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。     

Molting in workers of the Formosan subterranean termite Coptotermes formosanus

The Formosan subterranean termite, Coptotermes formosanus, with its huge colonies, is a major urban pest in several southern states and Hawaii as well as in South Asia. Because of their cryptic nature (underground habitat) and very long life cycle, not much is known about molting in termite workers. In C. formosanus, the workers stop foraging and lose their gut fauna, respectively, approximately 10 and 5 days prior to ecdysis. In any given colony an average of 1.01% (range 0.6-1.8) of the workers were found to molt each day under laboratory conditions. Workers destined to molt become sluggish and their head capsules develop a mottled texture one day prior to ecdysis. Ecdysis was generally accomplished with the assistance of other workers, which also fed on the exuviae. Immediately after molting worker mandibles were light pink in color and became fully melanized approximately two days later. Gut fauna were acquired on the fourth day after molting. Flagellates were transferred as small encysted cells from other workers through proctodeal feeding. Juvenile hormone III titer ranged between 30-41 pg/mg bodyweight in all stages except in workers sampled 6 days prior to ecdysis. In these workers the titer was 80.5 pg/mg. The high juvenile hormones (JH) titer may also be involved in causing defaunation. Ecdysteroid titer increased from 2.1 pg/mg in non-molting workers to 359.5 and 332.4 pg/mg one and two days following defaunation, respectively. There was a second smaller peak two days prior to ecdysis.     

Colony and population genetic structure of the Formosan subterranean termite,Coptotermes formosanus,in Japan

Subterranean termites have unusual plasticity in their breeding systems. As a result of their cryptic foraging and nesting habits, detailed information on the numbers and types of reproductive individuals in colonies has been difficult to obtain. In this study, we used microsatellite markers to infer the major features of the breeding system of the Formosan subterranean termite, Coptotermes formosanus, in southern Japan, where it is believed to have been introduced from China. A total of 30 colonies was sampled from two islands (Kyushu and Fukue) located 100 km apart. Twenty workers from each colony were genotyped at six microsatellite loci. Analysis of worker genotypes within colonies indicated that 27 colonies (90%) were simple (Mendelian) families. The remaining three colonies, all from Kyushu, were consistent with being extended families having begun as simple families but being currently headed by multiple neotenic (secondary) reproductives descended from the original king and queen. Workers from simple families in both populations were significantly inbred (FIT = 0.10 for Kyushu and 0.46 for Fukue) and highly related to their nestmates (coefficient of relatedness, r = 0.59 for Kyushu and 0.77 for Fukue), suggesting that many simple-family colonies were headed by closely related reproductives, especially in the Fukue population. This conclusion is supported by the high coefficient of relatedness between nestmate reproductives in simple-family colonies (r = 0.23 for Kyushu and 0.61 for Fukue) based on genotypes inferred from their worker offspring. There was moderate genetic differentiation (FST = 0.12) between the two populations, suggesting rather restricted gene flow between them. There was no significant isolation by distance among colonies, as might be expected given the limited dispersal of reproductives, presumably because of the frequent movement of colonies by humans. Finally, there was no evidence of a recent bottleneck, a finding possibly consistent with the more than 300-year history of this species in Japan.     

Effect of natural products on gut microbes in Formosan subterranean termite,Coptotermes formosanus

The ability of three natural products (neem extract, capsaicin, and gleditschia) to reduce the number of Formosan subterranean termite (FST) hindgut microbes was investigated. FSTs were placed in Petri dishes containing a food source soaked in one of these extracts/compounds. The numbers of three flagellated protozoan species that inhabit the FST hindgut (Pseudotrichonympha grassii, Spirotrichonympha leidyi and Holomastigotoides hartmanni) and spirochaetes were counted over a defined period and analysed for changes in abundance. The results indicated that the neem extract was capable of reducing the population of P. grassii and spirochaetes. Exposure to this extract resulted in significant FST mortality. However, gleditschia extract and capsaicin did not reduce the FST gut microbial population at the concentrations used in this study.     

Regulation of juvenile hormone titers by soldiers in the Formosan subterranean termite, Coptotermes formosanus

In field collections of the Formosan subterranean termite Coptotermes formosanus, soldiers averaged less than 10%. The proportion of soldiers increased to about 25% or higher when termites were kept in the laboratory, as did the juvenile hormone III (JH III) titers for both workers and soldiers. In laboratory experiments with a proportion of soldiers 25% or higher, very few new pre-soldiers were formed and the JH titer in existing soldiers remained constant. On the contrary, workers from groups containing less than 25% soldiers formed more pre-soldiers. In such cases, both workers and soldiers showed higher JH titers. Newly formed soldiers also had higher JH titers than older soldiers. It is speculated that populations containing higher soldier proportions inhibit further soldier differentiation, eventually holding the JH titers under the threshold or suppressing the activity of corpora allata resulting in lower JH titers in workers.     

