Composición y estructura de la comunidad de arañas en el sistema de cultivo de soja transgénica

Las arañas son artrópodos depredadores generalistas que tienen como presa a la mayoría de los taxa de artrópodos, incluídas otras arañas. Pueden desempeñarse como efectivos enemigos naturales de insectos herbívoros en muchos agroecosistemas, debido a su presencia constante y relativamente alta abundancia durante todas las fases de desarrollo de los cultivos, y a su capacidad de dispersión y colonización. En la Argentina, a partir de 1996 ocurrió una gran expansión territorial del cultivo de soja consistente en semilla transgénica tolerante al herbicida glifosato (N-[fosfonometil] glicina), mediante siembra directa. El gran incremento de este monocultivo en el área pampeana y extrapampeana aumentó la uniformidad del paisaje, lo cual implica serios riesgos desde el punto de vista ecológico. Por lo general, la diversidad de especies suele ser alterada por distintos tipos de disturbios, en particular aquellos de alta intensidad y/o frecuencia, suelen empobrecerla al simplificar el ambiente, eliminan en forma directa o indirecta las especies más sensibles. Otro factor relevante que impacta negativamente sobre las comunidades de arañas es el uso generalizado de plaguicidas. Si bien el conocimiento taxonómico de algunas familias de arañas es amplio en nuestro país, aspectos biológicos y ecológicos de las comunidades y poblaciones de arañas asociadas a distintos agroecosistemas son poco estudiadas. Teniendo en cuenta la escasa información acerca de la comunidad de arañas en el sistema del cultivo de soja en Argentina, se consideró de interés ampliar los estudios sobre esta temática en cultivos de soja transgénica RR (resistente al herbicida glifosato). Para ello, se determinó la composición taxonómica y estructura de la comunidad de arañas en cultivos de soja transgénica (soja RR) del partido de Chivilcoy, provincia de Buenos Aires. Complementariamente, se estudiaron los siguientes aspectos: 1) la biología y demografía de una de las especies más representativas del gremio de las arañas tejedoras orbiculares, Alpaida veniliae (Araneae, Araneidae), y 2) los efectos letales y subletales de distintos insecticidas comúnmente usados en este cultivo y del herbicida glifosato, tomando como modelo a la araña cazadora terrestre Hogna poliostoma (Araneae, Lycosidae) y a la tejedora orbicular, A. veniliae. Se trabajó en dos campos comerciales cultivados con soja transgénica (RR), durante la temporada 2005-2006 en soja de primera siembra (Noviembre – Abril) y en 2006-2007 en soja de segunda siembra (Diciembre – Junio).Facultad de Ciencias Naturales y Muse

Comparación de la edafofauna para cuatro usos de suelo

La edafofauna está constituida por organismos que modifican del suelo y las comunidades existentes se encuentran relacionadas a los tipos de uso y manejo. El objetivo de este trabajo es contribuir al reconocimiento de la edafofauna en diferentes usos de suelo: Bosque Nativo, Forestal, Campo Nativo y Cultivo en un predio de agricultura familiar, de suelos arenosos del norte de Uruguay. Se establecieron parámetros de abundancia, diversidad, similitud, y riqueza a partir de 1664 individuos de 16 órdenes capturados. El análisis estadístico no muestra diferencias significativas entre tratamientos, presentando dominancia del Orden Himenóptera en tres casos, seguido de Homóptera para el restante. La mayor similitud (70%) fue encontrada entre la forestación y campo natural según Sörensen.The soil fauna consists of organisms that modify the soil and existing communities are related to the types of use and handling. The goal of this study is to contribute to the recognition of soil fauna in different land uses: Native Forest, Forest, Native Field and orchard in an area of family farming in sandy soils of northern Uruguay. Diversity parameters, similarity, abundance, density and species richness, from individuals collected 1664 (16 orders). The statistical analysis shows no significant difference between treatments, presenting the Order Hymenoptera dominance in three cases, followed by Homoptera for the remainder. The highest similarity (70%) was found between afforestation and natural field according Sørensen.Eje A4: Ambiente, Naturaleza y Agroecología.Facultad de Ciencias Agrarias y Forestale

Sexual behavior of Alpaida veniliae (Araneae: Araneidae)

