Preparasitic Larvae Research Articles

Sensitivity of preparasitic stages of Chordodes nobilii (Gordiida, Nematomorpha) to malathion

The largest part of the life cycle of Gordiida, known as horsehair worms, occurs in aquatic environments usually affected by agricultural activities. The free-living adults reproduce in freshwater environments, where preparasitic larvae undergo development. Since malathion is an insecticide used in the distribution area of Chordodes nobilii, the aim of this study is to evaluate the effect of malathion concentrations which might be expected in the environment on preparasitic stages of this species. The embryonic development and the viability of larvae were analyzed after a short-term exposure to malathion concentrations ranging between 36 and 220 microg a.i./l. Embryo development was inhibited at 220 microg a.i./l and the infective capacity of larvae derived from malathion-exposed eggs was significantly decreased starting from the lowest concentration. Larvae developed from malathion-exposed eggs exhibited malformations. Directly exposed larvae also showed decreased infectivity since the lowest assayed concentration. Our results indicate that a short-term exposure to malathion at levels potentially present in the surface water in environments inhabited by Chordodes nobilii affects significantly its preparasitic stages and the infective capacity of parasitic larvae.

Toxicity of the herbicide glyphosate to Chordodes nobilii (Gordiida, Nematomorpha)

Nematomorpha (horsehair worms) is a poorly known group of worm-like animals similar to nematodes. Adults are free-living and reproduction takes place in freshwater environments, where preparasitic larvae undergo development. All species have a parasitic juvenil stage and infection may result in the host’s death, insects being the most frequent host. Most of the life cycle occurs in freshwater environments, which are often contaminated by different pollutants. Based on the lack of information on the toxicity of herbicides to horsehair worms, the objective of this study is to evaluate the effect of different concentrations of glyphosate (technical grade and formulated product) on Chordodes nobilii (Gordiida, Nematomorpha). Bioassays were performed with embryos and larvae (preparasitic stages), and adults (postparasitic stage). Test organisms were exposed for a short period of time to concentrations ranging between 0.1 and 8mga.e.l−1 of glyphosate (technical and formulated). Although embryo development was not inhibited, there was a significant decrease in the infective capacity of larvae derived from eggs that had been exposed to ⩾0.1mg/l. Similar results were obtained for directly exposed larvae. No differences in toxicity were detected between the active ingredient and formulated product. Adult exposed for 96h to 1.76mgl−1 formulated Gly shown a mortality of 50%. Results indicate that C. nobilii is affected at glyphosate concentrations lower than those expected to be found in freshwater environments and those specified in the legislation.

Global diversity of hairworms (Nematomorpha: Gordiaceae) in freshwater

Freshwater hairworms (Gordiaceae) and marine hairworms (Nectonematoidea) comprise the phylum Nematomorpha. Only the freshwater forms are discussed here. While freshwater hairworms develop as parasites of both aquatic and terrestrial arthropods, they all enter fresh water to mate, oviposit and produce infective stages (preparasitic larvae). The global species diversity of freshwater hairworms based on published descriptions is approximately 326 species and a conservative estimate for the global species diversity in this group would be around 2,000 species.

In vitro reactivation of Ancylostoma caninum tissue-arrested third-stage larvae by transforming growth factor-beta.

Developmental arrest in Ancylostoma caninum is associated with preparasitic, free-living third-stage (L3) larvae, as well as anthelmintic-resilient hypobiotic L3 larvae within the tissues of an infected dog. With the tissue-arrested larvae, pregnancy and, more specifically, the hormonal effects of estrogen and prolactin mediate reactivation resulting in transmammary transmission of infection to nursing puppies. Estrogen and prolactin have been shown to be critically involved in upregulation of transforming growth factor (TGF)-beta2 during pregnancy, and studies on the soil nematode Caenorhabditis elegans further implicate TGF-beta and insulin-like signaling pathways with larval arrest and reactivation. In this report, an in vitro assay was used to show that neither estrogen, prolactin, nor insulin had a direct effect on the feeding/reactivation response of tissue-arrested larvae; however, TGF-beta isoforms 1 and 2 both had significant stimulatory effects that were comparable to the effects of dog serum. The stimulatory effects of serum could be blocked by preincubation with anti-TGF-beta antibodies. Taken together, the results support the hypothesis that during pregnancy, host-derived TGF-beta can signal a parasite-encoded receptor to trigger the reactivation of tissue-arrested larvae. TGF-beta had no effect on preparasitic larvae, suggesting that different signals may be involved in reactivation of the 2 different arrested forms of A. caninum L3 larvae.

