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.     

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.     

Dual origin of gut proteases in Formosan subterranean termites (Coptotermes formosanus Shiraki) (Isoptera: Rhinotermitidae)

Cellulose digestion in lower termites, mediated by carbohydrases originating from both termite and endosymbionts, is well characterized. In contrast, limited information exists on gut proteases of lower termites, their origins and roles in termite nutrition. The objective of this study was to characterize gut proteases of the Formosan subterranean termite (Coptotermes formosanus Shiraki) (Isoptera: Rhinotermitidae). The protease activity of extracts from gut tissues (fore-, mid- and hindgut) and protozoa isolated from hindguts of termite workers was quantified using hide powder azure as a substrate and further characterized by zymography with gelatin SDS-PAGE. Midgut extracts showed the highest protease activity followed by the protozoa extracts. High level of protease activity was also detected in protozoa culture supernatants after 24 h incubation. Incubation of gut and protozoa extracts with class-specific protease inhibitors revealed that most of the proteases were serine proteases. All proteolytic bands identified after gelatin SDS-PAGE were also inhibited by serine protease inhibitors. Finally, incubation with chromogenic substrates indicated that extracts from fore- and hindgut tissues possessed proteases with almost exclusively trypsin-like activity while both midgut and protozoa extracts possessed proteases with trypsin-like and subtilisin/chymotrypsin-like activities. However, protozoa proteases were distinct from midgut proteases (with different molecular mass). Our results suggest that the Formosan subterranean termite not only produces endogenous proteases in its gut tissues, but also possesses proteases originating from its protozoan symbionts.     

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。     

Directional selection by the subterranean termite Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae) at tunnel intersections

Subterranean termites construct complicated tunnel networks for foraging below ground. Thus, they often encounter tunnel intersections during foraging activity. Directional selection by termites at intersections is likely to affect foraging efficiency because depending on their selection, the path length from food resources to the nest can vary significantly. In order to understand how termites are guided to choose the most economical path without the use of pheromones, we artificially excavated two tunnels of varying widths (W₁ and W₂; 2, 3, or 4 mm) that intersected at a 90° angle in each of nine soil‐filled arenas. We observed the directional selection of termites at intersections in arenas with combinations of W₁ (mm) and W₂ (mm) (W₁, W₂). For (W₁, W₂) = (2, 2) and (4, 4), termites statistically equally chose the three directions left, right, and straight, while for the (3, 3) arena combination, termites preferentially decided to go straight. On the other hand, for (W₁, W₂) = (2, 3) (2, 4), and (3, 4), termites advancing from narrower tunnels into intersections tended to turn right or left, while termites coming from the wider tunnel were more inclined to go straight. On the assumption that a wider tunnel is more frequently used by termites in the field, we can deduce that the wider tunnel may represent the most efficient/shortest path. Thus, this simple selection mechanism can prevent termites from deviating from the most economical path.     

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.     

Agonistic behavior among colonies of the Formosan subterranean termite,Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae), from Florida and Hawaii: Lack of correlation with cuticular hydrocarbon composition

Cuticular hydrocarbon patterns of the Formosan subterranean termite, Coptotermes formosanus Shiraki, were similar among colonies from the same geographical location. Hydrocarbon patterns of Florida colonies were easily distinguished from those of Hawaii colonies by using canonical discriminant analysis. Groups of termites from the same colony did not fight one another when placed in an arena. Intercolonial aggression was not recorded among C. formosanuspopulations from Florida but three colonies from Hawaii fought with the other Hawaiian and three Florida colonies. Of the 12 colonies (six each from Florida and Hawaii) tested, 3 Florida colonies did not direct or receive aggression from any other colony. Cuticular hydrocarbon patterns were not correlated with agonistic behavior.     

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.     

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.     

Distribution of Formosan subterranean termite (Isoptera: Rhinotermitidae) in Mississippi

An extensive monitoring and survey program in Mississippi was conducted from 2000 to 2004 to investigate the distribution of the Formosan subterranean termite, Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae). Seventy-two towns from 22 counties in southern Mississippi were monitored with a total of 3914 traps that catch alates during the swarming season. In addition, 259 licensed pest management professionals in Mississippi were surveyed to determine the locations of termite infestations treated. The alates of C. formosanus were recovered in 12 counties with light traps, and termite infestations were documented in an additional 13 from data collected in the termite survey. Infestations of C. formosanus have been documented in urban, urban cluster, rural, and forested areas of Mississippi. However, the distribution in mean total capture of alates for 4 yr differed significantly among the four ecological areas with the highest percentage in forested areas (31%) and the lowest percentage in urban cluster areas (17%). Most of the infestations of C. formosanus were geographically distributed along the coastal areas of southern Mississippi from Gulfport to Pascagoula. The greatest total number of alates captured in light traps was documented in Pearl River County. Mass swarming of C. formosanus occurred primarily in May or June, depending on weather conditions. The number of documented counties with the evidence of large and widely dispersed swarms of C. formosanus in different ecological areas, and the increase in total annual alate captures from 2000 to 2003, suggest that this invasive termite species is now firmly established in Mississippi.     

