Food and the spatial distribution of adult female pinworms parasitic in the hindgut of Periplaneta americana L.

Food and the spatial distribution of adult female pinworms parasitic in the hindgut of Periplaneta americana L. International Journal for Parasitology 4: 759–771. The spatial distribution of the two pinworms Hammerschmidtiella diesingi and Leidynema appendiculata in the adult cockroach Periplaneta americana was determined by examination of hind guts fixed by immersion in liquid air. The position of the mouths of the worms reveals that L. appendiculata favours a more anterior position and is more restricted in its distribution than H. diesingi. The position of each species in the colon is unaffected by the presence of the other species or by crowding. Moreover, the two species are segregated in terms of their radial distribution, with the mouth of H, diesingi being restricted to a position near the intima of the colon while that of L. appendiculata favours the lumen. The two nematodes differ in the structure of the stoma and pharynx which reflect a difference in their diet. The food of L. appendiculata consists of relatively large particles while that of H. diesingi is finely patticulate. The ability of these two species to coexist in the same host is explained by their longitudinal and radial distribution and by the different sources of their food.     

Dose- and time-response assessments ofHeterorhabditis heliothidis andSteinernema feltiae [Nem.: Rhabitida] againstAedes aegypti larvae

Steinernema feltiae (=Neoaplectana carpocapsae) andHeterorhabditis heliothidis were tested against 3^rd instarAedes aegypti larvae in the laboratory. Different dosages of the nematodes and varying durations of exposure were assessed.H. heliothidis was more effective thanS. feltiae. Larval mortality showed a positive linear correlation with both nematode dosage and the duration of exposure. The number of nematodes of both species that gained access to the haemocoele of larvae was always low, but increased with dosage and exposure time. The rate of melanization of the nematodes in the larvae was correlated with dosage, but was not affected by the duration of exposure.      

Endocrine relationships between nematodes and their insect hosts--a review

This paper reviews the evidence for a possible endocrine basis for the remarkable synchrony often observed between the development of entomophilic nematodes and that of their hosts. Although some suggestive observations have been made by various workers, there is no rigorous evidence which points to such an association. In those few cases which have been rigorously examined, there is some evidence that the synchrony is not based upon endocrine signals passing between host and parasite. The possibility that the parasite may manipulate the endocrinology of the insect in order to alter the metabolism and physiology of the host to favour the parasite has received less attention, but is nevertheless thought to constitute a promising areas of research.     

Hexamermis glossinae [Nematoda: Mermithidae] parasitizing tsetse [Diptera: Glossinidae] in Kenya

Glossina pallidipes Austen,G. brevipalpis Newstead andG. austeni Newstead were collected from 5 sites along the south Kenyan coast over a 2 year period. They were dissected and examined for nematodes. Three of the sites yielded tsetse parasitized by juvenile mermithids identified asHexamermis glossinae Poinar et al. Glossina pallidipes andG. brevipalpis are new host records for this parasite, whileG. austeni was captured infrequently and only at a site that failed to yield other parasitized tsetse. Parasite prevalence was low (0.16–0.61 %) and did not differ between male and female hosts. More tsetse than expected by chance harboured nematodes during the long rains season (April–August) than during the short rains (September–November) or dry season (December–March). Early juvenile stages (0.5–2.5 mm long) were recovered mainly from tsetse less than 50 days old, while late juvenile stages (35–85 mm long) were only found in flies older than 30 days. Late stages occurred singly while early ones usually occurred as two or more per host.     

EVect of the Entomopathogenic Nematodes, Steinernema feltiae and S. carpocapsae , on the Potato Cyst Nematode, Globodera rostochiensis , in Pot Trials

Two pot experiments, one in a glasshouse and the other in an outdoor sand plunge, were conducted to examine the influence of the entomopathogenic nematodes, Steinernema feltiae and S. carpocapsae , on the invasion and development of the potato cyst nematode, Globodera rostochiensis . Of a total of eight diVerent treatments with entomopathogenic nematodes in the glasshouse trial, three reduced the invasion of G. rostochiensis and one reduced the numbers of new cysts that were produced compared with controls. In the outdoor experiment, seven of the 12 treatments gave a reduction in invasion but none resulted in changes in the numbers of cysts found at plant senescence. In general, invasion of G. rostochiensis juveniles was reduced more eVectively by S. carpocapsae than by S. feltiae , and was greatest in the outdoor trial where larger inocula of entomopathogenic nematodes were used. Overall, the results indicated that use of S. feltiae and S. carpocapsae is unlikely to provide a viable control strategy for G. rostochiensis .     

Molecular taxonomy and phylogeny of entomopathogenic nematode species (Rhabditida: Steinernematidae) by RFLP analysis of the ITS region of the ribosomal DNA repeat unit

The ITS region of 19 isolates of the genus Steinernema Travassos, 1927 belonging to 17 species was PCR amplified. The resulting products were then digested with 17 different restriction endonucleases and the fragments generated were separated by agarose gel electrophoresis. Some enzymes yielded patterns which were highly diagnostic (e.g. Alu I, Dde I, Hha I and Hinf I) while others showed similar RFLP patterns for the majority of species (e.g. Hpa II). All of the species could be unequivocally identified using this method. A tree was constructed based on band sharing which resulted in clusters of species which exhibited similar morphological features.     

Entomopathogenic rhabditid nematodes and pest control

Imagine an insecticide that is effective against insects in cryptic habitats, has a wide spectrum of efficacy, is cheaply produced by high technology or cottage industry and hence is suitable for developing and developed countries, is non-toxic to vertebrates and plants, and persists at low levels in natural habitats. This is not a dream. These properties apply to a group of entomopathogenic nematodes belonging to the rhabditid families Steinernematidae and Heterorhabditidae. Bill Hominick reviews developments in the use of these nematodes for the control of insect pests. His article represents a departure in philosophy for parasitologists, in that entomophilic nematologists are devoted to increasing, rather than decreasing the number of nematodes in the environment.     

Entomopathogenic Nematodes: Biodiversity, Geographical Distribution and the Convention on Biological Diversity

This paper addresses three major issues. Firstly, molecular taxonomy and its application to elucidate the biodiversity and biogeography of entomopathogenic nematodes is considered. Accurate identification is fundamental for understanding biodiversity, and because these nematodes are morphologically conservative, molecular techniques will provide the insights necessary to develop a robust, morphologically based taxonomy. Secondly, a review of the knowledge on their biogeography and habitat specificity, including a consideration of the limitations to the available data is given. Much of the information is presented in two tables which summarize the distributions of recognized species at continental and national levels. Thirdly, this paper provides a brief consideration of the Convention on Biological Diversity and its implications for future work with entomopathogenic nematodes and biological control.