Biological control of nematode parasites in cattle with nematode-trapping fungi: a survey of Danish studies

In Denmark two series of experiments have been performed to study the interactions between larvae of bovine gastrointestinal nematode parasites and nematode-trapping fungi. For practical reasons we were interested in the possibility of depositing nematode-trapping fungi in cattle faeces after passage through the gastrointestinal tract. In the first series, laboratory tests with the fungus Arthrobotrys oligospora showed that motile free-living larvae of a wide range of animal-parasitic nematodes and some soil-living nematodes effectively induce the formation of traps. Larvae of all parasitic nematodes are rapidly captured in these traps. The induction of nets was influenced by temperature, number of larvae, atmosphere, light, and media composition. Captured first- and second-stage larvae were quickly penetrated and killed while third stage larvae were killed slowly, perhaps because they are partially protected by an outer dead sheath. Laboratory and field studies showed that when A. oligospora material was directly mixed into dung a significant reduction in the number of infective parasite larvae in the dung and surrounding herbage occurs. This reduction was also reflected in the acquired worm burden of calves grazing on a fungal treated pasture. However, the A. oligospora strain studied in the above mentioned experiments did not survive passage through the alimentary tract of cattle. This prompted us to start a second series of experiments to isolate fungi that could survive gut passage of cattle. Different soil and compost samples were screened by an in vitro stress selection technique. This simulated certain important stress factors which occur during passage through the alimentary tract of ruminants. Rumen exposure was found to be a major limiting factor, but some Arthrobotrys and Duddingtonia strains survived submersion in rumen fluid. In a subsequent in vivo experiment, some of these survivors were fed to calves, and it was hereby demonstrated that isolates of both genera, i.e. Arthrobotrys and Duddingtonia, were able to survive passage through calves and significantly reduce the number of developing preparasitic larvae in dung of fungal treated calves. In a controlled field experiment, isolatesof Duddingtonia reduced the level of infective third-stage larvae in herbage by 74–85%.

Effects of Oyster Mushroom Pleurotus pulmonarius on Preparasitic Larvae of Bovine Trichostrongyles

Effects of Oyster Mushroom Pleurotus pulmonarius on Preparasitic Larvae of Bovine Trichostrongyles

Fine structure of the larval eyes of Mantispa sp. (Neuroptera : Planipennia, Mantispidae)

The stemmata of the first-instar larvae of Mantispa sp. (Neuroptera) were studied by scanning (SEM) and transmission (TEM) electron microscopy. These preparasitic larvae have a pair of anterior eyes and a single posterior eye on each side of the head. Each eye possesses an outer lens; beneath it, there is a well-developed crystalline body and a 3-tiered retina made up of a maximum of 12 sensory cells. The central fused rhabdom appears always to be composed of 4 sensory cells, each filled with pigment granules. The nuclear region shows Golgi bodies and abundant rough endoplasmic reticulum; the rhabdomeric regions contain vesicles, prominent multi-vesicular bodies and lysosomes. The eyes, whether double or single, are surrounded by a perineurium, to which muscle cells are attached.

Etude du parasitisme des simulies (Diptera, Simuliidae) par des Mermithidae (Nematoda) en Afrique de l'ouest. II: Description de deux nouvelles espèces de Gastromermis

From material collected by R. Le Berre in 1972 and by J. J. Petersen and B. Mondet in 1975, two new species of Mermithidae are described from blackfly larvae, including Simulium damnosum s.l., for the first time in West Africa. These species, Gastromermis philipponi n.sp. and Gastromermis leberrei n.sp. possess a rudimentary excretory gland and the preparasitic larvae of the former contain a characteristic caudal appendage which is lost during penetration into the simuliid larvae. Therefore, these two species are the only ones of Gastromermis known to have six longitudinal cords.

A Reexamination of Neochordodes occidentalis (Montg.) comb. n. (Chordodidae: Gordioidea): Larval Penetration and Defense Reaction in Culex pipiens L.

The eggs, preparasitic larvae, and certain adult characters of Neochordodes occidentalis (Montg.) (Chordodidae: Gordioidea) are newly described. The method of penetration of preparasitic hairworms into larvae of Culex pipiens L. was examined. The parasites bored directly through the peritrophic membrane and epithelial gut cells to reach the host's body cavity. The hairworms encysted normally in most 2nd- and 3rd-stage mosquito larvae but elicited a rapid and often lethal defense reaction in 4th-stage hosts. This reaction consisted of the deposition of melanin on the surface of the parasite. Cyst material originated from a bilobed intestinal gland in the preparasitic larva and was not considered of host origin. Findings here indicate that characters found in the preparasitic larvae could be used for distinguishing between hairworm species.

Developmental Studies on Haemonchus contortus Rudolphi (1803)

Investigations on temperature and moisture requirements of Haemonchus contortus Rudolphi, have been meager (Veglia, 1915; Shotb, 1944) and in none was humidity carefully controlled. The present work was planned to determine temperature-humidity effects on the developing eggs and pre-parasitic larvae of this parasite, and to test the susceptibility of these life-history stages to several surface-active compounds.