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Toru Miura - One of the best experts on this subject based on the ideXlab platform.
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Histology of the hormone-producing glands in the damp-wood termite Hodotermopsis sjostedti (Isoptera, Termopsidae): A focus on soldier differentiation
Insectes Sociaux, 2008Co-Authors: Richard Cornette, Shigeyuki Koshikawa, Toru MiuraAbstract:Caste differentiation in termites depends on complex hormonal changes during postembryonic development. Juvenile hormone (JH) is a central player in this process. The present study examined histological changes in the main hormone-producing endocrine glands, the corpora allata and molt glands, in the Japanese dampwood termite Hodotermopsis sjostedti. We focused on the soldier caste differentiation pathway, which can be induced artificially using an analogue of JH. The corpora allata exhibited volumetric changes during soldier induction, reflecting variations in the quantity of cytoplasm. Corpora allata from alates and neotenics clearly showed differentiation accompanied by cell proliferation, preparing for the high-level JH production necessary for reproduction. However, the volume increase of corpora allata was not always correlated to high JH titers. In contrast, molt glands degenerated in the reproductive castes. The JH analogue induced hypertrophy of the molt glands, along with the formation of lacunae, possibly related to ecdysteroid production. The JH analogue effect, inducing soldier differentiation, was suggested to require both mimic of high JH titers and stimulation of the molt glands.
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Differences in cellulose digestive systems among castes in two termite lineages
Physiological Entomology, 2008Co-Authors: Ai Fujita, Toru Miura, Tadao MatsumotoAbstract:Termites (Isoptera) are eusocial insects and express polyphenism. Soldiers have specialized morphology for colony defense, but their feeding activity is dependent on other colony members. To determine differences in cellulose degradation between soldier and worker termites, enzymatic activity and cellulase gene expression, as well digestive tract histology, are examined in two phylogenetically distant species. In Hodotermopsis sjostesti (family Termopsidae), endo-β-1,4-glucanase activity is identified in the salivary glands, whereas β-glucosidase activity is identified in salivary glands and hindgut. The relative expression levels of endo-β-1,4-glucanase genes in soldiers are significantly lower than in workers. Thin sections of salivary gland of workers and soldiers are different in H. sjostedti. In Nasutitermes takasagoensis (family Termitidae), the endo-β-1,4-glucanase activity is restricted to the midgut in four tested castes (i.e. three types of workers and soldier). Examination of activity per termite reveals the highest activity in minor workers and the lowest activity in major workers and soldiers. The β-glucosidase activity is also concentrated on the midgut in all four castes. The relative expression level of the endo-β-1,4-glucanase gene does not correspond with its activity in the midgut. In thin sections prepared from N. takasagoensis, the folds and pulvillus in the gizzards, and cuticle structure of soldiers are less developed compared with the other three worker castes. The differences in digestive system among termite castes in terms of caste development in each species are discussed.
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Juvenile hormone titers and caste differentiation in the damp-wood termite Hodotermopsis sjostedti (Isoptera, Termopsidae).
Journal of Insect Physiology, 2008Co-Authors: Richard Cornette, Shigeyuki Koshikawa, Hiroki Gotoh, Toru MiuraAbstract:Abstract Termites are social insects, presenting morphologically distinct castes, performing specific tasks in the colony. The developmental processes underlying caste differentiation are mainly controlled by juvenile hormone (JH). Although many fragmentary data support this fact, there was no comparative work on JH titers during the caste differentiation processes. In this study, JH titer variation was investigated using a liquid chromatography-mass spectrometry (LC-MS) quantification method in all castes of the Japanese damp-wood termite Hodotermopsis sjostedti, especially focusing on the soldier caste differentiation pathway, which was induced by treatment with a JH analog. Hemolymph JH titers fluctuated between 20 and 720 pg/μl. A peak of JH was observed during molting events for the pseudergate stationary molt and presoldier differentiation, but this peak was absent prior to the imaginal molt. Soldier caste differentiation was generally associated with high JH titers and nymph to alate differentiation with low JH titers. However, JH titer rose in females during alate maturation, probably in relation to vitellogenesis. In comparison, JH titer was surprisingly low in neotenics. On the basis of these results in both natural and artificial conditions, the current model for JH action on termite caste differentiation is discussed and re-appraised.
