Defense mechanism of the termite, Coptotermes formosanus Shiraki, to entomopathogenic fungi

Termites, Coptotermes formosanus Shiraki, reared individually, were highly susceptible to entomopathogenic fungi, Paecilomyces fumosoroseus and Beauveria brongniartii and Metarhizium anisopliae, while termites reared in groups were highly resistant. Quantitative assays with an epifluoresent microscope revealed a significant difference in the number of conidia attachments among three entomopathogenic fungi. The conidia of B. brongniartii and P. fumosoroseus bound to termite cuticles more effectively than M. anisopliae conidia. Our results also suggested that self-grooming behavior is less effective, but mutual grooming is very effective in the removal of conidia from cuticles of their nestmates. Statistical analysis of removal rates indicated that conidia of P. fumosoroseus and B. brongniartii were removed more rapidly than M. anisopliae conidia from termite cuticles.     

成都地区首次发现台湾乳白蚁

2005年9月29日,本所施工人员在对成都市与温江区交界处文家场土龙公路某俱乐部的一栋别墅进行白蚁灭治施工时,发现大量活体白蚁,别墅木质装饰墙裙受到白蚁严重危害。经笔者现场鉴定,确认该处发现的白蚁为台湾乳白蚁（Coptotermes formosamus Shiraki）。     

台湾乳白蚁行为多型的研究

本文对台湾乳白蚁的打洞挖掘行为、取水行为、修饰行为和交哺行为进行了比较详细的定量分析,探讨了年龄和品级对台湾乳白蚁群体中行为多型的影响。实验结果表明大（老）龄工蚁承担了台湾乳白蚁群体内大多数的任务,对台湾乳白蚁群体的维持具有重要意义。另外品级也是影响台湾乳白蚁群体内劳动分化的一个重要因素。在营养交哺方面,若蚁尚不具备完好的取食行为,是群体中营养交哺的受益者,而兵蚁在台湾乳白蚁群体中占据着较重要的地位,享受着营养物质优先供应的特殊权利。     

Dual cellulose-digesting system of the wood-feeding termite,Coptotermes formosanus Shiraki

The distribution of endo-beta-1,4-glucanase (EG) components in the digestive system of the wood-feeding termite, Coptotermes formosanus Shiraki, was investigated by zymogram analysis using polyacrylamide gel electrophoresis, followed by N-terminal protein sequencing. EG components similar to glycoside hydrolase family (GHF) 9 members were restricted to the salivary glands, the foregut, and the midgut, whereas components similar to GHF7 members were confined to the hindgut where numerous cellulolytic flagellates were harbored. RT-PCR experiments revealed that five GHF9 EG mRNAs (1348 bp) homologous to other termite EGs were expressed in the salivary glands and the midgut. The crude extract prepared from the midgut as well as that from the hindgut produced glucose from crystalline cellulose. These data suggest that C. formosanus has two independent cellulose-digesting systems: one in the midgut where cellulose digestion is accomplished by endogenous cellulases and the other in the hindgut which makes use of other cellulases possibly from symbiotic flagellates.     

The complete mitogenome of the Formosan termite, Coptotermes formosanus Shiraki

The Formosan termite Coptotermes formosanus Shiraki is a well-known invasive pest that causes severe damage to wooden structures in many parts of the world. Although several studies examined its phylogeographic patterns using a few mitochondrial genes, the phylogenetic relationships among C. formosanus are poorly understood because of the small number of mutations known among its mitochondrial genes. To provide a useful genetic tool for further analyses, we analyzed the complete mitochondrial genome sequence of C. formosanus using specimens collected from three isolated islands in the Ryukyu Archipelago of Japan. The circular mitogenome of these termites consisted of genes encoding 22 transfer RNAs, two ribosomal RNAs, and 13 mitochondrial proteins, as is the case for most animal mitochondrial genomes. The G + C content was 34.1%, and the total length varied slightly between 16,234 and 16,236 base pairs. The complete mitochondrial genomes of the three populations were more than 99.9% identical to each other and showed differences at six nucleotide positions. The COII, 12S rRNA, and 16S rRNA genes that are commonly used for phylogenetic analyses revealed only one substitution or no substitutions. The mitogenome sequences determined here should contribute to the design of new molecular markers for the clarification of the historical distribution process of C. formosanus and for further phylogenetic analyses with this and related termite species.     

