Gut-specific actinobacterial community structure and diversity associated with the wood-feeding termite species, Nasutitermes corniger (Motschulsky) described by nested PCR-DGGE analysis

This comprehensive survey studied the actinobacterial community structure and putative representative members associated with the gut of the wood-feeding termite, Nasutitermes corniger (Motschulsky), using nested PCR-DGGE and 16S rDNA sequences analyses. The closest relatives of the actinobacteria inhabiting the gut of Nasutitermes corniger were in five families, regardless of the geographical origin of the termite colony: Propionibacteriaceae, Streptomycetaceae, Cellulomonodaceae, Corynebacteriaceae and Rubrobacteraceae. Feeding termites on beech wood did not result in substantial changes in the actinobacterial community structure as revealed by DGGE banding patterns. Most of the 16S rDNA sequences obtained after excision and sequencing of DGGE bands clustered with those previously retrieved in termite guts. These results confirm the presence of gut-specific actinobacteria. Except for the 16S rDNA sequences affiliated to Streptomycetaceae and Cellulomonodaceae, no sequence had more than 97% similarity with the closest isolated strains, indicating the presence of microorganisms that have not yet been cultivated. These results suggest that members of the Actinomycetales order account for the largest proportion of the Actinobacteria phylum inhabiting the gut of the termite N. corniger.     

Ergatoid reproductives in Nasutitermes corniger (Motschulsky) (Isoptera: Termitidae)

Several hundred ergatoid reproductives were found in a queenless colony of Nasutitermes corniger (Isoptera: Termitidae) in the Republic of Panama. The ergatoids are derived in 2 molts from both small (male) and large (female) workers. The transition series of molting individuals found in this colony demonstrated that: (1) ergatoids are derived from more than one worker instar; (2) sexual transformation is initiated in a worker before molting into an ergatoid; (3) the transition is prolonged enough so that all stages are found concurrently in one colony; and (4) ergatoids are probably fed by normal workers beginning in the instar prior to differentiation. Morphological and histological analyses revealed that ergatoid size, pilosity, fat body, and endocrine glands are enlarged compared with sterile workers. Ocelli and reduced eyes appear in ergatoids, but they are probably not functional. Development of genital organs is conspicuous but the ovaries never reach a complete oogenesis and, in some cases, degenerate. Ergatoid development in the phylogenetically advanced termite genus Nasutitermes appears to be quite rare, but their maturation as replacement reproductives seems a real possibility.     

Nitrogen fixation by intact colonies of the termite Nasutitermes corniger

Summary Biosteres longicaudatus Ashmead (Hymenoptera: Bracon dae) is a solitary endoparasite of Anastrepha suspensa larvae (Diptera: Tephritidae), which live in fruit tissue. Larvae make andible noises within macerated fruit or larval medium in which they are reared. Parasite females readily located normal, mobile larvae and spent a mean of 16.5±4.7 min/visit to parasitize these hosts. In contrast, females were unable to locate etherized or dead hosts and abandoned them after only 1.9±0.9 and 2.3±0.8 min, respectively. Females of all ages, with and without oviposition experience, exhibited non-random search and ovipositor probe behaviors in response to artifically created vibration. This response was influenced primarily by the number of mature eggs in the ovaries. These findings suggest that 1) an accumulation of mature eggs in the ovaries increase the appetitive drive of females to find and oviposit in hosts and 2) host sound/vibration produced either by movement of hosts through the medium and/or by the rasping mouth hooks during feeding. is used by parasites as a releaser for host finding behavior as well as a cue to the location of the host within the substrate.     

Microsatellite markers for the polygamous termite Nasutitermes corniger (Isoptera: Termitidae)

We developed eight highly variable microsatellite markers for the termite Nasutitermes corniger. Allele number per locus ranged from nine to 34, and expected heterozygosity from 0.45 to 0.94, in samples from seven sites in the former canal zone of Panama. The utility of these markers was assessed for five congeners varying in phylogenetic distance to N. corniger. The markers will be useful for fine‐scale examination of population and colony genetic structure in N. corniger and other closely related species.     

Queen fecundity and reproductive skew in the termite Nasutitermes corniger

A major goal of studies on social animals is to understand variation in reproduction within and between groups. We used hierarchical regressions to analyze oviposition rates in the neotropical termite Nasutitermes corniger, a species with both monogynous and polygynous colonies. Queen fecundity was a non-linear, saturating function of queen weight. Greater queen weight was associated with larger nest size and with lower numbers of queens per nest, suggesting competition among queens for resources acquired by the colony. The collective egglaying rate of pairs of queens exceeded that of single queens, but further increases in queen number did not raise total fecundity. Skew in oviposition rates, as quantified by Morisita’s index I _δ, averaged 1.2, indicating inequalities in reproductive rates that are only moderately greater than expected for random apportionment. The leveling off of oviposition with increasing queen weight suggests that it is costly for individual females to produce eggs at high rates, which could favor tolerance of reproduction by other females, reducing reproductive skew. We hypothesize that the incentive to tolerate reproduction by other females is especially pronounced for heavier queens, because these queens are close to the limit of their own reproductive capacity. Consistent with this hypothesis, skew in oviposition rates was inversely related to the mean weight of queens within a nest. Received 8 March 2007; revised 17 September 2007; accepted 3 October 2007.     

