RESUMEN
Facultatively sexual entomopathogenic nematodes are a promising model for the experimental study of the adaptive values of sex. Our experiments in the laboratory showed that entomopathogenic nematodes display at least two different strategies in regulating the degree of amphimix as a response to nutritional stress. One strategy promotes the production of males, amphimix and the genetic variability of the offspring, improving the chances for a successful new adaptation. Another strategy increases the production of hermaphrodites at the expense of males, increasing the total number of reproductive individuals and thus the total number of offspring produced. Surprisingly, the strategy used depends upon the strain of symbiotic bacteria the nematodes are growing. The relevance of the results, in helping to discriminate between rival theories for the evolutionary maintenance of sex, is discussed.
Asunto(s)
Mariposas Nocturnas/fisiología , Nematodos/fisiología , Simbiosis , Animales , Trastornos del Desarrollo Sexual , Femenino , Masculino , Mariposas Nocturnas/parasitología , Nematodos/genética , ReproducciónRESUMEN
The genetic diversity of symbiotic Xenorhabdus and Photorhabdus bacteria associated with entomopathogenic nematodes was examined by a restriction fragment length polymorphism analysis of PCR-amplified 16S rRNA genes (rDNAs). A total of 117 strains were studied, most of which were isolated from the Caribbean basin after an exhaustive soil sampling. The collection consisted of 77 isolates recovered from entomopathogenic nematodes in 14 Caribbean islands and of 40 reference strains belonging to Xenorhabdus and Photorhabdus spp. collected at various localities worldwide. Thirty distinctive 16S rDNA genotypes were identified, and cluster analysis was used to distinguish the genus Xenorhabdus from the genus Photorhabdus. The genus Xenorhabdus appears more diverse than the genus Photorhabdus, and for both genera the bacterial genotype diversity is in congruence with the host-nematode taxonomy. The occurrence of symbiotic bacterial genotypes was related to the ecological distribution of host nematodes.
Asunto(s)
Enterobacteriaceae/clasificación , Nematodos/microbiología , ARN Ribosómico 16S/genética , Animales , Análisis por Conglomerados , Enterobacteriaceae/genética , Enterobacteriaceae/aislamiento & purificación , Enterobacteriaceae/fisiología , Geografía , Insectos/parasitología , Nematodos/aislamiento & purificación , Fenotipo , Filogenia , Reacción en Cadena de la Polimerasa/métodos , Mapeo Restrictivo , Suelo/parasitología , Especificidad de la Especie , Simbiosis , Indias OccidentalesRESUMEN
Entomopathogenous nematodes are well known biocontrol agents of insects. They live in the superficial layer of the soil, a location where ticks accomplish their molt and where they oviposit their eggs, making them, theoretically, the preys of infective larvae of nematodes. Seventeen strains of entomopathogenous nematodes: eight strains of Steinernema and nine strains of Heterorhabditis were placed in contact with each of the free living stages of three tick species: Amblyomma variegatum, Boophilus microplus and B. annulatus. The first two species were resistant to all the nematode strains that were tested, whereas B. annulatus was susceptible to all of them. Ovipositing females were more susceptible than females during the preoviposition period. There were no anatomical differences between the two species of Boophilus which can account for such differences in their susceptibility. The use of nematodes to control some species of ticks should be considered.
Asunto(s)
Rhabditoidea/patogenicidad , Garrapatas/parasitología , Animales , Femenino , Rhabditoidea/aislamiento & purificación , Control de Ácaros y GarrapatasRESUMEN
In 1992, two cases of abdominal angiostrongylosis were reported in young Guadeloupean children. With a view to determine the natural infestation rate of Guadeloupe rodents (Rattus rattus, R. norvegicus) by Angiostrongylus costaricensis, 656 rats caught in the country have been examined. Both murine species are naturally infested (6.2% in R. rattus and 14.9% in R. norvegicus), which gives a total prevalence of 7.5%. This total prevalence is higher in the tourist area. A complementary investigation proves to be necessary to identify in Guadeloupe the alleged intermediate hosts (slugs, land snails) in which the human illness has its direct origins.
Asunto(s)
Angiostrongylus/aislamiento & purificación , Muridae/parasitología , Animales , Preescolar , Reservorios de Enfermedades , Humanos , Lactante , Ratas , Infecciones por Strongylida/parasitología , Infecciones por Strongylida/transmisión , Indias OccidentalesRESUMEN
Some vertebrate species in Guadeloupe are predators of free or parasitic stages of Amblyomma variegatum (Fabricius). Among birds, 1.9% of the 421 identified animals found in the stomachs of grackles (Quiscalus lugubris), 1.6% of the 364 animals found in the stomachs of free-ranging chickens, and 0.3% of the 4642 animals found in the stomach of cattle egrets (Bubulcus ibis) were A. variegatum ticks. The most efficient predator of ticks was the tropical fire ant, Solenopsis geminata, which was observed to only attack engorged stages of ticks. An average of 8% of the 564 individual ticks or batch of ticks released on the ground, mainly in a grass environment, were attacked by this ant species. Mice (Mus musculus) and mongooses (Herpestes auropunctatus) feed on engorged nymphs and female ticks. None of the 15 strains of entomophagous nematodes, genera Steinernema and Heterorhabditis, experimentally put in contact with engorged larvae and nymphs were able to parasitize them. In the laboratory, the insects Megaselia scalaris (Diptera) and Tineola sp. (Lepidoptera) were occasionally found to feed on engorged and unfed ticks, respectively.