Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Nymph”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 991 records · Page 55Linked to original sources
PubMedDate not supplied

[The manifestation of sexual dimorphism in the preimago phases of 2 species of the genus Hyalomma (Ixodoidea, Ixodidae)].

Experiments on laboratory cultures of Hyalomma asiaticum and H. anatolicum have shown that at the nymphal phase sexual dimorphism manifests itself in statistically reliable differences between general sizes and mass of the body of male and female individuals. Larger nymphs moult mostly into females, small ones mostly into males. Reliable differences have been noted in the sizes of scutum, gnathosoma and its appendages in male and female nymphs of both species. At the larval phase sexual dimorphism does not manifest itself in the sizes of individuals.

Animals↗
PubMed1988

Growth and development of winter tick, Dermacentor albipictus, on moose, Alces alces.

Moose, Alces alces, were infested with 21,000 or 42,000 larval Dermacentor albipictus at the end of September. Larvae grew rapidly and molted to the nymphal stage 10-22 days after infestation. The nymphal stage lasted approximately 3 mo until mid-January and was characterized by a diapause. The diapause is likely an adaptation to survival in cold climates. Nymphs started engorging in January and adults were seen with increasing abundance from mid-January to March and April. The minimum parasitic period was 175 days. Growth of larvae and nymphs was similar on moose given different numbers of larvae and was generally similar between a moose infested in November and moose infested earlier. Dimensions and stages of development throughout the parasitic phase are given. Game enforcement officers are encouraged to use these data for determination of season of death of moose.

Analysis of Variance↗
PubMed1987

Impact of fenoxycarb, a carbamate insect growth regulator, on some aquatic invertebrates abundant in mosquito breeding habitats.

The insect growth regulator, Fenoxycarb, induced various morphogenetic aberrations in Notonecta unifasciata, Anax junius and Pantala hymenaea after treatment of late nymphal stages. Most affected nymphs died while molting from nymphs to adults. Fenoxycarb is also ovicidal to young eggs of N. unifasciata. The treatment rate of 0.034 kg AI/ha fenoxycarb induced some reduction in N. unifasciata population densities and produced a few morphogenetic abnormalities in some Odonata. However, planktonic organisms and aquatic beetles regularly found in the mosquito breeding habitats showed no deleterious effect.

Animals↗
PubMed1977

Studies on the proteins of Poecilocera picta. I-changes taking place in the haemolymph protein during moulting.

The haemolymph proteins of the 6th nymph of P. picta were fractioned by the polyacrylamide gel disc electrophoresis. A total of seven proteins fractions have been detected from the haemolymph. The chemical nature of different protein fractions have been examined by histochemical methods. The changes taking place in the cuticle and epidermal cells have been examined during the transformation of 6th nymph into adult. The fat body proteins have been electrophoretically fractioned and the changes in the concentration of different protein fractions have been examined. It is suggested that the protein fraction 3 of the haemolymph is utilized in the formation of new cuticle. It is concluded by the histochemical observations that proteins of the band 3 are synthesized in the fat body.

Animals↗
PubMed1980

Artificial infection of Rhipicephalus appendiculatus with Theileria parva by percutaneous injection.

Rhipicephalus appendiculatus nymphs were inoculated with fresh or cryopreserved blood containing Theileria parva piroplasms, or with cell culture grown stages of T parva. The use of fresh blood was successful. Cryopreserved blood containing dimethylsulphoxide (DMSO), killed most nymphs after inoculation: DMSO could be removed by slow dialysis, without destroying the infectivity of the blood. Attempts to infect ticks by inoculating cell culture grown stages of T parva failed, even when large numbers of merozoites were present in the inoculum.

Animals↗
PubMed1978

Repeated feeding of Amblyomma herbraeum (Acarina: Ixodidae) immatures on laboratory hosts. Host effects on tick yield, engorged weight and engorgement period.

Rabbits and sheep are unable to acquire a resistance to larvae and nymphs of Amblyomma hebraeum. After repeated infestation of hosts there is no progressive decline in either the tick yield or the engorged weight of fed ticks. Seasonal fluctuations in engorged weights do occur however, with the weight declining in early to midwinter and increasing in early to midsummer. Changes in hose physiology as a result of low temperature acclimatization appear to be responsible for the fluctuations. Tick yield is determined by the amount of grooming undertaken by hosts. The feedings periods of larvae and nymphs are dependent on the skin temperature of the host.

