Species-specific sex pheromones secreted from new sexual glands in two sympatric fungus-growing termites from northern Vietnam, <Emphasis Type="Italic">Macrotermes annandalei</Emphasis> and <Emphasis Type="Italic">M. barneyi</Emphasis>

Summary Reproductive isolation in termites is not well known. Our study carried out on two sympatric species from northern Vietnam, Macrotermes annandalei and M. barneyi, showed that dispersal flights and sex pheromones were two important factors in their reproductive isolation. These fungus-growing termites were isolated, partially due to the timing of their respective dispersal flights. M. annandalei flew the first day after rain, while the flights of M. barneyi occurred the second day after rain. However, the flights can also be simultaneous in the two species. Sex pheromones of M. annandalei and M. barneyi were shown to be species-specific. In both species, they were secreted by females from two glandular sources, from tergal glands located on tergite 6 to 10 in M. annandalei and tergite 5 to 10 in M. barneyi, and from posterior sternal glands located on sternite 6 and 7 in both species. These posterior sternal glands, found for the first time in the Termitidae, were sex-specific glands. Although not fully identified, sex pheromones of M. annandalei and M. barneyi were clearly different from the trail-following pheromone secreted by the sternal gland stricto sensu located on the sternite 5. These results show that in termites, the sexual behaviour, the glandular origin of sex pheromones and their role in reproductive isolation greatly vary depending on the species and deserve to be more extensively studied.Received 8 April 2003; revised 1 September 2003; accepted 10 September 2003.     

Ultrastructure of posterior sternal glands of Macrotermes annandalei (Silvestri): new members of the sexual glandular set found in termites (Insecta)

In female alates of Macrotermes annandalei, two types of abdominal glands are involved in the secretion of sex pheromone. Tergal glands are found at the anterior margin of tergites 6-10 and posterior sternal glands (PSGs) are located at the anterior margin of sternites 6-7. The cytological features of both types of glands are quite similar. The fine structural organization of PSGs is studied more precisely and described for the first time. The glandular cuticle is pitted with narrow apertures corresponding to the openings of numerous subcuticular pouches. Several Class 3 glandular units open in each pouch. One canal cell and one secretory cell make an individual glandular unit. The canal cell is enlarged apically and is connected with the other canal cells to form a common pouch. Based on the structural features found in these glands, we propose a common secretory process for PSGs and tergal glands. During the physiological maturation of alates inside the nest, secretory vesicles amass in the cytoplasm of secretory cells, while large intercellular spaces collapse the cuticular pouches. At the time of dispersal flight, pouches are filled with the content of secretory vesicles while intercellular spaces are sharply reduced. After calling behavior, no secretion remains in the glands and pouches collapse again, while secretory cells are drastically reduced in size. The structure and the secretory processes of PSGs and tergal glands are compared to those of abdominal sexual glands known in termites.     

Cockroach mating behaviors,sex pheromones,and abdominal glands (Dictyoptera: Blaberidae)

Two chemical signals are essential in all cockroach sexual behavioral sequences: the sex pheromone released by one partner, generally the female (for long distance attraction), and an aphrodisiac sex pheromone produced exclusively by male tergal glands (for female mounting and tergal contact or feeding behavior). Unlike the other cockroach groups, the males of the Oxyhaloinae species produce both chemical signals: the pheromone and the aphrodisiac. The occurrence of three patterns of mating behavior (A, B, and C), the production of male sex pheromones, and the existence in the male of developed sternal and tergal glands in seven related Oxyhaloinae species, make these cockroaches a useful model for studying the evolution of mating behavior patterns. The various types of mating behavior were not classified in the previous studies by Roth and Barth. In this report, they have been named type A (female in upper position), B (male in upper position), and C (male and female end to end). In type A mating, the male tergal glands, which are licked by the females, are well developed, whereas in types B and C, there is no licking of the male's tergal secretion by the females and the tergal glands are much less developed; the aphrodisiacs secreted by the tergal glands may no longer act in this case through contact chemoreception, but through an olfactory process involving volatile components. One common sex pheromone component seems to be acetoin. I suggest that the mating behavior tends from A toward B and C during the evolutionary process with a concomitant regression of the tergal glands and changes in the aphrodisiac emission levels. The mating behavioral sequences of cockroaches (Dictyoptera) and crickets (Orthoptera) show a striking degree of similarity and are probably examples of convergent evolution.     

