Identification by GC-EAD of the two-component trail-following pheromone of Prorhinotermes simplex (Isoptera, Rhinotermitidae, Prorhinotermitinae)

GC/MS analysis confirmed that neocembrene is the major component of the trail pheromone in the three species of the termite genus Prorhinotermes (P. simplex, P. canalifrons, P. inopinatus). In addition, EAG and GC-EAD experiments with P. simplex strongly suggest that dodecatrienol is a quantitatively minor component but a qualitatively important component of this trail pheromone. Trail-following bioassays confirmed the two-component nature of the trail pheromone. This is the first report of the use of the GC-EAD for the identification of trail pheromone in termites. These original results underline once again the special phylogenetic status of the Prorhinotermitinae among Rhinotermitidae.     

Inhibition of Metarhizium anisopliae in the alimentary tract of the eastern subterranean termite Reticulitermes flavipes

Reticulitermes flavipes workers were individually inoculated with 10,000 conidia of the entomopathogenic fungus Metarhizium anisopliae. After being kept in groups of 20 individuals for 1-6 d, histopathological approach showed that most of the inoculated conidia were groomed from the surface of the cuticle by nestmates within 24 h, and that a large number of conidia was subsequently found in different parts of the gut of the groomers. Our observations showed that, among thousands of conidia found in the termite’s gut, conidial germination never occurred in all inspected specimens, even when the conidia had the chance to bind to the surface of the cuticular lining of the gut. In addition, when termites were left for decomposition several days after death caused by an external infection of M. anisopliae, the hyphal growth was generalized in the body cavity of the cadaver, but was never observed in the lumen of the gut even 2 d post-mortem. Our observation suggests that the putative biochemicals involved in the termite’s gut defense against fungal pathogens are from multiple origins.     

Cellular encapsulation in the eastern subterranean termite, Reticulitermes flavipes (Isoptera), against infection by the entomopathogenic fungus Metarhizium anisopliae

Reticulitermes flavipes workers were topically inoculated with ≈10,000 conidia of the entomopathogenic fungus Metarhizium anisopliae. After being kept in groups of 20 individuals for 1-9 d, histopathological examination showed that termites had an individual immune reaction. The nodule formation at the point of entrance of the fungal hyphae was identified as a cellular encapsulation and the different steps in the nodule formation are described. The relative number of hemocytes per termite increased 24 h after fungal exposure and remained high in the hemolymph for at least 3 d before decreasing back to pre-exposure levels. The role of an individual immune cellular reaction in social insects is discussed.     

Deciphering the synergism of endogenous glycoside hydrolase families 1 and 9 from Coptotermes gestroi

Termites can degrade up to 90% of the lignocellulose they ingest using a repertoire of endogenous and symbiotic degrading enzymes. Termites have been shown to secrete two main glycoside hydrolases, which are GH1 (EC 3.2.1.21) and GH9 (EC 3.2.1.4) members. However, the molecular mechanism for lignocellulose degradation by these enzymes remains poorly understood. The present study was conducted to understand the synergistic relationship between GH9 (CgEG1) and GH1 (CgBG1) from Coptotermes gestroi, which is considered the major urban pest of São Paulo State in Brazil. The goal of this work was to decipher the mode of operation of CgEG1 and CgBG1 through a comprehensive biochemical analysis and molecular docking studies. There was outstanding degree of synergy in degrading glucose polymers for the production of glucose as a result of the endo-β-1,4-glucosidase and exo-β-1,4-glucosidase degradation capability of CgEG1 in concert with the high catalytic performance of CgBG1, which rapidly converts the oligomers into glucose. Our data not only provide an increased comprehension regarding the synergistic mechanism of these two enzymes for cellulose saccharification but also give insight about the role of these two enzymes in termite biology, which can provide the foundation for the development of a number of important applied research topics, such as the control of termites as pests as well as the development of technologies for lignocellulose-to-bioproduct applications.     

Evaluation of ACQ-D treated Chinese fir and Mongolian Scots pine with different post-treatments after 20 months of exposure