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Effects of Precocenes on the Corpora Allata and the JH Titer in the Damp-Wood Termite Hodotermopsis sjostedti (Isoptera: Termopsidae)
Sociobiology, 2008Co-Authors: Hiroki Gotoh, Shigeyuki Koshikawa, Richard Cornette, Toru MiuraAbstract:Juvenile hormone (JH) is an insect hormone that is responsible for the control of a variety of physiological and developmental states. In termites, JH has long been considered to play an important role in caste differentiation, although the detailed mechanisms underlying the actions of the hormone are not well understood. In this study, we applied three types of precocenes, anti-JH agents that destroy the corpora allata (CA), to pseudergates (workers) of the damp-wood termite Hodotermopsis sjostedti, and evaluated the effects on the CA volume and JH titer after the treatments. Results showed degeneration of the CA at day 14 in the precocene-II-treated group, which was not observed in the control group. Conversely, no significant difference in the JH titer was apparent between precocene-II-treated groups and their corresponding controls. These results indicate that CA degeneration is not always correlated with a decrease inJH titer. Precocenes are thus not effective as anti-JH agents in the focal termite species. These findings indicate that simultaneous examination of JH titer and CA size are important considerations for evaluating the effects of anti-JH agents.
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differences in mechanosensory hairs among castes of the damp wood termite hodotermopsis sjostedti isoptera Termopsidae
Sociobiology, 2007Co-Authors: Yuki Ishikawa, Shigeyuki Koshikawa, Toru MiuraAbstract:Termites are one of the major groups of social insects, which comprise alates, workers (pseudergates), and soldiers within a species. These castes have different roles and behaviors, and undertake division of labor to increase the inclusive fitness of their colony. On the basis of the different behavioral repertoires, caste-specific neural modifications are predicted, such as modification of sensory systems, i.e., inputs into the nervous system. This study evaluated these sensory-system differences based on mechanoreceptive sensilla length among castes of the damp-wood termite Hodotermopsis sjostedti. We found that soldiers and alates had longer sensilla than pseudergates, and that this variation among castes differed with body region. Specifically, the differences were particularly conspicuous on head capsules and pronota, while sensilla on mouthparts and legs were of similar lengths among castes. It is proposed that soldiers and alates use these long mechanoreceptive structures to sense faint vibrations, an important capability for their defensive role in detecting enemies and cracks in nest wood.
Tadao Matsumoto - One of the best experts on this subject based on the ideXlab platform.
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Differences in cellulose digestive systems among castes in two termite lineages
Physiological Entomology, 2008Co-Authors: Ai Fujita, Toru Miura, Tadao MatsumotoAbstract:Termites (Isoptera) are eusocial insects and express polyphenism. Soldiers have specialized morphology for colony defense, but their feeding activity is dependent on other colony members. To determine differences in cellulose degradation between soldier and worker termites, enzymatic activity and cellulase gene expression, as well digestive tract histology, are examined in two phylogenetically distant species. In Hodotermopsis sjostesti (family Termopsidae), endo-β-1,4-glucanase activity is identified in the salivary glands, whereas β-glucosidase activity is identified in salivary glands and hindgut. The relative expression levels of endo-β-1,4-glucanase genes in soldiers are significantly lower than in workers. Thin sections of salivary gland of workers and soldiers are different in H. sjostedti. In Nasutitermes takasagoensis (family Termitidae), the endo-β-1,4-glucanase activity is restricted to the midgut in four tested castes (i.e. three types of workers and soldier). Examination of activity per termite reveals the highest activity in minor workers and the lowest activity in major workers and soldiers. The β-glucosidase activity is also concentrated on the midgut in all four castes. The relative expression level of the endo-β-1,4-glucanase gene does not correspond with its activity in the midgut. In thin sections prepared from N. takasagoensis, the folds and pulvillus in the gizzards, and cuticle structure of soldiers are less developed compared with the other three worker castes. The differences in digestive system among termite castes in terms of caste development in each species are discussed.