Antibiotic resistance modulation by natural products obtained from Nasutitermes corniger (Motschulsky, 1855) and its nest

Insects and their products are included in the traditional pharmacopoeia of various ethnic groups worldwide. In the Brazilian semiarid region can be highlighted the use of the termite Nasutitermes corniger for the treatment of various diseases. This study evaluated the ethanol extract of N. corniger and its nest as an antimicrobial agent and as a modulator of bacterial resistance against multidrug strains. The Minimum Inhibitory Concentration (MIC) of the extract on Staphylococcus aureus and Escherichia coli by microdilution was determined, as well as MIC of antibiotics in the presence and absence of extract. Despite having no significant antimicrobial activity (MIC ⩾ 1000 μg mL⁻¹), the extract showed additive activity to the antibiotic efficacy, significantly reducing its MIC. These results suggest that N. corniger and its nest are promising natural products for use in antimicrobial therapy.     

The origins and relatedness of multiple reproductives in colonies of the termite Nasutitermes corniger

Colonies of the termite Nasutitermes corniger often contain multiple reproductive queens and kings. We used double-strand conformation polymorphism (DSCP) analysis of mitochondrial DNA (mtDNA) to determine the probable origins of co-occurring reproductives. Colonies differed in queen and king number, in the number of nests containing reproductives, and in the genetic relationships among reproductives. Most of the 44 colonies contained a single pair of maternally unrelated reproductives. In the two single-nest colonies with a pair of queens, the two queens differed in mtDNA haplotype, suggesting nest-founding by unrelated queens. In the seven single-nest colonies with larger numbers of reproductives (11–49), all reproductives shared the same haplotype, a pattern consistent with replacement of a single pair by several offspring. As predicted by theory, the number of coexisting queens was greater for replacement reproductives than for co-foundresses. Several complex colonies contained multiple queens of two or more haplotypes distributed among several interconnected nests. This indicates that several matrilines can persist within a colony through one or more generations of budding and replacement, a hypothesis confirmed by orphaning experiments. The various modes of termite colony formation rival the diversity seen in ant species and demonstrate the remarkable convergence of behaviours between the two groups.     

Interspecific variation in the defence secretions of Nasutitermes soldiers

Termite soldiers of the genus Nasutitermes (Isoptera, Termitidae, Nasutitermitinae) eject a viscous, sticky defense secretion composed of non-polar monoterpene hydrocarbons and polyoxygenated diterpenes from the frontal gland. Chemical compositions are described in detail for the East African species, N. kempae and N. infuscatus, and for the Neotropical species N. ephratae. Additional comparisons with the new world species N. costalis, N. rippertii and N. octopilis are presented. The structure of a new monohydroxykempene from N. ephratae is described, and a physicochemical model for the stickiness of the glue is presented. Although the structures of the individual secretion components vary within the genus, the glue-like nature of the secretion remains essentially unchanged. Chemical analysis of soldier defense secretions may be useful in studying the systematic biology of termites.     

The regulatory mechanism in mass foraging and the recruitment of soldiers inPheidole

Summary Observations of the recruitment behaviour ofPheidole within the nest reveal the existence of a complex behavioural mechanism which operates in the recruitment of nestmates, including the soldiers, to mass foraging. Highly excited recruiters, arriving at the nest, perform, in addition to trail-laying, a motor recruitement display comprising running, accelerated antennal beatings and body oscillations. While moderately excited recruiters perform this display only on encounters with soldiers, highly excited recruiters display it also on encounters with workers. The release of the motor display appears to be influenced by the attractiveness of the food on one hand, and the mechanical stimulation received from the partner, on the other.The scent trail and the motor display acting together are far more effective than the quiet scent trail recruitment. During the later stage of the experiment, when the reaction of the workers to the recruiting stimuli has already weakened considerably, the motor display still brings about recruitment. The motor display is a highly exciting factor, arousing ants from the resting to the active state. This form of alert is particularly important in the recruitment of soldiers.The formation of recruitment depends on both the number of recruiters and the character of the recruiting performance. The releasing value of the recruiting stimuli decreases with time, as habituation increases. This process, together with excess recruitment, constitues a mechanism which controls the level and limits of recruitment and determines the time of its termination.

