Search

Behavioral lab bioassays involving termites must be promptly performed to allow intended observations prior to death from dissecation, typical of these soft-bodied insects. To this end, topic markers have been proposed as an alternative to histological stains which, while not always toxic are inevitably lengthy to apply. Among recommended topic markers, gouache is easy to apply, dries out quickly, but it is known affect termites in the long run, being suitable only to short-term bioassays. Its alternative, colored glue, is also easy to apply, but it takes long to dry and it is too dense and heavy, being thus prone to affect termite walking patterns. Here we tested a mix of gouache and colored glue aiming to combine the qualities of both into a suitable topical marker for Cornitermes cumulans termites. Similar patterns of survival presented by marked and unmarked termites ruled out concerns about toxicity of this mixture. Such results were consistent across distinct group densities evidencing that the mixture does not interfere with, nor it is affected by, crowding effects. Because crowding regulates interindividual interactions and these underlie most behaviors, the mixture can be thought to be suitable to behavioral studies. We argue that this 1:2 glue:gouache mixture is an excellent alternative to mark termites for lab bioassays. Being atoxic, cheap, easy to apply, and non-invasive, this mixture may happen to be useful not only for termites but also in bioassaying other similarly soft-bodied insects. Resumo Bioensaios comportamentais em laboratório com cupins devem ser realizados rapidamente a fim de garantir observações antes da morte por dissecação, típico desses insetos de corpo mole. Para este fim, marcadores tópicos têm sido propostos como uma alternativa para marcadores histológicos que, embora nem sempre tóxico, possuem uma aplicação demorada. Entre os marcadores tópicos recomendados, tinta guache é de fácil aplicação, rápida secagem, porém afeta os cupins em bioensaios longos, sendo adequado apenas para bioensaios curtos. Sua alternativa, cola colorida, também é de fácil aplicação mas leva muito tempo para secar e é muito denso e pesado, afetando os padrões de caminhamento dos cupins. No presente estudo, nós testamos uma mistura de tinta guache e cola colorida objetivando combinar as qualidades de ambos os marcadores tópicos em um marcador tópico adequado para Cornitermes cumulans. Padrões similares de sobrevivência entre cupins marcados e controle indicam a ausência de toxicidade na mistura de tinta guache e cola colorida. Tais resultados são consistentes em grupos de densidades distintas, o que comprova que a mistura não interfere, nem sofre efeitos de aglomeração. Uma vez que a aglomeração regula as interações inter-individuais e afetam a maioria dos comportamentos, a mistura pode ser adequada para estudos comportamentais. Nós argumentamos que a mistura de tinta guache e cola (1:2) é uma excelente alternativa como marcador tópico em cupins para bioensaios em laboratório. Sendo atóxico, barato, fácil de aplicar e não invasivo, esta mistura pode ser útil não só para os cupins, mas também em bioensaios com outros insetos de corpo mole.

The study of self-propelled particles is a fast growing research topic where biological inspired movement is increasingly becoming of much interest. A relevant example is the collective motion of social insects, whose variety and complexity offer fertile grounds for theoretical abstractions. It has been demonstrated that the collective motion involved in the searching behaviour of termites is consistent with self-similarity, anomalous diffusion and Lévy walks. In this work we use visibility graphs—a method that maps time series into graphs and quantifies the signal complexity via graph topological metrics—in the context of social insects foraging trajectories extracted from experiments. Our analysis indicates that the patterns observed for isolated termites change qualitatively when the termite density is increased, and such change cannot be explained by jamming effects only, pointing to collective effects emerging due to non-trivial foraging interactions between insects as the cause. Moreover, we find that such onset of complexity is maximised for intermediate termite densities., This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior—Brasil (CAPES)—Finance Code 001, as well as the Minas Gerais State Foundation for the Support of Scientific Research (Fapemig), and the Brazilian National Council for Scientific Development (CNPq). We are grateful to Prof. Eraldo Lima for granting access to Ethovision and the facilities of the Semiochemicals lab at Federal Univ. of Viçosa. ODS holds CNPq Fellowship # PQ 307990/2017-6. SGA holds CNPq Fellowship # PQ 306778/2015-7. O M acknowledges a financial support from a UNAM-PAPIIT Grant # IN107619 and a CIENCIA SEM FRONTEIRAS grant from CAPES-Brazil (2013-2015). O M also thanks the Lab of Termitology at UFV-Brazil for their hospitality during multiple research visits to them. L L acknowledges funding from project DYNDEEP (EUR2021-122007) and project MISLAND (PID2020-114324GB-C22), both projects funded by Spanish Ministry of Science and Innovation.