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Histological Analysis of Fat Body Development and Molting Events During Soldier Differentiation in the Damp-Wood Termite, Hodotermopsis sjostedti (Isoptera, Termopsidae)
Zoological Science, 2007Co-Authors: Richard Cornette, Tadao Matsumoto, Toru MiuraAbstract:The caste system of termites is well defined, with a high degree of polyphenism among colony members. Polyphenic caste characteristics are hormonally regulated, and juvenile hormone (JH) is particularly involved in caste determination, as is the case with many other social insects. In the present study, soldier differentiation in the damp-wood termite, Hodotermopsis sjostedti, was induced by treatment with a JH analog (pyriproxyfen) in order to establish the chronology of tissular modifications appearing in response to the hormone. The fat body is involved in the physiological events that prepare the insect for the molting transition. The development of the fat body started within three days after hormonal treatment, and it filled the entire abdominal cavity for about four days prior to the molt to presoldier, maintaining this state until the next molt to soldier. Fat body development was accompanied by the accumulation of protein granules in the cytoplasm, but these granules disappeared during the few days preceding the molt to presoldier. The timing of consumption of these storage proteins corresponded to the window of epidermal growth, which was conspicuous about 14 days after hormonal treatment, and synthesis of the new cuticle, which was initiated 10 days after treatment. We summarize the chronology of the histological events under hormonal control.
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Caste-specific cytochrome P450 in the damp-wood termite Hodotermopsis sjostedti (Isoptera, Termopsidae).
Insect Molecular Biology, 2006Co-Authors: Richard Cornette, Tadao Matsumoto, Shigeyuki Koshikawa, Masaru Hojo, Toru MiuraAbstract:Termites are eusocial insects with a well-defined caste system, which is an example of polyphenism. This polyphenism is based on hormonally controlled differential gene expression. In the damp-wood termite Hodotermopsis sjostedti , we induced differentiation into the soldier caste by using juvenile hormone analogue treatment. We then investigated specific gene expression, which appeared during the hormonal response and triggered caste differentiation, using fluorescent differential display. A candidate cDNA sequence with similarity to cytochromes P450, CYP6AM1, was characterized and its transcript shown to be repressed between 1 and 3 days after hormone treatment. CYP6AM1 was specifically expressed in the fat body of pseudergates and soldiers. The putative function of this P450 is discussed with respect to the caste differentiation system.
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Soldier-like Intercastes in the Rotten-wood Termite Hodotermopsis sjostedti (Isoptera: Termopsidae)
Zoological Science, 2004Co-Authors: Shigeyuki Koshikawa, Tadao Matsumoto, Toru MiuraAbstract:Abstract All termite species possess a distinct sterile-soldier caste in their colonies, although reproductive soldiers, with soldier characteristics and reproductive ability, have been reported from several species of the family Termopsidae. Such intercastes have been considered the primitive-soldier caste, and based on this many researchers have discussed the evolutionary origin of termite soldiers. We investigated whether such soldier-reproductive intercastes also exist in the Japanese rotten-wood termite Hodotermopsis sjostedti. Abnormal individuals with soldier-like characteristics were found and designated as soldier-like intercastes, which appeared to have both soldier and reproductive characteristics. Based on our morphometric analyses and histological examinations, we suggest that the developmental origin of this inter-caste is a pseudergate, nymph or sixth-instar larva. In addition, the intercaste was found to have relatively well-developed gonads, although mature oocytes and spermatozoa were no...
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Winged Presoldiers Induced by a Juvenile Hormone Analog in Zootermopsis nevadensis: Implications for Plasticity and Evolution of Caste Differentiation in Termites
Journal of Morphology, 2003Co-Authors: Toru Miura, Shigeyuki Koshikawa, Tadao MatsumotoAbstract:To elucidate the switching mechanism of caste differentiation in termites and to examine the possible induction of soldier-reproductive intercastes experimentally, we investigated the effects of juvenile hormone on the morphologies of soldier caste by applying a juvenile hormone analog (JHA) to nymphs of the damp-wood termite Zootermopsis nevadensis (Isoptera : Termopsidae). JHA treatment for about 2 weeks induced a variety of intermediate castes, showing both alate and soldier morphological features. The principal component analysis (PCA) of those morphological characters showed that those intercastes were a deviation from the developmental line into alates to soldier differentiation, which is known to be triggered by juvenile hormone. Detailed morphological examination of the compound eyes, wing joint, and mandibles showed that those intercastes expressed soldier features, although they had started to develop alate characteristics. The morphology of the resultant intercastes seemed to be determined by the nymphal stage, at which JHA treatment was applied. The induced intercastes with exaggerated soldier-specific characteristics (e.g., mandibles) repressed alate-specific characteristics (e.g., wings), namely, the alate and soldier morphological characteristics in induced intercastes show opposite responses against the application of JHA. On the other hand, ovarian development was not suppressed by the JHA application, even in the soldier-like individuals. Naturally differentiated presoldiers also possessed developed ovarioles, although ovaries of mature soldiers were degenerated. Our results suggest that the juvenile hormone plays complicated roles in the expression of caste morphologies and ovarian development in termites. J. Morphol. 257:22–32, 2003. © 2003 Wiley-Liss, Inc.
