An experimental analysis of the relationships between fitness components and malic enzyme genotypes inTribolium confusum

The hypothesis that natural selection is capable of maintaining allozyme variation in natural populations was tested using a species of flour beetles,Tribolium confusum. We selected a polymorphic locus (a locus encoding variation for malic enzyme) in an experimental population ofT. confusum and scored the genotypes at this locus for a series of fitness components on different flour types. Measurements included survival rate, development time, fecundity, and rate of egg cannibalism. Flour type had significant effects on most traits. Significant differences among genotypes for fecundity and rates of egg cannibalism and the presence of genotype × flour type interactions for development time were demonstrated. Thus, changes in allele frequencies at the malic enzyme locus could in part be under the influence of natural selection. The existence of genotype × flour type interactions suggests that environmental heterogeneity could maintain allozyme variation at the malic enzyme locus.     

Response of Tribolium castaneum larvae to synthetic aggregation pheromone

Responses of larval Tribolium castaneum Herbst. to the synthetic adult aggregation pheromone (4,8-dimethyldecanal) were studied. Larvae of T. castaneum were attracted both by contact and vapour of 4,8-dimethyldecanal at concentrations of 1, 5 and 10 g. g^-1 of medium.

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Reaktion von Tribolium castaneum Larven auf synthetisches Aggregationspheromon

Zusammenfassung Die Reaktionen der Larven von T. castaneum auf das kunstliche Aggregations pheromon (4,8-dimethyldecanal) in Versuchen in Petrischalen untersucht. Die Larven wurden angezogen, wenn sie mit Pheromon auf Filterpapier oder mit verdampftem Pheromon in Kontakt kamen. Diese Reaktion wurde bei Konzentrationen von 1, 5 und 10 g · g^-1 Medium festgestellt. Die höchste Konzentration rief die grosste Reaktion hervor. Fruhe Larvenstadien zeigten stärkere Reaktionen als spatere Stadien.

     

赤拟谷盗和杂拟谷盗的生殖隔离研究

赤拟谷盗和杂拟谷盗是两个同域发生的近缘储粮害虫。为明确它们的生殖隔离程度和机制,本研究比较分析了赤拟谷盗和杂拟谷盗雄虫对同种和异种雌虫的交配选择;赤拟谷盗与杂拟谷盗交配后,测定了精子在异种雌体内的存活情况;将赤拟谷盗和杂拟谷盗进行正反杂交,研究其F1代、F2代和回交代杂种是否产生及其雌雄比。结果显示,赤拟谷盗和杂拟谷盗雄虫对同种雌虫的爬跨率和交配率高于其对异种雌虫的爬跨率和交配率,表明赤拟谷盗和杂拟谷盗种间性隔离不完全;赤拟谷盗和杂拟谷盗交配后精子在异种雌体内是存活的,杂交所产的F1代卵为受精卵,说明交配后完成了精子传送和受精过程,表明种间机械隔离和配子隔离不完全;赤拟谷盗和杂拟谷盗的杂种F1代自交和回交产生了F2代和回交代,表明种间不存在杂种不育;一些杂交组合产生的F2代和回交代数量少且存在雌雄性比偏离,表明种间存在部分杂种不活和杂种衰败。本研究明确了赤拟谷盗和杂拟谷盗的生殖隔离机制,这对于揭示它们的物种进化关系有着重要意义。     

A STUDY ON THE OVIPOSITION SYNERGISTS FOR IN VITRO REARING TRICHOGRAMMA SPP.*

Abstract Solutions or suspensions of polyvinyl alcohol, gelatin, white latex, agar cassava powder, rice flour and starch were used as synergists to improve the oviposition of Trichogramma dendrolimi, T. confusum and T. evanescens with in vitro rearing method. The ovipositional response of Trichogramma spp. to these synergists was different. All the 7 preparations improved the trichogrammatid oviposition much on the artificial host “eggs”. Specific difference of trichogrammatid ovipositional response to these synergists was observed. So, the most effective and economical synergists can be used for increasing the efficiency of rearing different species of Trichogramma in vitro.     

Electrohydrodynamic mortality of insects: a plausible mechanism

 An electrohydrodynamic (EHD) system with a point-to-plane electrode, which produced air ions within a strong electric field, was used to study mortalities of pupae, larvae, and adults of Tribolium confusum (TC) and larvae of Plodia interpunctella (PI). The treatments included a neutral air stream, negative ions, positive ions, and the air stream superimposed with ions of either polarity. The negative ions caused the maximum mortality in TC pupae and PI larvae whereas the TC adults were least affected, but the negative ion flux was higher than the positive one at the constant high voltage of the power supply used in the present experiments. The differences in the mean mortalities of the treatment groups were highly significant (P<0.0001). Mortality was primarily attributed to the body fluid losses caused by the electric wind of the EHD system. Mortality and weight loss relationships were linear with negative slopes (r ²=0.52, and r ²=0.98 for TC and PI, respectively). The superimposition of the air stream with either positive or negative ion fluxes increased the survival fractions compared with those of the ion fluxes alone. Received: 27 May 1996 / Accepted: 9 September 1996     

Insect feeding deterrent property of alantolactone

The sesquiterpene lactone, alantolactone, significantly reduces feeding and survival of Tribolium confusum. These findings support the view that alantolactone may protect plants such as composites from insect attack.     