Animals↗
PubMed1981

Ecological studies on Ixodes (Afrixodes) matopi Spickett, Keirans, Norval & Clifford, 1980 (Acarina: Ixodidae).

Ixodes (Afrixodes) matopi occurs in association with the klipspringer (Oreotragus oreotragus) in rocky areas in Zimbabwe. The adult ticks are specific parasites of this antelope and the immature stages feed on klipspringers, hydraxes (Procavia capensis and Heterohyrax brucei) and red rock hares (Pronolagus crassicaudatus). Adults are active only in the wet season and prior to feeding are found on bushes growing adjacent to rocks. The ticks aggregate on twigs which have been marked with the secretions of the pre-orbital glands of klipspringers. Larvae are evident in greatest numbers in the latter part of the wet season and nymphs in the cool dry season. Unfed larvae and nymphs occur predominantly on mats of humid leaf litter in the cracks and gaps between rocks, and both show well-defined patterns of daily activity.

Animals↗
PubMed1994

Host specificity of Rhabdochona canadensis (Nematoda: Rhabdochonidae) in Nebraska.

Intermediate and definitive host specificity of Rhabdochona canadensis in Nebraska were investigated. Mayfly nymphs Trichorythodes sp. and Caenis sp. were found to serve as experimental intermediate hosts. Development inside the nymphs required approximately 10 days, with the worms passing through 2 molts and then becoming encapsulated in the hemocoel as infective third-stage juveniles. Survey data revealed that only the red shiner Cyprinella lutrensis serves as definitive host for R. canadensis in nature. Laboratory infections of Notropis dorsalis, N. stramineus, and Fundulus zebrinus, all of which were uninfected in nature, were attempted to determine if observed specificity was due to physiological or ecological factors. Two individuals of N. dorsalis became infected with R. canadensis, but no development was observed. Both N. stramineus and F. zebrinus were incapable of becoming infected. Thus, definitive host specificity in this system seems to be mediated by both physiological and host ecological factors.

Animals↗
PubMed1994

Influence of season and habitat on Ixodes scapularis infestation on white-footed mice in northwestern Illinois.

The effects of season and habitat on the infestation of the white-footed mouse (Peromyscus leucopus) by immature Ixodes scapularis were studied at Castle Rock State Park, northwestern Illinois, during June-October 1991. Relative density of larvae on mice was higher in mid-late summer (13.7 ticks per mouse) than during the rest of the study period, whereas prevalence of nymphal infestation was highest in early summer (33.3%). Relative density of I. scapularis larvae and prevalence of nymphs on mice did not differ significantly among bottomland forest, field-forest ecotone, and upland forest habitats. In bottomland forest, total number of ticks collected from mice (472 larvae and 13 nymphs) and P. leucopus population density (6.6 mice per 0.36 ha) were higher than in the other habitats. Temporal patterns of numbers of larvae collected from mice and through dragging in bottomland forest were significantly correlated.

Animals↗
PubMed1994

Absence of acquired resistance to nymphal Ixodes ricinus ticks in BALB/c mice developing cutaneous reactions.

BALB/c mice underwent 3 successive infestations with 15 Ixodes ricinus nymphs. No resistance was acquired as assessed by evaluating tick attachment, duration of blood meal, weights of engorged nymphs, and molting success. However, the hosts developed cutaneous immediate- and delayed-type hypersensitivity reactions when reinfested. Histological examination of tick attachment sites showed that inflammatory cells consisting of neutrophils, eosinophils, and mononuclear cells (lymphocytes and monocytes) infiltrated the skin more intensively during reinfestations. The number of intact mast cells did not vary between successive infestations, whereas the number of degranulated mast cells increased in the early stages of reinfestations. Basophils, which represent 12% of total infiltrating cells, were only observed and quantified in the skin of reinfested mice using transmission electron microscopy (TEM). Degranulating eosinophils were also observed by use of TEM.

Animals↗
PubMed1996

Refeeding activity of immature ticks of Ixodes persulcatus and transmission of Lyme disease spirochete by partially fed larvae.

The refeeding activity of immature ticks of Ixodes persulcatus was studied under laboratory conditions. BALB/c mice were used as blood sources. Feeding larvae and nymphs spontaneously detached themselves from parasitized mice when the mice were killed 1 or 2 days after tick exposure. Partially fed ticks were reexposed on other mice. Both larvae and nymphs were able to refeed on mice. The resultant engorged ticks normally molted to the next developmental stages. We also examined the transmission of the Lyme disease spirochete, Borrelia garinii, by bites of partially fed ticks. Larvae that had fed on infected mice for 1 or 2 days transmitted the spirochete to mice by refeeding.

