Nematodes (Mermithidae) parasitizing grasshoppers (Orthoptera: Acrididae) in the Pampean region, Argentina / Nematóides (Mermithidae) parasitando gafanhotos (Orthoptera: Acrididae) nos Pampas região, a Argentina

Abstract This work provides the results of a survey of entomonematodes parasites of grasshoppers in grasslands of the Pampean Region, Argentina. Nymphs of Staurorhectus longicornis Giglio-Tos, Laplatacris dispar Rhen, 1939, Dichroplus elongatus Giglio-Tos, 1894 and Metaleptea brevicornis (L.) (Orthoptera: Acrididae) were collected. Mermithidae was the only family registered with seven species: Agamermis decaudata Cobb, Steiner and Christie, 1923, Amphimermis bonaerensis Miralles and Camino, 1983, Amphimermis dichroplusi Camino and Lange, 1997, Amphimermis ronderosi Camino and Lange, 1997, Hexamermis coclhearius Stock and Camino, 1992, Hexamermis ovistriata Stock and Camino, 1992, and Longimermis acridophila Camino and Stock, 1989. The values of parasitism ranged between 1-12%, and intensity not overcome the number of 5.0 nematodes per larva. The nematodes observed showed specificity, not registering the same species of parasite in more than one host species. The Pampean region constituted an area with high diversity of mermithids where new species could be consider as bioregulator agents of this troublesome insect pests in agricultural areas of Argentina.

Resumo Este trabalho apresenta os resultados de uma pesquisa entomonematode parasitando gafanhotos em pastagens da região pampeana, Argentina. Ninfas de Staurorhectus longicornis Giglio-Tos, Laplatacris dispar Rhen de 1939, Dichroplus elongatus Giglio-Tos, 1894 e Metaleptea brevicornis (L.) (Orthoptera: Acrididae) foram coletados. Mermithidae era a única família registrado com sete espécies: Agamermis decaudata Cobb, Steiner and Christie, 1923, Amphimermis bonaerensis Miralles and Camino, 1983, Amphimermis dichroplusi Camino and Lange, 1997, Amphimermis ronderosi Camino and Lange, 1997, Hexamermis coclhearius Stock and Camino, 1992, Hexamermis ovistriata Stock and Camino, 1992, e Longimermis acridophila Camino and imagem, de 1989. Os valores de parasitismo variou entre 1-12%, e intensidade não superar o número de 5,0 nematóides por larva. Os nemátodos observados demonstraram especificidade, não registar as mesmas espécies de parasita em mais do que uma espécie de hospedeiro. A região pampeana constituída uma área com alta diversidade de mermithids onde novas espécies poderiam ser consideradas como agentes bio-reguladores deste incômodos insetos pragas em áreas agrícolas da Argentina.

Romanomermis culicivorax (Nematoda:Mermithidae): una alternativa para el control de vectores de malaria en Nicaragua / Romanomermis culicivorax (Nematoda: Mermithidae): an alternative for malaria vector control in Nicaragua

Introducción: la aparición de casos de malaria en zonas donde se creía controlada, como lo es la Región Autónoma Atlántica Norte en Nicaragua, se debe a múltiples factores como el costo de los productos químicos para el control vectorial, zonas de difícil accesibilidad y altos índices de pobreza. Recientemente existe un marcado interés en disminuir la incidencia y prevalencia de la malaria en esta área, mediante la producción y aplicación de alternativas biológicas de control. Objetivos: establecer y estandarizar la cría de Romanomermis culicivorax para la producción masiva en condiciones de laboratorio y su utilización en criaderos naturales para reducir la población de Anopheles albimanus en 3 municipios de la Región Autónoma Atlántica Norte. Métodos: se utilizaron cultivos de una cepa de Romanomermis culicivorax provenientes del Instituto de Medicina Tropical Pedro Kourí de La Habana, Cuba. El establecimiento y la producción de esta cepa se hizo siguiendo la metodología descrita por especialistas cubanos. El trabajo se realizó en 7 criaderos de 5 barrios pertenecientes a los municipios Puerto Cabezas, Waspam y Rosita, desde noviembre de 2009 a marzo de 2011. Resultados: se estableció y estandarizó la cría del nematodo, utilizando la dosis de infestación de 7:1 (7 pre-parasíticos por larva) en condiciones de laboratorio. La dosis de aplicación en los criaderos fue 1 000 pre-parasíticos/m²,demostrando ser adecuada para las condiciones de campo. Se lograron porcentajes de reducción elevados y en menor tiempo en los municipios Waspam y Rosita. Se demostró la permanencia del nematodo en los criaderos. Conclusiones: se establece por primera vez y con éxito la producción masiva de Romanomermis culicivorax en Nicaragua. Los resultados en el terreno demostraron la eficiencia de este nematodo para controlar densidades larvales de Anopheles albimanus, lo cual constituye una alternativa de control vectorial(AU)