Morphological,molecular identification and phylogenetic analysis of termites from western Ghats of Karnataka,India

Western Ghats of Karnataka, an important biodiversity hot spot in the world, rich in insect fauna including termites. Diversity of termites from this region poorly understood. In the present study, we have redescribed 12 species and termites belonging to two families viz., Rhinotermitidae and termitidae based on morphological and molecular differences employing mitochondrial 16s rRNA. Further we have employed Bayesian inference in order to understand phylogenetic relationships among different termite species studied. The integrative taxonomic approach was successful in delimiting the species studied in the present investigation.     

Tarsomere and distal tibial glands: Structure and potential roles in termites (Isoptera: Rhinotermitidae,Termitidae)

Social insects have numerous exocrine glands, but these organs are understudied in termites compared to hymenopterans. The tarsomere and distal tibial glands of the termites Heterotermes tenuis, Coptotermes gestroi and Silvestritermes euamignathus were investigated by scanning and transmission electron microscopy. Pore plates are visible in scanning micrographs on the distal tibial surfaces and on the ventral surface of the first and second tarsomeres of workers of H. tenuis and C. gestroi. In contrast, workers of S. euamignathus have isolated pores spread throughout the ventral surfaces of the first, second, and third tarsomeres and the distal tibia. In all three species each pore corresponds to the opening of a class-3 secretory unit, composed of one secretory and one canal cell. Clusters of class-3 glandular cells are arranged side by side underneath the cuticle. The main characteristics of these exocrine glands include their presence on all the legs and the electron-lucent secretion in the secretory cells. Possible functions of these glands are discussed.     

Location,morphology and function of nephrocytes in termites

Insect nephrocytes are cells bathed in hemolymph and considered to have an excretory function. These cells have ambiguous nomenclature and are understudied in termites. This study is the first report on the occurrence, morphology and function of nephrocytes in different termite castes. Cytological characteristics in specific developmental stages and castes enable physiological functions to be inferred. Perforate diaphragms indicate a role in filtration, while the extensive peripheral invaginations of the cell membrane suggest active endocytosis. A sequence of morphologies in putative digestive vacuoles infers a lysosomal system and the occurrence of phosphatases suggests a function involving detoxification of substances sequestered from hemolymph. Pericardical nephrocytes took up the dye trypan blue injected in live termites, suggesting their activity connected to the filtration of the hemolymph. Additionally, histochemical tests showed the existence of stored proteins in their cytoplasm. These cells present a well-developed Golgi apparatus and abundant rough endoplasmic reticulum, consistent with protein synthesis. This study highlights the importance of nephrocytes in Isoptera and opens perspectives for further research of these cells.     

Interaction of pheromones during food exploitation by the termite Schedorhinotermes lamanianus

Abstract. Chemical signals from secretions of different exocrine glands modulate a variety of behavioural patterns in termite societies. These signals have multiple functions and may be interactive. During food exploitation workers of the African termite Schedorhinotermes lamanianus (Isoptera: Rhinotermitidae) employ, on foraging trails, the secretion from the sternal gland both for orientation and recruitment to a food source. The secretion from the labial gland, released onto the food by gnawing termites, stimulates additional workers to gnaw at the same site, thereby forming aggregations of gnawing termites. An interaction between these two pheromones during food exploitation is demonstrated for the first time. The volatile signal from the sternal gland inhibits in a dose-dependent manner the non-volatile, highly persistent, signal from the labial gland. The development of gnawing aggregations is inhibited and established ones are dissolved. Behavioural evidence for the perception of both the volatile signal from the sternal gland by olfactory neurones and of the non-volatile signal from the labial gland by gustatory neurones on the antennae is given. The interaction of the two pheromones as a basis for the development of distinct commuting and gnawing zones on the food source, and as a means for a dynamic regulation of food exploitation, is discussed.     