鄂西特有植物提取物的杀虫活性

首次报道悬铃木叶苎麻、龟背竹、李叶绣线菊、扇脉杓兰、鞘柄木、青牛胆、仙茅和大叶金腰的杀虫活性。质量分数为1%的(下同)千里光茎、李叶绣线菊花、龟背竹、扇脉杓兰茎叶、悬铃木叶苎麻和鞘柄木叶甲醇提取物对舍蝇Musca domestica vicinaMacquart 48 h的致死率在70%以上,其中千里光茎为96.55%。仙茅、扇脉杓兰和李叶绣线菊花对赤拟谷盗Tribolium castaneum(Herbst)种群60 d繁殖抑制率达50%以上,其中最高仙茅为83.52%。仙茅和李叶绣线菊花对赤拟谷盗30 d的毒杀率在60%以上。悬铃木叶苎麻对斜纹夜蛾Spodoptera lituraFabricius 3龄幼虫48 h的拒食率为84.00%。李叶绣线菊花、青牛胆、悬铃木叶苎麻和大叶金腰对亚洲玉米螟Ostrinia furnacalis(Guen?e)3龄幼虫具较好拒食效果,其中,李叶绣线菊花48 h对亚洲玉米螟3龄幼虫的拒食率为81.17%,这几种植物还引起试虫体重不增加、化蛹延迟、畸形蛹或部分蛹死亡现象。所筛选植物对致倦库蚊Culex pipiens quinguefasciatusSay 4龄幼虫48h的毒杀率均低于20%。以甲醇冷浸提取法对所采集的植物材料进行冷浸提取时,提取率分布在1.92%至12.92%之间。     

Formation of the arthropod labrum by fusion of paired and rotated limb-bud-like primordia

The nature and origin of the arthropod labrum is a matter much under dispute. We show here that in Tribolium castaneum (Herbst, 1797) the labrum develops from two individual primordia, termed labral buds. Expression of the genes decapentaplegic (dpp) and wingless (wg) in these buds is identical to the buds of the metameric appendages (e.g. thoracic legs), except that the patterns are reversed. We propose that this reversal is the result of the rotation of the labral buds through an angle of approximately 180°. We also for the first time study dpp and wg expression in the fully developed labrum of older embryonic stages. Here, gene expression patterns show that the labrum proper is formed by fusion of the labral buds along their dorsal sides, while their ventral sides are facing outward forming the lateral sides of the fused labrum. Furthermore, we show that there are very similar patterns in another arthropod species, the spider Cupiennius salei (Keyserling, 1877), although in this species the labrum develops as a single structure and not from two separate primordia. However, in C. salei the expression of engrailed is also reversed in addition to the reversal of dpp and wg expression: engrailed is expressed in the anterior half of the labrum, and not in the posterior half like in the remaining appendages. Our results suggest that the arthropod labrum is derived evolutionarily from paired limb-bud-like primordia by rotation and fusion, and that this process is recapitulated ontogenetically to a different extent in different arthropod species.     

Larval leg integrity is maintained by Distal-less and is required for proper timing of metamorphosis in the flour beetle, Tribolium castaneum

The dramatic transformation from a larva to an adult must be accompanied by a coordinated activity of genes and hormones that enable an orchestrated transformation from larval to pupal/adult tissues. The maintenance of larval appendages and their subsequent transformation to appendages in holometabolous insects remains elusive at the developmental genetic level. Here the role of a key appendage patterning gene Distal-less (Dll) was examined in mid- to late-larval stages of the flour beetle, Tribolium castaneum. During late larval development, Dll was expressed in appendages in a similar manner as previously reported for the tobacco hornworm, Manduca sexta. Removal of this late Dll expression resulted in disruption of adult appendage patterning. Intriguingly, earlier removal resulted in dramatic loss of structural integrity and identity of larval appendages. A large amount of variability in appendage morphology was observed following Dll dsRNA injection, unlike larvae injected with dachshund dsRNA. These Dll dsRNA-injected larvae underwent numerous supernumerary molts, which could be terminated with injection of either JH methyltransferase or Methoprene-tolerant dsRNA. Apparently, the partial dedifferentiation of the appendages in these larvae acts to maintain high JH and, hence, prevents metamorphosis.