mitochondria per cell is marked by an up to fourfold increase during peak differentiation. Other cell structures (rER, sER) are characterized by a similar propagation behavior. The nucleus and nucleolus grow simultaneously with the cell, indicating high production of site-specific macromolecules. Infolds of the basal cell membrane cause a progressive enlargement of the basal cell surface ensuring an increased uptake of secretory precursors from the hemolymph. Quantitative studies show that the total production of secretion increases with proceeding age and can be correlated with a rising egg-laying activity, starting on the eighth day of adult's life. This underlines the main function of the secretion as a lubricant for a facilitated transport of the eggs through the ovipositor.     

印氏卵翅蝗的一例间性体(直翅目:卵翅蝗亚科)

首次报道印氏卵翅蝗Caryanda yini Mao et Ren,2006的一例偏雄性间性体.该个体总体特征为雄性,特别是雄性外生殖器发育完全,雄性下生殖板锥形,但出现了一些典型的雌性特征:前翅棕色、腹部两侧棕色、第十腹节背板后缘无尾片、肛上板三角形、尾须顶端直;腹内有一条线形动物寄生,未见性腺.推测该间性体的形成可能与线形动物的寄生有关.     

Postendocytic Provitellin Processing in the Growing Oocyte of the Short Horned Grasshopper, Oxyajaponicajaponica (Orthoptera: Acrididae)

Polyclonal antibodies made against 86 kDa (86 k), 80 kDa (80 k) and 54 kDa (54 k) vitellins of Oxya japonica japonica are used for Western blotting. Anti‐80k vitellin antibody is cross‐reacted with a 95 kDa (95 k) vitellin. While 95 k vitellin is present both in the female hemolymph and in the oocyte, 80 k vitellin is detected only in the oocyte and the laid egg. In the growing oocytes, as 95 k vitellin is faded out gradually, 80 k vitellin is accumulated increasingly, indicating postendocytic processing of 95 k vitellin brings 80 k vitellin. Further conforming the hypothesis, partial digestion of 95 k vitellin with pepsin and α‐chymotrypsin makes several protein bands of molecular weight around 80 kDa. Thus, the 95k vitellin may have a cleavage site (s) to produce 80 k vitellin which forms fairly stable tertiary structure. In the reduced condition (20 mM glutathion), both 95 k and 80 k vitellins were digested throughly by endogenous proteinase at pH 4. Both 86 k and 54 k vitellins, respectively, show no apparent molecular weight changes in the growing oocyte and in the hemolymph.