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.     

Ecdysone agonist halofenozide affects corpora allata and reproductive physiology of the Formosan subterranean termite,Coptotermes formosanus

Following a short swarming flight, winged adults of the Formosan subterranean termite, Coptotermes formosanus lose their wings and form tandem pairs. These dealates or primary reproductives then form incipient colonies. Topical application of 5 microg of the non-steroidal ecdysone agonist RH-0345 (halofenozide) in 0.1 microl DMSO to the primary reproductives during the 2000 season resulted in significant reduction in the number of eggs laid. There was however complete recovery of the treated females. Apparently the non-treated partner removed the treatment chemical while grooming indicating oral activity. In 2001 both topical application as well as feeding methods were tried. Significant effects were observed only in the topical treatment group, perhaps because of inconsistency in feeding. In this group, total progeny, the number of ovarioles in ovaries and the size of the female's corpora allata (CA) were all significantly reduced. Ultrastructure of the CA of treated females showed extensive vacuolation near the surface of the gland. The experiment was repeated in 2002 using both topical application and an improved oral feeding method. Whereas there was apparent recovery in the topically treated group after 90 days, the oral treatment was more persistent in its effect perhaps due to a higher amount of halofenozide consumed during feeding.     

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.     

Presence of nitrogen fixing Klebsiella pneumoniae in the gut of the Formosan subterranean termite (Coptotermes formosanus)

A gram-negative facultative anaerobic enteric bacterium, Klebsiella pneumoniae was isolated from the hindgut of the Formosan subterranean termite (FST). It was characterized using, fatty acid methyl ester (FAME) analysis, BIOLOG assay, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and biochemical studies. The role of this isolate seems to be nitrogen fixation because the termite's diet is nitrogen deficient and the isolate produced significant amounts of ammonia when it was grown on nitrogen deficient medium under anaerobic condition with nitrogen gas in the headspace.     

Factors affecting post-flight behavior in primary reproductives of the Formosan subterranean termite, Coptotermes formosanus (Isoptera: Rhinotermitidae)

After swarming, reproductive dealates of the Formosan subterranean termite, Coptotermes formosanus, run together in tandem. The tandem running is an age-related behavioral activity in C. formosanus. This behavior was not evoked in pre-flight alates less than 6-d-old that were artificially dealated. Female age was more important than male age for evoking tandem behavior. Females and males, older than 35 days, did not exhibit this behavior. Mating status was not important for female and male dealates to form the tandem pairs. The titers of the major tergal gland component, trilinolein, did not decline significantly and remained high, not only in virgin females, but also in mated females for a period of time after swarming. On the other hand, increasing amounts of the female-specific compound trilinolein were detected in male dealates 7, 14, and 42 days after pairing. This suggests that trilinolein in the females might be transferred to the males as a nuptial gift in C. formosanus. In addition, females have structurally different lateral setae that may constitute a morphological factor involved in the tandem behavior in this species. Covering the setae with dimethyl sulfoxide prevented the tandem behavior.     

Novel free ceramides as components of the soldier defense gland of the Formosan subterranean termite (Coptotermes formosanus)

Of the lipid extracts of the defense secretion from the Formosan subterranean termite, Coptotermes formosanus Shiraki, on high-performance thin-layer chromatography analysis, no glycolipids or phospholipids were detected, but free fatty acids and three novel ceramides were found (termed TL-1, TL-2, and TL-3). Free fatty acids were confirmed to be lignoceric acid (C24:0) and hexacosanoic acid (C26:0), as described previously [Chen, J., G. Henderson, and R. A. Laine. 1999. Lignoceric acid and hexacosanoic acid: major components of soldier frontal gland secretions of the Formosan subterranean termite (Coptotermes formosanus). J. Chem. Ecol. 25: 817-824]. TL-1, TL-2, and TL-3 were characterized as ceramides differing in hydrophobicity based on results of matrix-assisted laser desorption-ionization time-of-flight mass spectrometry analysis, mild alkaline treatment, GC-MS analysis of fatty acid methylesters, and GC-MS analysis of sphingoid long-chain bases (LCBs) as trimethylsilyl derivatives. Fatty acids in TL-1 and TL-2 were C18:0, C20:0, and C22:0, and those in TL-3 were 2-hydroxy C18:0, C20:0, and C22:0. The most predominant LCB in TL-2 was a novel trihydroxy C(14)-sphingosine, 1,3,9-trihydroxy-2-amino-6-tetradecene. TL-3 contained C(18)-sphinganine and two kinds of novel sphingadienines, 1,3-dihydroxy-2-amino-7,10-hexadecadiene and 1,3-dihydroxy-2-amino-11,14-eicosadiene. Although examination of the biological activities of these novel ceramides was beyond the scope of these studies, because of the minuscule quantities available from termite secretions, it will be interesting in the future to synthesize these molecules for biological testing.     