Palestra onde se discute o que é Ciência Aberta e porque devemos adotá-la.

As the number or density of interacting individuals in a social group increases, a transition can develop from uncorrelated and disordered behavior of the individuals to a collective coherent pattern. We expand this observation by exploring the fine details of termite movement patterns to demonstrate that the value of the scaling exponent [Formula: see text] of a power law describing the Lévy walk of an individual is modified collectively as the density of animals in the group changes. This effect is absent when termites interact with inert obstacles. We also show that the network of encounters and interactions among specific individuals is selective, resembling a preferential attachment mechanism that is important for social networking. Our data strongly suggest that preferential attachments, a phenomenon not reported previously, and favorite interactions with a limited number of acquaintances are responsible for the generation of Lévy movement patterns in these social insects.

Most animals move intermittently, pausing or slowing down for short moments and short moves, and darting away towards a new location where to hover again. This pattern occurs at a range of spatial and temporal scales (thence, resembling 'scale-free'), from the quick inspection of local areas to the sum of all movements performed from birth to death. While this pattern has been extensively described, its proximate drivers remain open to debate. A current hypothesis states that underlying proximate generative mechanisms of intermittent movement of animals are linked to external stimuli, e.g., interactions with the abiotic environment, resources, and other individuals. Here we investigated a prediction from this hypothesis, using termites as a biological model. We verified whether the social background in which a termite is inserted will modify the parameters of its intermittent scale-free spatial displacement. This relates to the hypothesis because it inspects how do external stimuli coming from intraspecifics can affect this type of movement. We tracked the trajectories of a focal termite confined along its nestmates in experimental clueless arenas, every 0.5 s along about six hours. Arenas varied in group size and comprised 22 distinct caste compositions, yielding 75 trackings (400 h) and more than two million Cartesian coordinates. Most of these trajectories (96% or 72/75) were classified as intermittent scale free (Lévy-like), indicating prevalence of this type of movement over non-Lévy-like ones (P=1.62×10

Metalliferous soils can selectively shape plant species’ physiology towards tolerance of high metal concentrations that are usually toxic to organisms. Some adapted plant species tolerate and accumulate metal in their tissues. These metals can serve as an elemental defence but can also decrease growth. Our investigation explored the capacity of natural metal accumulation in a tropical tree species, Eremanthus erythropappus (Asteraceae) and the effects of such bioaccumulation on plant responses to herbivory. Seedlings of E. erythropappus were grown in a glasshouse on soils that represented a metal concentration gradient (Al, Cu, Fe, Mn and Zn), and then the exposed plants were fed to the herbivores in a natural habitat. The effect of herbivory on plant growth was significantly mediated by foliar metal ion concentrations. The results suggest that herbivory effects on these plants change from negative to positive depending on soil metal concentration. Hence, these results provide quantitative evidence for a previously unsuspected interaction between herbivory and metal bioaccumulation on plant growth.

The journal Sociobiology announces the adoption of a series of editorial innovations that aim to speed up review and publication time, to select high quality articles for publication, to adopt transparent and ethical editorial standards and to reinforce the culture of open acess scientific publishing.