Animals↗
PubMed1976

Development of Ehrlichia canis, causative agent of canine ehrlichiosis, in the tick Rhipicephalus sanguineus and its differentiation from a symbiotic Rickettsia.

Certain aspects of the development of Ehrlichia canis, causative agent of canine ehrlichiosis (tropical canine pancytopenia) in Rhipicephalus sanguineus ticks were studied. It was found that partial feeding of nymphs infected as larvae with E canis was a desirable, if not necessary, preliminary treatment for successful infection of dogs with ground-up ticks. It remains unclear whether feeding increased the number or altered the virulence of ehrlichiae within tick tissues. Ehrlichia canis organisms were detected by immunofluorescent microscopy in the midgut and hemocytes and by electron microscopy in the midgut and salivary glands of partially engorged adult ticks which had been infected as larvae and nymphs. Organisms were not observed in the ovary. Intracytoplasmic inclusions contained 1 to 80 elementary bodies, each provided with 2 distinct membranes. Infection of the midgut and salivary gland was confirmed by injecting homogenates of these tissues into susceptible dogs. Staining of gut smears of partially engorged adult ticks by fluorescein-conjugated anti-E canis antibody was found to be a reliable indicator of the infection.

Animals↗
PubMed1997

Transmission of tick-borne bunyaviruses by cofeeding ixodid ticks.

Palma and Bhanja bunyaviruses replicated in Dermacentor marginatus, D. reticulatus, Rhipicephalus sanguineus, R. appendiculatus and Ixodes ricinus ticks after parenteral inoculation and appropriate incubation and feeding. Palma virus was transmitted to D. marginatus and D. reticulatus males, D. reticulatus and R. sanguineus females, and R. appendiculatus nymphs while cofeeding with infected ticks on laboratory mice. Bhanja virus was transmitted to D. marginatus males and R. appendiculatus nymphs. Laboratory mice developed low levels of viraemia detectable only by intracranial (i.c.) inoculation of newborne laboratory mice.

Animals↗
PubMed1998

Dynamics of free-living ixodid ticks on a game ranch in the Central Province, Zambia.

Free-living ixodid ticks were collected at monthly intervals from January to December 1996 by dragsampling the vegetation of Mtendere Game Ranch in the Chisamba District of the Central Province, Zambia. Ticks belonging to 11 species were recovered. Rhipicephalus appendiculatus was most abundant, comprising 90% of the total number collected. All life stages of this tick showed a definite seasonal pattern of activity. The adults were present mainly during the rainy season (February and March), the larvae during the cool and dry season (May to August), and the nymphs during the hot and dry season (August to October). Adults were most abundant in the wooded areas and nymphs in the open grasslands. Larvae of Amblyomma variegatum were only found from May to September, while larvae of Boophilus decoloratus were present throughout the year with peaks of abundance from January to February and again from August to November. Rhipicephalus evertsi larvae occurred throughout the year. Recent burning of the vegetation did not seem to affect the number of ticks collected. A possible burning regime to achieve a degree of tick control is discussed.

Animals↗
PubMed1998

Entomopathogenic nematodes as control agents of developmental stages of the black-legged tick, Ixodes scapularis.

Thirteen species or strains of entomopathogenic nematodes of the genera Steinernema and Heterorhabditis were tested in vitro against unfed and engorged larvae, nymphs, and adults of the black-legged tick, Ixodes scapularis. Nematodes were pathogenic to engorged female ticks, but not to unfed or engorged larvae, nymphs, males, and unfed females. Steinernema riobravis (355) and Heterorhabditis megidis (M145) killed ticks most rapidly, with mean day of death postinfection of 2.5 and 3.5 days, respectively. However, all nematode strains and species were lethal to engorged female ticks within 7.5 days. Development of juveniles and reproduction of nematodes did not occur inside the tick cadavers, because no infective juveniles (IJs) emerged from cadavers after 40 days, and no nematode life-cycle stages other than the primary IJs could be isolated from cadavers. Egg masses were produced by 4 of 702 nematode-infected, engorged females. Egg masses produced were not significantly smaller than masses produced by control ticks; however, only 1 of the 4 egg masses hatched, whereas all of the egg masses produced by the control ticks hatched. Entomopathogenic nematodes may be useful as an alternative management method for I. scapularis populations, and may be more acceptable than acaricidal chemicals for use in infested areas.

