Description of the life cycle of Dolops discoidalis (Bouvier, 1899) (Branchiura: Argulidae), a parasite of the fish species Rhytiodus argenteofuscus (Kner, 1858) from the Brazilian Amazon.

The genus Dolops (Audouin, 1837) is endemic among ectoparasites present in fish, with nine species described in Brazil, five of which are from the Amazon region. Among the genus, the species Dolops discoidalis (Bouvier, 1899) stands out due to its high prevalence of parasitism in Amazonian fish. The present study aims to characterize the development phases of D. discoidalis. The parasites were obtained from infected fish species Rhytiodus argenteofuscus from a natural environment, kept in polyethylene experimental boxes (500 liters). The physical-chemical parameters of the water (pH, electrical conductivity, dissolved oxygen and temperature) were monitored daily. A total of 30 egg layings were analyzed. After identification of the oviposition, the eggs were transferred to another container containing water (0.5 liters). The number of eggs was recorded, with observations made in stereomicroscopic and photographic records until hatching occurred. The egg layings exhibited differences in colour throughout their development. On the seventh day, the embryos exhibited visible ocelli and on the 17th day the hatching period began. Hatching occurred in batches, with around 5­10 hatches/day/laying. However, peak hatching was recorded on the 19th day of the cycle. Therefore, the cycle of D. discoidalis comprised a total period of 17­22 days at 28.C, with hatching in batches and pigmentation of the eggs observed close to hatching. Newly hatched parasites did not survive for more than 24 hours in the absence of the host. This study contributes to knowledge of the biology of D. discoidalis, and adds to information regarding possible studies into its control.

The essential oil of Lippia alba and its components affect Drosophila behavior and synaptic physiology.

Lippia alba is a flowering shrub in the verbena family and its essential oil (EO) is known for its sedative, antidepressant and analgesic properties. In the Amazon region of Brazil, it is used in aquaculture to anesthetize fish during transport. Many of the specialized metabolites found in EOs presumably evolved to protect plants from herbivores, especially insects. We used Drosophila to test the behavioral and physiological actions of this EO and its components. We found that a 150 min exposure to the EO vapors resulted in immobilization of adult flies. Gas chromatography-mass spectrometry identified the major components of the EO as the monoterpenes citral (59%), carvone (7%) and limonene (7%). Fly immobilization by the EO was due to citral and carvone, with citral producing more rapid effects than carvone. We tested whether the EO affected synaptic physiology by applying it to the larval neuromuscular junction. The EO delivered at 0.012% (v/v) produced over a 50% reduction in excitatory postsynaptic potential (EPSP) amplitude within 3-4 min. When the EO components were applied at 0.4 mmol l-1, citral and carvone produced a significant reduction in EPSP amplitude, with citral producing the largest effect. Measurement of miniature EPSP amplitudes demonstrated that citral produced over a 50% reduction in transmitter release. Calcium imaging experiments showed that citral produced about 30% reduction in presynaptic Ca2+ influx, which likely resulted in the decrease in transmitter release. Thus, the EO blocks synaptic transmission, largely due to citral, and this likely contributes to its behavioral effects.

Citral and linalool chemotypes of Lippia alba essential oil as anesthetics for fish: a detailed physiological analysis of side effects during anesthetic recovery in silver catfish (Rhamdia quelen).

The viability using Lippia alba essential oil as an anesthetic for fish was studied, particularly with respect to physiological effects during recovery. Anesthesia of silver catfish (Rhamdia quelen) using 100 and 300 µL L-1 of two different chemotypes of L. alba essential oil (citral EO-C and linalool EO-L) prevented the increase of plasma cortisol levels caused by handling, but did not avoid alterations in energetic metabolism. Silver catfish did not have increased the levels of thiobarbituric acid reactive species in the kidney and liver during recovery after anesthesia with either EO, avoiding lipid damage. On the other hand, fish anesthetized with EO-C showed higher protein carbonylation levels, superoxide dismutase, catalase, and glutathione S-transferase activities and non-protein thiol group levels in both tissues compared to controls. Our results suggest that both oils show antioxidant capacity, but anesthesia with EO-L does not cause damage to lipids or proteins, only temporary changes, typical of physiological adjustments during recovery from anesthesia. Therefore, EO-L is an effective anesthetic for silver catfish with fewer side effects than EO-C.

Trypanocidal action of Lippia alba and Lippia origanoides essential oils against Trypanosoma evansi in vitro and in vivo used mice as experimental model.

Parasitic diseases have an enormous health and economic impact and are a particular problem in tropical regions of the world. Disease caused by protozoa, such as trypanosomiasis, are the cause of most parasite related morbidity and mortality. Thus, the aim of this study was to verify the trypanocidal effectiveness of Lippia alba and Lippia origanoides against Trypanosoma evansi in vitro and in vivo. L. alba and L. origanoides were used in vitro on trypomastigotes at different concentrations (0.5, 1.0 and 2.0 %) and exposure times (0, 1, 3, 6 and 9 h). The three concentrations tested showed trypanocidal activity in vitro, completely eliminating the parasites in small concentration after 6 h of assay. In vivo tests were performed using mice as the experimental model. T. evansi infected mice were treated with L. alba and L. origanoides with dose of 1.5 mL kg-1 during 5 days. These protocols did not provide curative efficacy, however the mice treated with L. origanoides showed a significant increase in the longevity when compared to control group. Active compounds present in essential oils, such as L. origanoides, may potentiate the treatment of trypanosomosis when associated with other trypanocidal drugs.

A social and ecological assessment of tropical land uses at multiple scales: the Sustainable Amazon Network.

Science has a critical role to play in guiding more sustainable development trajectories. Here, we present the Sustainable Amazon Network (Rede Amazônia Sustentável, RAS): a multidisciplinary research initiative involving more than 30 partner organizations working to assess both social and ecological dimensions of land-use sustainability in eastern Brazilian Amazonia. The research approach adopted by RAS offers three advantages for addressing land-use sustainability problems: (i) the collection of synchronized and co-located ecological and socioeconomic data across broad gradients of past and present human use; (ii) a nested sampling design to aid comparison of ecological and socioeconomic conditions associated with different land uses across local, landscape and regional scales; and (iii) a strong engagement with a wide variety of actors and non-research institutions. Here, we elaborate on these key features, and identify the ways in which RAS can help in highlighting those problems in most urgent need of attention, and in guiding improvements in land-use sustainability in Amazonia and elsewhere in the tropics. We also discuss some of the practical lessons, limitations and realities faced during the development of the RAS initiative so far.