Introduction: the emergence of malaria cases in areas where the disease was thought to be controlled, such as the North Atlantic Autonomous Region in Nicaragua, is due to a variety of factors, such as the cost of chemicals for vector control, the inaccessibility of areas and the high rates of poverty. A marked interest has recently arisen in reducing the incidence and prevalence of malaria in the region by developing and implementing biological control alternatives. Objectives: establish and standardize the breeding of Romanomermis culicivorax for mass production under laboratory conditions and for its use in natural breeding sites to reduce the population of Anopheles albimanus in three municipalities of the North Atlantic Autonomous Region. Methods: the study was based on cultures of a Romanomermis culicivorax strain obtained from Pedro Kourí Tropical Medicine Institute in Havana, Cuba. The strain was established and produced following the methodology described by Cuban specialists. The research was conducted at 7 breeding sites from 5 districts in the municipalities of Puerto Cabezas, Waspam and Rosita, from November 2009 to March 2011. Results: breeding of the nematode was established and standardized with a 7:1 infestation dose (7 preparasites per larva) under laboratory conditions. The application dose at breeding sites was 1 000 preparasites/m², which proved to be appropriate for field conditions. High reduction percentages were obtained. These were achieved in a shorter time in the municipalities of Waspam and Rosita. It was found that the nematodes remained at the breeding sites. Conclusions: successful mass production of Romanomermis culicivorax is established for the first time in Nicaragua. Field results show the efficiency of this nematode to control larval densities of Anopheles albimanus, constituting a vector control alternative(AU)

Efecto de la temperatura sobre la longevidad e infección con preparásitos del nematodo Strelkovimermis spiculatus (Nemata: Mermithidae), parásito de mosquitos culícidos / Effect of temperature on longevity and infection with the nematode Strelkovimermis spiculatus (Nemata: Mermithidae), a parasite of mosquitoes

Strelkovimermis spiculatus is a common parasite of culicid species in Argentina. Effect of temperature on longevity and infectivity of juvenile preparasites of S. spiculatus was determined at 4, 10, 20 and 27 degrees C. Three containers with 100 ml of dechlorinate water and 300 preparasites (12 hour-old), were placed for each day and temperature, during 40 days (total = 480 containers). Survived preparasites were counted on 12 containers per day (three for each temperature). When number of survived preparasites was determined, second instar larvae of Aedes aegypti were added to each container in a 10:1 ratio (preparasites:mosquito) to determine infectivity of daily survived preparasites. Longevity of preparasites decreased at higher temperatures. Maximum longevity of preparasites maintained at 4, 10, 20 and 27 degrees C were 35, 30, 25 and 27 days, respectively. Survivorship of preparasites, exposed to the same temperatures, varied from 57 to 100 at day two, from 21 to 77 at day five and from 9 to 33 at day ten. Infectivity of preparasites maintained at temperatures from 4 to 27 degrees C was always higher than 70. Extended longevity with maintenance of the infectivity capacity of preparasites, are important attributes to consider S. spiculatus an effective mean of controlling a large number of culicid species between 4 and 27 degrees C.

Mortality in immatures of the floodwater mosquito Ochlerotatus albifasciatus (Diptera: Culicidae) and effects of parasitism by Strelkovimermis spiculatus (Nematoda: Mermithidae) in Buenos Aires Province, Argentina