Effect of imidacloprid tree treatments on the occurrence of Formosan subterranean termites,Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae), in independent monitors

Periodic sampling of 87 independent monitors, initially active with the Formosan subterranean termite, Coptotermes formosanus Shiraki, was conducted. Monitors, located in eight sectors adjacent to seven buildings, were various distances (1-46 m) from 57 trees treated with 0.1% imidacloprid foam. Termites collected from six of the eight sectors showed latent mortality attributed to imidacloprid intoxication at all monitor-tree distances. Approximately 6 mo after treatment, termite populations had recovered in these sectors. Another sector showed termite population suppression for approximately 15 mo, followed by recovery. Imidacloprid tree treatments did not control C. formosanus populations in independent monitors adjacent to the treatments.     

Formosan subterranean termite swarming behavior and alate sex-ratio (Isoptera: Rhinotermitidae)

Summary The Formosan subterranean termite (Coptotermes formosanus Shiraki) was first sighted in the cities of New Orleans and Lake Charles, Louisiana, in 1966. Its distribution in the historic French Quarter of New Orleans 23 years later (1989) and in 1991 and 1992 is reported here using counts of alates from light-traps. Light-trappings revealed a Quarter-wide distribution of the termite.C. formosanus shows an extended pause in flight behavior in the middle of the two-month flight season that is predictable and independent of weather. A colony-level mechanism, namely, developmental inhibition of nymphs by alates, may regulate this intermission in flight. The sex-ratio of light-trapped alates varies over time, but is generally female-biased, especially at the height of the flight season.     

Feeding site selection by workers of the Formosan subterranean termite Coptotermes formosanus (Isoptera: Rhinotermitidae) - a re-analysis of field data from a mark-recapture study

During the early stages of the development of termite baits, dyed paper was placed in specified feeding stations to ascertain whether a slow-acting toxicant could be placed in a few bait stations to be delivered to the entire colony members of the Formosan subterranean termite, Coptotermes formosanus Shiraki. Feeding frequency data, as measured by the dye concentration in individual termites, suggested the absence of feeding site fidelity. However, these results were often misinterpreted as random movement of termites that were marked and released for population estimate studies, or the random search of food in soil by subterranean termites. A computer simulation program was constructed to re-examine this feeding frequency data, and confirmed the earlier conclusion that the lack of feeding site fidelity was the most likely explanation for the data.     

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.     

Resistance of insecticide-treated foam board insulation against the eastern subterranean termite and the Formosan subterranean termite (Isoptera: Rhinotermitidae)

Three foam board types, one untreated control, one containing 2,000 ppm disodium octaborate tetrahydrate (DOT), and one containing 1,000 ppm deltamethrin, were exposed to field populations of the eastern subterranean termite, Reticulitermes flavipes (Kollar), and the Formosan subterranean termite, Coptotermes formosanus Shiraki. There was no significant difference in termite damage between foam boards treated with 2,000 ppm DOT and the untreated control. Form boards containing 1,000 ppm deltamethrin were not damaged by R. flavipes, whereas only minor damage occurred after exposure to C. formosanus.     

乳白蚁属Coptotermes(Isoptera: Rhinotermitidae)检疫分子鉴定研究进展

白蚁是一类受到世界广泛关注的重要社会性昆虫,对人类生活、经济以及生态环境等有很大的影响,特别是乳白蚁属Coptotermes众多种类危害尤为严重。乳白蚁常随木质包装或原木远距离传播异地建群,其为害隐蔽、潜伏期长,一旦爆发则为害严重且难防治,因其种类多、形态趋同,同一巢群中有龄期不一的虫态和多种生物型,可用分类特征少,造成形态分类困难、人为分类现象普遍。近年来分子生物学技术的日益发展,使得白蚁的分类鉴定更加快速、灵敏和可靠,系统发育分析研究更为深入全面,遗传进化方面取得大量研究成果。本文对基于生物信息学的乳白蚁属检疫分类鉴定和系统发育研究方法进行了介绍和评述,并对DNA技术在乳白蚁属分类和进化研究中的应用进行了讨论。     

Evaluation of hexaflumuron for controlling the subterranean termite Coptotermes curvignathus (Isoptera: Rhinotermitidae) in Malaysia

Cellulosic bait matrices containing 0.5% hexaflumuron were tested against field colonies of the subterranean termite Coptotermes curvignathus Holmgren in Malaysia. Foraging activities of the termites were first monitored for several months by using survey stakes and wood bundles placed in underground monitoring traps. Infested stakes were replaced with bait devices. Termite workers to act as recruits were collected from infested stakes and placed in the bait devices. Subsequent activities of the termites were monitored by examining and weighing the wood in the monitoring traps. Data show that the four colonies had populations of 166,288-709,052 foragers and mean wood consumption rates of 305.9-508.2 g/mo per trap. These colonies ceased their activities at all monitoring devices 25-44 d after baiting had commenced. Colonies consumed approximately 27-79 g of bait matrix or 137.5-395 mg of hexaflumuron. Thus, C. curvignathus colonies could be monitored, characterized, baited, and foraging eliminated by using a bait matrix containing hexaflumuron.     

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.