Behavioral and electrophysiological responses of Coptotermes formosanus Shiraki towards entomopathogenic fungal volatiles

Termites adjust their response to entomopathogenic fungi according to the profile of fungal volatile organic compounds (VOCs). This study demonstrates the pathogenicity of Metarhizium anisopliae, Beauveria bassiana and Isaria fumosorosea (=Paecilomyces fumosoroseus) towards the Formosan subterranean termite, Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae). Using no-choice assays, M. anisopliae was found to be highly virulent (LT₅₀ 3.10 d) when compared to B. bassiana (LT₅₀ 6.62 d) and I. fumosorosea (LT₅₀ 12.39 d). Also using choice assays, the foraging behavior of C. formosanus was determined in the presence of pathogenic fungi. The highly pathogenic fungi (M. anisopliae) elicited a repellent response, causing most of the termites to forage in a safe zone farthest from the fungal source. This repellency resulted in relatively low mortality similar to the controls. The repellency of M. anisopliae conidia can be used to protect human belongings and timber from termites. While I. fumosorosea cultures were not repellent to C. formosanus workers, the termites were highly susceptible to infection. Electroantennographic responses of workers showed approximately 47% and 78% lower level of response to conidia of B. bassiana and I. fumosorosea, respectively, as compared to M. anisopliae. The VOC profile of repellent cultures of M. anisopliae mainly consisted of paraffins (60.97%), while the major proportion of the I. fumosorosea profile consisted of branched and cyclic alkanes (84.41%). From the above findings, we conclude that the incorporation of I. fumosorosea may increase the control potential of bait.     

台湾乳白蚁跟踪信息素粗提物活性与应用研究

台湾乳白蚁是我国为害最凶的一种白蚁。对它的防治早就引起国内外白蚁工作者的广泛重视。目前越来越多的做法是将“诱”与“杀”两个步骤合二为一。也有许多学者已将白蚁的跟踪信息素用于白蚁的诱集上作了研究。本文介绍了台湾乳白蚁跟踪信息素粗提物生物活性,包含信息素的提取、跟踪反应、引诱效应、感受距离测定,以及在台湾乳白蚁防治上的实际应用等。     

五种染色剂对台湾乳白蚁的染色效果

对于白蚁种群动态的研究可以利用多种不同颜色的染料作为标记物.为了寻找适用于台湾乳白蚁Coptotermes formosanus的标记物及其使用浓度,本文选取中性红、苏丹红Ⅳ、结晶紫、孔雀石绿以及天青Ⅱ五种染色剂作为标记物,分析测定了它们对台湾乳白蚁的染色效果.结果表明,浓度为0.2%中性红适用于估计种群数量;浓度分别为0.1%、0.2%和0.5%中性红,0.5%苏丹红,0.2%结晶紫,0.5%孔雀石绿以及0.1%天青Ⅱ均适合作为监测群体活动范围的标记物.     

Morphology and ultrastructure of the antennal chemoreceptors and mechanoreceptors of worker Coptotermes formosanus Shiraki

Summary Three types of setae were found on the antenna of workers of C. formosanus. Sensilla basiconica function as chemoreceptors. They are non-socketed, with fixed plate base, thin walled, and perforated. Pore tubules are contained within the cuticular pores of s. basiconica. The pore tubules have direct contact with the dendritic branches within the sensilla. The other sensilla are tactile mechanoreceptors. The longest setae (sensilla trichodea) are thick walled, socketed, mononeuronic, and non-perforated. The shorter mechanoreceptors (sensilla chaetica) have the same characteristics as s. trichodea, exept that they are sometimes dineuronic. The numbers and distribution of the sensilla were established.Supported by the College of Agricultural and Life Sciences, University of Wisconsin, Madison, and in part by the M.U.C.I.A. program, the National Science Foundation Grant No. 36700, and the U.S.D.A., Forest Service Cooperative Project 12-13. The authors also acknowledge the SEM and TEM assistance of S. D. Carlson, M. Garment, and G. Gaard, respectively     

木质素增量取食对台湾乳白蚁消化系统的影响

木质素代谢是白蚁消化木质纤维素的关键环节之一。本文利用木质素增量喂食台湾乳白蚁Coptotermes formosanus Shiraki,通过测定其取食量、体内酚氧化酶含量、纤维素酶活性的变化及后肠微生物群落16s rRNA基因Illumina Hi Seq高通量测序比较分析来研究木质素取食对低等白蚁消化系统的影响。结果表明:木质素取食组内源性(前肠/唾液腺)酚氧化酶含量的显著大于大于对照组,内源及外源性纤维素酶活性均小于对照组,尤其BG酶活性显著小于对照组;1%木质素对乳白蚁取食有一定的抑制作用,其后肠细菌多样性及丰度较对照组有所下降,但无显著的组间群落结构差异;Metastat、LDA(LDA Effect Size)及组间T-检验属水平群落差异分析显示,乳白蚁后肠核心菌群(相对丰度1%)Dysgonomonas属、弧菌属在木质素取食组中相对丰度显著小于对照组,Candidatus Azobacteriodes属相对丰度则显著大于对照组,它们在木质素增量取食引起的细菌群落变化中起关键作用。     