James F. A. Traniello - One of the best experts on this subject based on the ideXlab platform.
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Disease resistance in the drywood termite, Incisitermes schwarzi: does nesting ecology affect immunocompetence?
Journal of Insect Science, 2010Co-Authors: Daniel V. Calleri, Rebeca B. Rosengaus, James F. A. TranielloAbstract:Termites live in nests that can differ in microbial load and thus vary in degree of disease risk. It was hypothesized that termite investment in immune response would differ in species living in nest environments that vary in the richness and abundance of microbes. Using the drywood termite, Incisitermes schwarzi Banks (Isoptera: Kalotermitidae), as a model for species having low nest and cuticular microbial loads, the susceptibility of individuals and groups to conidia of the entomopathogenic fungus, Metarhizium anisopliae Sorokin (Hypocreales: Clavicipitaceae), was examined. The survivorship of I. schwarzi was compared to that of the dampwood termite, Zootermopsis angusticollis Hagen (Termopsidae), a species with comparatively high microbial loads. The results indicated that I. schwarzi derives similar benefits from group living as Z. angusticollis: isolated termites had 5.5 times the hazard ratio of death relative to termites nesting in groups of 25 while termites in groups of 10 did not differ significantly from the groups of 25. The results also indicated, after controlling for the influence of group size and conidia exposure on survivorship, that Z. angusticollis was significantly more susceptible to fungal infection than I. schwarzi, the former having 1.6 times the hazard ratio of death relative to drywood termites. Thus, disease susceptibility and individual investment in immunocompetence may not be dependent on interspecific variation in microbial pressures. The data validate prior studies indicating that sociality has benefits in infection control and suggest that social mechanisms of disease resistance, rather than individual physiological and immunological adaptations, may have been the principle target of selection related to variation in infection risk from microbes in the nest environment of different termite species.
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Inducible immune proteins in the dampwood termite Zootermopsis angusticollis
Naturwissenschaften, 2007Co-Authors: Rebeca B. Rosengaus, Tara Cornelisse, Katerina Guschanski, James F. A. TranielloAbstract:Dampwood termites, Zootermopsis angusticollis (Isoptera: Termopsidae), mount an immune response to resist microbial infection. Here we report on results of a novel analysis that allowed us to electrophoretically assess changes in hemolymph proteins in the same individual before and after exposure to a pathogen. We demonstrate that contact with a sublethal concentration of the entomopathogenic fungus Metarhizium anisopliae (Deuteromycotina:Hypomycetes) induces the production of protective proteins in nymphs, pseudergates (false workers), and soldiers. Termites exposed to an immunizing dosage of fungal conidia consistently showed an enhancement of constitutive proteins (62–85 kDa) in the hemolymph as well as an induction of novel proteins (28–48 kDa) relative to preimmunization levels. No significant differences in protein banding patterns relative to baseline levels in control and naïve termites were observed. Incubating excised and eluted induced proteins produced by immunized pseudergates or immunized soldiers with conidia significantly reduced the germination of the fungus. The fungistatic effect of eluted proteins differed significantly among five colonies examined. Our results show that the upregulation of protective proteins in the hemolymph underscores the in vivo immune response we previously recorded in Z. angusticollis .
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Effect of Enhanced Dietary Nitrogen on Reproductive Maturation of the Termite Zootermopsis angusticollis (Isoptera: Termopsidae)
Environmental Entomology, 2002Co-Authors: Colin S. Brent, James F. A. TranielloAbstract:We determined the effect of enhanced dietary nitrogen on the ovarian maturation of female primary and neotenic reproductives of the termite Zootermopsis angusticollis Hagen. Supplementing the wood diet of newly paired reproductives with a 0.05% uric acid solution resulted in both primaries and neotenics gaining less body mass. This may have occurred because the increased nitrogen content of their food allowed reproductives to consume less wood to meet their dietary needs, thereby reducing the mass of their gut contents. An abundance of exogenous nitrogen may have also stimulated females to excrete excess uric acid rather than store it, further reducing mass gain. Nitrogen supplementation resulted in significant increases in ovariole number and fecundity for neotenic females but not primary females. These results suggest that although enhancing dietary nitrogen may release newly molted neotenics from nutritional limitations on their fecundity, dietary enhancement with 0.05% uric acid does not significantly effect the reproductive development of recently dealated primaries. Possible reasons for each reproductive form’s response to enhanced dietary nitrogen are discussed.