Life tables were constructed for six cohorts of immature stages of the floodwater mosquito Ochlerotatus albifasciatus (Macquart) in a park in Buenos Aires, highlighting the mortality attributable to the parasitic nematode, Strelkovimermis spiculatus Poinar & Camino. Two cohorts were selected to compare parasite incidence in all mosquito stages when low and high parasitism occurred. Development time of Oc. albifasciatus from first instar to adult was 7.7-10 days in the spring, 6 days in the summer, and 10.9-21.9 days in the fall. Survival was estimated as 0-1.4 percent in the spring, 2 percent in the summer and 0.2-4.4 percent in the fall. The highest "K" value (Killing power) occurred during a fall cohort when prevalence of the parasite was 86.9 percent, and the lowest in a spring cohort. Parasitism occurred during all seasons, but S. spiculatus persisted to adult only in the summer and fall, when adult mosquitoes developed from parasitized third and fourth instars larvae. The abundance of S. spiculatus differed between old and young larvae only when parasite prevalence was the highest. Although pupae and adults of Oc. albifasciatus were parasitized, no pupal mortality attributable to parasitism was recorded. The proportion of parasitized adults ranged from 14.2 percent and 5.7 percent in the two cohorts compared. Pupal wet weight and adult wing lengths did not differ between parasitized and unparasitized individuals

Susceptibilidad de Anopheles nuneztovari Gabaldón y Aedes aegypti L a la infección con Romanomermis iyengari Welch (rhabditida: mermitidae) / Susceptibility to the infestation of Anopheles nuneztovari Gabaldón and Aedes aegypti L with Romanomermis iyengari Welch (rhabditida: mermithidae)

Con la finalidad de valorar la capacidad de infestación del nemátodo parásito de mosquitos, Romanomermis iyengari Welch, sobre larvas de las especies Anopheles nuneztovari Gabaldón y Aedes aegypti L1, se condujo un estudio en condiciones de laboratorio. Para cada especie se tomaron 900 larvas de los estadios L1 al L3. Estos se infestaron con larvas preparasíticas de R. iyengari en proporciones de 5:1 y 10:1. Se obtuvieron promedios de infestación de 3,9 y 6,7 para Anopheles nuneztovari y de 1,9 y 4,7 para Aedes eagypti respectivamente. Los niveles de mortalidad oscilaron entre 95 y 100 por ciento para ambas especies, observándose mayor susceptibilidad al parasitismo en las larvas de Anopheles nuneztovari

Produccion masiva de Romanomermis iyengari (Nematoda: Mermithidae) y su aplicacion en criaderos de anofelinos en Boa Vista (Roraima), Brasil / Mass produced Romanomermis iyengari (Nematoda: Mermithidae) applied to anopheline breeding sites in Boa Vista (Roraima), Brazil

Para desarrollar la produccion masiva del nematodo Romanomermis iyengari Welch, se llevo a cabo el diseno y montaje de una bioplanta en las instalaciones de la Universidad Federal del Estado de Roraima, Brasil, tras un convenio con la Secretaria de Salud del mencionado estado. El objetivo de este trabajo fue establecer el proceso basico de cria masiva del parasito para su posterior aplicacion en criaderos de anofelinos. Se obtuvieron 68 cultivos por cada ciclo de siete dias, con un total de 272 cultivos por mes. Antes de los tratamientos de campo se realizaron pruebas de laboratorio en las que se comprobo la gran susceptibilidad de las larvas de anofelinos a la infestacion por R. iyengari, con tasas de parasitismo de 71 a 98 por ciento. Para evaluar la capacidad parasitaria de R. iyengari en condiciones de campo, se seleccionaron 12 criaderos naturales de anofelinos, con areas que oscilaron entre 50 y 450 m2, en los que se observo la presencia de larvas de mosquitos de las especies Anopheles albitarsis Lynch-Arribalzaga y Anopheles rondoni Neiva-Pinto, con densidades de 34 a 66 larvas/m2. Para la dispersion del biolarvicida en los 12 criaderos se utilizo una bomba costal manual de fabricacion nacional a una presion de dos atmosferas y se aplico una dosis de 2000 preparasitos/m2. Siete dias despues de los tratamientos se observo una marcada reduccion (85 a 97 por ciento) de las poblaciones de anofelinos. Los resultados obtenidos demostraron la posibilidad de utilizar R. iyengari para controlar las poblaciones larvarias de ambas especies de anofelinos

The Romanomermis iyengari parasite for Anopheles pseudopunctipennis suppression in natural habitats in Oaxaca State, Mexico