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Résumé Des observations sur le comportement de recrutement dePheidole, à l'intérieur du nid, révèle l'existence d'un mécanisme complexe qui aboutit au recrutement de compagnes, parmi lesquelles même des soldats, pour amasser de la nourriture. Des recruteuses extrêmement agitées, en arrivant au nid, réalisent, en plus du dépôt de traces odorantes, une parade motrice de recrutement qui comprend des va-et-vient, des battements accélérés des antennes et des oscillations du corps. Tandis que les recruteuses modérément agitées n'accomplissent cette parade qu'en présence de soldats, les recruteuses extrêmement agitées l'accomplissent également en présence de travailleuses. L'attrait de la nourriture, d'une part, et la stimulation mécanique reçue par la partenaire, d'autre part, semblent déclencher la parade motrice.Les traces odorantes et la parade motrice tout à la fois, sont de loin plus effectives que le simple recrutement par traces odorantes. Pendant le dernier stade expérimental, alors que la réaction des travailleuses aux stimulants de recrutement s'est déjà considérablement atténuée, la parade motrice, elle, conduit encore au recrutement. La parade motrice a un pouvoir extrêmement stimulant capable de faire sortir les fourmis de leur état de repos. Cette forme d'alerte est particulièrement importante dans le recrutement des soldats.La formation de recrutement dépend à la fois du nombre de recruteuses et du caractère de l'acte recruteur. La valeur du déclenchement des stimuli recruteurs diminue avec le temps, et avec l'habitude. Ce processus ajouté à un recrutement excessif constitue un mécanisme qui contrôle le niveau et les limites du recrutement et détermine le moment de son achèvement.

     

Queen-specific volatile in a higher termite Nasutitermes takasagoensis (Isoptera: Termitidae)

In social insect colonies, queen-produced pheromones have important functions in social regulation. These substances influence the behavior and physiology of colony members. A queen-produced volatile that inhibits differentiation of new neotenic reproductives was recently identified in the lower termite Reticulitermes speratus. However, there are no known queen-specific volatiles of this type in any other termite species. Here, we report volatile compounds emitted by live queens of the higher termite Nasutitermes takasagoensis. We used headspace gas chromatography mass spectroscopy (HS GC-MS) to analyze volatiles emitted by live primary queens, workers, soldiers, alates, and eggs collected in a Japanese subtropical forest. Among 14 detected compounds, 7 were soldier-specific, 1 was alate-specific, 1 was egg-specific, and 1 was queen-specific. The queen-specific volatile was phenylethanol, which is different than the compound identified in R. speratus. The identification of this queen-specific volatile is the first step in determining its functions in higher termite social regulation. Comparisons of queen pheromone substances regulating caste differentiation among various termite taxa will contribute to a better understanding of the evolution of social systems in termites.     

Exploratory and recruitment phases in soldier-mediated foraging activities in the termite, Coptotermes intermedius Silvestri (Rhinotermitidae: Coptotermitinae)

Coptotermes intermedius is a damp-wood subterranean termite, which attacks timber and other woody materials with heavy losses in the southern part of Nigeria. The process leading to search for wood and eventual damage was investigated, with focus on how this search is initiated and by which of the termite castes. Results showed that minor soldiers initiate the exploratory phase of search, while the workers are involved in the eventual recruitment process. Under appropriate soldier-worker caste ratio or percentages, exploratory activities in C. intermedius may be regulated.     

The evolution of symmetrical snapping in termite soldiers need not lead to reduced chemical defence

Termite soldiers use a multitude of defensive strategies, often combining mechanical weapons with defensive chemicals secreted from their frontal gland. In higher termites (Termitidae), both these weapons are situated in the head of the soldiers. Their simultaneous occurrence is supposed to be subjected to energetic and spatial constraints and the resulting trade‐off often leads to a full development of only one of the weapons and reduction of the other. Mandibular snapping represents an extreme and efficient anatomical adaptation, allowing the soldier to knock out arthropod enemies with a violent strike of elongated mandibles. The head of snapping soldiers harbours massive adductor muscles while the frontal gland is reported to be reduced and the chemical defence absent. Here we show that the symmetrical snapping soldiers of the Neotropical termite Cavitermes tuberosus possess a well‐developed frontal gland situated in the frontal projection on their head. The gland produces a blend of unbranched alkenes and alkadienes combined with three diterpene hydrocarbons, derived from a novel bicyclic hydrocarbon skeleton. We characterized the molecular structure of the most abundant of these diterpenes and proposed for it a trivial name, cavitene. We conclude that the evolution of the mandibular snapping has not necessarily been accompanied by the reduction or loss of chemical defensive adaptations and that the two defensive modes are not mutually incompatible. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, ●● , ●●–●●.     