Studies in transgenic soybean cropsin Buenos Aires province, Argentina, revealed that Alpaida veniliae is one of the most abundant species in the guild of orb web spiders. This species is an effective natural enemy of insect pests affecting this crop. In the present study we carried out a descriptive and quantitative analysis of sexual behavior (courtship, mating and post-mating) of A. veniliae. The spiders were collected in transgenic soybean crops located in Chivilcoy (35º01' S - 60º06' W), Buenos Aires, Argentina, and reared under laboratory conditions. Based on observations of 20 couples (with virgin females), behavioral units of male and female in terms of postures and movements,including details on duration and frequency, were described at all stages of sexual activity (courtship, mating and post-mating). Courtship exhibited the greatest number and duration of behavioral units in both sexes. Male and female had a sequence of 16 and nine units, respectively, being the frequency of repetitions of the units significantly higher in the male. Mating was brief and males used a single palp to fill only one of the female spermathecae, after which the female became unreceptive. Mating had two behavioral units in the male and only one in the female. During post-mating males had three and females two behavioral units. The average duration of the whole sexual behavior was 541.90 ± 123.1 seconds for the male and 338.20 ± 74.1 seconds for the female. Alpaida veniliae females rarely accept a second mating with the same or another male (remating), indicating a strict monogamy. In 46% of observed mating, the female cannibalized the male after it. Females became unattractive after mating, since stop producing sex pheromones, causing a reduction of the male vibratory courtship. The high cost of courtship, including the risk of cannibalism, would reinforce the selectivity of males towards receptive virgin females.Centro de Estudios Parasitológicos y de Vectore

Sexual behavior of Alpaida veniliae (Araneae: Araneidae)

Studies in transgenic soybean cropsin Buenos Aires province, Argentina, revealed that Alpaida veniliae is one of the most abundant species in the guild of orb web spiders. This species is an effective natural enemy of insect pests affecting this crop. In the present study we carried out a descriptive and quantitative analysis of sexual behavior (courtship, mating and post-mating) of A. veniliae. The spiders were collected in transgenic soybean crops located in Chivilcoy (35º01' S - 60º06' W), Buenos Aires, Argentina, and reared under laboratory conditions. Based on observations of 20 couples (with virgin females), behavioral units of male and female in terms of postures and movements,including details on duration and frequency, were described at all stages of sexual activity (courtship, mating and post-mating). Courtship exhibited the greatest number and duration of behavioral units in both sexes. Male and female had a sequence of 16 and nine units, respectively, being the frequency of repetitions of the units significantly higher in the male. Mating was brief and males used a single palp to fill only one of the female spermathecae, after which the female became unreceptive. Mating had two behavioral units in the male and only one in the female. During post-mating males had three and females two behavioral units. The average duration of the whole sexual behavior was 541.90 ± 123.1 seconds for the male and 338.20 ± 74.1 seconds for the female. Alpaida veniliae females rarely accept a second mating with the same or another male (remating), indicating a strict monogamy. In 46% of observed mating, the female cannibalized the male after it. Females became unattractive after mating, since stop producing sex pheromones, causing a reduction of the male vibratory courtship. The high cost of courtship, including the risk of cannibalism, would reinforce the selectivity of males towards receptive virgin females.Centro de Estudios Parasitológicos y de Vectore

Efectos de distintos insecticidas convencionales y biorracionales, en la biología de una araña tejedora (<i>Alpaida veniliae</i>) en soja

El uso de insecticidas de amplio espectro son comunes en el cultivo convencional, su alta toxicidad en artrópodos especialmente en enemigos naturales ha sido demostrado. El objetivo fue evaluar efectos subletales de plaguicidas convencionales y biorracionales en arañas, a nivel de comportamiento predador y reproductor. Se utilizaron concentraciones subletales de: cipermetrina, endosulfan, spinosad y metoxifenocida; suministrados a través de la presa Musca domestica. Se observó retraso en la construcción de la tela con cipermetrina, spinosad y endosulfan. Presencia de cuerpos grasos en ovarios y reducción del diámetro de oocitos, disminución en la fecundidad y fertilidad con todos los insecticidas. Se demuestra el efecto de los insecticidas en aspectos relacionados al desempeño disminuyendo su potencialidad de agentes controladores de poblaciones de insectos, reduciendo drásticamente su papel como enemigo natural de plagas en los cultivos.The use of broad-spectrum insecticides are common in conventional farming, high toxicity especially arthropod natural enemies has been demonstrated. The aim was to assess sublethal effects of conventional insecticides and biorracionales in spiders, predatory level and reproductive behavior. Sublethal concentrations were used: cypermethrin, endosulfan, spinosad and methoxyfenozide; provided through the prey Musca domestica. Delay in web building with cypermethrin, spinosad and endosulfan was observed. Presence of fatt body in ovaries and oocytes diameter reduction, decreased fecundity and fertility with all insecticides. The effect of insecticides on issues related to performance decreasing its potential control agents of insect populations, drastically reducing their role as natural enemies of crop pests is demonstrated.Eje A4: Ambiente, Naturaleza y Agroecología.Facultad de Ciencias Agrarias y Forestale