1. Termitophily in some rove beetles is commonly attributed to the striking termite worker resemblance that is provided by the beetles' hypertrophic (‘physogastric’) abdomen. However, a termite nest may offer to a termitophile additional benefits, such as a continuously repaired shelter. 2. This could apply to Corotoca melantho (Aleocharinae: Corotocini), a viviparous obligatory termitophile staphylinid beetle species. While conferring morphological congruence to its host worker termites, its physogastry may impair mobility, leading to vulnerability and the need for a secure environment. It seems plausible to hypothesise that physogastry in C. melantho would imply in interactions between this termitophile and its host termites as well as its host termitarium. 3. This study provides evidence to build such a hypothesis by inspecting the morpho‐anatomical reproductive traits of this termitophile. It was found that a gradient of growth stages of embryos and larvae in the oviduct explains physogastry in females while pointing to iteroparity. The asynchronous development of oocytes in females, combined with a full developing sequence of sperm cells indicative of continuous spermatogenesis in males, suggests frequent matings. 4. While improving guest–host similarity, physogastry and flightlessness should confer vulnerability to pregnant females, forcing C. melantho to seek close and sheltered environments. These could facilitate the frequent male–female contacts demanded by iteroparity. It is possible, therefore, that physogastry in C. melantho is not only associated with the termites themselves but also with the physical structure of the termitarium. Thus, C. melantho can be hypothesised to be a termitariophile in addition to being a termitophile.

Symbiotic associations underlie hierarchical evolutionary transitions being crucial to understanding biological complexity. But which proximate triggers promote the first successful contact between guests and their hosts? We tackle this problem, studying the macro-symbiotic model system comprised by two termite species (Blattodea: Isoptera) cohabiting termitaria as a host and its obligatory inquiline. We tested the hypothesis that ergonomic adjustments in resource allocation force termite colonies to trade current defence for future reproduction, thence easing inquiline infiltration. To do so, we combined mathematical modelling and field bioassays. Initially, we created a dynamic model to inspect colony’s resource allocation as a result of the competition between a physical “defence specialist” caste (soldiers) competing for resources with a reproductive caste (alates) and with a physical resource-gatherer specialist caste (workers). This model differs from Oster & Wilson’s “bang–bang” model by the explicit inclusion of solders as a physical defence specialist. Then, we sought empirical support for the end results of our model (i) censusing the population and (ii) measuring the patrolling efforts by soldiers, in 154 mature field termite colonies along a year-long reproductive season. Finally, we verified in the field whether reproducing termite colonies would be more likely to house inquilines than colonies still not at reproductive stage. Modelling and field results matched closely, supporting our hypothesis. Inquiline termites (Inquilinitermes microcerus) sneaked into nests of host termites (Constrictotermes cyphergaster) as these latter colonies undergone a defence-reproduction tradeoff. As the host colony entered reproduction, their soldier numbers and patrolling waned, enhancing the proneness of infiltration by obligatory inquilines. Our results indicate that defence-reproduction tradeoffs, more than a strategy to optimise resource use, can be important initiators of symbioses by loosening self/non-self discrimination and enhancing tolerance. We speculate that, if changes in the internal stasis of an organism or superorganism can enhance tolerance, it could be invoked to explain why symbioses are frequently enhanced by stress and disturbance.

Symbiosis, the living‐together of unlike organisms, underlies every major transition in evolution and pervades most ecological dynamics. Among examples of symbioses, the simultaneous occupation of a termite nest by its builder termites and intruding invertebrate species (so‐called termitophily) provides suitable macroscopic scenarios for the study of species coexistence in confined environments. Current evidence on termitophily abounds for dynamics occurring at the interindividual level within the termitarium, but is insufficient for broader scales such as the community and the landscape. Here, we inspect the effects of abiotic disturbance on termitophile presence and function in termitaria at these broader scales. To do so, we censused the termitophile communities inhabiting 30 termitaria of distinct volumes which had been exposed to increasing degrees of fire‐induced disturbance in a savanna‐like ecosystem in southeastern Brazil. We provide evidence that such an abiotic disturbance can ease the living‐together of termitophiles and termites. Putative processes facilitating these symbioses, however, varied according to the invader. For nonsocial invaders, disturbance seemed to boost coexistence with termites via the habitat amelioration that termitaria provided under wildfire, as suggested by the positive correlation between disturbance degree and termitophile abundance and richness. As for social invaders (ants), disturbance seemed to enhance associational defenses with termites, as suggested by the negative correlation between the presence of ant colonies and the richness and abundance of other termitarium‐cohabiting termitophiles. It is then apparent that disturbance‐modulated distinct symbioses in these termite nests.