基于RNA干扰的台湾乳白蚁纤维素酶活抑制效果分析

白蚁纤维素酶在白蚁营养代谢中发挥着非常重要的作用,为了探索RNAi在白蚁防治中的应用技术,本文研究了RNAi技术与壳寡糖和曲酸联合对台湾乳白蚁纤维素酶活的抑制作用。在实验室条件下将dsCfEG与壳寡糖和曲酸分别联合浸湿滤纸饲喂白蚁,采用还原糖法测定白蚁的滤纸酶活性(FPA)及内切β-1,4-葡聚糖酶(EG)的比活力,并观测记录供试白蚁的体重与死亡率变化。结果显示:联合处理组测定的FPA和EG比活力均显著低于空白对照组,dsCfEG+曲酸处理组在喂食7 d和5 d后分别对FPA和EG的抑制效果显著高于dsCfEG对照组;喂食7 d后处理组白蚁活力比对照组明显降低,处理组白蚁体重均有不同程度的减少;dsCfEG+壳寡糖联合处理后白蚁的校正死亡率提高,其与曲酸处理的效果之间无显著性差异。研究表明RNAi技术可增强一些酶活抑制物对白蚁纤维素酶活的抑制效果,可为白蚁的安全防控新技术研究提供参考。     

Influence of the diet components on the symbiotic microorganisms community in hindgut of Coptotermes formosanus Shiraki

Artificial diet was developed for rearing of lower termites (workers) Coptotermes formosanus. C. formosanus was fed with either wood powder of Japanese red pine, cellulose, cellobiose, or glucose for 30 days. The effect of carbon sources in the diet on the structure and function of the symbiotic intestinal microbial community and on the physiological activity of C. formosanus was studied. Three symbiont protozoa, Pseudotrichonympha grassi, Holomastigotoides hartmanni, and Spirotrichonympha leidyi, were found in the hindgut of C. formosanus that fed on the diets containing carbon sources with high molecular weight (MW). However, when artificial diets containing carbohydrate with low MW were used, both P. grassi and H. hartmanni disappeared, and only few S. leidyi were alive. This suggested that both P. grassi and H. hartmanni play important roles in the digestion and utilization of carbohydrate with high MW. The denaturing gradient gel electrophoresis analysis of bacterial community in the hindgut of termites showed that the similarity between intestinal bacteria community in termites fed with diets containing high-MW carbon sources and those with low MW was only about 40%. It was apparent that changes in diets resulted to changes in intestinal microbial community, and this in turn affected cellulase activity in C. formosanus.An erratum to this article can be found at     

Distribution and properties of endo-beta-1,4-glucanase from a lower termite, Coptotermes formosanus (Shiraki)

A multi-enzyme distribution of endo-beta-1,4-glucanase activity was found in the digestive system of a worker caste of the lower termite Coptotermes formosanus (Shiraki) by zymogram analysis. Its distribution analysis demonstrated that about 80% of this activity was localized in salivary glands from where only one component (EG-E) was secreted into the digestive tract. EG-E was isolated by a combination of chromatographic and electrophoretic techniques. Its molecular mass, optimal pH and temperature, isoelectric point, and Km were 48 kDa, 6.0, 50 degrees C, 4.2, and 3.8 (mg/ml on carboxymethylcellulose), respectively. EG-E hydrolyzed cellooligosaccharides with a degree of polymerization of 4 and larger, and had low activity on crystalline cellulose. Main reaction products from low molecular weight cellulose were cellobiose and cellotriose. The N-terminal amino acid sequence of EG-E has similarity with fungal endo-beta-1,4-glucanases and cellobiohydrolases of the glycosyl hydrolase family 7 rather than the other insect endo-beta-1,4-glucanases of family 9.     