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Social influence of larvae on ovarian maturation in primary and secondary reproductives of the dampwood termite Zootermopsis angusticollis
Physiological Entomology, 2001Co-Authors: Colin S. Brent, James F. A. TranielloAbstract:We tested the effect of larvae on the reproductive maturation and fecundity of female primary and secondary reproductives of the termite Zootermopsis angusticollis Hagen (Isoptera; Termopsidae) by varying the number of third- to fourth-instar larvae nesting with heterosexually paired reproductives. Primary females had higher fecundities and oviposited sooner when nesting with larvae than females lacking larvae, but gained less body mass and had fewer functional ovarioles per ovary. Secondary reproductives nesting with larvae also had higher fecundities and oviposited sooner, but unlike primaries, they gained more body mass and had more functional ovarioles when larvae were present. The specific response of both primary and secondary females varied according to the number of larvae present. These results suggest that larvae can enhance the fecundity of primary and secondary females. Larvae may increase the energetic reserves of reproductives by performing colony labour, reducing pathogen load and providing trophallactic secretions. Trophallaxis with larvae may significantly enhance endogenous nitrogen, which is a limiting nutrient for termites. Primary females, which normally need to produce a first brood quickly to initiate a new colony, may expend limited nutritional resources on oogenesis rather than producing additional ovarioles. Primaries may also store fewer energetic reserves for long-term brood care, and therefore gained less mass when larvae were present to attend to non-reproductive tasks. Secondary females may exhibit a greater positive response to larvae than primaries because they begin reproductive life with fewer stored resources and thus their development and fecundity are more dependent on assistance from larvae. Both primary and secondary reproductives may become more dependent on the contributions of larvae as their rate of egg production increases with subsequent bouts of oviposition.
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Disease resistance: a benefit of sociality in the dampwood termite Zootermopsis angusticollis (Isoptera: Termopsidae)
Behavioral Ecology and Sociobiology, 1998Co-Authors: Rebeca B. Rosengaus, Amy B. Maxmen, Laran E. Coates, James F. A. TranielloAbstract:The benefit of sociality in relation to disease susceptibility was studied in the dampwood termite Zootermopsis angusticollis. Although contact with high concentrations of fungal conidia is lethal, the survivorship of nymphs exposed to spore suspensions ranging from 6 × 106 to 2 × 108 spores/ml of the fungus Metarhizium anisopliae increased with group size. The survivorship (measured as LT50) of isolated individuals ranged from 3.0 to 4.8 days, but infected nymphs living in groups of 10 and 25 individuals survived significantly longer (5.6–8.3 and 5.6–9.1 days, respectively). In most cases, there were no significant differences in the survival distributions of the 10- and 25-termite groups. When nymphs were infected with concentrations of 7 × 101–7 × 104 spores/ml and allowed to interact with healthy nestmates, fungal infections were not contracted by the unexposed termites. Moreover, infected termites benefitted from social contact with unexposed nestmates: their survival rates were significantly higher than those of infected termites living with similarly infected nestmates. Allogrooming, which increased in frequency during and after exposure to conidia, appeared to remove potentially infectious spores from the cuticle, thus increasing termite survivorship. These results suggest that allogrooming plays a crucial role in the control of disease and its death hazard in termites. The infection-reducing advantage of group living may have been significant in the evolution of social behavior in the Isoptera.
Shigeyuki Koshikawa - One of the best experts on this subject based on the ideXlab platform.