The fine structural organization of sternal glands of pseudergates and workers in termites (Isoptera): a comparative survey

Thirty-nine species belonging to different families of termites are studied to give a comprehensive view of the evolution of the sternal glands. Several modifications occurring at cuticular and cytological levels are described in neuter castes. The outer epicuticle is always pierced by epicuticular pores. In advanced termites the epicuticular filaments greatly increase in number and length creating a thick layer. The pore canals gradually enlarge while the cuticle changes into a lattice structure lining an extracellular space in which the secretion is stored. Two classes of cells are present in basal termites (Mastotermitidae, Hodotermitidae, Termopsidae and Kalotermitidae) but their glandular structures greatly differ between families. A more complex organization with three classes of cells is found in the Serritermitidae and Rhinotermitidae. A regressive evolution occurs in the Termitidae where only two classes of cells are present. A dual nervous control (campaniform sensilla and neurosecretory fibers) is found in lower termites, except for the Hodotermitidae which have mechanosensory bristles. In the other families, neurosecretory fibers are lacking. A comparison with phylogenetic data is given. A more versatile role of sternal glands in neuter castes is hypothesized.     

A phylogenetic analysis of micro-organisms isolated from subsurface environments

Three methods were used to provide information on the identity and phylogenetic relatedness of 19 aerobic, chemoheterotrophic bacteria isolated from topsoil and deep subsurface sediments at a site in South Carolina. These methods were (i) analysis of selected physiological traits, (ii) restriction endonuclease analysis (REA) of genomic DNA, and (iii) analysis of 16S ribosomal RNA sequences. When the 16S rRNA sequences were compared with those for 12 standard strains, two topsoil isolates and six subsurface strains formed a tight group with the high-G+C Gram-positive bacteria and appeared to be most closely related to Arthrobacter globiformis— a coryneform-actinomycete bacterium with unusually effective survival capabilities. The rest of the subsurface isolates were scattered among the standard strains from the Proteobacteria— including the pseudomonads and Agrobacterium tumefaciens— or the low-G+C Gram-positive bacteria.     

Arolia in termites (Isoptera): functional significance and evolutionary loss

Summary. Termite workers from all families examined had no arolia (=adhesive pads) on their tarsi and are unable to climb smooth vertical surfaces such as glass or polypropylene plastic. This contrasts with ants where both workers and alates of most species possess arolia and are able to climb these surfaces. Arolia were present in alates of the majority of species investigated from three of the four most basal termite families (Mastotermitidae, Termopsidae and Kalotermitidae), though absent from the basal family Hodotermitidae that contains only three genera. Alates in the two kalotermitid species tested readily climbed glass walls. The complete evolutionary loss of arolia from alates in the specious two most apical termite families (Rhinotermitidae and Termitidae) suggests paedomorphosis. Very smooth surfaces probably cannot be used to completely prevent entry of rhinotermitid termites into buildings because these termites can eventually build galleries of feces and soil over these surfaces. However, an experiment with Coptotermes formosanus showed that a smoother surface significantly slows down the rate of gallery building.Received 12 February 2004; revised 17 June 2004; accepted 29 June 2004.     

Species composition of termites of the Nyika plateau forests, northern Malawi, over an altitudinal gradient

Termites were surveyed at three altitudes (Brachystegia woodland at 1676 m and 1905 m, and Juniper woodland at 2210 m) in forests within the Nyika Plateau, northern Malawi. Sampling was by a standardized 100 m transect protocol. Termite diversity was highest in the mid‐altitude site and lowest in the Juniper forest. The assemblages were dominated by soil‐feeding termites in the Termitidae subfamilies Apicotermitinae and Termitinae, and included one new soldierless Apicotermitinae genus. The structure of the assemblages was clearly due to a mixture of altitudinal and site history factors. This was especially true of the lowest altitude forest where burning and other anthropogenic disturbance factors appear to have reduced termite diversity relative to the mid‐altitude site. The Nyika plateau shows a much higher diversity at mid‐altitudes than similar SE Asian sites, probably due to the larger area of highland in Africa than in SE Asia. In addition, the clade composition of the Nyika assemblages differs completely from that found at similar altitudes in SE Asia. This preliminary study supports the hypothesis that mid‐ to high‐ altitude assemblages in both SE Asia and Africa appear to be derived from depauperated random subsets of the lowland fauna rather than from clades specifically adapted to higher altitudes.     