In September and November 1996 Romanomermis yengari Welch, a parasite of larval mosquitoes, was released in 44 natural larval habitat sites of Anopheles pseudopunctipennis Theobald in an attempt to reduce the larval populations of this important malaria vector. The selected treatment sites ranged in size from 5 to 500 m2. The study was carried out in Pochutla District of Oaxaca State, on the Pacific coast of Mexico. Chemical pesticides to reduce vector populations have been the principal tool in malaria supression campaigns. However, the excessive use of these chemiclas has created pesticide resistance and other serious collateral problems. Therefore, a biological control project using agents that are pathogens of Anopheles larvae was initiated in 1996. The principal objective was to establish mass rearing capacities for R. iyengari. Detailed methodology for rearing and introducing these nematodes into mosquito larval habitats was established at the National Polytechnic Institute of Oaxaca State. Before application of the parasites to larval habitats, site characterirstics were determined, including size, depth, aquatic vegetation, salinity, ph, conductivity, temperature, and pretreatment larval density. With a compressed air sprayer, infective mermithid parasites were released at rates of either 2 000 or 3 000/m2, and the parasites produced high levels of infection. Anopheles populations were sampled 72 h posttreatment, and the larvae obtained were taken to the laboratory and examined through microscopic dissection to determine infection levels and mean parasitism. Nematode parasitism ranged from 85 to 100 per cent at all the treatment sites, even though no previous information concerning field parasitism of An. pseudopunctipennis by R. iyengari has been reported. In addition, a significant reduction of mosquito larval density at the treatment sites was found five days after the nematode application. Levels of parasitism were indicative of the number of mosquito larvae killed by the treatment since infected larvae never progressed to the pupal stage. Results from sampling nine of the sites 2 months after the initial application of nematodes indicated that a high number of mosquito larvae were infected by parasites that had emerged from eggs previously deposited in the stratum. This work suggests the potential of this mermithid to reduce An. pseudopunctipennis populations in Oaxaca State

Limnomermis subtropicalis n. sp. (Neumatoda: Mermithidae) a parasite of larvae of Simulium orbitale Lutz (Diptera: Simuliidae) in Argentina

Limnomermis subtropicalis n. sp. (Nematoda: Mermithidae) a parasite of larvae of Simulium orbitale Lutz (Diptera: Simuliidae) found in Argentina is described and illustrated. This species is characterized by having medium sized amphids, pocket-shaped, medium sized vagina, sculptured spicule, and by having 9 preanal, 7 postanal papillae in the ventral row, and 12 papillae in the lateral rows.

Ocorrencia de nematoides parasitas em conocephalus (orthoptera; tettigoniidae) / Ocurrence of nematodes parasites in conocephalus (orthoptera; tettigoniidae)

Os gafanhotos do gênero Conocephalus, segundo hospedeiro intermediário de Eurytrema coelomaticum (Trematoda: Dicroceiliide) no Brasil, foram capturados de pastagens e dissecados no laboratório. Nematóides parasitas foram encontrados na cavidade celomática dos insetos e foram indetificados como pertenecentes á familia Mermithidae. Estes nematóides podemos ser uma importante ferramenta para o controle biológicos destes insetos na naturaleza

Demostración de la actividad biolarvicida de Romanomermis iyengari (Nematoda: Mermithidae) en condiciones de laboratorio / Demostration of the biolarvicidae activity of Romanomermis iyengari (Nematoda: Mermithidae) in laboratory conditions

Se llevaron a cabo pruebas de laboratorio para demostrar la eficacia del mermítido Romanomermis iyengari como agente biorregulador de larvas de Culex quinquefasciatus y Anopheles albimanus vectores de filariasis y de malaria en el área del caribe. Se probaron dosis de preparasíticos a larvas hospederas de 3:1, 5:1 y 10:1, encontrandose que las especies de mosquitos ensayadas se comportaron de manera similar presentando medias de infectación más elevadas a medida que se incrementaba la dosis. Fue demostrando la selectividad de R. iyengari por larvas de los estadíos más jóvenes de ambas esapecies, las cuales mostraron altas tasas de infectación y los porcentajes más altos de parasitismo. Los ensayos realizados para valorar la edad de los cultivos del mermítido con el objeto de determinar el tiempo óptimo de almacenamiento, demostraron que los preparasíticos provenientes de cultivos almacenados durante 6 semanas a temperatura ambiente arrojaron los más altos índices de infectación en larvas de C. quinquefasciatus del insectario. Estos resultados permitieron concluir que R. iyengari puede ser utilizado como agente potecial de control biológico, para poblaciones larvales de mosquitos especialmente de los estadíos más jóvenes