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Histology of the hormone-producing glands in the damp-wood termite Hodotermopsis sjostedti (Isoptera, Termopsidae): A focus on soldier differentiation
Insectes Sociaux, 2008Co-Authors: Richard Cornette, Shigeyuki Koshikawa, Toru MiuraAbstract:Caste differentiation in termites depends on complex hormonal changes during postembryonic development. Juvenile hormone (JH) is a central player in this process. The present study examined histological changes in the main hormone-producing endocrine glands, the corpora allata and molt glands, in the Japanese dampwood termite Hodotermopsis sjostedti. We focused on the soldier caste differentiation pathway, which can be induced artificially using an analogue of JH. The corpora allata exhibited volumetric changes during soldier induction, reflecting variations in the quantity of cytoplasm. Corpora allata from alates and neotenics clearly showed differentiation accompanied by cell proliferation, preparing for the high-level JH production necessary for reproduction. However, the volume increase of corpora allata was not always correlated to high JH titers. In contrast, molt glands degenerated in the reproductive castes. The JH analogue induced hypertrophy of the molt glands, along with the formation of lacunae, possibly related to ecdysteroid production. The JH analogue effect, inducing soldier differentiation, was suggested to require both mimic of high JH titers and stimulation of the molt glands.
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Juvenile hormone titers and caste differentiation in the damp-wood termite Hodotermopsis sjostedti (Isoptera, Termopsidae).
Journal of Insect Physiology, 2008Co-Authors: Richard Cornette, Shigeyuki Koshikawa, Hiroki Gotoh, Toru MiuraAbstract:Abstract Termites are social insects, presenting morphologically distinct castes, performing specific tasks in the colony. The developmental processes underlying caste differentiation are mainly controlled by juvenile hormone (JH). Although many fragmentary data support this fact, there was no comparative work on JH titers during the caste differentiation processes. In this study, JH titer variation was investigated using a liquid chromatography-mass spectrometry (LC-MS) quantification method in all castes of the Japanese damp-wood termite Hodotermopsis sjostedti, especially focusing on the soldier caste differentiation pathway, which was induced by treatment with a JH analog. Hemolymph JH titers fluctuated between 20 and 720 pg/μl. A peak of JH was observed during molting events for the pseudergate stationary molt and presoldier differentiation, but this peak was absent prior to the imaginal molt. Soldier caste differentiation was generally associated with high JH titers and nymph to alate differentiation with low JH titers. However, JH titer rose in females during alate maturation, probably in relation to vitellogenesis. In comparison, JH titer was surprisingly low in neotenics. On the basis of these results in both natural and artificial conditions, the current model for JH action on termite caste differentiation is discussed and re-appraised.
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Effects of Precocenes on the Corpora Allata and the JH Titer in the Damp-Wood Termite Hodotermopsis sjostedti (Isoptera: Termopsidae)
Sociobiology, 2008Co-Authors: Hiroki Gotoh, Shigeyuki Koshikawa, Richard Cornette, Toru MiuraAbstract:Juvenile hormone (JH) is an insect hormone that is responsible for the control of a variety of physiological and developmental states. In termites, JH has long been considered to play an important role in caste differentiation, although the detailed mechanisms underlying the actions of the hormone are not well understood. In this study, we applied three types of precocenes, anti-JH agents that destroy the corpora allata (CA), to pseudergates (workers) of the damp-wood termite Hodotermopsis sjostedti, and evaluated the effects on the CA volume and JH titer after the treatments. Results showed degeneration of the CA at day 14 in the precocene-II-treated group, which was not observed in the control group. Conversely, no significant difference in the JH titer was apparent between precocene-II-treated groups and their corresponding controls. These results indicate that CA degeneration is not always correlated with a decrease inJH titer. Precocenes are thus not effective as anti-JH agents in the focal termite species. These findings indicate that simultaneous examination of JH titer and CA size are important considerations for evaluating the effects of anti-JH agents.
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differences in mechanosensory hairs among castes of the damp wood termite hodotermopsis sjostedti isoptera Termopsidae
Sociobiology, 2007Co-Authors: Yuki Ishikawa, Shigeyuki Koshikawa, Toru MiuraAbstract:Termites are one of the major groups of social insects, which comprise alates, workers (pseudergates), and soldiers within a species. These castes have different roles and behaviors, and undertake division of labor to increase the inclusive fitness of their colony. On the basis of the different behavioral repertoires, caste-specific neural modifications are predicted, such as modification of sensory systems, i.e., inputs into the nervous system. This study evaluated these sensory-system differences based on mechanoreceptive sensilla length among castes of the damp-wood termite Hodotermopsis sjostedti. We found that soldiers and alates had longer sensilla than pseudergates, and that this variation among castes differed with body region. Specifically, the differences were particularly conspicuous on head capsules and pronota, while sensilla on mouthparts and legs were of similar lengths among castes. It is proposed that soldiers and alates use these long mechanoreceptive structures to sense faint vibrations, an important capability for their defensive role in detecting enemies and cracks in nest wood.
