Reticulitermes Grassei Research Articles

Survey of subterranean termites (Isoptera: Rhinotermitidae) in a managed silvicultural plantation in Portugal, using a line-intersection method (LIS)

Subterranean termites (Reticulitermes grassei) were surveyed over successive seasons in a managed eucalyptus plantation in southeastern Portugal for 26 months. Termite activity in seven diameter categories of lying dead wood was investigated by a modified line intersection method (LIS). Each item sampled was inspected and assessed for termite attack and for general (i.e. fungal) decay status using standard protocols. Line intersection is quantitative to the extent that it can link foraging and decay parameters to woody biovolume. It was found that termites selected items with larger diameter, the observed trend showing an exponential character with greater termite attack as diameter increased. Attack by termites was positively associated with prior decay by fungi. A clear positive relationship was shown between rainfall and total woody biovolume containing live termites, underlining the importance of moisture for termite activity. Subterranean termites appeared to be important wood decomposers in the woodland studied, with an average of 30% of lying dead wood branches showing signs of termite attack.

Tunnel geometry of the subterranean termite Reticulitermes grassei (Isoptera: Rhinotermitidae) in response to sand bulk density and the presence of food

AbstractThe cryptic habits of subterranean termites restricts detailed analysis of their foraging patterns in situ, but the process is evidently dominated by tunnel constructions connecting the nest with woody resources discovered within the territory of each colony. In this study, tunnel formation and orientation were studied experimentally in the termite Reticulitermes grassei (Clément), using 2‐dimensional laboratory foraging arenas containing fine sand as the substratum. The building of exploratory tunnels over a 10‐day period and the geometry of the resulting network are described. Fractal analysis showed that tunnel geometry had a fractal dimension, regardless of the total length tunnelled whether foragers encountered the food source or not. The bulk density of the sand in the arenas affected the distances tunnelled, with higher density reducing construction, but did not affect tunnel geometry. Tunnels were not discernibly orientated with respect to the positioning of the food source, even in a situation where termites had failed to find the food source at a distance of less than 50 mm, suggesting that volatiles from wood are not attractants.

Colony interactions in Reticulitermes grassei population assessed by molecular genetic methods

The cryptic habits of subterranean termites impair studies of colony delimitation and the organization of foraging. Whereas feeding sites can be identified and the movements of foragers between them can be assessed using traditional mark-release techniques, the assignment of the termites found at feeding sites to their parent colonies remains problematical. Thus the extent and overlap of individual colony foraging territories are unknown. We used microsatellite markers to delineate colonies of R. grassei and compared the results with data from a mark-release-recapture study (Nobre et al., 2007) carried out in the same population and over the same period of time. The majority of colonies exhibited only a single-feeding site, but presented, even at a local scale, a high degree of variability in colony structure and no evidence of inbreeding. F-statistics for some colonies were consistent with pleometrosis. The population as a whole contained individual colonies that were separately identified as Mendelian, mixed family or pleometrotic families. Furthermore, microsatellite data suggest that what was represented by the MRR technique as a single foraging group could be drawn from more than one colony. Colony delineation is discussed as a tool for understanding overall population structure and termite feeding strategies.

Coevolution of symbiotic spirochete diversity in lower termites.

The phylogenetic relationships of symbiotic spirochetes from five dry-wood feeding lower termites (Cryptotermes cavifrons, Heterotermes tenuis, Kalotermes flavicollis, Neotermes mona, and Reticulitermes grassei) was compared to those described in previous reports. The 16S rDNA bacterial genes were PCR-amplified from DNA isolated from intestinal samples using a spirochete-selective primer, and the 16S amplicons were cloned into Escherichia coli. Sequences of the cloned inserts were then used to determine closest relatives by comparison with published sequences. Clones sharing more than 97% sequence identity were grouped into the same phylotype. Forty-three new phylotypes were identified. These termite whole-gut-spirochetes fell into two previous defined clusters, designated as Treponema Clusters I and II, and one new Cluster III. Thirty-seven phylotypes were grouped in Cluster I. Cluster II comprised three phylotypes, two from Reticulitermes grassei (LJ029 and LJ012) and one from Heterotermes tenuis (LQ016). Three phylotypes, LK057, LK050 and LK028, were affiliated to Cluster III. Members of Cluster I showed the following characteristics: (i) spirochete phylotypes from a particular species of termite were more closely related to each other than to phylotypes of other termite species; (ii) spirochetes obtained from different genera of the same family, such as Cryptotermes sp., Kalotermes sp., and Neotermes sp., all from the family Kalotermitidae, were also related to each other. It was therefore concluded that spirochetes are specific symbionts that have coevolved with their respective species of termites, are stably harbored, and are closely related to members of the same termite family.

