Sexual communication in the termite Prorhinotermes simplex (Isoptera, Rhinotermitidae) mediated by a pheromone from female tergal glands

We studied the post-flight behavior and sex attraction in imagoes of the termite Prorhinotermes simplex (Rhinotermitidae, Prorhinotermitinae). Pairing is mediated by the secretion from tergal glands, exposed by females in a calling posture and highly attractive to males. Analysis of extracts of these glands by means of gas chromatography with electroantennographic detection indicated a chromatographic area corresponding to an intense physiological response of males. The retention characteristics of this area proved to be identical with those of (3Z,6Z,8E)-dodeca-3,6,8-trien-1-ol. Electroantennographic and behavioral assays revealed that units of picograms of the compound represent a stimulus qualitatively and quantitatively equivalent to one female tergal gland. Thus, we hypothesize that (3Z,6Z,8E)-dodeca-3,6,8-trien-1-ol is a major component of the female sex pheromone in P. simplex.     

Respiratory concerts revealed by scanning microrespirography in a termite Prorhinotermes simplex (Isoptera: Rhinotermitidae)

Respiratory metabolism of different developmental stages (larvae, pseudergates, nymphs, soldiers, neotenic reproductives; 0.6-4.5 mg body mass) of Prorhinotermes simplex was individually monitored by scanning respirographic method sensitive to subnanoliter amounts of O(2) consumption or CO(2) output per minute. Specimens exposed to dry air after removal from the colony performed enormously large, discontinuous bursts of CO(2) lasting usually 2 min. The volume of CO(2) produced during the burst often surpassed the volume of the whole body and it was 10- to 20-fold in excess of the air-filled endogenous tracheal volume. The initial velocity of CO(2) production during the burst was more than 90-fold faster in comparison to O(2) consumption. In the presence of enough moisture within the respiratory vessel, the termites breathed continuously without any larger outburst of CO(2). This fact fully corroborates validity of the so-called water retention theory in discontinuous CO(2) release. The highest rates of O(2) consumption were found in the second instar larvae (0.9 mg, 1000-2000 microl O(2)/g/h), the soldier caste was intermediate (700 microl O(2)/g/h) while pseudergates and neotenic reproductives consumed between 300 and 600 microl O(2)/g/h, at 25 degrees C. All developmental stages feeding on a cellulose diet had CO(2)/O(2) values (RQ) over 1 (1.2-1.4, i.e. carbohydrate metabolism), pigmented soldiers fed by the workers had RQ around 0.75 (predominating lipid or protein metabolism). The unusually large, sudden eruptions of CO(2) in specimens exposed to dry air allow us to make the following conclusions: (1) the bursts were due to special chemical processes, such as by enzymatic hydration of carbonic acid by carbonic anhydrase and; (2) the bulk of chemically evolved gaseous CO(2) escaped from the body by a mass flow supported by active ventilation, not by a passive diffusion. These results demonstrated that the periodic emissions of CO(2) and the associated homeostatic regulation of the respiratory acidaemia were under perfect physiological control. The termites could thus actively select the type of CO(2) release best suited to the extant environmental or internal physiological conditions, i.e. from a completely continuous respiration to occasionally cyclic or completely discontinuous CO(2) release.     

Ultrastructural ontogeny of the labial gland apparatus in termite Prorhinotermes simplex (Isoptera, Rhinotermitidae)