Chemical composition and antitermitic activity against Coptotermes formosanus Shiraki of Cryptomeria japonica leaf essential oil

Cryptomeria japonica D. Don, called 'sugi' in Japanese, is an abundant and renewable potential resource of valuable natural products that may serve as natural biocides in Taiwan. Hydrodistillation (HD) and steam distillation (SD) were used for extracting the essential oils from C. japonica leaves in this study. The chemical constituents of the two leaf essential oils were identified by GC/MS analysis, and their antitermitic activities were evaluated. The results from the antitermitic tests against Coptotermes formosanus Shiraki showed that the leaf essential oils extracted by HD and SD had excellent antitermitic activities, with LD(50) values of 1.57 and 1.72 mg/g after 7 d of testing, respectively. Comparison of the chemical composition of the two leaf essential oils revealed that oxygenated diterpenes (kaur-16-ene) and oxygenated sesquiterpenes (β-elemol) were the dominant constituents. In addition, 13 constituents isolated from the C. japonica leaf essential oils were tested individually against C. formosanus. Among these constituents, β-elemol and α-terpineol achieved 100% termite mortality at the dosage of 1 mg/g after 7 d of testing. These results demonstrated that both C. japonica leaf essential oils as well as β-elemol and α-terpineol possessed commendable antitermitic activity.     

木腐菌对台湾乳白蚁取食偏好性的影响

本文测定了经红芝、紫芝、茯苓、黄孢原毛平革菌和密褐褶孔菌5种木腐菌腐蚀的马尾松木屑对台湾乳白蚁行为和取食反应的影响.在双重选择性试验中,与未经木腐菌腐蚀的马尾松木屑相比,台湾乳白蚁嗜好聚集和取食木腐菌腐蚀过的马尾松木屑.在多重选择性试验中,结果显示台湾乳白蚁偏好取食经茯苓、红芝或密褐褶孔菌腐蚀过的马尾松木屑.     

Insecticide susceptibility and detoxication enzyme activities among Coptotermes formosanus Shiraki workers sampled from different locations in New Orleans

Coptotermes formosanus Shiraki worker termites were sampled from 20 locations in the City Park area of New Orleans, LA. The termites were subsequently assayed to determine their susceptibility to cypermethrin, chlordane and chlorpyrifos, and detoxication enzyme activity. Cypermethrin was most toxic against Formosan subterranean termite workers, chlorpyrifos exhibited intermediate toxicity and chlordane was least toxic. A comparison of insecticide susceptibility between the most and least tolerant colonies revealed 1.9-, 1.7- and 1.8-fold differences in susceptibility for cypermethrin, chlorpyrifos and chlordane, respectively. As with the bioassay data, although significant differences were noted, a great deal of overlap was observed among the colonies for total cytochrome P450 content (difference of 2.2-fold between high and low value) aldrin epoxidation (3.6-fold) and cytosolic esterase (3.9-fold) activity. No significant differences were observed among the colonies for methoxyresorufin O-demethylase or glutathione S-transferase activity. Conversely, microsomal esterase activity varied greatly; a 38-fold difference was observed between the most (Cf1776) and least (Cf1387) active colonies. However, no significant correlation was observed between insecticide susceptibility and microsomal esterase activity. In fact, no significant correlations were observed between any of the enzyme activities measured and insecticide susceptibility. These results are discussed in the context of insecticide selection and future control effectiveness.     

Endosymbiotic Bacteroidales Bacteria of the Flagellated Protist Pseudotrichonympha grassii in the Gut of the Termite Coptotermes formosanus

A unique lineage of bacteria belonging to the order Bacteroidales was identified as an intracellular endosymbiont of the protist Pseudotrichonympha grassii (Parabasalia, Hypermastigea) in the gut of the termite Coptotermes formosanus. We identified the 16S rRNA, gyrB, elongation factor Tu, and groEL gene sequences in the endosymbiont and detected a very low level of sequence divergence (<0.9% of the nucleotides) in the endosymbiont population within and among protist cells. The Bacteroidales endosymbiont sequence was affiliated with a cluster comprising only sequences from termite gut bacteria and was not closely related to sequences identified for members of the Bacteroidales attached to the cell surfaces of other gut protists. Transmission electron microscopy showed that there were numerous rod-shaped bacteria in the cytoplasm of the host protist, and we detected the endosymbiont by fluorescence in situ hybridization (FISH) with an oligonucleotide probe specific for the 16S rRNA gene identified. Quantification of the abundance of the Bacteroidales endosymbiont by sequence-specific cleavage of rRNA with RNase H and FISH cell counting revealed, surprisingly, that the endosymbiont accounted for 82% of the total bacterial rRNA and 71% of the total bacterial cells in the gut community. The genetically nearly homogeneous endosymbionts of Pseudotrichonympha were very abundant in the gut symbiotic community of the termite.