Wood excavations of three species of subterranean termites

We compared the feeding excavations on wood blocks of three species of subterranean termites, Coptotermes formosanus Shiraki, Reticulitermes flavipes (Kollar), and R. virginicus (Banks). Feeding rate followed the order C. formosanus > R. flavipes > R. virginicus. Wood surface area (mm²) exposed per unit feeding was higher for C. formosanus and R. flavipes than for R. virginicus. This was caused by the tendency of C. formosanus and R. flavipes to make internally penetrating tunnels, thereby increasing surface area, whereas R. virginicus made trough- and bowl-like depressions on the outside of blocks, sometimes decreasing the size of blocks outwardly without a corresponding high increase in surface area typical with the tunnels of the other species. Consequently, wood surface area was sometimes reduced, rather than increased as a result of feeding by R. virginicus. Different patterns of wood excavation suggest that these termites have divergent roles in wood decay processes.

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Résumé Les organismes pionniers qui modifient le bois et le rendent acceptable par les insectes qui le perforent sont généralement des champignons du bois pourri. Cependant, une fois que les termites ou autres insectes perforant le bois ont pénétré, leurs galeries favorisent les bactéries fixatrices d'azote, permettent l'invasion d'autres organismes décomposeurs, et de ce fait régularisent la décomposition du bois (Ausmus, 1977). L'exposition de la surface à l'intérieur des perforations jouant un rôle très important dans le processus de pourrissement, il est souhaitable de pouvoir quantifier la surface des galeries dues à l'alimentation des termites. Une courbe type permettant de prédire l'aire de la surface perforée a été construite en perçant 109 morceaux de bois de trous cylindriques de différents diamètres, en calculant l'aire de la surface des morceaux de bois, en appliquant et pesant une couche de vernis pour bois au polyuréthane, et en divisant la masse de polyuréthane par l'aire de la surface. Le modèle prédictif qui en découle est: Y=0,01443×-3,51825 (P=0,0001; r=0,68), y étant la masse de polyuréthane (en g) et x la surface (en mm²) du morceau de bois. En traitant de la même façon au polyuréthane les morceaux de bois perforés par les termites, nous pourrions déduire leur surface.Une expérience a été effectuée avec 3 espèces de rhinotermitides,- Coptotermes formosanus Shiraki, Reticulitermes flavipes (Kollar) et R. virginicus (Banks). Des groupes de chaque espèce se sont alimentés pendant 11 ou 12 jours sur des morceaux de bois non contaminés par des champignons. Nous avons déterminé la survie, la consommation, la modification de la surface du morceau de bois (par utilisation du modèle prédictif) et le changement de surface par terminte.La survie est la même, mais la consommation est dans l'ordre suivant: C. formosanus > R. flavipes > R. virginicus. L'aire de la surface exposée par unité d'alimentation était plus élevée pour C. formosanus et R. flavipes que pour R. virginicus (Tab. 1). Ceci est dû à la tendance de C. formosanus et R. flavipes de creuser des galeries vers l'intérieur, tandis que R. virginicus fait des cuvettes à la surface du bois. Les attaques superficielles de R. virginicus réduisent parfois le volume du morceau de bois sans accroître proportionnellement la surface comme le font les espèces creusant des galeries. Ainsi, avec R. virginicus la surface peut être réduite au lieu d'augmenter. Des différences entre colonies s'observent avec toutes les variables (Tab. 2).Nos résultats suggèrent que C. formosanus et R. flavipes contribuent plus que R. virginicus à exposer le bois aux autres organismes décomposeurs. Cependant, ces résultats peuvent être modifiés par un conditionnement préalable du bois par des champignons.