The labial glands in Prorhinotermes simplex consist of secretory cells organized into acini, water sacs and the ducts connecting the gland parts to the basis of the labium. Acini are composed of central and parietal cells. Central cells type I contain predominantly lucent vacuoles and are involved probably in hydroquinone production. They are lacking in soldiers. Type II central cells produce vacuoles of proteinaceous content which are of the same electron density (type IIa) or present in more shades (type IIb). Type IIa cells are present in all older individuals, whereas type IIb are lacking in soldiers and neotenics. Type III cells represent a specific stage of type I cells development, but they are definite functional secretory cells in soldiers. Acini of first instar larvae contain undifferentiated cells which differentiate into type I cells during the second instar. Specific larval central cells start to change into type II cells during first instar. The central cells of presoldiers show a transition from the pseudergate into the soldier situation. The parietal cells keep a uniform structure throughout the whole ontogeny. Only one type of cells form the water sacs in all castes. The cells are very flat with scarce organelles. The water sac cells produce lipid-like secretion, small lucent vacuoles and bunches of angulated vacuoles. The water sac probably functions as water storage organ only. Ontogenetical changes in water sac development are small. The acinar ducts originate inside the acinus where they are formed by flat cells with rare organelles. At the acinus border, cells equipped with mitochondria, microvilli and basal invaginations appear. The water sac ducts are formed by flat cells with rare organelles. Acinar ducts outside the acinus and water sac ducts are equipped with taenidiuam.     

Parthenogenetic reproduction in neotenics of the subterranean termite Reticulitermes speratus (Isoptera: Rhinotermitidae)

Experiments with artificial colonies consisting of only female workers and those of female nymphs and workers of a subterranean termite, Reticulitermes speratus, showed that neotenics (ergatoids and nymphoids) can reproduce parthenogenetically. The larvae hatched from the eggs produced partheno‐genetically by the neotenics were all female and did not have any aberrant external morphology. They had 42 chromosomes and were diploid. The analysis of genotypes at microsatellite loci revealed that the eggs produced parthenogenetically had only one of the two alleles that the mother neotenics possessed, indicating that the eggs were produced by automixis.     

Distribution and composition of colony founding associations of a subterranean termite, Reticulitermes kanmonensis

We investigated distribution and sexual composition of founding associations of Reticulitermes kanmonensis, the Japanese subterranean termite, which occurs only in the Kanmon area. These properties are discussed in relation to body size and mitochondrial genotype of the dealates. The founding colonies showed a highly aggregated distribution with a ‘hot spot’ of colony founding; however, mitochondrial haplotypes of the dealates suggested random mating. Monogamous colonies were predominant, but solitary colonies and colonies with two females and/or males also occurred. Paired dealates tended to be larger than solitary founders, suggesting that both sexes were under sexual selection related to body size.     

Relatedness and kin-structured migration in a founding population: Plymouth Colony, 1620-1633

To test the common assumption of no genetic relationship in a founding population, we calculated average relatedness (r) for the emigrants to Plymouth Colony from Europe on seven voyages from 1620 to 1633. Of 355 individuals, 255 could be individually identified and 4 generations of genealogic depth accounted for. Mean r was 0.00399 (S.D. = 0.00395) and ranged from 0 for 76 individuals to 0.01574 for a single female. There was a strong sex difference in relatedness; 91 females had a mean r of 0.00557 (S.D. = 0.00428), and 161 males had a lower mean r of 0.00308 (S.D. = 0.00349) (t = 4.71, p less than 0.001). The major difference was in the lower proportion of females with no relations (n = 12, 13.2%) compared with males (n = 64, 39.8%) (t = 5.05; p less than 0.001). If relatedness is calculated only for those with relations, females still have a significantly higher mean r value (0.00641, S.D. = 0.00393) than males (0.00511, S.D. = 0.00312) (t = 2.38, p less than 0.05). Thus a higher proportion of females had relatives migrating to the colony, and relatedness is significantly higher among them. The majority of kin links (79.8%) were those within the nuclear family--parents, children or siblings. For the continuity of kin-structured migration, relatedness was highest among voyagers in the same boat load and lower between voyages, with no apparent time trend. The low relatedness value of the Plymouth migrants is a result of community history and recruitment practices for the new colony. For this European population average relatedness was approximately an order of magnitude below that of traditional groups, and the assumption of no genetic relationship is not unwarranted.     

