The dark-colour-inducing neurohormone of locusts: strain-dependent and phase-independent effects on adults of the migratory locust, Locusta migratoria

Abstract.  An albino strain that had originated from Okinawa, Japan, and a normally coloured strain that had originated from West Africa, were used to study the darkening response to injection of graded doses of dark-colour-inducing neurohormone of locusts (DCIN) ([His⁷]-corazonin) of gregarious and solitarious adults of the migratory locust, Locusta migratoria (L.). By repeated crossings, congenic albinos and normal phenotypes were obtained, both with a 99.6% West African genome, and their darkening response was compared with the original Okinawa and West African strains. Within each of these four strains, no difference was found in DCIN-induced darkening between gregarious and solitarious adults despite previous publications in the literature claiming an absence of 'fire-darkening' in gregarious adults of this species. Okinawa albino adults showed a markedly higher darkening response than the other three strains, including albinos with a 99.6% West African genome. This finding demonstrates that the differential darkening response of the Okinawa albinos is caused not by albinism, but by the geographical origin (Okinawa) of the strain. This is the first report of geographical-strain-dependent differences in the response of an insect to a neurohormone. The darkening response of adults reached a maximum on day 10 after injection; subsequently, the dark colour faded slowly. Adults injected 1 day after their moult showed a greater darkening response than those injected after 14 or 28 days.     

Characterizing phase‐related differences in behaviour of Schistocerca gregaria with spatial distribution analysis

The behaviour of locusts has been studied extensively using two approaches: (1) analysing a single individual's response to a group stimulus or (2) using group conditions to look at aggregation patterns. The second approach has, in contrast with the first one, not been improved in terms of statistical analyses since the 1960s. In the present study, we propose a spatial statistics approach of point‐pattern analysis to improve the group‐based assessment of behavioural phase characterization. This diagnostic tool was developed and tested in the laboratory with comparative analysis of solitarious (isolation‐reared) and gregarious (crowd‐reared) desert locusts, Schistocerca gregaria (Forskål) (Orthoptera: Acrididae). The spatial distribution patterns of 10 either solitarious or gregarious third‐instar hoppers were characterized with nearest neighbour distance measurements in a circular arena. The temporal sequence of spatial disposition of locusts was recorded with a digital camera taking photographs at regular intervals. The approach of point‐pattern analysis focused on the spatial distribution of observed events and allowed us to make inferences about the underlying process that generated them. The results confirmed that our diagnostic tool could identify that crowd‐reared hoppers tended to aggregate more to conspecifics than isolation‐reared ones. We could also verify that isolation‐reared hoppers were less active than crowd‐reared ones, but this was only true at the beginning of the experiments. The spatial statistics approach proposed in the present study could help with observations of phase‐related differences in the behaviour of locusts.     

安徽澳汉蚱属一新种记述（直翅目：蚱总科：枝背蚱科）

记述采自安徽的澳汉蚱属Austrohancockia 1新种,即岳西澳汉蚱A. yuexiensis Zha, Deng & Zheng sp. nov.。该新种近似于嘉氏澳汉蚱A. gressitti和武夷山澳汉蚱A. wuyishanensis, 主要区别为：1）头顶宽是1眼宽的3.0倍;2）颜面隆起纵沟宽为触角基节宽的1.5倍;3）前胸背板肩前的片状隆起具1靠后的深凹陷;4）前胸背板后突不达后足股节顶端,端部中央浅凹;5）雌性生殖板后缘中央三角形突出,后缘两侧弧形突出。模式标本存放于淮北师范大学生命科学学院标本室。     

The olfactory co-receptor Orco from the migratory locust (Locusta migratoria) and the desert locust (Schistocerca gregaria): identification and expression pattern

In locusts, olfaction plays a crucial role for initiating and controlling behaviours, including food seeking and aggregation with conspecifics, which underlie the agricultural pest capacity of the animals. In this context, the molecular basis of olfaction in these insects is of particular interest. Here, we have identified genes of two orthopteran species, Locusta migratoria and Schistocera gregaria, which encode the olfactory receptor co-receptor (Orco). It was found that the sequences of LmigOrco and SgreOrco share a high degree of identity to each other and also to Orco proteins from different insect orders. The Orco-expressing cells in the antenna of S. gregaria and L. migratoria were visualized by in situ hybridization. Orco expression could be assigned to clusters of cells in sensilla basiconica and few cells in sensilla trichodea, most likely representing olfactory sensory neurons. No Orco-positive cells were detected in sensilla coeloconica and sensilla chaetica. Orco expression was found already in all nymphal stages and was verified in some other tissues which are equipped with chemosensory hairs (mouthparts, tarsi, wings). Together, the results support the notion for a decisive role of Orco in locust olfaction.     