     

Sampling termites in forest habitats: A reply to Roisin and Leponce

Abstract To characterize the structure and species density of termite assemblages in tropical forests, we developed a sampling protocol based on a single large quadrat (belt transect) that standardises sampling effort and area. Emphasizing the estimation of species richness, Roisin and Leponce (2004, Austral Ecology, 29 : 637–46) recommend sampling numerous small quadrats, and varying the number of quadrats depending on local species density. However, their method would result in the loss of standardisation and speed, taking up to four times longer to collect and process the samples. We show that even for a subtropical forest with low species density, our protocol produces robust results.     

Anatomy and phylogenetic analysis of the neotropical callichthyid catfishes (Ostariophysi, Siluriformes)

Based mainly on morphological characters, the phylogenetic relationships among genera and some species groups of the neotropical family Callichthyidae were examined. A study of the osteology of a generalized callichthyid, Callichthys callichthys (Linnaeus), with detailed comparisons among representatives of the remaining genera in the family, is presented and used as a basis for the phylogenetic analysis. A single most parsimonious tree supported the monophyly of the family Callichthyidae based on 28 derived features and the division of the family in the subfamilies Corydoradinae and Callichthyinae. In the subfamily Corydoradinae, the genus Aspidoras is the sister-group of the clade formed by Corydoras plus Brochis. Five derived features support the monophyly of this clade and four support the monophyly of Brochis. No characters, however, were found to support the genus Corydoras. In the subfamily Callichthyinae, Dianema and Hopbstemum are sister-taxa. Megalechis represents the sister-group of Dianema plus Hoplosternum and Lepthoplosternum represents the sister-group to Megalechis plus Dianema plus Hopbstemum. Finally, Callichthys is considered the least derived member of the subfamily, and is hypothesized as the sister-group of the remaining species. A key to all callichthyid genera is provided.     

Intraspecific interactions in a community of arboreal nesting termites (Isoptera: Termitidae)

In coconut plantations of northern New Guinea, the arboreal nesting termite community comprises three species:Nasutitermes princeps, N. novarumhebridarum, andMicrocerotermes biroi. In orde to assess the importance of intraspecific interactions in this community, we conducted pairwise encounters between batches of individuals in the laboratory and between entire nest populations in seminantural conditions. Three levels of agonism were defined in laboratory bioassays: anagonism, moderate agonism, and strong agonism. Anagonism was observed during all control tests with homocolonical groups and in some tests with allocolonial groups of all species. Moderate agonism included initial aggressiveness that subsequently faded out, and initially passive encounters where aggression progressively built up and led to fighting. Strong agonism corresponded to initial aggressiveness and fighting. Results obtained in alboratory bioassays were consistent with bioassays in seminatural conditions. WhenNasutitermes colonies were anagonists in laboratory bioassays, their foraging trails merged without aggression in field tests.N. princeps nests that were moderately agonistic in laboratory tests fought and either continued to avoid each other or finally joined after elimination of the most aggressive individuals. The most aggressiveM. biroi andN. princeps colonies fought and their foraging trails diverged afterward. Direct attacks on alien nests were winnessed inM. biroi. In all species, anagonism occurred in 21–34% of the combinations tested, between either geographically close or distantcolonies. An exeption was a group of 112 anagonist nests ofN. princeps, which most probably constituted a supercolony. The level of agonism betweenNasutitermes colonies was constant during the wet and dry season. Termite colonies excluded each other, both intra- and interspecifically, from the coconut trees, and their territories seem distributed in a mosaic pattern. Agonism between colonies may result in the elimination of the weakest colonies or in trail divergence, maintaining this mosaic. In cotrast, lack of agonism between some colonies suggests the possibility of colony fusion and gene exchanges without nuptial flights.     