Effect of temperature on different stages of Romanomermis iyengari, a mermithid nematode parasite of mosquitoes

The effect of temperature (20 degrees-35 degrees C) on different stages of Romanomermis iyengari was studied. In embryonic development, the single-cell stage eggs developed into mature eggs in 4.5-6.5 days at 25-35 degrees C but, required 9.5 days at 20 degrees C. Complete hatching occurred in 7 and 9 days after egg-laying at 35 and 30 degrees C, respectively. At 25 and 20 degrees C, 85-96 of the eggs did not hatch even by 30th day. Loss of infectivity and death of the preparasites occurred faster at higher temperatures. The 50 survival durations of preparasites at 20 and 35 degrees C were 105.8 and 10.6 hr respectively. They retained 50 infectivity up to 69.7 and 30.3 hr. The duration of the parasitic phase increased as temperature decreased. Low temperature favoured production of a higher proportion of females which were also larger in size. The maximum time taken for the juveniles to become adults was 14 days at 20 degrees C and the minimum was 9 days at 35 degrees C. Oviposition began earlier at higher temperature than at lower temperature. However, its fecundic period was shorter at 20 degrees C than at 35 degrees C indicating enhanced rate of oviposition at 20 degrees C. Fecundity was adversely affected at 20 degrees C and 35 degrees C. It is shown that the temperature range of 25 degrees-30 degrees C favours optimum development of R. iyengari.

Infectivity of a mermithid nematode Romanomermis iyengari (Welch) in different conductivity levels under laboratory and field conditions.

Infectivity of R. iyengari was examined by exposing mosquito (Culex quinquefasciatus) larvae to the preparasite at different conductivity levels. The preparasite infected 63.5, 30, 11, 1.5 and 0.5% of the mosquito larvae respectively at 2000, 2500, 3000, 3300 and 3600 mu ho/cm. Although, 62-69% of the preparasite survived at 4000-5400 mu ho/cm, it did not infect. Application of preparasite to tree-holes resulted in 53-63% infection of Aedes albopictus larvae initially. On 6th day the infection level was 40% which decreased further to 7% by 15th day. The infection reappeared on 38th day indicating that R. iyengari has not only infected mosquito larvae as soon as they were applied to tree-holes in which the conductivity was 600-2800 mu ho/cm but also got established there.

Estudio sobre la infestación y el desarrollo parasítico en Romanomermis Culicivorax (Ross y Smith, 1976) (Rhabditida, Mermithidae) en larvas de Anopheles (Nyssorhynchus) Albimanus Wiedeman, 1821 (Diptera: Culicidae) en condiciones de laboratorio / Study on infestation and parasite development of Romanomermis Culicivorax (Ross and Smith, 1976) (Rhabditida, Mermithidae) in larvae of Anopheles (Nyssorhynchus) Albimanus Wiedeman, 1821 (Diptera: Culicidae) under laboratory conditions

Se realizó un estudio para observar la capacidad infectiva y el desarrollo de la fase parasítica del nemátodo Romanomermis culicivorax (Ross y Smith, 1976) en larvas de Anopheles albimanus Wiedeman, 1821 en diferentes estadíos de desarrollo. Se exponen los resultados y realizan las conclusiones

Estudio de la edad de los cultivos de Romanomermis culicivorax (Ross y Smith, 1976) (Rhabditida: Mermithidae) en la infestación de larvas de mosquito de la especie Culex Quinquefasciatus Say, 1823 en condiciones de laboratorio / Study of age of cultures of Romanomermis culicivorax (Ross and Smith, 1976) (Rhabditida: Mermithidae) in the infestation of mosquito larvae culex quinquefasciatus say, 1823 under laboratory conditions

Se comparó el efecto de 3 cultivos de un parásito nemátodo, Romanomermis culicivorax (Ross y Smith, 1976), son distintos tiempos de almacenaje a un rango de temperatura de 25 a 27 -C, en la infestación de larvas de mosquito de la especie Culex Quinquefasciatus Say, 1823 en segundo estado de desarrollo. Para ello se utilizaron 900 larvas de mosquito separadas en 3 grupos de 300, un testigo o control sin infestar y formas preparasíticas del nemátodo, obtenidas de la eclosión de huevos de cultivos de 5, 13 y 24 semanas de edad, en la proporción de 1:5, se observaron, finalmente, diferentes medias de infestación y tanto por ciento de mortalidad