Habitat-specific life-history variation in the Caribbean termite Nasutitermes acajutlae (Isoptera: Termitidae)

Abstract.  1. Population and individual colony characteristics of Nasutitermes acajutlae on St John, U.S. Virgin Islands were studied over a 5-year period.
2. Four habitat types (dry forests, moist forests, sparse vegetation, and woodlands) were sampled for N. acajutlae , using quadrat-based methods. Lying dead wood was also quantified in the same sites.
3. Habitats differed significantly in the volume of lying dead wood, and total termite nest volume within quadrats was positively related to wood volume. It was hypothesised that the volume of dead wood affected growth, reproduction, and yearly survival of individual colonies.
4. In a sample of > 100 colonies assessed in 1998, 2000, 2001, and 2002, no significant differences in the growth rate of colonies (= increase in nest volume) could be found between habitat types; however, colonies in sparse vegetation were smaller, less likely to survive, and reproduced at a smaller size compared with those in the other three habitats.
5. Overall nest volume in sparse vegetation was high, compared with dry and moist forest, but colonies showed, on average, poorer survival (interpreted as lower fitness), and produced alates at an early stage of development. Optimum habitat characteristics for N. acajutlae may include not only favourable microclimate but also the reliable acquisition of new dead wood after storms.     

The potential of Isaria spp. as a bioinsecticide for the biological control of Nasutitermes corniger

The termite Nasutitermes corniger is a serious pest infesting urban areas of Brazil and many other countries. Control largely depends on synthetic pesticides whose indiscriminate use can impact the environment and the health of humans and other animals. Alternative strategies against insect pests, such as biological control by entomopathogenic fungi, could be effective while minimising these deleterious effects. We analysed the actions of the entomopathogenic fungi Isaria farinosa, Isaria fumosorosea, and Isaria javanica against the insect N. corniger. Our results indicated that the fungi examined were pathogenic against N. corniger, with I. farinosa ESALQ1355 being the most efficacious strain, resulting in the death of 95% of the workers (LC₅₀ 6.66?×?10⁴ conidia/mL) and 85% of the soldiers (LC₅₀ 6.81?×?10⁴ conidia/mL). This is the first report of the pathogenicity of Isaria spp. on N. corniger. These in vitro results suggest that I. farinosa ESALQ1355 demonstrates a significant biological potential for controlling N. corniger.     

Localization of symbiotic clostridia in the mixed segment of the termite Nasutitermes takasagoensis (Shiraki)

Phylogeny and the distribution of symbiotic bacteria in the mixed segment of the wood-eating termite Nasutitermes takasagoensis (Shiraki) were studied. Bacterial 16S rRNA genes (rDNA) were amplified from the mixed segment of the gut by PCR, and two kinds of sequences were identified. The phylogenetic tree was constructed by neighbor-joining and maximum parsimony methods to identify symbionts harbored in the mixed segment. They are classified as low-G+C-content gram-positive bacteria and are most closely related to the genus Clostridium. The distribution of these bacteria throughout the whole gut was examined by PCR using specific primers, which suggested that they are confined to the mixed segment despite the presence of bacteria throughout the gut. In situ hybridization indicated that the symbiotic bacteria were localized to the ectoperitrophic space between the midgut wall and the peritrophic membrane in the mixed segment. Electron microscopy revealed the close association between these bacteria and the mesenteric epithelium, suggesting that they have some interactions with the gut tissue of termites.     

Morphology and gonad development of normal soldiers and reproductive soldiers of the termite Zootermopsis nevadensis nevadensis (Isoptera, Archotermopsidae)

Reproductive or neotenic soldiers of the Archotermopsid Zootermopsis nevadensisnevadensis (Hagen) are compared to sterile soldiers and primary male reproductives. Several head capsule morphometrics correlate significantly with gonad size across all forms and both sexes of soldiers. The easily observed field character of ratio of mandible length to labrum length is a consistent and reliable feature of head capsule external morphology for predicting gonad development and reproductive potential of soldier forms regardless of age, sex, or live weight.     

The effect of nonnestmates on foraging trail caste ratios ofNasutitermes corniger (Isoptera: Termitidae)

The mean number of workers on foraging trails ofNasutitermes corniger Motschulsky decreases after the introduction of nonnestmate conspecifics or congeneric heterospecifics. The mean number of soldiers on foraging trais does not vary when nestmates, conspecific nonnestmates or heterospecific workers are introduced. When heterospecific soldiers are introduced to the trail, however, the number ofN. corniger soldiers increases. Consequently, the ratio of soldiers to workers increases. These findings demonstrate that the addition of nonnestmates temporarily alters caste ratios on foraging trails, representing a shift in the distribution of castes in response to environmental perturbation.