Alda González

An in vitro Evaluation of Tagetes minuta Essential Oil for the Control of the Honeybee Pathogens Paenibacillus larvae and Ascosphaera apis, and the Parasitic Mite Varroa destructor

Abstract Biological activity was evaluated of the Tagetes minuta essential oil in different in vitro laboratory experiments on the mite (Varroa destructor), honeybees (Apis mellifera), the bacterium that causes the American Foulbrood (Paenibacillus larvae), and the fungus that produces chalkbrood (Ascosphaera apis). Two methods of complete exposure were used for mite lethality test: by spraying in Burgerjons tower with 10 mg of active ingredient in solution with distilled water and emulsion, and in unmodified Petri dishes (60 x 20 mm) with oil (different concentrations) diluted in 1 mL of ethanol. Ratio selection was obtained as: LD50 of Apis mellifera/LD50 of V. destructor. Determination of Minimal Inhibitory Concentrations (MIC): to P. larvae was tested at concentrations of 25, 50, 100, 150, 200, 250, 350, 450, 500, 600, 650, 700, 800 and 1000 ppm. An A. apis strain was grown on agar MY20 supplemented with variable concentrations (between 0–800 ppm) of T. minuta oil was evaluated. Results obtained in tests of total exposure showed that the concentration was able to kill 50% of mites in 24 h (DL50) and was estimated to be 4.37 mg/cage. The efficacy after spray treatment reached 56%. The ratio selection was 3:11. Against P. larvae, the oil showed MIC values ranging from 700–800 μL/L depending on the tested bacterial strains. Tagetes minuta oil in agar MY20 inhibited mycelial growth of A. apis above concentrations of 200 ppm (p = 0.0001). Oil concentrations of 700 and 800 ppm achieved maximum growth inhibition of A. apis (67% of growth inhibition on average). Tagetes minuta oil demonstrated in vitro antibacterial, antifungical and miticide activity, although this oil shows a moderate inhibitor effect compared with other essential oils of native plants from Argentina. However, this oil presents a ratio selection that would allow it to be used in field conditions with a good safety margin. It is possible that this oil can be used in combination with others, in integrated pest management strategies in bee colonies.

Short and long-term effects of three neurotoxic insecticides on biological and behavioural attributes of the orb-web spider Alpaida veniliae (Araneae, Araneidae): implications for IPM programs

Soybean pest control in Argentina is done just by chemical control using broad-spectrum pesticides. Alpaida veniliae (Araneae, Araneidae) is one of the most abundant spider species of the orb web weaver guild in soybean, and it is considered a very important polyphagous predator, attacking different insects’ families. The objective of this study was to determine if neurotoxic insecticides commonly used in soybean crops and a new active ingredient registered in Argentina (spinosad) adversely affected survival, prey consumption, mating behaviour, web building and reproductive capacity of A. veniliae females, under standard laboratory conditions. Spinosad was the most harmful insecticide due to high acute toxicity, even at lower concentrations than those registered for its field use and for its sublethal effects also. Cypermethrin caused several sublethal effects although its acute toxicity on spider was lower than other insecticides. It reduced prey consumption, affected web building, caused abnormalities in eggs sacs and decreased drastically the fecundity and fertility at sublethal concentrations. Endosulfan did not reduce prey consumption but it affected web building, caused abnormalities in eggs sacs and egg masses, and decreased the fecundity and fertility. Spinosad was also the compound with the most drastic effect on web building, it did not reduce prey consumption and fecundity, but fertility was reduced and abnormalities in egg sacs and egg masses were observed. The use of these insecticides in IPM programs according to their potential toxicity on spider communities is discussed.

Historical biogeography of mygalomorph spiders from the peripampasic orogenic arc based on track analysis and PAE as a panbiogeographical tool

A panbiogeographical analysis of Mygalomorphae spiders was undertaken in order to determine generalized tracks and biogeographical nodes in the peripampasic orogenic arc. This arc comprises mountainous systems that harbour a high number of endemic species, while they exhibit biotic connections that have become fragmented probably during Tertiary tectonics. They are considered relevant areas for biodiversity conservation. A total of 1078 records of 51 Mygalomorphae species were analysed and ten areas were delimited based on geological data. We used track analysis and parsimony analysis of endemicity as a panbiogeographical tool. Five generalized tracks and three nodes were recovered. The tracks recovered in Argentina could be explained as a consequence of two events: (i) Atlantic marine transgressions during the Middle and Late Miocene; and (ii) changes in the climate of southern South America from the Miocene to Pliocene, caused by the gradual raising of the Andean chain and also, the additional uplift of Pampean and Subandean ranges. The southeastern Brazil and Uruguayan generalized tracks could be explained by the Rio de La Plata Craton.

Mygalomorph Spider Community of a Natural Reserve in a Hilly System in Central Argentina

Abstract The diversity, abundance, spatial distribution, and phenology of the mygalomorph spider community in the “Ernesto Tornquist” Strict Nature Reserve were analyzed in this study. Located in southwestern Buenos Aires, Argentina, the Reserve is representative of the Ventania system, which is a sigmoidal mountain belt 180 km in length. This exceptional hilly ecosystem is home for many endemic species and rich native fauna and flora. Spider abundance was sampled monthly from October 2009 to October 2010 by hand capture and pitfall traps on grassland slopes. The species recorded in the study area were: Actinopus sp.1 (Actinopodidae); Grammostola vachoni and Plesiopelma longisternale (Theraphosidae); Acanthogonatus centralis (Nemesiidae); and Mecicobothrium thorelli (Mecicobothriidae). Grammostola vachoni and Acanthogonatus centralis were the dominant species in hand capture and pitfall traps, respectively. The seasonal variation, diversity, and abundance of the mygalomorph community are analyzed and discussed here. The Mygalomorphae of the Ventania system comprises an important group of sedentary and cryptozoic spiders that seem to be highly dependent on habitat type and environmental factors.