Estimation of foraging territories of Reticulitermes grassei through mark–release–recapture

AbstractSubterranean termites have highly cryptic life habits and their foraging activities are as a rule confined to below‐ground level gallery systems. Mark–release–recapture (MRR) using fat‐soluble histological dyes is a candidate method for the study of foraging dynamics and territories, but has not hitherto been standardized experimentally. A wide range of dye types and concentrations is reported in the literature. In this study, six potential dyes were evaluated at different concentrations for marking workers of Reticulitermes grassei (Clément) (Isoptera: Rhinotermitidae), under laboratory and simulated field conditions. Neutral red (1% wt/wt) was considered the most effective while showing acceptably low toxicity. In a subsequent field trial using dye impregnated into a wooden bait, the MMR procedure was used to map the foraging territory perimeter of a single colony. Assumptions inherent in the interpretation of MMR data are reviewed. To map the foraging territory perimeter by this method, two theoretical approaches are defined (a conservative and a non‐conservative hypothesis). We show that the approach adopted may affect the estimate obtained by as much as 100%. Results are discussed in the context of the ecology and behaviour of subterranean termite colonies.

Immunological and ultrastructural characterization of spirotrichonymphid flagellates from Reticulitermes grassei and R. flavipes (syn. R. santonensis), with special reference to Spirotrichonympha, Spironympha and Microjoenia

Five species of spirotrichonymphids representing three genera have been studied by light and immunofluorescence microscopy, and by transmission electron microscopy. The genus Spirotrichonympha, represented by S. flagellata from Reticulitermes grassei, is characterized by a compound axostyle composed of several fibers or subaxostyles. The genus Spironympha, represented by S. kofoidi from Reticulitermes flavipes (syn. R. santonensis) and by the two new species S. verticis and S. lanceata, is characterized by flagellar lines restricted to the anterior area and a simple, tubular axostyle. Spironympha verticis and S. lanceata are mainly distinguished by ultrastructural details of their flagellar lines and axostyle. These three Spironympha species were found in hosts identified as R. flavipes or R. santonensis, but not in R. grassei. This provides additional support for the synonymy of R. santonensis with R. flavipes recently demonstrated by molecular methods. The generic diagnosis of Microjoenia is emended, based on an ultrastructure study of M. fallax.

Distribution and genetic variation of Reticulitermes (Isoptera: Rhinotermitidae) in Portugal

The genus Reticulitermes has a Holartic distribution and is widely represented in southern Europe. It is established in Portugal, across the full range of ambient environmental conditions, using different types of wood resources, as available, and nesting ubiquitously in many types of soil. Sequencing of part of the mtDNA COII gene revealed that all the specimens sampled on a north-south transect of the country were Reticulitermes grassei (considered synonymous with R. lucifugus grassei). Nevertheless, an association between the genetic and the geographical distances of sampled specimens was shown, leading to the conclusion that discrete termite populations have differentiated in situ. The geographic component of the genetic polymorphism should be the subject for further research.

The breeding system and population structure of the termite Reticulitermes grassei in Southwestern France

We assessed colony and population structure in three French populations of the termite Reticulitermes grassei using eight polymorphic microsatellite loci. Although most colonies contained the offspring of multiple, highly related replacement reproductives (complex families), some contained the offspring of a single pair of reproductives (simple families), and the proportion of such colonies varied across populations. Populations also showed variability in the numbers of reproductives within complex families; the F-statistics of these families in one population were consistent with having upwards of 100 replacement reproductives, while in another population these colonies contained fewer than 10 pairs of reproductives. Colony boundaries in all populations were well defined, in spite of reports of a widespread breakdown in nestmate recognition and unicolonial populations of R. grassei from these regions in France. A second unexpected finding was a lack of significant isolation by distance among colonies within populations, indicating that colony reproduction by budding was rare or absent. The lack of this form of colony reproduction even within populations where it is expected to be common suggested that the propensity for colony budding may not be as common as suggested by the literature.

An application of the independent component analysis to monitor acoustic emission signals generated by termite activity in wood

In this paper an extended robust independent components analysis (ERICA) algorithm based on cumulants is applied to identify vibrational alarm signals generated by soldier termites in southern Spain (reticulitermes grassei), by drumming their heads against the substratum, and measured by low cost equipment. A seismic accelerometer is employed to strongly characterize these acoustic emissions. To support the proposed technique, vibrational signals from a low cost microphone have been mixed with known signals, and the mixtures processed by ERICA. The experimental results confirm the validity of the proposed method, which has been taken as the basis for the development of a low cost, non-invasive, termite detection system.