Aquaporin water channel in the salivary glands of the Formosan subterranean termite Coptotermes formosanus is predominant in workers and absent in soldiers

Termite society is unique because the worker caste fetches and carries free water, utilizing it as a solvent for nest construction and gallery building and to maintain wetness for their nestmates. Such water management in a social organization relies largely upon the function of the workers in the colony, as well as on the individuals controlling the location and movement of water inside their bodies. The movement of water via aquaporins (AQPs; water channels) into and out of cells is a key feature of the numerous physiological functions related to whole‐insect water balance. In the present study, the homologue of the water‐specific Drosophila AQP [Drosophila integral protein (DRIP)] is characterized in workers of the Formosan subterranean termite Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae), a highly active wood decomposer. Immunoblot analysis of DRIP‐type AQP using an antibody from the silkworm Bombyx mori reveals that the Coptotermes DRIP (formerly cloned as ‘CfAQP1’) with a molecular mass of approximately 25.7 kDa is expressed predominantly in the salivary (labial) gland of the workers. The Coptotermes DRIP is present at the basal plasma membrane of the parietal cells, as demonstrated by immunocytochemistry. By contrast, there is no DRIP detected within the salivary glands of soldier termites, and neither caste expresses DRIP in their labial gland reservoir (water sac), a tissue that is suggested to have a function as a water sink. The AQP present in the salivary glands is of physiological importance with respect to salivation, aiding in the secretion of cellulolytic enzymes for wood ingestion by the workers of the subterranean termite.     

Response variability of juvenile hormone and juvenile hormone analogs in workers of the Formosan subterranean termite (Coptotermes formosanus Shiraki)

Juvenile hormone (JH) or juvenile hormone analog (JHA) can induce soldier formation in termites. However, different studies have yielded inconsistent results on the effects of JHA on soldier production in Coptotermes formosanus Shiraki. Using filter paper as the testing substrate, the effects of JH III, pyriproxyfen and methoprene on the intact filter paper left, worker mortality and presoldier formation were tested on six colonies. Our results showed that pyriproxyfen and methoprene were more repellent than JH III. No significant difference in toxicity was observed among methoprene, pyriproxyfen and JH III. JH III and pyriproxyfen did not cause workers to differentiate into presoldiers, but methoprene can induce formation of presoldiers. Colony response variability to methoprene was observed. The confirmation of the effects of JH/JHA on C. formosanus establishes the foundation for molecular studies of soldier differentiation in this species.     

Effects of antibiotics on hydrogen production and gut symbionts in the Formosan subterranean termite Coptotermes formosanus (Isoptera: Rhinotermitidae)

Abstract Symbiotic microorganisms that inhabit the gut of Coptotermes formosanus enable this termite to degrade lignocelluloses and further produce hydrogen as an important intermediate to be recycled in its hindgut or as a byproduct to be emitted to the atmosphere. Both symbiotic protists and prokaryotes in the guts of termites demonstrated some different roles with respect to hydrogen production. In this study, the effects of two antibiotics, ampicillin and tetracycline, on hydrogen emission and the gut symbionts of C. formosanus were investigated. Hydrogen emission from termite guts was significantly enhanced when termites fed on wood diets treated with either ampicillin or tetracycline. The greatest H₂ emission rates, 2 519 ± 74 and 2 080 ± 377 nmol/h/g body weight, were recorded with the treatments of ampicillin and tetracycline, respectively, which showed 6–7 times more H₂ production than that of controls. Antibiotic‐treated diets negatively affected the prokaryotic communities and reduced their abundances, particularly on those ectosymbionts inhabiting the gut walls or in the gut fluid of C. formosanus, such as spirochetes. However, no significant reductions in the counts of gut cellulolytic protists, Pseudotrichonympha grassii and Holomastigotoids hartmanni, were recorded; and with a further observation by confocal laser scanning microscopy, the endosymbionts inhabiting P. grassii generally survived the antibiotic treatments. These results suggest that some prokaryotes may serve as the main hydrogen consumers, while P. grassii, together with its endosymbionts, may function as the main contributors for hydrogen production in the hindgut of C. formosanus.     