Concentration-dependent parsimonious releaser roles of gregarious male pheromone of the desert locust, Schistocerca gregaria

The responses of (i) groups of crowd-reared mature males of desert locust, Schistocerca gregaria to a choice of two columns of air, one permeated with different concentrations of phenylacetonitrile (PAN), the major component of gregarious-phase male-produced pheromone, and the other untreated, and (ii) individual crowd-reared mature males of the insect to varying concentration gradients of PAN, were studied in two different types of arena. In the choice assay, locusts preferred to be within PAN-permeated air column at low relative doses of the pheromone, but away from PAN at high relative doses. In the second assay, individual locusts were arrested close to PAN source at low PAN concentration gradients, but away from the source at high concentration gradients. The results are consistent with two reported releaser functions of the adult male-released pheromone that are dependent on different sensory thresholds: arrestment and cohesion at lower relative concentrations and male-male homosexual avoidance at higher relative concentrations.     

Interaction between Paranosema locustae and Metarhizium anisopliae var. acridum, two pathogens of the desert locust, Schistocerca gregaria under laboratory conditions

The interaction between two pathogens, the microsporidian Paranosema locustae Canning and the fungus Metarhizium anisopliae var. acridum Driver and Milner was studied under laboratory conditions in an attempt to develop an improved method of microbial control for the desert locust, Schistocerca gregaria Forsk?l. Fifth-instar locust nymphs, reared in the laboratory, were treated with various concentrations of one of the two pathogens or with both pathogens. The numbers of locusts killed were recorded each day and the production of pathogen spores within the dead locusts was assessed at the end (day 21) of each experiment. Locust nymphs treated with both P. locustae and M. anisopliae died sooner than nymphs infected with only one of the pathogens. At the lower concentrations of pathogen tested, the effects of the two pathogens were additive. At the higher concentrations the combined effects were synergistic. In terms of locust mortality, there was no evidence of any antagonistic effects between the two pathogens. However, the production of spores by P. locustae was reduced considerably when the host insects were infected also with M. anisopliae. For example, nymphs treated initially with P. locustae and then treated 3 and 10 days later with M. anisopliae produced 3-20 times and 2.5-8 times fewer spores, respectively, than nymphs treated only with P. locustae. Hence, in areas where M. anisopliae is applied, the natural persistence of P. locustae in the local grasshopper and locust populations may be diminished.     

Investigations on influencing plant-associated bacteria in tissue cultures of black locust (<Emphasis Type="Italic">Robinia pseudoacacia</Emphasis> L.)

During tissue culture of black locust (Robinia pseudoacacia L.), serious problems with plant-associated bacteria led to a reduction of propagation potential in several clones. Four dominant strains of plant-associated bacteria could be isolated and were assigned to the genera Acidovorax, Dyella, Microbacterium and Sphingomonas. Out of five essential oils tested, thyme and lemongrass oil at a concentration of 0.03% each and 0.015% of both oils in combination clearly inhibited the growth of these bacteria strains on bacteriologic medium. There were no significant differences in total bacterial population density when penicillin, thyme and lemongrass oil or thyme plus lemongrass oil were added to the plant propagation media. The use of lemongrass oil changed the proportion of dominant bacterial strains.     

盐胁迫下刺槐无性系生长和矿质营养平衡研究

以一年生盆栽刺槐无性系BH327和B56为材料,对盐胁迫下刺槐无性系生长和矿质营养平衡进行了研究。结果表明：盐胁迫下BH56生长受抑不明显,组织水平上K^＋、Ca^2＋、Mg^2＋保持较高水平,尤其是在高盐下上部叶片足Ca^2＋、Mg^2＋的选择性吸收增强;而BH327,的生长受盐胁迫明显的抑制,组织水平上K^＋、Ca^2＋、Mg^2-水平相对较低,在高盐下上部叶片对Ca^2-、Mg^2＋的选择性吸收能力低于BH56。同时,从体内离子分配及选择性运输角度讨论了各无性系盐伤害或耐盐的原因。     

改治结合,根除蝗害的关键因子是“水”!

改治结合,根除蝗害的关键因子是“水”。其主要原因为:(1)水灾是为东亚飞蝗创造发生地和转移到临近地区危害的关键因子;(2)东亚飞蝗产卵的适宜的土壤含水量为10%～20%(沙土为10%～12%,壤土为15%～18%,粘土为18%～20%);(3)先涝后旱,飞蝗成片;(4)黄(河)患是东亚飞蝗蝗害发生的源泉。南水北调东线工程的实施,有利于滨湖(库)蝗区东亚飞蝗的持续控制。