Plants produce volatile chemical compounds that can negatively affect the preference (antixenosis) or the performance (antibiosis) of herbivorous insects. It is thought that these volatile compounds are used as cues by herbivorous insects to determine the suitability of the plant for egg deposition and, hence, offspring performance. Here, we investigated whether volatiles produced by tomato plants play a role in modulating the flight and oviposition behavior of mated Tuta absoluta females. We found that the behavioral steps displayed by mated females did not differ when they flew toward resistant or susceptible tomato genotypes, but they reached the susceptible genotypes faster than the resistant ones. Moreover, females landed more often and laid more eggs on the most susceptible genotype, the Santa Clara variety. Because this variety is known to be of high quality for the development of T. absoluta larvae, the female’s decision to land and lay more eggs on this genotype seems to be mainly to maximize offspring performance. However, this is not so straightforward because the proportion of landings and eggs laid by T. absoluta on another susceptible genotype tested in this study was not significantly higher than on the resistant genotypes. Finally, although future studies are still needed, considering the antixenotic and antibiotic traits of the resistant genotypes studied here, they are likely to succeed if used in integrated pest management.

The heterospecific termite-termite cohabitation in a single termitarium, so called in-quilinism, is a common event whose basal mechanisms remain hypothetical. While some termite hosts have plenty of inquilines, others house only a few. Among these, Constrictotermes cyphergaster are frequently found cohabiting with a single obligate inquiline species but have been unknown to house any facultative inquilines. Here we present the first record of facultative inquilines (Embiratermes festivellus, Nasutitermes kemneri, Obitusitermes bacchanalis and Subulitermes) to this host, evidencing that this was unlikely to have happened fortuitously. In an attempt to pose hypotheses on the mechanisms behind such invasions, we explored likely connections between the settlement of obligate and facultative inquilines and nest wall’s physical traits. We found that nests bearing atypical external walls (moist, eroded, and partially covered by mosses) held higher richness of facultative inquilines than nests presenting walls void of such traits (χ2 = 8.3965, 1 df, n = 17, P = 0.0038). The presence of healthy host colonies in all nests, including the atypical ones, reinforces the hypothesis that the settlement of these facultative inquilines depends less on host colonies biotic status and more on abiotic features associated to the nest. In addition, the presence of obligate inquilines was not affected by the nest wall status (χ2 = 8.3965, 1 df, n = 17, P = 0.0038), implying that invasion by facultative and obligate inquilines in these nests would obey distinct restrictions. While warning that these hypotheses require further testing, we suggest that their understanding could shed light on the determinants of cohabitation not only in C. cyphergaster but in termites in general. cohabitation interspecific interaction nest invasion barriers

Artigo da Entomologia Termite inquilines specialize on living in and feeding on a host termite nest. However, the mechanisms allowing survival of two mutually hostile populations confined to a single nest are not understood. Here we report on inquiline termites that respond to their host's alarm cues. Upon detecting these cues, the inquilines do not join in with the host's nest defence, but use this information for their own benefit, to escape danger. Using behavioural bioassays under laboratory conditions, we show that the obligatory inquiline Inquilinitermes microcerus (Termitidae: Termitinae) responds both to its own alarm signal and to alarm cues from its host, Constrictotermes cyphergaster (Termitidae: Nasutitermitinae). Conversely, this host responded only to its own alarm signal. Despite perceiving their host's alarm cues, inquilines were never observed sharing nest defence with their host in experimentally damaged nests in the field. We argue that this allows inquilines not only to minimize encounters and hence conflict with their hosts, but also to use their host alarm information to escape the host's enemies, which are also likely to be enemies of the inquilines. Our results show a new benefit that inquilines gain from the host, and we discuss the inquiline way-of-life from an evolutionary perspective, as the outcome of constraints and benefits imposed by living in host nests.

