Ana Paula A. Araújo

Insecticidal and repellence activity of the essential oil of Pogostemon cablin against urban ants species.

Ants are highly abundant in neotropical regions, with certain species adapted to the urban environment, where they can cause damage to human health. The main method for controlling ants consists of using organosynthetic insecticides, which are potentially toxic to the environment. Essential plant oils are considered a viable alternative to the use of conventional insecticides. In this study, we analyze the bioinsecticidal activity and repellence of patchouli essential oil (Pogostemon cablin) against three species of urban ants: Camponotus melanoticus, Camponotus novograndensis, and Dorymyrmex thoracicus. The chemical composition of the essential oil was analyzed by GC-MS and GC-FID. The major compounds were patchoulol (36.6%) followed by α-bulnesene (13.95%), and α-guaiene (11.96%). Toxicity and repellency bioassays were performed using the essential oil over the ants, and mortality evaluations were performed at 4, 24, and 48 h after performing the bioassays. Mortality percentage of the ants on 7 μg/mg was on average 84%. The essential oil of P. cablin displayed toxicity against all three species of urban ants, with the lowest LD₅₀ being observed for D. thoracicus (2.02 μg oil/mg insect) after 48 h of exposure compared to C. melanoticus (2.34 μg oil/mg insect) and C. novogranadensis (2.95 μg oil/mg insect). The essential oil of P. cablin was strongly repellent to the three species of ants in all concentrations tested (0.01% and 1% v/v). Considering the potential toxicity and repellency of the P. cablin essential oil to the urban ants, future studies could investigate the practical application of this oil to control of this insects.

Diet Segregation between Cohabiting Builder and Inquiline Termite Species.

How do termite inquilines manage to cohabit termitaria along with the termite builder species? With this in mind, we analysed one of the several strategies that inquilines could use to circumvent conflicts with their hosts, namely, the use of distinct diets. We inspected overlapping patterns for the diets of several cohabiting Neotropical termite species, as inferred from carbon and nitrogen isotopic signatures for termite individuals. Cohabitant communities from distinct termitaria presented overlapping diet spaces, indicating that they exploited similar diets at the regional scale. When such communities were split into their components, full diet segregation could be observed between builders and inquilines, at regional (environment-wide) and local (termitarium) scales. Additionally, diet segregation among inquilines themselves was also observed in the vast majority of inspected termitaria. Inquiline species distribution among termitaria was not random. Environmental-wide diet similarity, coupled with local diet segregation and deterministic inquiline distribution, could denounce interactions for feeding resources. However, inquilines and builders not sharing the same termitarium, and thus not subject to potential conflicts, still exhibited distinct diets. Moreover, the areas of the builder’s diet space and that of its inquilines did not correlate negatively. Accordingly, the diet areas of builders which hosted inquilines were in average as large as the areas of builders hosting no inquilines. Such results indicate the possibility that dietary partitioning by these cohabiting termites was not majorly driven by current interactive constraints. Rather, it seems to be a result of traits previously fixed in the evolutionary past of cohabitants.

Toxicity, behavior impairment, and repellence of essential oils from pepper-rosmarin and patchouli to termites

Plant essential oils are potential sources of insecticidal compounds, but have rarely been explored for their effect on termites. In the present study, we assessed the chemical composition of essential oils of Lippia sidoides Cham. (pepper‐rosmarin; Verbenaceae) and Pogostemon cablin (Blanco) Benth. (patchouli; Lamiacaeae) and evaluated their toxicity, behavioral impairment, and repellence to termite species of the genera Amitermes and Microcerotermes (Isoptera: Termitidae: Termitinae). The main components of essential oils of L. sidoides and P. cablin were thymol (44.6%) and patchouli alcohol (36.6%), respectively. The essential oil of P. cablin was most potent against Amitermes cf. amifer Silvestri and had the lowest LD50 (0.63 μg mg−1). There was no difference in toxicity for Microcerotermes indistinctus Mathews between the essential oils of L. sidoides (LD50 = 1.49 μg mg−1) and P. cablin (LD50 = 1.67 μg mg−1). Pogostemon cablin essential oil was the most toxic to M. indistinctus (LC50 = 0.32 μl ml−1) and A. cf. amifer (LC50 = 0.29 μl ml−1). The essential oils analyzed exhibited high toxicity and repellence to the termites, in addition to reducing behavioral interactions among individuals, thus constituting potential termiticides.

Artisanal Fishery of the Mangrove Crab Ucides cordatus (Ucididae) and First Steps Toward a Successful Co-Management in Bragança, North Brazil

The Braganca district in north Brazil offers a unique opportunity for examining the functioning of a small-scale mangrove crab fishery. North Brazilian mangroves are extensive and the large crab Ucides cordatus is very abundant, even though this slow-growing species has been exploited for decades all year round. Ucides sustains a considerable annual yield of ∼7 tons per km² in this district, and 42% of the rural coastal households are involved in the collection or commercialisation of this crab. We describe capture techniques and main outcomes of 8 years of participatory fisheries monitoring, evaluate the status of the U. cordatus population and characterize the commercialisation of the crabs. The average number of crab collectors working on Braganca peninsula each day was 121 ± 105 (<1 man-day per km² per day; data source 2003). In 2003, their net income was 1.5- to 2.5-fold higher (US

Combined foraging strategies and soldier behaviour in Nasutitermes aff. coxipoensis (Blattodea: Termitoidea: Termitidae).