Historical relationships among Argentinean biogeographic provinces based on mygalomorph spider distribution data (Araneae: Mygalomorphae)

The present study used the previously defined biogeographic provinces from Argentina as the starting point for a parsimony analysis of endemicity and cluster analysis. The goal of the study was to use a dataset of distributional patterns of mygalomorph spiders from Argentina to evaluate the historical relationships of the biogeographic provinces. The analyses showed the following relationships: Yungas and Puna; Pampa and Chaco, Monte and Prepuna; Parana Forest and Araucaria angustifolia Forest; Central and Subandean Patagonia. Biogeographical regionalizations are useful as general reference models and their heuristic value should be explored by examining the geographical distribution of other taxa.

Sexual Behaviour of Mygalomorph Spiders: when Simplicity Becomes Complex; an Update of the Last 21 Years

Summary A generally common impression seems to be that the mygalomorphs have simple repertoires of behaviours, but many authors have concluded that this traditional portrayal of mygalomorph behaviours is misleading. An increasing number of studies of reproductive behaviour of mygalomorphs have revealed intricate and complex mechanisms of communication employed by this group. Our objective was to provide a synthetic treatment of the literature published in the last 21 years about sexual behaviour of mygalomorph spiders, in order to contribute in improving our understanding on the widespread and unique behaviours they exhibit. We provide a brief introduction to reproductive behaviour of mygalomorph spiders, and then examine some of the general patterns of courtship and mating behaviours known on some mygalomorph families.

Copulatory behavior of Microstigmatidae (Araneae: Mygalomorphae): a study with Xenonemesia platensis from Argentina

Abstract Microstigmatidae are small ground-dwelling and free-living spiders. The present study reports on the copulatory behavior of Xenonemesia platensis Goloboff 1989, constituting the first report on sexual behavior of the Microstigmatidae. Our findings in X. platensis did not show evidence of pheromones associated with silk. The courtship behavioral units of males was comprised of quivers by legs I and II, brusque movements of the palps, and leg tapping with legs II. During mating, a novel courtship behavior by males was observed that consisted of tapping and scraping with legs II on the female legs. The present study not only gives a description of mating behavior in Microstigmatidae for the first time, but also reports strong evidence of nongenital copulatory courtship activity in mygalomorph spiders.

Predation by Misumenops pallidus (Araneae: Thomisidae) on insect pests of soybean cultures in Buenos Aires Province, Argentina.

Abstract This study analyzes predation by adult females of Misumenops pallidus (Keyserling 1880) on pairs of prey items representing non-pest insects and potential pests. The phenology of the potential pests was such that each insect guild peaked sequentially, while non-pest herbivorous and insectivorous insects were present during the entire period. Field experiments were made in a commercial 50-ha soybean plot during two successive years. Ten cages 1 × 1 × 0.5 m were placed in peripheral furrows of a soybean commercial plot. The pest species were preyed on differentially, with the order from the most favored species to the least with respect to non-pest herbivorous and insectivorous insects was as follows: defoliating lepidopterous larvae, seed feeding pentatomids in their early nymphal instars, stem boring lepidopterous larvae, and seed feeding pentatomids in older nymphal and adult instars. Adult females of M. pallidus fed on all the insect species offered, but in the presence of defoliator larvae, they hardly accepted alternative prey, whereas in the presence of other prey, they maintained a more generalized diet.

Identification of priority areas for conservation in Argentina: quantitative biogeography insights from mygalomorph spiders (Araneae: Mygalomorphae)

Conservation biogeography involves the application of biogeographical principles and methods to conservation issues. The identification of areas of endemism is important for both historical biogeography and conservation. Mygalomorphs spiders have poor vagility, limited dispersal mechanisms and sedentary habits. In this study we use a panbiogeographical approach (through track analysis) and the optimality criterion (NDM) to analyze the distributional patterns in order to identify areas of endemism and to prioritize areas for conservation in Argentina. We identified seven generalized tracks and four biogeographical nodes. The analysis of the 2° matrix examined by NDM allowed the identification of eight areas of endemism; from the analysis of the 1.5° matrix, NDM resulted in three areas of endemism; and the analysis of the 1° and 0.5° matrices identified one area of endemism each. The more relevant areas identified in this study were located at the Atlantic Forest, Pampa, Monte and Chaco. Other identified areas were Yungas and the hilly systems of Ventania and Tandilia (southern Pampa). We suggest that these results can indicate where to prioritize investment in creating new protected areas, in order to preserve the processes that generate the biogeographic patterns exhibited by this biota.

Postembryonic development and population parameters of Alpaida veniliae (Araneae, Araneidae), reared in the laboratory

We studied the postembryonic development from hatching to the adult stage and determined population parameters of Alpaida veniliae. It is one of the most abundant species of the orb-weaving guild of the spider community of soybean crops in Buenos Aires province, Argentina. The first three instars occurred inside the egg sac, and instar IV (spiderlings) started the dispersion from it. The female of Alpaida veniliae achieved greater adult size and adult longevity than the male. Mean fecundity, mean number of egg sacs per female, mean number of eggs per egg sac, as well as the net reproductive rate, the intrinsic rate of increase (r), the generation time (T), and the reproductive values (V x) of three cohorts were determined under laboratory conditions, indicating a high capacity for growth. Their biological and ecological attributes indicate the importance of conservation of this predator as a natural enemy of soybean crop pests.