Resource can regulate animal foraging range, which in turn determines the chances of species co-occurrence. Here, we addressed the question of whether resource determines the co-occurrence of soil-forager termite species (i.e. those foraging in subterranean tunnels). Eight quadrats (4 × 4 m) were marked in seven sites of Brazilian Atlantic rainforests, giving a total area sampled of 896 m2. Inside each quadrat, we measured the co-occurrence of soil forager species and the resource suitability (N:C ratio of the soil and litter biomass). The number of records of more than one soil-forager termite species at a single foraging spot, relative to the total number of foraging spots detected in each forest, was taken as a surrogate for spatial co-occurrence. We tested whether termite co-occurrence was mediated by random or nonrandom processes. Data were subjected to linear regression to test how the termite species co-occurrence responds to resources. We compared this method with a null model analysis. Soil-forager termites comprised 885 records, 20 species and 14 genera. From those records, 29% indicated species co-occurrence. Co-occurrence was not random: occurred more frequently when resource suitability was very high or very low. This result suggests an optimised use of space by termite communities.

1. Termites are important ecosystem engineers that improve primary productivity in trees and animal diversity outside their mounds. However, their ecological relationship with the species nesting inside their mounds is poorly understood. 2. The presence of termite cohabitant colonies inside 145 Cornitermes cumulans mounds of known size and location was recorded. Using network-theoretical methods in conjunction with a suite of statistical analyses, the relative influence of biotic and abiotic drivers of termite within-mound diversity on the composition and species richness of the termite community was investigated, specifically builder presence and physical aspects of the mound. 3. We found that richness inside the mound increases with mound size, and the species similarity between mounds decreases with distance. The physical attributes (abiotic drivers) of termite mounds (size and relative distance to other mounds) are the strongest predictors of termite species richness and composition. The biotic driver (presence of a builder colony) has an important, though smaller, negative effect on within-mound termite species richness. 4. The findings suggest that the termites' physical manipulation of their environment is an important driver of within-mound community diversity. More generally, the approach taken here, using a combination of statistical and network-theoretical methods, can be used to determine the relative importance of abiotic and biotic drivers of diversity in a wide range of communities of interacting species.

The presence of foreign organisms in the colonies of social insects could affect energy allocation to growth and reproduction of these hosts. Highly specialized invaders of such long-lived hosts, however, can be selected to be less harmful. After all, it pays for these symbionts to keep their host's good health thereby prolonging cohabitation in the homeostatic environment of the termite colony. Here, we investigated such a hypothesis, focusing on populational parameters of a termite host sharing its nest with an obligatory termite inquiline. To this end, 19 natural colonies of Constrictotermes cyphergaster (Silvestri, 1901) (Termitidae: Nasutitermitinae) were sampled and the (i) number of individuals, (ii) proportion of soldier/workers in the colonies, and (iii) presence/absence of obligatory inquiline Inquilinitermes microcerus (Silvestri, 1901) (Termitidae: Termitinae) were measured. Results revealed a negative correlation between the number of individuals and the proportion of soldier/workers in the host colonies with the presence of I. microcerus colonies. In search of causal mechanisms for such a correlation, we inspected life history traits of both, inquilines and hosts, hypothesizing that such a result could indicate either (i) a dampening effect of the inquiline upon its host population or (ii) the coincidence of the moment of inquiline infiltration with the natural reduction of C. cyphergaster populational growth at the onset of its reproductive phase.

Inter-specific symbiotic links are often reinforced by morphological, physiological, or behavioural trait modification undergone by the associated species. In some cases, such as in physogastric termitophile staphylinids, such modifications do facilitate the social interaction. Here we inspect chemical traits of the physogastric staphylinid Corotoca melantho (Insecta: Coleoptera) and its termite host Constrictotermes cyphergaster (Insecta: Blattodea: Isoptera), aiming to verify whether staphylinids resemble their host. First, we compared CHC profiles of hosts and guests within and among termitaria, to gather evidence on the origin of such profiles in guests. Then, we examined nitrogen and carbon isotopic signatures of these cohabitants to inspect whether chemical disguise is achieved by predation of host workers by staphylinids. Beetles presented CHC more similar to the CHC of their cohabiting termites than to (i) their conspecifics and (ii) termites from another nest, thereby favouring the hypothesis on CHC acquisition by guests. Isotopic signatures revealed that such similarities could not be majorly determined by share nutrition between these cohabitants. In general, our results evidenced that chemical disguise in termitophiles may function as a strategy for social integration in morphological mimics.