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Caste-specific cytochrome P450 in the damp-wood termite Hodotermopsis sjostedti (Isoptera, Termopsidae).
Insect Molecular Biology, 2006Co-Authors: Richard Cornette, Tadao Matsumoto, Shigeyuki Koshikawa, Masaru Hojo, Toru MiuraAbstract:Termites are eusocial insects with a well-defined caste system, which is an example of polyphenism. This polyphenism is based on hormonally controlled differential gene expression. In the damp-wood termite Hodotermopsis sjostedti , we induced differentiation into the soldier caste by using juvenile hormone analogue treatment. We then investigated specific gene expression, which appeared during the hormonal response and triggered caste differentiation, using fluorescent differential display. A candidate cDNA sequence with similarity to cytochromes P450, CYP6AM1, was characterized and its transcript shown to be repressed between 1 and 3 days after hormone treatment. CYP6AM1 was specifically expressed in the fat body of pseudergates and soldiers. The putative function of this P450 is discussed with respect to the caste differentiation system.
Richard Cornette - One of the best experts on this subject based on the ideXlab platform.
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Chemical communication in termites: syn-4,6-Dimethylundecan-1-ol as 3 trail-following pheromone, syn-4,6-dimethylundecanal and 4 (5E)-2,6,10-trimethylundeca-5,9-dienal as the respective male and female sex 5 pheromones in Hodotermopsis sjoestedti (Is
Journal of Insect Physiology, 2011Co-Authors: M. J. Lacey, David Sillam-dussès, Alain Robert, Jana Krasulová, Irena Valterová, Etienne Sémon, Richard Cornette, Michal Hoskovec, Petr Zacek, Christian BordereauAbstract:The trail-following pheromone and sex pheromones were investigated in the Indomalayan termite Hodotermopsis sjoestedti belonging to the new family ArchoTermopsidae. Gas chromatography coupled to mass spectrometry (GC-MS) after solid phase microextraction (SPME) of the sternal gland secretion of pseudergates and trail-following bioassays demonstrated that the trailfollowing pheromone of H. sjoestedti was syn-4,6-dimethylundecan-1-ol, a new chemical structure for termite pheromones. GC-MS after SPME of the sternal gland secretion of alates also allowed the identification of sex-specific compounds. In female alates, the major sex-specific compound was identified as (5E)-2,6,10-trimethylundeca-5,9-dienal, a compound previously identified as the female sex pheromone of the termite Zootermopsis nevadensis. In male alates, the major sex-specific compound was identified as syn-4,6-dimethylundecanal, a homolog of syn-4,6-dimethyldodecanal, which has previously been confirmed as the male sex pheromone of Z. nevadensis. The presence of sex-specific compounds in alates of H. sjoestedti strongly suggests for this termite the presence of sex-specific pairing pheromones which were only known until now in Z. nevadensis. Our results showed therefore a close chemical relationship between the pheromones of the taxa Hodotermopsis and Zootermopsis and, in contrast, a clear difference with the taxa Stolotermes and Porotermes, which is in total agreement with the recent creation of the families ArchoTermopsidae and Stolotermitidae as a substitute for the former family Termopsidae.
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Histology of the hormone-producing glands in the damp-wood termite Hodotermopsis sjostedti (Isoptera, Termopsidae): A focus on soldier differentiation
Insectes Sociaux, 2008Co-Authors: Richard Cornette, Shigeyuki Koshikawa, Toru MiuraAbstract:Caste differentiation in termites depends on complex hormonal changes during postembryonic development. Juvenile hormone (JH) is a central player in this process. The present study examined histological changes in the main hormone-producing endocrine glands, the corpora allata and molt glands, in the Japanese dampwood termite Hodotermopsis sjostedti. We focused on the soldier caste differentiation pathway, which can be induced artificially using an analogue of JH. The corpora allata exhibited volumetric changes during soldier induction, reflecting variations in the quantity of cytoplasm. Corpora allata from alates and neotenics clearly showed differentiation accompanied by cell proliferation, preparing for the high-level JH production necessary for reproduction. However, the volume increase of corpora allata was not always correlated to high JH titers. In contrast, molt glands degenerated in the reproductive castes. The JH analogue induced hypertrophy of the molt glands, along with the formation of lacunae, possibly related to ecdysteroid production. The JH analogue effect, inducing soldier differentiation, was suggested to require both mimic of high JH titers and stimulation of the molt glands.