Estudio de la macrofauna edáfica (orden araneae). Su riqueza y abundancia en invernáculos sujetos a un manejo convencional y en transición agroecológica. Partido de La Plata, Argentina

Taking into account the ecological role of spiders in agroecosystems, the aim of this paper was to study its richness and abundance in two greenhouses in La Plata, one under conventional management (IC) and another in agroecological transition (IT). Individuals were capture using pitfall traps. It was collected 2818 individuals in IT and 1585 in IC, which belonged to 21 families: 20 in (IT ) and 19 in (IC). The Families better represented were Lycosidae, Linyphiidae, Hahnidae, Tetragnathidae, Anyphaenidae and Corinnidae. It was found similar guilds under both managements and similar proportions between them.The better represented groups in both treatments were hunter running spiders and spinning wanders of irregular web like sheet. Nevertheless it was observed differences in abundance, may be related to IT management based on a reduced use of agrochemical, higher biodiversity of crops and spontaneous plant that favor habitat, shelter and food for spiders, which would act as potential pest controllers. Pesticide reduction and increase in biodiversity are fundamentals strategies to take into account to reach biotic regulation in agroecosystems.Considerando el importante rol ecológico de las arañas en los agroecosistemas, se propuso estudiar su presencia en dos invernáculos del partido de La Plata, uno con manejado convencional (IC) y otro en transición agroecológica (IT ). Para la captura de las arañas se utilizaron trampas pitfall. Se colectaron 2818 en (IT) y 1585 en (IC), pertenecientes a 21 familias, 20 en (IT) y 19 en (IC). Las familias mejor representadas fueron Lycosidae, Linyphiidae, Hahnidae, Tetragnathidae, Anyphaenidae y Corinnidae. Se encontraron los mismos gremios de arañas en ambos tratamientos y la proporción relativa se mantuvo en cada caso. Los mejor representados para ambos tratamientos fueron las cazadoras corredoras en suelo y las tejedoras errantes de tela irregular tipo sabana. Se observó un comportamiento diferencial en la abundancia de individuos. Estos resultados muestran que el mayor número de individuos en IT estaría relacionado con el manejo, que se caracteriza por una disminución en el uso de agroquímicos, mayor diversidad de cultivos y presencia de vegetación espontánea que proporcionarían hábitat, refugio y alimentos para las arañas, las que actuarían como potenciales controladores de plagas. La disminución en la aplicación de agroquímicos y el aumento de la agrobiodiversidad, son aspectos fundamentales a tener en cuenta si se pretende alcanzar la autorregulación biótica de los agroecosistemas

Paisagens rurais no Pampa: um olhar sobre sistemas biodiversos: Rural landscapes in the Pampa: a look at biodiverse systems

O modelo econômico vigente tem promovido o desenho de paisagens rurais que alimentam processos de impacto ambiental. É um reflexo da história que vê sociedade e natureza como elementos distintos. A agricultura é considerada causa da destruição de ecossistemas em nome da intensificação agrícola-tecnológica. A região sul do Brasil se destaca como propulsora de iniciativas de implementação de sistemas produtivos biodiversos, como os Sistemas Agroflorestais. Especialmente na área de domínio do Pampa, destacada pelo uso inadequado do solo, há a necessidade de estudos que promovam sistemas produtivos restaurativos e aliem conservação da biodiversidade e geração de renda. Assim, existe a possibilidade de novos desenhos que incluam as atividades em curso pelos produtores familiares pampeanos em sistemas produtivos que promovam a permeabilidade da paisagem local. Nessa perspectiva, sob a base agroecológica do conhecimento local, a utilização de grupos de espécies nativas de retorno econômico é uma tecnologia estratégica à gestão da paisagem. Este estudo tem como objetivo analisar e refletir a partir da estrutura socioecológica do Bioma Pampa, soluções agroecológicas para a conservação e recuperação dos serviços ecossistêmicos do território pampeano

Sexual behavior of Alpaida veniliae (Araneae: Araneidae)

