ABSTRACT
Gregarines (Apicomplexa) are a diverse group of protozoan parasites, which infects gut and other body cavities of invertebrate hosts. In reproductive system of insects, gregarine has been reported only in the accessory glands and spermathecae of females; therefore, this is the first report of a gregarine species in seminal vesicles of insects. Different developmental stages, including sporozoytes, oocysts and trophozoites were described from morphological descriptions using light and electron transmission microscopy. The parasites were described in seminal vesicles of the beetle Tribolium castaneum a model organism and an important insect pest. DNA sequence analysis suggests that the protozoan parasite was an Ascogregarina sp.
Subject(s)
Apicomplexa/classification , Apicomplexa/growth & development , Coleoptera/parasitology , Sequence Analysis, DNA/methods , Animals , Apicomplexa/genetics , Apicomplexa/ultrastructure , DNA, Protozoan/genetics , Female , Male , Microscopy, Electron, Transmission , Phylogeny , Seminal Vesicles/parasitologyABSTRACT
Plant essential oils have been suggested as a suitable alternative for controlling stored pests worldwide. However, very little is known about the physiological or behavioral responses induced by these compounds in insect populations that are resistant to traditional insecticides. Thus, this investigation evaluated the toxicity (including the impacts on population growth) as well as the locomotory and respiratory responses induced by clove, Syzygium aromaticum L., and cinnamon, Cinnamomum zeylanicum L., essential oils in Brazilian populations of the maize weevil Sitophilus zeamais. We used populations that are resistant to phosphine and pyrethroids (PyPhR), only resistant to pyrethroids (PyR1 and PyR2) or susceptible to both insecticide types (SUS). The PyPhR population was more tolerant to cinnamon essential oil, and its population growth rate was less affected by both oil types. Insects from this population reduced their respiratory rates (i.e., CO2 production) after being exposed to both oil types and avoided (in free choice-experiments) or reduced their mobility on essential oil-treated surfaces. The PyR1 and PyR2 populations reduced their respiratory rates, avoided (without changing their locomotory behavior in no-choice experiments) essential oil-treated surfaces and their population growth rates were severely affected by both oil types. Individuals from SUS population increased their mobility on surfaces that were treated with both oil types and showed the highest levels of susceptibility to these oils. Our findings indicate that S. zeamais populations that are resistant to traditional insecticides might have distinct but possibly overlapping mechanisms to mitigate the actions of essential oils and traditional insecticides.
Subject(s)
Cinnamomum zeylanicum/chemistry , Insecticides/pharmacology , Oils, Volatile/pharmacology , Plant Oils/pharmacology , Syzygium/chemistry , Weevils/drug effects , Zea mays/parasitology , Animals , Locomotion/drug effects , Pest Control , Plant Diseases/parasitology , Weevils/physiologyABSTRACT
Essential oils have been suggested as suitable alternatives for controlling insect pests. However, the potential adaptive responses elicited in insects for mitigating the actions of these compounds have not received adequate attention. Furthermore, as is widely reported with traditional insecticides, sublethal exposure to essential oils might induce stimulatory responses or contribute to the development of resistance strategies that can compromise the management of insect pests. The current study evaluated the locomotory and respiratory responses as well as the number of larvae per grain produced by the maize weevil, Sitophilus zeamais Motschulsky, after being sublethally exposed to the essential oils of clove, Syzygium aromaticum L., and cinnamon, Cinnamomum zeylanicum L. The essential oils showed similar insecticidal toxicity (exposure route: contact with dried residues; Clove LC95 = 3.96 [2.78-6.75] µl/cm(2); Cinnamon LC95 = 3.47 [2.75-4.73] µl/cm(2)). A stimulatory effect on the median survival time (TL50) was observed when insects were exposed to low concentrations of each oil. Moreover, a higher number of larvae per grain was produced under sublethal exposure to clove essential oil. S. zeamais avoided the treated areas (in free-choice experiments) and altered their mobility when sublethally exposed to both essential oils. The respiratory rates of S. zeamais (i.e., CO2 production) were significantly reduced under low concentrations of the essential oils. We recommend the consideration of the potential sublethal effects elicited by botanical pesticides during the development of integrated pest management programs aiming to control S. zeamais.
Subject(s)
Behavior, Animal/drug effects , Clove Oil/toxicity , Oils, Volatile/toxicity , Respiration/drug effects , Weevils/drug effects , AnimalsABSTRACT
The aim of the present study was to assess the effect of six different temperatures on the development of Acarophenax lacunatus (Cross & Krantz) using eggs of Tribolium castaneum (Herbst) and Cryptolestes ferrugineus (Stephens) as hosts. The temperature affected the development of A. lacunatus. The largest values for the progeny (19 mites in T. castaneum and 15 mites in C. ferrugineus) were obtained at about 30 degrees C, as also observed for the net reproductive rate (Ro), which revealed that the A. lacunatus population increased 18 times in T. castaneum and 14 times in C. ferrugineus in a generation. The intrinsic rate of increase (r m) gradually increased with temperature, reaching the maximum value at 35 degrees C in T. castaneum (1,608) and C. ferrugineus (1,289). The generation time was negatively correlated with temperature, ranging from 1,60 to 4,85 days in T. castaneum and from 1,96 to 5,34 days in C. ferrugineus. These results suggest that the mite A. lacunatus may be used in programs of biological control of T. castaneum and C. ferrugineus in the tropics.