In termites, substrate-borne vibrations play an important role in communication among nestmates. The adaptive significance of such an ability has led to an ever-increasing number of studies aimed at improving knowledge on vibroacoustic communication in these insects. Such studies are commonly carried out in laboratory arenas consisting of Petri dishes made of plastic or glass. However, the rigidness of such materials may limit the transmission of vibrational waves impairing accurate records of the feeble vibrations produced by termites. This is one of the reasons why such experiments must be carried out under strictly controlled conditions, using extremely sensitive equipment, usually connected to amplifiers. If, instead, arenas bear a flexible floor (hence simulating a tympanum), vibrations might not be dampened or even easily amplified, thereby overcoming the need for such a specialized setup. Here we test such a hypothesis, using an accelerometer to measure and record vibrations whose intensity was tailored to mimic the feeble vibrations of a small termite species, Constrictotermes cyphergaster. Results support the notion that tympanic arenas portray such vibrations far more accurately than arenas made of plastic or glass. We hence recommend this type of arena as a cheap, albeit accurate, alternative in studies of vibroacoustic behaviors of termites and other insects of comparable size, especially in situations where noise is minimally controlled. These arenas, then, can be useful in conducting such studies just after termite collection in remote regions where well-equipped labs are not available. In doing so, we minimize the stress involved in transporting termites over long distances.

Laboratory assays using animals require strategies to avoid stress and keep animals alive as long as the test demands. Termites live in a constant dark environment in their nests, but in studies that demand video recording, termites are exposed to light. Since light is a condition opposed to what termites naturally live, it is possible that this condition might stress termites. To find how suitable are lights in video recording termites, we evaluated the effect of infrared lights and cold white light in the survival of workers of \textit{Cornitermes cumulans} (Termitidae: Syntermitinae) confined in Petri dishes. We compared the survival of termites in the light treatments and termites kept in the dark. As our null hypothesis, time until death would not differ between termites exposed to cold white lights, infrared lights, and termites kept in the dark. We found that the survival of \textit{C. cumulans} workers was not affected by light since there was no statistical difference in the mortality between the three treatments. Here we show that both infrared lights and cold white lights can be used in lab assays to video record termites, as such lights did not affect workers survival.

Social insects can live in densely populated colonies where mortality risks are increased by inter-individual transmission of pathogens. Thus, diverse strategies are employed against such infection risks, including the display of sophisticated behavioural traits. Considering that the waste of the leaf-cutting ant contains pathogens, worker ants that tend the fungus garden – here called fungus garden workers – should exhibit avoidance behaviour toward midden workers to minimize contamination of the fungus garden. We studied the behaviour of garden workers when confronted with midden and forager workers in colonies of Atta sexdens (Linnaeus, 1758). Eight colonies were used: in four colonies, the midden was inoculated with spores of the weed fungus Escovopsis weberi (Muchovej and Della Lucia, 1990), and in the other four colonies there was no artificial contamination. Grooming, self-grooming, inspection, immobilization and aggression behaviours were quantified. Additionally, we checked for fungal con...

A range of organisms can be found inside termite nests where the degree of association can vary from facultative to obligatory dependence. Studies of the dynamics of nest invasion are still unresolved, so how and when cohabitants enter termite nests remain open questions. This study analyzed one specific aspect of the dynamics of termite nest invasion by obligatory termitophiles and inquilines, i.e., whether cohabitants were more likely to invade a nest when it reached a critical nest size. We collected 36 Constrictotermes cyphergaster nests of different sizes and sampled their cohabitant fauna. Our results indicated that the invasion of C. cyphergaster nests by obligatory termitophiles and inquilines was dependent on nest size. There appeared to be a critical nest size above which nests were more prone to invasion. Above this size, there was a significantly higher likelihood of finding obligatory cohabitants. Termitophile species were observed in nests ≥2.2 L, whereas inquiline species were only occur in nests ≥13.6 L. This may indicate that the obligatory cohabitants studied here did not occupy C. cyphergaster nests at random and that they were dependent on features that made these nests suitable for cohabitation, which are linked to colony development.