Studies in transgenic soybean cropsin Buenos Aires province, Argentina, revealed that Alpaida veniliae is one of the most abundant species in the guild of orb web spiders. This species is an effective natural enemy of insect pests affecting this crop. In the present study we carried out a descriptive and quantitative analysis of sexual behavior (courtship, mating and post-mating) of A. veniliae. The spiders were collected in transgenic soybean crops located in Chivilcoy (35º01' S - 60º06' W), Buenos Aires, Argentina, and reared under laboratory conditions. Based on observations of 20 couples (with virgin females), behavioral units of male and female in terms of postures and movements,including details on duration and frequency, were described at all stages of sexual activity (courtship, mating and post-mating). Courtship exhibited the greatest number and duration of behavioral units in both sexes. Male and female had a sequence of 16 and nine units, respectively, being the frequency of repetitions of the units significantly higher in the male. Mating was brief and males used a single palp to fill only one of the female spermathecae, after which the female became unreceptive. Mating had two behavioral units in the male and only one in the female. During post-mating males had three and females two behavioral units. The average duration of the whole sexual behavior was 541.90 ± 123.1 seconds for the male and 338.20 ± 74.1 seconds for the female. Alpaida veniliae females rarely accept a second mating with the same or another male (remating), indicating a strict monogamy. In 46% of observed mating, the female cannibalized the male after it. Females became unattractive after mating, since stop producing sex pheromones, causing a reduction of the male vibratory courtship. The high cost of courtship, including the risk of cannibalism, would reinforce the selectivity of males towards receptive virgin females.Centro de Estudios Parasitológicos y de Vectore

Efectos de distintos insecticidas convencionales y biorracionales, en la biología de una araña tejedora (<i>Alpaida veniliae</i>) en soja

El uso de insecticidas de amplio espectro son comunes en el cultivo convencional, su alta toxicidad en artrópodos especialmente en enemigos naturales ha sido demostrado. El objetivo fue evaluar efectos subletales de plaguicidas convencionales y biorracionales en arañas, a nivel de comportamiento predador y reproductor. Se utilizaron concentraciones subletales de: cipermetrina, endosulfan, spinosad y metoxifenocida; suministrados a través de la presa Musca domestica. Se observó retraso en la construcción de la tela con cipermetrina, spinosad y endosulfan. Presencia de cuerpos grasos en ovarios y reducción del diámetro de oocitos, disminución en la fecundidad y fertilidad con todos los insecticidas. Se demuestra el efecto de los insecticidas en aspectos relacionados al desempeño disminuyendo su potencialidad de agentes controladores de poblaciones de insectos, reduciendo drásticamente su papel como enemigo natural de plagas en los cultivos.The use of broad-spectrum insecticides are common in conventional farming, high toxicity especially arthropod natural enemies has been demonstrated. The aim was to assess sublethal effects of conventional insecticides and biorracionales in spiders, predatory level and reproductive behavior. Sublethal concentrations were used: cypermethrin, endosulfan, spinosad and methoxyfenozide; provided through the prey Musca domestica. Delay in web building with cypermethrin, spinosad and endosulfan was observed. Presence of fatt body in ovaries and oocytes diameter reduction, decreased fecundity and fertility with all insecticides. The effect of insecticides on issues related to performance decreasing its potential control agents of insect populations, drastically reducing their role as natural enemies of crop pests is demonstrated.Eje A4: Ambiente, Naturaleza y Agroecología.Facultad de Ciencias Agrarias y Forestale

Efectos de distintos insecticidas convencionales y biorracionales, en la biología de una araña tejedora (<i>Alpaida veniliae</i>) en soja

El uso de insecticidas de amplio espectro son comunes en el cultivo convencional, su alta toxicidad en artrópodos especialmente en enemigos naturales ha sido demostrado. El objetivo fue evaluar efectos subletales de plaguicidas convencionales y biorracionales en arañas, a nivel de comportamiento predador y reproductor. Se utilizaron concentraciones subletales de: cipermetrina, endosulfan, spinosad y metoxifenocida; suministrados a través de la presa Musca domestica. Se observó retraso en la construcción de la tela con cipermetrina, spinosad y endosulfan. Presencia de cuerpos grasos en ovarios y reducción del diámetro de oocitos, disminución en la fecundidad y fertilidad con todos los insecticidas. Se demuestra el efecto de los insecticidas en aspectos relacionados al desempeño disminuyendo su potencialidad de agentes controladores de poblaciones de insectos, reduciendo drásticamente su papel como enemigo natural de plagas en los cultivos.The use of broad-spectrum insecticides are common in conventional farming, high toxicity especially arthropod natural enemies has been demonstrated. The aim was to assess sublethal effects of conventional insecticides and biorracionales in spiders, predatory level and reproductive behavior. Sublethal concentrations were used: cypermethrin, endosulfan, spinosad and methoxyfenozide; provided through the prey Musca domestica. Delay in web building with cypermethrin, spinosad and endosulfan was observed. Presence of fatt body in ovaries and oocytes diameter reduction, decreased fecundity and fertility with all insecticides. The effect of insecticides on issues related to performance decreasing its potential control agents of insect populations, drastically reducing their role as natural enemies of crop pests is demonstrated.Eje A4: Ambiente, Naturaleza y Agroecología.Facultad de Ciencias Agrarias y Forestale