On the origin of termite workers: weighing up the phylogenetic evidence

Resolving the phylogenetic history of a 'true' worker caste in termites is essential to our understanding of termite eusocial evolution. Whether this caste is ancient and monophyletic or derived and polyphyletic will have a tremendous impact on our interpretation of termite eusocial history and remains an outstanding question in termite biology. Recent work has begun to re-examine this question in light of new phylogenetic information, but new questions have now arisen about how best to model character state changes in termite caste systems. In the present paper, we compare the models of Grandcolas and D'Haese [J. Evol. Biol. 15 (2002) 885] and Thompson et al. [J. Evol Biol. 13 (2000) 8691 and attempt to make explicit how these proposals differ with respect to the number of, and homology between, character states. We highlight the support each model has for the two principal, but competing, evolutionary hypotheses outlined above.     

异叶苣苔属地上茎的生长式样及其系统发育意义

对异叶苣苔属植物地上茎形态发生过程的观察旨在揭示该属地上茎的生长式样。该研究发现异 叶苣苔属植物地上茎的生长式样并不是以往所认为的简单顶端生长。该属植物的顶芽已完全受到抑制。其地上茎实际上是萌发于小型叶叶腋的侧芽替代顶芽生长所形成的各级侧枝系统,即合轴分枝系统。异叶苣苔属植物地上茎的不分枝情况是位于大型叶叶腋的腋芽受到抑制所致,纯粹是一种次生现象,并不是尖舌苣苔族植物原始祖先的孑遗性状。尖舌苣苔族其他属植物地上茎的生长式样并不均是从异叶苣苔属植物的生长式样演化而来。出蕊苣苔属和异叶苣苔属植物地上茎的生长式样可能来自同一个不太远的祖先,但已经向着不同的方向演化。独叶苣苔属植物复杂的圆锥状对花聚伞花序并非从异叶苣苔属地上茎上部,即生殖生长部分退化而来,乃幼态成熟的复化过程所致。尖舌苣苔属的总状花序可能更接近尖舌苣苔族的原始祖先类型。     

The growth pattern of shoots in Whytockia (Gesneriaceae) with phylogenetic implications

The morphogenesis of shoots in Whytockia W. W. Smith was investigated in order to reveal its growth pattern. The shoot in Whytockia has lost apical growth, which is contrary to the present knowledge about its growth pattern. Its stem is in fact a lateral branch system formed by sprouting of lateral buds in axils of small leaves substituting for the thoroughly restrained phyllogens. The unbranched stem of the genus is due to the restrained state of axillary buds in axils of large leaves. This so-called simple stem is secondary in phylogeny rather than relict in Epithemateae. According to the revealed growth pattern of the shoot in Whytockia, the present paper discusses the phylogenetic relationships between Whytockia and Loxonia, Monophyllaea and Rhynchoglossum in Epi-themateae.     

Attraction and vibration: Effects of previous exposure and type of food resource in the perception of allocolonial odors in termites

Social insects have an efficient recognition system that guarantees social cohesion and protection against intruders in their colonies and territories. However, the energy costs in constant conflicts with neighboring colonies could promote a reduction in the fitness of colonies. Here, we evaluated the effect of previous exposure to allocolonial odor and the consumption of similar food resources on aggressive behavior and choice of allocolonial cues in Nasutitermes aff. coxipoensis (Termitidae: Nasutitermitinae). Our results showed that intercolonial aggressiveness was not affected by previous exposure to allocolonial odor and by the consumption of similar food resources. However, individuals previously exposed to allocolonial odor were more attracted to these odors than individuals who had no prior exposure to allocolonial odor. In addition, individuals from colonies of N. aff. coxipoensis that use similar food resources increased alertness via a greater number of vibration than individuals who consumed different food resources. In general, our results indicate that colonies of N. aff coxipoensis perceive allocolonial cues that have been previously exposed and that the consumption of similar resources triggers an alert signal between individuals. Additional studies are necessary to assess how widespread this capacity of perception is present among the different Isoptera groups and the consequences of colony recognition odor cues on termite space use.