The field test of alkaline copper quat-type D (ACQ-D) treated Chinese fir (Cunninghamia lanceolata Hook.) and Mongolian Scots pine (Pinus sylvestris Linn. var. mongolica Litv.) stakes after different post-treatments was performed in two test plots (Chengdu and Guangzhou, China). The ACQ-D treatments used two concentration levels (0.5 and 1.1%) and four different post-treatments: air drying for 1 month (AD), conditioning at 70 °C and 80% relative humidity for 24 h (HC), oven drying at 110 °C for 24 h (DO) and boiling in water for 15 h (HW). The decay and termite ratings of the stakes after 6 and 20 months of exposure were recorded according to the method described in AWPA standard E07-07. The copper retention and compression strength parallel to grain before and after exposure were also compared. The results showed that Chinese fir had slightly better natural durability than Mongolian Scots pine but the untreated sapwood stakes for both wood species were mostly destroyed after 20 months exposure. After ACQ-D treatment, the sapwood of both wood species showed much better biological performance. Among the four post-treatments, HC exhibited the best performance by showing excellent biological resistance, less copper depletion and a slight reduction in compression strength after 20 months outdoor exposure. While the performance of the other post-treated stakes were impaired heavily in some cases in terms of wood species, test plots and the concentration levels of ACQ-D solutions. Furthermore, the study confirms that ACQ-D treated plantation-grown Chinese fir could be used for outdoor above ground and ground-contact applications.     

Efficacy of karanjin and phorbol ester fraction against termites (Odontotermes obesus)

The non-edible oil seeds of Jatropha curcas (physic nut) and Pongamia pinnata (karanja) contain some toxic components (phorbol esters in J. curcas and karanjin in P. pinnata), which may be used as biopesticides. In this study, the active components of J. curcas and P. pinnata oil were extracted and their efficacy against the termites Odontotermes obesus (Rambur), was tested. The phorbol ester fraction of J. curcas and karanjin of P. pinnata oil were found to be effective against termites. A mortality rate of 100% was achieved in 6 h with karanjin and in 12 h with phorbol ester fraction. The LC₅₀ levels of karanjin and phorbol esters fractions were 0.038 and 0.071 g ml⁻¹, respectively, after 24 h at a 95% (0.05) confidence limit.     

Effect of lectins from Opuntia ficus indica cladodes and Moringa oleifera seeds on survival of Nasutitermes corniger

Biodegradation by termites is a serious problem for wood and crop industries worldwide, and new environmentally friendly alternatives for termite control have been developed. This work investigated the effects of crude and purified preparations containing lectins from Opuntia ficus indica cladodes (OfiL) and Moringa oleifera seeds (WSMoL and cMoL) on Nasutitermes corniger workers and soldiers. Purified OfiL was more active than cladode extracts, showing a stronger termiticidal activity against workers (LC₅₀ of 0.116 mg ml⁻¹) than against soldiers. OfiL was active against soldiers only at 1.5 mg ml⁻¹. All preparations containing WSMoL and cMoL were active only at concentrations of 1.0 and 1.5 mg ml⁻¹. The tested preparations did not exert repellent activity against N. corniger. OfiL was able to kill workers and therefore is potentially a new tool for N. corniger control; as a consequence, this lectin could disturb organization, structure, and maintenance of termite colonies.     

Isolation of cockroach Phe-Gly-Leu-amide allatostatins from the termite Reticulitermes flavipes and their effect on juvenile hormone synthesis

Immunoreactivity to cockroach Diploptera punctata allatostatin-7 (Dippu AST-7) has been demonstrated previously in axons innervating the corpora allata of the termite Reticulitermes flavipes. This peptide and Dippu AST-11 inhibited juvenile hormone (JH) synthesis by corpora allata (CA) of brachypterous neotenic reproductives (secondary reproductives) of termites. The present study shows that R. flavipes CA are also inhibited by Dippu AST-2, AST-5, AST-8, and AST-9 at approximately the same rank order of potency as demonstrated in D. punctata. Another allatostatin from Periplaneta americana (Peram AST-12) also inhibits JH synthesis by R. flavipes CA. Sensitivity to the allatostatins is higher in glands with low rates of JH synthesis than in those with relatively high JH synthetic rates as has been demonstrated in CA from male and female secondary reproductives as well as in those from non-egg-laying and egg-laying females. The identical inhibitory effects of R. flavipes brain extract on CA from both D. punctata and R. flavipes and the isolation and identification of five cockroach allatostatins (Dippu AST-1, AST-2, AST-5, AST-8, and Peram AST-12) from termite brain extract reflect the close relationship between cockroaches and termites.     

Record of a gregarine (Apicomplexa: Neogregarinida) in the abdomen of the termite Coptotermes gestroi (Isoptera, Rhinotermitidae)

Coptotermes gestroi is an exotic species of termite that is a pest of great economical importance in Brazil. This paper relates the occurrence of a coelomic gregarine (Apicomplexa: Neogregarinida) in the abdomen of the foraging workers recently collected from field colonies of this termite. The termite hosts presented large, white abdomens because they carried 1 up to 3 cysts of gregarines filled with numerous lemon-shaped spores. Earlier developmental stages of this gregarine were not observed in the scanning microscope preparations nor in the histological slides of the infected termites. However, the lemon-shaped spores suggest a parasite gregarine of Mattesia genus, family Lipotrophidae.