We measured mobility patterns that describe walking trajectories of individual Me’Phaa peasants searching for and collecting fuel wood in the forests of “La Montaña de Guerrero” in Mexico. These 1-day excursions typically follow a mixed pattern of nearly-constant steps when individuals displace from their homes towards potential collecting sites and a mixed pattern of steps of different lengths when actually searching for fallen wood in the forest. Displacements in the searching phase seem not to be compatible with Lévy flights described by power-laws with optimal scaling exponents. These findings, however, can be interpreted in the light of deterministic searching on heavily degraded landscapes where the interaction of the individuals with their fuel wood-scarce environment produces alternative searching strategies than the expected Lévy flights. These results have important implications for future management and restoration of degraded forests and the improvement of the ecological services they may provide to their inhabitants.

Goncalves, T. T., DeSouza, O. and Billen, J. 2010. A novel exocrine structure of the bicellular unit type in the thorax of termites — Acta Zoologica (Stockholm) 91: 193–198 Studying the thorax of some Termitidae species, we found two pairs of hitherto unknown lateral glands in the mesothorax and metathorax of both workers and soldiers. The glands consist of distinct clusters of class 3 secretory cells accompanied by their duct cells, located in the upper lateral portion of the thoracic wall. Ultrastructural observations reveal numerous mitochondria, a well-developed Golgi apparatus and vesicular smooth endoplasmic reticulum, indicating a cytoplasm with intensive metabolic activity. The gland is reported to occur in Microcerotermes strunckii, Cornitermes cumulans and Nasutitermes minor, three species comprising an interesting morpho-behavioural gradient, respectively, from only mechanical, through mechanical–chemical, to only chemical defence systems. The extent of such a gradient allows speculations that this gland would be related to the general needs of termites, rather than to some specificities of a single group. We warn, however, that complementary studies are needed, before any conclusions can be drawn.

Structural and functional traits of organisms are known to be related to the size of individuals and to the size of their colonies when they belong to one. Among such traits, propensity to inquilinism in termites is known to relate positively to colony size. Larger termitaria hold larger diversity of facultative inquilines than smaller nests, whereas obligate inquilines seem unable to settle in nests smaller than a threshold volume. Respective underlying mechanisms, however, remain hypothetical. Here we test one of such hypotheses, namely, that nest defence correlates negatively to nest volume in Constrictotermes cyphergaster termites (Termitidae: Nasutitermitinae). As a surrogate to defence, we used 'patrolling rate', i.e., the number of termite individuals attending per unit time an experimentally damaged spot on the outer wall of their termitaria. We found that patrolling rate decayed allometrically with increasing nest size. Conspicuously higher patrolling rates occurred in smaller nests, while conspicuously lower rates occurred in larger nests presenting volumes in the vicinity of the threshold value for the establishment of inquilinism. This could be proven adaptive for the host and guest. At younger nest age, host colonies are smaller and presumably more vulnerable and unstable. Enhanced defence rates may, hence, prevent eventual risks to hosts from inquilinism at the same time that it prevents inquilines to settle in a still unstable nest. Conversely, when colonies grow and maturate enough to stand threats, they would invest in priorities other than active defence, opening an opportunity for inquilines to settle in nests which are more suitable or less risky. Under this two-fold process, cohabitation between host and inquiline could readily stabilize.