Animals↗
PubMed2000

Proteolytic activation of canatoxin, a plant toxic protein, by insect cathepsin-like enzymes.

Canatoxin is a protein isolated from jackbean (Canavalia ensiformis), seeds. Injected intraperitoneally, the toxin is lethal to mice but it is inactive if given orally. Canatoxin is also lethal when fed to insects with cathepsin-based digestion while insects with trypsin-based digestion are not affected. The hypothesis that canatoxin is proteolytically activated by cathepsins was investigated. Experiments were performed with 4(th) instar and adult Rhodnius prolixus fed meals containing canatoxin (2.5 microg/mg weight body). While 100% of nymphs died, no effect was observed in adults. Hemolymph taken from nymphs and adults showed the presence of canatoxin's proteolytic fragments. Reduced lethality was seen in R. prolixus 4(th) instars fed meals containing canatoxin and inhibitors of cathepsin enzymes, E-64 (2.0 microM) or Pepstatin-A (2. 0 microM). In another approach, canatoxin was digested in vitro with enzymes from the bruchid, Callosobruchus maculatus, and the resulting peptides were tested in R. prolixus. Three groups of toxic peptides (8,000-12,000 kD range) were separated by gel-filtration. When these peptides were fed to the insects simultaneously with the cathepsin inhibitors, no protective effect was seen. These results confirm the proteolytic activation of canatoxin by insect cathepsin-like enzymes to produce entomotoxic peptide(s). Furthermore, our data point towards overlooked differences in the digestive physiology of distinct life stages of R. prolixus. Arch.

Animals↗
PubMed2003

Caste morphology and development in Termitogeton nr. planus (Insecta, Isoptera, Rhinotermitidae).

The termite family Rhinotermitidae displays a wide diversity in its patterns of social organization in castes. The genus Termitogeton probably branched off early in the evolution of this family. We studied the developmental pathways of a putative undescribed species from New Guinea, Termitogeton nr planus. The development begins with two white inactive instars (larvae), the second of which possesses small wing buds. These are followed by a relatively homogenous group of active immature stages (pseudergates) among which a biometric study revealed the presence of four instars. The first of these instars possesses wing buds that regress at subsequent molts. The external morphology of older instars resembles that of higher termite workers. Older pseudergates can differentiate into presoldiers and then into soldiers, but they are also able to molt into a unique stage with long wing pads (nymph), preceding the imago. Colony maturity can be reached with about 10(3) individuals. The sex ratio is near 1:1 in all castes except soldiers, among which females are more numerous than males. The caste pattern of T. nr. planus is reminiscent of those of the Kalotermitidae and Termopsidae, and of Prorhinotermes among the Rhinotermitidae. None of these taxa possess a true worker caste, permanently diverted from imaginal development: social tasks are done by unspecialized immatures that retain a full array of developmental options, including that of proceeding to the imago. The most remarkable trait of T. nr. planus is the presence in all second-instar individuals of wing buds that later regress to reappear in the single nymphal stage. We suggest that the traditional definitions of the terms larvae, nymphs, and pseudergates should be revised because they cannot be satisfactorily applied to the castes of Termitogeton.

Animals↗
PubMed2002

Ephemeroptera egg chorion characters: a test of their importance in assessing phylogenetic relationships.

The egg chorion ultrastructures of the Hermanella-Traverella (Insecta: Ephemeroptera) species complex were studied from a comparative point of view and used for the first time in a cladistic analysis. Egg characters, along with other nymphal and adult morphological characters, were used to assess the phylogenetic relationships of the species complex. In order to test the value of egg characters, analyses were performed on three matrices: 1) egg characters alone, 2) adult and nymphal characters, and 3) adult, nymphal, and egg characters. The computer program Pee-Wee was used to carry out the analysis. The cladistic analysis confirmed the value and potential of egg chorionic characters in assessing the phylogenetic relationships among ephemeropteran species. Egg characters, when added to the nymphal and adult character matrix, provided extra support to the monophyletic nature of the Hermanella-Traverella complex. Previously weakly defined clades were also resolved based on the new evidence. In the species studied the egg chorionic structures as well as their shape did not change after oviposition or water immersion, remaining constant through the different maturation stages of each species (mature nymph, subimago, and imago). For this reason, the eggs are a valuable source of information to unambiguously identify and associate a nymph to its correspondent adult stage when rearing is not possible.

Animals↗