Subject(s)
Acari/growth & development , Coleoptera/parasitology , Animals , Ovum/parasitology , TemperatureABSTRACT
O presente trabalho teve por objetivo avaliar o efeito de seis temperaturas (20, 25, 28, 30, 32 e 35°C) sobre os parâmetros biológicos de Acarophenax lacunatus (Cross & Krantz) utilizando ovos de Tribolium castaneum (Herbst) e Cryptolestes ferrugineus (Stephens) como hospedeiros. A temperatura influenciou o desenvolvimento do ácaro A. lacunatus. Os maiores valores para a progênie (19 ácaros em T. castaneum e 15 ácaros em C. ferrugineus) foram obtidos a 30°C. O mesmo foi observado para a taxa líquida de reprodução (Ro), que revelou que a população de A. lacunatus aumentou 18 vezes em T. castaneum e 14 vezes em C. ferrugineus em uma geração. A taxa intrínseca de crescimento (r m) aumentou com a elevação da temperatura, atingindo o valor máximo a 35°C em T. castaneum (1,608) e em C. ferrugineus (1,289). O tempo de geração foi inversamente proporcional à temperatura, variando de 1,60 a 4,85 dias em T. castaneum e de 1,96 a 5,34 dias em C. ferrugineus. Esses resultados sugerem que o ácaro A. lacunatus pode ser utilizado em programas de controle biológico de T. castaneum e de C. ferrugineus em regiões tropicais.
The aim of the present study was to assess the effect of six different temperatures on the development of Acarophenax lacunatus (Cross & Krantz) using eggs of Tribolium castaneum (Herbst) and Cryptolestes ferrugineus (Stephens) as hosts. The temperature affected the development of A. lacunatus. The largest values for the progeny (19 mites in T. castaneum and 15 mites in C. ferrugineus) were obtained at about 30°C, as also observed for the net reproductive rate (Ro), which revealed that the A. lacunatus population increased 18 times in T. castaneum and 14 times in C. ferrugineus in a generation. The intrinsic rate of increase (r m) gradually increased with temperature, reaching the maximum value at 35°C in T. castaneum (1,608) and C. ferrugineus (1,289). The generation time was negatively correlated with temperature, ranging from 1,60 to 4,85 days in T. castaneum and from 1,96 to 5,34 days in C. ferrugineus. These results suggest that the mite A. lacunatus may be used in programs of biological control of T. castaneum and C. ferrugineus in the tropics.
Subject(s)
Animals , Acari/growth & development , Coleoptera/parasitology , Ovum/parasitology , TemperatureABSTRACT
Os objetivos deste trabalho foram avaliar os efeitos imediato e latente da temperatura do grão, durante a pulverização, sobre a persistência e eficácia biológica do inseticida bifentrina, no controle de Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) e Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae). Para tal, bifentrina foi pulverizada em grãos de milho com diferentes temperaturas (25, 30, 35, 40 e 45°C). Para avaliação da sua persistência fez-se a extração e análise do resíduo a cada 30 dias, iniciando logo após a pulverização do inseticida, até os 90 dias de armazenamento. Para avaliação da eficácia biológica, 20 adultos de cada espécie foram colocados em placasde-petri contendo grãos tratados, sendo mantidas em câmaras do tipo B.O.D., a 27 °C e 55 por cento de UR durante 48 horas. Estas avaliações foram realizadas em intervalos de 15 dias, com início logo após a pulverização e término aos 90 dias de armazenamento. Observou-se que tanto a persistência quanto a eficácia biológica da bifentrina reduziram à medida que o período de armazenamento e a temperatura do grão aumentaram. Observou-se, ainda, que S. zeamais apresentou maior tolerância à bifentrina, que T. castaneum.
Subject(s)
Animals , Insecticides/pharmacology , Pyrethrins/pharmacology , Temperature , Tenebrio/drug effects , Weevils/drug effects , Zea mays/parasitologyABSTRACT
The objective of this work was to evaluate the immediate and latent effects of the grain temperature, during the spraying process, on the persistence and biological efficacy of the biphenthrin insecticide against Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) and Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae). For such, biphenthrin was sprayed on the grain at the temperatures: 25, 30, 35, 40 and 45 degrees C. To access the persistence of biphenthrin, insecticide residue analyses were carried out monthly, just after spraying until 90 days of storage. To evaluate the biological efficacy of biphenthrin, 20 adults of each species were placed in petri dishes with sprayed grain, and kept in climate cabinets under 27 degrees C and 55% of RH, during 48h. Evaluations were done every 15 days, starting just after spraying and finishing at 90 days of storage. Both persistence and biological efficacy of biphenthrin reduced as storage time and grain temperatures increased. Additionally, S. zeamais was more tolerant to biphenthrin than T. castaneum.