Termites are key organisms in tropical soil processes, accounting for a marked role in pedobioturbation and nutrient cycling. We report on the mound-building termite effects across a representative soil/vegetation gradient in Ironstone Rupestrian Grassland (canga) in Carajas, Brazilian Amazonia. This complex is formed by three main different environments: Grassland, Low forest and Tall forest. The chemical composition of termite mounds was compared with adjacent soil in all environments; also the termite species richness and abundance were estimated. Termite richness varied across the Ironstone Rupestrian Grassland complex: 24 genera in Tall forest >18 genera in Low forest >9 genera in Grassland. Termite activity significantly increased the concentration of organic matter, available P and exchangeable Ca, K, N, Mg in the soil. Mound-building termites comprised 70 % of termite species in Grassland decreasing to 40 % in deeper forested soils. The chemical improvements resulting from mound-building termite activities were relatively more relevant to Grassland compared with Forests. Mound-building termites are key organisms in structuring the Ironstone Rupestrian Grassland complex in Amazonian ironstone.

A study was performed in Vicosa, Minas Gerais, Brazil, to determine the feasibility of using solar radiation to disinfect treated domestic wastewater (TDWW). The effluent from a residential development, after passing through a pre-treatment unit (bar screen and grit channel) and a septic tank, was used as supply. After the septic tank, the TDWW had mean values of 286 mg L -1 COD, 54 mg L -1 TSS, and 65 NTU turbidity. A square cement block reactor was constructed (located at 20° 45' 14" S, 42° ° 52 ' 53 " W) and used to disinfect the reclaimed TDWW Fixed depths of water (0.05, 0.10, 0.15, and 0.20 m) were tested at different exposure times from November 2004 to May 2005. Solar UV disinfection (SODIS) was effective in reducing mean concentration of indicator microorganisms, i.e., total coliform (TC) and Escherichia coli (E. coli), after 8 h of exposure to direct sunlight. Statistical analysis showed that the inactivation rates of E. coli did not significantly vary due to turbidity or dissolved oxygen. A model was developed to estimate the surviving E. coli population after SODIS from its initial population, depth of water treated, and solar energy received. The model indicated that, for a fluence accumulated of 32.91 MJ m -2 , a 4 log reduction of E. coli population was achieved with a wastewater depth of 0.05 m in the SODIS reactor.

Olfaction is fundamental for most animals and critical for different aspects of triatomine biology, including host-seeking, reproduction, avoidance of predators, and aggregation in shelters. Ethological and physiological aspects of these olfactory-mediated behaviors are well-understood, but their molecular bases are still largely unknown. Here we investigated changes in the molecular mechanisms at the peripheral olfactory level in response to different physiological and developmental conditions. For this, the antennal expression levels of the odorant (Orco) and ionotropic (IR8a, IR25a, and IR76b) coreceptor genes were determined in Rhodnius prolixus by means of quantitative real-time PCR (qRT-PCR) analysis. Gene expression changes were analyzed to test the effect of feeding and imaginal molt for both sexes. Moreover, we analyzed whether expression of these genes changed during the early life of adult bugs. Under these conditions bugs display distinct behavioral responses to diverse chemical stimuli. A significantly decreased expression was induced by blood feeding on all coreceptor genes. The expression of all genes was significantly increased following the imaginal molt. These results show that olfactory coreceptor genes have their expression altered as a response to physiological or developmental changes. Our study suggests that olfactory coreceptor genes confer adaptability to the peripheral olfactory function, probably underlying the known plasticity of triatomine olfactory-mediated behavior.

The present study aimed to verify (1) whether seasonal increases in neotropical populations of Plutella xylostella are directly provoked by regular influxes of migrants, and (2) whether temporal variation in food availability is the ecological process behind such predictable events. Over 3 years, plants that P. xylostella prefers were cultivated and irrigated in order to provide a continuous and abundant supply of food. Nevertheless, seasonal oscillations in the population of the herbivore still occurred. The hypothesis of seasonal availability of host plants could not explain the population pattern. In April, when the insect was practically extinct from the area, an artificial infestation (immigration) with 10,000 pupae established a precocious population. Therefore, the start of the natural cycles of population growth, during July–August, seems to be due to external factors, rather than an improvement in local conditions for resident individuals. In the beginning of the natural cycles, the increase in the density of adults significantly preceded the increase in immatures. Plutella xylostella does not diapause, and therefore immigration is the proximate cause of the seasonal population increases. Hypotheses about local factors are suggested to explain the decreasing phase of the predictable population cycles.