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Juvenile hormone titers and caste differentiation in the damp-wood termite Hodotermopsis sjostedti (Isoptera, Termopsidae).
Journal of Insect Physiology, 2008Co-Authors: Richard Cornette, Shigeyuki Koshikawa, Hiroki Gotoh, Toru MiuraAbstract:Abstract Termites are social insects, presenting morphologically distinct castes, performing specific tasks in the colony. The developmental processes underlying caste differentiation are mainly controlled by juvenile hormone (JH). Although many fragmentary data support this fact, there was no comparative work on JH titers during the caste differentiation processes. In this study, JH titer variation was investigated using a liquid chromatography-mass spectrometry (LC-MS) quantification method in all castes of the Japanese damp-wood termite Hodotermopsis sjostedti, especially focusing on the soldier caste differentiation pathway, which was induced by treatment with a JH analog. Hemolymph JH titers fluctuated between 20 and 720 pg/μl. A peak of JH was observed during molting events for the pseudergate stationary molt and presoldier differentiation, but this peak was absent prior to the imaginal molt. Soldier caste differentiation was generally associated with high JH titers and nymph to alate differentiation with low JH titers. However, JH titer rose in females during alate maturation, probably in relation to vitellogenesis. In comparison, JH titer was surprisingly low in neotenics. On the basis of these results in both natural and artificial conditions, the current model for JH action on termite caste differentiation is discussed and re-appraised.
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Effects of Precocenes on the Corpora Allata and the JH Titer in the Damp-Wood Termite Hodotermopsis sjostedti (Isoptera: Termopsidae)
Sociobiology, 2008Co-Authors: Hiroki Gotoh, Shigeyuki Koshikawa, Richard Cornette, Toru MiuraAbstract:Juvenile hormone (JH) is an insect hormone that is responsible for the control of a variety of physiological and developmental states. In termites, JH has long been considered to play an important role in caste differentiation, although the detailed mechanisms underlying the actions of the hormone are not well understood. In this study, we applied three types of precocenes, anti-JH agents that destroy the corpora allata (CA), to pseudergates (workers) of the damp-wood termite Hodotermopsis sjostedti, and evaluated the effects on the CA volume and JH titer after the treatments. Results showed degeneration of the CA at day 14 in the precocene-II-treated group, which was not observed in the control group. Conversely, no significant difference in the JH titer was apparent between precocene-II-treated groups and their corresponding controls. These results indicate that CA degeneration is not always correlated with a decrease inJH titer. Precocenes are thus not effective as anti-JH agents in the focal termite species. These findings indicate that simultaneous examination of JH titer and CA size are important considerations for evaluating the effects of anti-JH agents.
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Histological Analysis of Fat Body Development and Molting Events During Soldier Differentiation in the Damp-Wood Termite, Hodotermopsis sjostedti (Isoptera, Termopsidae)
Zoological Science, 2007Co-Authors: Richard Cornette, Tadao Matsumoto, Toru MiuraAbstract:The caste system of termites is well defined, with a high degree of polyphenism among colony members. Polyphenic caste characteristics are hormonally regulated, and juvenile hormone (JH) is particularly involved in caste determination, as is the case with many other social insects. In the present study, soldier differentiation in the damp-wood termite, Hodotermopsis sjostedti, was induced by treatment with a JH analog (pyriproxyfen) in order to establish the chronology of tissular modifications appearing in response to the hormone. The fat body is involved in the physiological events that prepare the insect for the molting transition. The development of the fat body started within three days after hormonal treatment, and it filled the entire abdominal cavity for about four days prior to the molt to presoldier, maintaining this state until the next molt to soldier. Fat body development was accompanied by the accumulation of protein granules in the cytoplasm, but these granules disappeared during the few days preceding the molt to presoldier. The timing of consumption of these storage proteins corresponded to the window of epidermal growth, which was conspicuous about 14 days after hormonal treatment, and synthesis of the new cuticle, which was initiated 10 days after treatment. We summarize the chronology of the histological events under hormonal control.