Ultrastructure of epidermal glands in neotenic reproductives of the termite Prorhinotermes simplex (Isoptera: Rhinotermitidae)

The ultrastructure of epidermal glands in neotenic reproductives of Prorhinotermes simplex is described and their development is compared among young and old neotenics of both sexes. Secretory cells forming the epidermal gland are attached to the cuticle all over the body. The glands are formed by class 1 and class 3 secretory cells and corresponding canal cells with secretory function. Class 1 cells are sandglass-like and class 3 secretory units are located among them. Class 1 cells contain predominantly tubular endoplasmic reticulum, the major part represents the smooth and the minor the rough form. Numerous electron dense granules occur in the cytoplasm, they are always disintegrated prior to be released. Class 3 secretory cells contain a large amount of vacuoles, which are always lucent in males while newly produced vacuoles are dense in females. Dense vacuoles are frequently transformed into lucent ones before being released. Canal cells are locally equipped with microvilli. The conducting canal is surrounded by an electron dense secretion of regular inner structure. The cytoplasm of the canal cell contains numerous mitochondria, rough endoplasmic reticulum and a large proportion of microtubules. The young neotenic reproductives differ from the old ones by a lower amount of secretory products. Epidermal glands probably produce substances inhibiting the occurrence of superfluous reproductives.     

Colony dynamics of the Formosan subterranean termite in a frequently disturbed urban landscape

The success of evaluating areawide control of the Formosan subterranean termite, Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae), in urban landscapes hinges on detailed understanding of colony movement and plasticity of the breeding system. Most previous studies of colony affiliation and breeding systems of C. formosanus have been conducted in relatively undisturbed park-like areas. However, disturbance in the form of landscaping, construction, and nearby treatment may impact termite colony dynamics in urban habitats. Therefore, we used microsatellite genotyping to identify the number of colonies, assess colony movement, and investigate the breeding structure of colonies surrounding the Supreme Court Building in New Orleans, LA. During 4 yr, 18 distinct colonies were identified in the study area. In contrast to earlier studies in park-like areas, which indicated stable foraging areas, colonies in this study moved frequently into and out of inground stations. Five colonies were simple families; two of these colonies were headed by inbred nestmate pairs, and three of these colonies were headed by outbred unrelated pairs. Thirteen colonies were extended families headed by fewer than five neotenic reproductives. During the study, the predominant breeding system shifted; simple family colonies either moved or were eliminated, and they were replaced with new extended family colonies. In one case, a generation turnover within a colony from simple to extended family was observed.     

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.     

Colony founding in the primitively eusocial wasp, Ropalidia marginata (Hymenoptera: Vespidae)

Abstract.

• 1 In a 16-month study in Bangalore, India, about 35% of the newly founded colonies of Ropalidia marginata were single foundress colonies and the remainder were multiple foundress colonies with two to twenty-two individuals.
• 2 Larger colonies did not have a significantly higher per capita productivity, did not produce significantly heavier progeny and did not produce them significantly faster than smaller colonies did.
• 3 Predation by the hornet Vespa tropica appeared to be independent of group size.
• 4 Single foundress colonies failed more often but not often enough to make them have a lower average per capita productivity, compared to multiple foundress colonies.
• 5 Some of the advantages of multiple foundress associations came from the greater predictability of their attaining the mean per capita productivity, the relatively lower rates of usurpation experienced by them compared to single foundress colonies, and the opportunities provided by queen turnovers for workers to become replacement queens and gain direct individual fitness.

     

Colony founding and initial nest design of honey bees, Apis mellifera L

Thirty-two colonies of bees with varying populations were established in 1·2-m³ boxes for 24 days. At the end of this time, the bees were killed, and the comb structure, design, and placement were examined to obtain information about the initiation of bee nests. The analysis of variance of three dimensions of the comb (height, width, and length) showed no statistical differences when all thirty-two colonies were considered as a group.Comb built by queenless bees differed from any described in the literature. We think it is comb characteristically built by queenless bees that is neither worker nor drone in size but intermediate.The occurrence of multiple clusters building comb with and without queen in the same box is recorded but unexplained at present.An explanation is offered for the curl appearing in the lower edges of straight combs.     