Isolation and assessment of gut bacteria from the Formosan subterranean termite,Coptotermes formosanus (Isoptera: Rhinotermitidae), for paratransgenesis research and application

Paratransgenesis targeting the gut protozoa is being developed as an alternative method for the control of the Formosan subterranean termite (FST). This method involves killing the cellulose‐digesting gut protozoa using a previously developed antiprotozoal peptide consisting of a target specific ligand coupled to an antimicrobial peptide (Hecate). In the future, we intend to genetically engineer termite gut bacteria as “Trojan Horses” to express and spread ligand‐Hecate in the termite colony. The aim of this study was to assess the usefulness of bacteria strains isolated from the gut of FST as “Trojan Horses.” We isolated 135 bacteria from the guts of workers from 3 termite colonies. Sequencing of the 16S rRNA gene identified 20 species. We tested 5 bacteria species that were previously described as part of the termite gut community for their tolerance against Hecate and ligand‐Hecate. Results showed that the minimum concentration required to inhibit bacteria growth was always higher than the concentration required to kill the gut protozoa. Out of the 5 bacteria tested, we engineered Trabulsiella odontotermitis, a termite specific bacterium, to express green fluorescent protein as a proof of concept that the bacteria can be engineered to express foreign proteins. Engineered T. odontotermitis was fed to FST to study if the bacteria are ingested. This feeding experiment confirmed that engineered T. odontotermitis is ingested by termites and can survive in the gut for at least 48 h. Here we report that T. odontotermitis is a suitable delivery and expression system for paratransgenesis in a termite species.     

Estimating population density of the Formosan subterranean termite, Coptotermes formosanus(Isoptera: Rhinotermitidae) using the effective sampling area of in-ground monitoring stations

The effective sampling area of a monitoring station, alpha, was calculated for several Coptotermes formosanus Shiraki colonies in Broward County, Florida, USA. A simple mark-recapture protocol provided data on termite station catch within a foraging range of a colony. Average recapture probability was 0.005 close to the release point (< 5 m) and declined to 0.0008 at a distance of 51 to 60 m. The relation between the log % termites recaptured was fitted with log distance, to determine P(x), the average proportion of captured termites that started at distance x from the release point. The effective sampling area was estimated by using P(x) and the equation, alpha 2 pi integral [ x P(x)] dx. Integrating this equation, an average estimate alpha that ranged from 0.607 to 14.5 m2 was obtained. Factors influencing the variation of alpha among the colonies are discussed. The effective sampling area estimated should be taken as a reliable estimator that translates subterranean termite catches into termite population density.     

Fire ant predation on native and introduced subterranean termites in the laboratory: effect of high soldier number in Coptotermes formosanus

Abstract.

• 1 Native Reticulitermes spp. Holmgren and the introduced Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae) were exposed to predation in the laboratory by Solenopsis invicta Buren (Hymenoptera: Formicidae), a known predator of Reticulitermes.
• 2 In one experiment, both taxa contained the 2.4% soldiers commonly found in Reticulitermes. In a second experiment, Reticulitermes contained 2.4% and C.formosanus a more normal 18.3% soldiers.
• 3 When soldier proportions were equal, C.formosanus soldiers suffered less of a decrease in survivorship due to predation compared with Reticulitermes soldiers. Little difference was found between taxa in the effect of predation on termite workers or in the effect of termites on predator survivorship.
• 4 When soldier proportions were unequal, both C.formosanus castes suffered less from predation than those of Reticulitermes. Again, little difference was found in the effect of termites on ants.
• 5 C.formosanus showed less movement into new containers when soldier number was abnormally low, compared with both taxa with normal caste proportions.

     

Genetic diversity and genotypic differentiation between the sexes in swarm aggregations decrease inbreeding in the Formosan subterranean termite

The life of a colony of subterranean termites, such as Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae), has natural inbreeding and outbreeding cycles. Reproductives of mature colonies can be replaced by their offspring, which increases the degree of inbreeding in each generation. High degrees of inbreeding may lead to inbreeding depression. In this study we focused on mechanisms for inbreeding avoidance during swarming that do not require kin recognition. We investigated genetic differentiation between swarm aggregations (isolation by distance), genetic diversity within swarm aggregations (multiple colony origin) and genetic differentiation between sexes. Alates were collected from five swarm aggregations in New Orleans, La. The genetic make-up of each swarm aggregation was then described by microsatellite genotyping. Alates from the different swarm aggregations were genetically differentiated; however, no isolation by distance up to at least 1000 m was detected. The dispersal distance of alates was sufficient to guarantee mixing of an average of 13 colonies within swarm aggregations. On average, eleven percent of all possible pairs of alates in each swarm aggregation were putative full siblings. Genotypic frequencies differed significantly between males and females. This could not be explained by sex-biased dispersal. We hypothesize sex-biased investment at the colony level to account for this difference. Genetic differentiation between the sexes and dispersal distances sufficient to promote high genetic diversity within swarm aggregations each facilitate inbreeding avoidance. These observations are consistent with the results of previous studies demonstrating that the majority of simple family colonies in Louisiana populations are headed by unrelated and outbred pairs of reproductives. Received 11 August 2005; revised 5 December 2005; accepted 20 December 2005.     

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.