122–196) than the national minimum wage in that year (US

Allometric Scaling of Patrolling Rate and Nest Volume in Constrictotermes cyphergaster Termites: Hints on the Settlement of Inquilines.

80), but still insufficient given an average household size of five people. Mean carapace width of the catch between 1998 and 2005 differed at the most by 2.5 mm, without showing a particular trend. The total crab population of Braganca peninsula was estimated at ∼231 million specimens and fisheries landings were 22% below the calculated annual maximum sustainable yield (1,044,881 crabs). The latter fact is considered important for reducing the risk of a sudden non-linear down-fishing of the economically valuable upper size classes in this slow-growing species, in which the first negative effects of the fishery may remain masked for some time. Further key factors which have prevented rapid overfishing until today include conservative capture techniques that prevent blanket-coverage exploitation, the current size (and sex) selectivity by fishermen and consumers and the integrity and connectivity of the mangrove habitat. At the request of local user communities, the area was declared an “Extractive Marine Reserve” (RESEX) in 2005, a relatively new management approach in coastal Brazil, crucially depending on direct involvement of resource users. The presence of researchers in the study area and participation of locals in our crab fisheries monitoring had positively influenced confidence and decision-making capacities of the latter, making Braganca district an ideal site for RESEX. Registration of resource users and legislation must now be improved for the successful implementation of a co-management plan for sustainable use.

Acaricidal properties of vetiver essential oil from Chrysopogon zizanioides (Poaceae) against the tick species Amblyomma cajennense and Rhipicephalus (Boophilus) microplus (Acari: Ixodidae)

A range of behavioural strategies and sensory abilities allows animals to minimize costs involved in food search. By building a network of tunnels and presenting a large number of soldiers (i.e., trophically dependent individuals), Nasutitermes spp. termites feature behaviours that imply additional costs during this process. Here we evaluated N. aff. coxipoensis foraging strategies focusing on the role of soldiers during foraging. Field experiments were carried out via nests transplantation to dune areas, and laboratory experiments evaluated termite responses to sternal gland chemical signals from workers and soldiers. N. aff. coxipoensis presented primarily nocturnal foraging. Soldiers typically initiated foraging; however, in established trails, the number of workers was always higher than that of soldiers. The number of trails remained constant over time, while the number of tunnels increased linearly over time. A higher proportion of tunnels originated in surrounding areas than directly from the nests. At observation points with tunnels, there were more stationary than walking soldiers; the opposite was true at observation points without tunnels. In mixed groups, the workers chose to follow soldier chemical signals, and in these groups, soldiers were the first to follow trails. Our results allowed us to identify a not common foraging strategy in termite species; which included the establishment of trails followed by construction of tunnels. Such foraging strategies occur predominantly at night and soldiers play a key role in the foraging process. This foraging strategy reported here seems to be employed to optimize energetic gain.

Essential Oil of Aristolochia trilobata: Synthesis, Routes of Exposure, Acute Toxicity, Binary Mixtures and Behavioral Effects on Leaf-Cutting Ants

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.

Resource suitability modulating spatial co‐occurrence of soil‐forager termites (Blattodea: Termitoidea)

Ticks are arthropods widely distributed in tropical and subtropical regions, which can transmit infectious agents also responsible for zoonoses. Excessive use of conventional acaricides has resulted in the onset of drug resistance by these parasites, thus the need to use alternative methods for their control. This study evaluated the acaricidal activities of Chrysopogon zizanioides (vetiver) essential oils containing different zizanoic and khuzimol (high and low acidity) acid concentrations on Amblyomma cajennense and Rhipicephalus microplus (Acari: Ixodidae). To this aims, toxicity tests of different concentrations of examined essential oils were conducted on adult females and larval stages. Results showed that the essential oils of C. zizanioides with high and low acidity reduced oviposition of females, eggs hatch and larval survival, being more effective than some commercial products widely used to control these ectoparasites. These results indicate that the C. zizanoides essential oils are promising candidates as acaricidal agents and represent also an add value to vetiver oil with high acidity, which is commercially undervalued in the cosmetic industry.

Heterospecific detection of host alarm cues by an inquiline termite species (Blattodea: Isoptera: Termitidae)

Plants of the genus Aristolochia have been frequently reported as important medicinal plants. Despite their high bioactive potential, to date, there are no reports of their effects on leaf-cutting ants. Therefore, the present study aimed to evaluate the insecticidal activity of the essential oil of Aristolochia trilobata and its major components on Atta sexdens and Acromyrmex balzani, two species of leaf-cutting ants. The bioassays were performed regarding routes of exposure, acute toxicity, binary mixtures of the major components and behavioral effects. Twenty-five components were identified in the essential oil of A. trilobata using a gas chromatographic system equipped with a mass spectrometer and a flame ionization detector. The components found in higher proportions were sulcatyl acetate, limonene, p-cymene and linalool. The essential oil of A. trilobata and its individual major components were efficient against A. balzani and A. sexdens workers when applied by fumigation. These components showed fast and efficient insecticidal activity on ants. The components acted synergistically and additively on A. balzani and A. sexdens, respectively, and caused a strong repellency/irritability in the ants. Thus, our results demonstrate the great potential of the essential oil of A. trilobata and its major components for the development of new insecticides.