Nestmate recognition mediated by intestinal bacteria in a termite, Reticulitermes speratus

Discrimination and aggressive responses toward non-nestmates have been observed in a number of termite species, but the mechanism is poorly understood. Here I present the novel hypothesis that differential intestinal bacteria composition leads to production of colony-specific chemical cues that enable nestmate recognition.
The intestinal microflora of a lower termite, Reticulitermes speratus , consisted of many bacteria species. The composition of the intestinal bacteria was exclusively colony-specific. Termites that had adsorbed an unfamiliar odor of bacteria sampled from another colony were fiercely attacked by nestmates. Experimental manipulation of the composition of bacteria by antibiotics successfully changed the recognition behavior toward nestmates. These results indicate that intestinal bacteria play an important role in nestmate recognition.     

The ontogeny of soldiers in Prorhinotermes simplex (Isoptera, Rhinotermitidae)

The ontogeny of the soldier caste in Prorhinotermes simplex is studied with emphasis on the instar origin of soldiers, the duration of the presoldier stage, and changes in external anatomy during the soldier morphogenesis. The soldiers of different instar origin are compared morphometrically and by analysis of the soldier defensive secretion. The soldiers were found to develop from larvae of the second up to the eighth instar, via a short (13–17 days) presoldier stage. The early soldier instars were found exclusively in incipient colonies while the mature colony contains late instar soldiers only. The abrupt change in the external anatomy occurs in two steps. During the larva-presoldier moult, the head increases in length but only slightly in width. During the presoldier-soldier moult, both the length and width of the head increase markedly and the typical cordate shape is attained; the relative size of the pronotum increases considerably. The long falcate mandibles develop mainly during the larva-presoldier moult. One antennal segment is added during these two moults. With increasing instar age of soldiers a relative increase of the pronotum and the head size in its posterior region was observed. No functional differences in external anatomy were found among the six soldier instars. The composition of the frontal gland secretion is similar in the six soldier instars, an extraordinarily high amount of a defensive substance, (E)-1-nitropentadecene, was detected together with (Z,E)-α-farnesene, presumably an alarm substance. The strategy of soldier production is discussed. We conclude that the observed patterns of soldier production in P. simplex correspond well to its ecological strategy of an advanced single-site nester able to migrate and form foraging groups. Received 16 August 2005; revised 21 November and 6 February 2006; accepted 16 February 2006.     

Colony genetic organization and colony fusion in the termite Reticulitermes flavipes as revealed by foraging patterns over time and space

Temporal and spatial analyses are seldom utilized in the study of colony genetic structure, but they are potentially powerful methods which can yield novel insights into the mechanisms underlying variation in breeding systems. Here we present the results of a study which incorporated both of these dimensions in an examination of genetic structure of subterranean termites in the genus Reticulitermes (primarily R. flavipes). Most colonies of this species (70%) were simple families apparently headed by outbred primary reproductives, while most of the remaining (27% of the total) colonies contained low effective numbers of moderately inbred reproductives. Mapping the spatial distribution of colony foraging sites over time revealed that despite the high colony density, the absolute foraging boundaries of most R. flavipes colonies were persistent and exclusive of other conspecific colonies, which suggests that this species is more territorial than has been implied by laboratory studies of intraspecific aggression. Nevertheless, we found a single colony (3% of all colonies) which contained the offspring of more than two unrelated reproductives. Although other studies have also described subterranean termite colonies with a similarly complex genetic composition, we demonstrate here that such colonies can form under natural conditions via the fusion of whole colonies. This study underscores how repeated sampling from individual colonies over time and space can yield information about colony spatial and genetic structure that cannot be obtained from conventional analyses or sampling methods.     

