白蚁的分子生物学研究进展

白蚁是危险性社会昆虫,建立安全有效的白蚁防治方法有赖多学科的参与,分子生物学已经成为白蚁研究的重要工具。目前,DNA序列分析方法已应用于白蚁鉴定和分类,其中线粒体基因是最通用的分子标记;基因工程技术成功构建了可用于白蚁防治的白蚁肠道工程菌;Hexamerin、COX Ⅲ、纤维素酶等白蚁功能基因以及白蚁品级分化相关的若干蛋白相继得到了分离和鉴定。文章从白蚁分类、防治、功能基因、品级分化4个方面综述白蚁分子生物学的研究进展,为白蚁的防治提供新的方法和思路。     

几种白蚁诱饵防霉剂的防霉效果比较

比较了8种供试防霉剂对黑翅土白蚁Odontotermes formosanus(Shiraki)喜食饵料小米粉的防霉效果,结果表明2‰山梨酸钾和0.75‰对小米粉的防霉效果较好,两者都能使野外试验坑中的小米粉样品8d后不发霉。室内试验结果表明,2‰山梨酸钾不影响黑翅土白蚁对小米粉的取食量;而0.75‰百菌清显著降低了黑翅土白蚁对小米粉的取食量,对黑翅土白蚁有明显的驱避作用。野外试验进一步表明,投饵8d后,小米粉诱饵、小米粉+2‰山梨酸钾诱饵、小米粉+0.75‰百菌清诱饵的发霉率分别为100,20和30%,而三者的被食率分别为27.67,53.70和19.15%。由此可见,2‰山梨酸钾最适合作为白蚁诱饵的防霉剂。     

Mutualistic acacia ants exhibit reduced aggression and more frequent off‐tree movements near termite mounds

In many ant–plant mutualisms, ants establish colonies in hollow thorns, leaf pouches, or other specialized structures on their host plants, which they then defend from herbivores. Resource heterogeneity could affect the maintenance of these mutualisms if it leads to one or both partners altering their investment in the interaction. Such a phenomenon may be especially pertinent to the Acacia–ant mutualism found in East African savannas, where termite mounds have a profound effect on the spatial structuring of resources used by both plants and ants. Here, we examined whether the proximity to termite mounds of Acacia drepanolobium trees is associated with variation in the behavior of one of their ant associates, Crematogaster nigriceps. We found that ant colonies near termite mounds had decreased aggressive responses to simulated herbivory as well as increased off‐tree movement. We hypothesize that these changes are the result of resident ant colonies near termite mounds shifting investment from defense of their host plant to foraging for nearby resources.     

Physical contact between soldier and worker is essential in soldier self-regulation of Coptotermes formosanus (Isoptera, Rhinotermitidae)

In a termite society, the soldier proportion is regulated at a species-specific level with a seasonal fluctuation. A feedback mechanism in soldier proportion regulation is well recognized, while the proximate means by which the presence of soldiers inhibits the new soldier formation from workers remains mostly elusive. In the present study, some possible means for this inhibition were tested with the Formosan subterranean termite, Coptotermes formosanus Shiraki. The results showed that neither soldier-originated volatiles nor non-volatile chemicals without physical contact were responsible for the inhibition of new soldier formation. The essentiality of physical contact between workers and soldiers in soldier regulation was established. However, by physical contacts, as the soldier-replacement experiment showed, workers could not individually recognize or “count” soldiers to maintain a set soldier proportion. The possible feedback mechanisms for soldier regulation are discussed.     

Production and characterization of a recombinant beta‐1,4‐endoglucanase (glycohydrolase family 9) from the termite Reticulitermes flavipes

Cell‐1 is a host‐derived beta‐1,4‐endoglucanase (Glycohydrolase Family 9 [GHF9]) from the lower termite Reticulitermes flavipes. Here, we report on the heterologous production of Cell‐1 using eukaryotic (Baculovirus Expression Vector System; BEVS) and prokaryotic (E. coli) expression systems. The BEVS‐expressed enzyme was more readily obtained in solubilized form and more active than the E. coli–expressed enzyme. K_m and V_max values for BEVS‐expressed Cell‐1 against the model substrate CMC were 0.993% w/v and 1.056 µmol/min/mg. Additional characterization studies on the BEVS‐expressed enzyme revealed that it possesses activity comparable to the native enzyme, is optimally active around pH 6.5–7.5 and 50–60°C, is inhibited by EDTA, and displays enhanced activity up to 70°C in the presence of CaCl₂. These findings provide a foundation on which to begin subsequent investigations of collaborative digestion by coevolved host and symbiont digestive enzymes from R. flavipes that include GHF7 exoglucanases, GHF1 beta glucosidases, phenol‐oxidizing laccases, and others. © 2010 Wiley Periodicals, Inc.     

Structure and function of defensive glands in soldiers of Glossotermes oculatus (Isoptera: Serritermitidae)

The soldier caste represents the most conspicuous realization of termite eusociality, characterized by an extreme anatomical, behavioural, and physiological specialization. Numerous strategies have evolved in soldiers, including extreme adaptations such as self‐sacrifice by autothysis. In the present study, we investigated the structure and function of defensive glands in Glossotermes oculatus soldiers aiming to understand their use in combat. Three glands are involved in defence: labral, frontal, and labial glands. Mandibles are used to bite the enemy, whereas the secretions of labral and labial glands are discharged into the wound. A striking characteristic of G. oculatus is the lack of the frontal pore; the secretion of the frontal gland is discharged by a rupture of the body wall. We hypothesized that this self‐sacrifice is an efficient way of blocking a gallery under attack. A similar development of the frontal gland occurs in Serritermes serrifer, which supports the close relationship between the two genera inferred from morphological and genetic analyses. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99 , 839–848.     

Role of termites in the restoration of soils and plant richness on bowé in West Africa

Bowé (hardened ferricrete soils formed by erosion, drought or deforestation) are often associated with termite mounds, but little is known about these mounds and their role in the restoration of soils and plant biodiversity on bowé. This study examined termite mounds on bowé and their effects on soil depth and plant richness. Sixty-four sampling plots were laid out randomly on bowé sites with mounds and on adjacent bowé sites without mounds. The height and circumference of each mound were measured. Species inventories were made and soil depth measured in each plot. Linear mixed effects and generalised mixed effects models with Poisson error distribution were used to assess the variation in soil depth and plant species richness in mound and nonmound microsites. Two types of mounds (small vs. large) associated with different termite species were observed on bowé, with the small mounds being most common. Plots with either large or small mounds had deeper soils and higher plant richness than the adjacent plots without mounds. Conservation of termite mounds is important for restoring soils and plant richness on bowé, and termite mounds should be taken into consideration in biodiversity and soil management strategies for bowé.