Efficient gene silencing by delivery of locked nucleic acid antisense oligonucleotides,unassisted by transfection reagents

For the past 15–20 years, the intracellular delivery and silencing activity of oligodeoxynucleotides have been essentially completely dependent on the use of a delivery technology (e.g. lipofection). We have developed a method (called ‘gymnosis’) that does not require the use of any transfection reagent or any additives to serum whatsoever, but rather takes advantage of the normal growth properties of cells in tissue culture in order to promote productive oligonucleotide uptake. This robust method permits the sequence-specific silencing of multiple targets in a large number of cell types in tissue culture, both at the protein and mRNA level, at concentrations in the low micromolar range. Optimum results were obtained with locked nucleic acid (LNA) phosphorothioate gap-mers. By appropriate manipulation of oligonucleotide dosing, this silencing can be continuously maintained with little or no toxicity for >240 days. High levels of oligonucleotide in the cell nucleus are not a requirement for gene silencing, contrary to long accepted dogma. In addition, gymnotic delivery can efficiently deliver oligonucleotides to suspension cells that are known to be very difficult to transfect. Finally, the pattern of gene silencing of in vitro gymnotically delivered oligonucleotides correlates particularly well with in vivo silencing. The establishment of this link is of particular significance to those in the academic research and drug discovery and development communities.     

Courting strategies and conflicts in a monogamous,biparental termite

In species where parental investment is extensive for both sexes, both males and females are predicted to exhibit choosiness when seeking their lifetime partners. Evidence is presented that both courting males and females are choosy in the wood-dwelling, biparental termite Zootermopsis nevadensis. There are, however, sex differences both in the method of mate rejection and in the mate-choice criteria. In particular, females are more likely than males to invite an extra suitor into the nest, whereas males are more likely than females to leave their nest and partner and seek a replacement elsewhere. Correlational analyses of adults show that head width is a mate-choice criterion used by females, whereas body mass and fat mass are used by males. Among males and females that sought replacement mates, those that had been rejected previously were more likely to end up paired with an adult that also had been rejected, compared with adults that had not been rejected. Additional findings reveal a rich repertoire of courting behaviours characterized by extensive intra- and intersexual conflict, including mate rejection, intrasexual combat, and even intrapair aggression.     

Distribution patterns of four Termitomyces species cultivated by a fungus-growing termite,Odontotermes formosanus,in Taiwan

Fungus-growing termites inoculate the obligate symbiotic fungus Termitomyces into the fungus comb in their colonies. In this study, Taiwanese Termitomyces species were determined by diagnostic PCR using the metagenome of the body of Odontotermes formosanus (the only host termite living in Taiwan) as a template. Phylogenetic analyses revealed that four different Termitomyces species are cultivated by O. formosanus in Taiwan. Three have previously been registered in the DNA database, but one was first recorded in Taiwan. Only Termitomyces sp. Type C was distributed in all areas investigated in Taiwan, whereas the other three species were distributed regionally. Field observations indicated that the flush period and the number of fruit bodies in each colony varied between species. The distribution patterns of Termitomyces spp. in Taiwan may be related to the Taiwanese climate and/or the fruiting pattern.     

Colony social organization and population genetic structure of an introduced population of formosan subterranean termite from New Orleans, Louisiana

The Formosan subterranean termite, Coptotermes formosanus Shiraki, is an invasive species in many parts of the world, including the U.S. mainland. The reasons for its invasive success may have to do with the flexible social and spatial organization of colonies. We investigated the population and breeding structure of 14 C. formosanus colonies in Louis Armstrong Park, New Orleans, LA. This population has been the focus of extensive study for many years, providing the opportunity to relate aspects of colony breeding structure to previous findings on colony characteristics such as body weight and number of workers, wood consumption, and intercolony aggression. Eight colonies were headed by a single pair of outbred reproductives (simple families), whereas six colonies were headed by low numbers of multiple kings and/or queens that were likely the neotenic descendants of the original colony (extended families). Within the foraging area of one large extended family colony, we found genetic differentiation among different collection sites, suggesting the presence of separate reproductive centers. No significant difference between simple family colonies and extended family colonies was found in worker body weight, soldier body weight, foraging area, population size, or wood consumption. However, level of inbreeding within colonies was negatively correlated with worker body weight and positively correlated with wood consumption. Also, genetic distance between colonies was positively correlated with aggression levels, suggesting a genetic basis to nestmate discrimination cues in this termite population. No obvious trait associated with colony reproductive structure was found that could account for the invasion success of this species.