The development of Eustrongylides tubifex (Nematoda: Dioctophymatoidea) in oligochaetes

Egg development of Eustrongylides tubifex (Nitzsch in Rudolphi, 1819) J?gerski?ld, 1909, was studied at 5, 10, 15, 20, 25, and 30 C. Eggs developed at 20, 25, and 30 C. Development ceased at 0, 5, 10, and 15 C but resumed when temperatures were raised. Eggs contained first-stage larvae in 23-26 days at 25 C. Seven species of aquatic oligochaetes were exposed experimentally to eggs of E. tubifex containing first-stage larvae. Third-stage larvae of E. tubifex developed in the aquatic oligochaetes, Limnodrilus hoffmeisteri Claparède, 1862, and Tubifex tubifex (Müller, 1774). Larvae developed in the ventral blood vessel of oligochaetes. Second-stage larvae were seen first in oligochaetes 30 days postinfection and third-stage larvae were seen 70-109 days postinfection at 25 C. Third-stage larvae in oligochaetes retained the cuticle of the first and second molt.     

Eustrongylides tubifex (Nitzsch) encystment in an American ell Anguilla rostrata (Le Sueur)

A diseased American ell, Anguilla rostrata (Le Sueur), was captured during a survey of Little Mosquito Creek, Accomac County, Virginia, U.S.A. Two skin lesions were present. One was caused by the dermal encystment of a nematode, Eustrongylides tubifex ; the other was of undetermined origin.     

Pathology of larval Eustrongylides in the rabbit

Three fishermen from Maryland who swallowed live bait-minnows developed severe abdominal pain within 24 hr; 2 required abdominal surgery. Larvae of the nematode Eustrongylides sp. were found in the peritoneal cavity of both (Guerin et al., 1982). In the current study, the lesions produced by Eustrongylides larvae were investigated in New Zealand white rabbits. None of these exhibited any signs of clinical illness; however, postmortem examination within 24 hr of inoculation revealed that larvae had migrated through the walls of the esophagus and stomach and viable larvae were recovered from the pleural and peritoneal cavities as well as from gastric contents. Necropsies performed at different intervals of time postinoculation showed that the migrating larvae had produced multi-focal peritonitis and multiple granulomata in the liver.     

The first genetically confirmed case of Dioctophyme renale (Nematoda: Dioctophymatida) in a patient with a subcutaneous nodule

We describe a nematode larva in a subcutaneous nodule excised from a 44-year-old Chinese male who had been living in Japan for 15 years. Morphological features suggested that the worm was a dioctophimatid nematode. PCR amplification and sequencing of small subunit ribosomal DNA and mitochondrial cytochrome subunit c oxidase genes allowed us to identify the larva as the giant kidney worm, Dioctophyme renale (Goeze, 1972). This is the first molecularly confirmed human case of a dermal D. renale infection.     

Microtopography of Nippostrongylus brasiliensis (Nematoda: Heligmosomatidae): Free-living larval stages

Microtopographic features of the various growth stages of the three free-living larval stages of the rat hookworm Nippostrongylus brasiliensis (Nematoda) were surveyed by scanning electron microscopy. These worms have a rounded anterior end and an elongated tail. Cuticular annulations were observed along the body, which also bore two ribbon-like lateral alae. Two rings of six lip-like lappets were observed around the triradiate oral opening in all larval stages. The cephalic space contained two lateral amphidial pits. The excretory pore in the third anterior part was observed in a ventral view of the larvae. No deirids were observed. The anus with a crescent-shape opening was located posteriorly. Phasmidial apertures, only observed in the third-stage larvae, opened on the lateral alae in the tail region. © 1993 Wiley-Liss, Inc.     

Population biology of Contracaecum rudolphii sensu lato (Nematoda) in the great cormorant (Phalacrocorax carbo) from northeastern Poland

Parameters related to the occurrence, aggregation, and population structure of the nematode Contracaecum rudolphii Hartwich, 1964 , in the great cormorant ( Phalacrocorax carbo ) from northeastern Poland were analyzed. A total of 491 birds of different ages (adults, immatures, and nestlings) was examined; the cormorants studied were taken from both fresh- and brackish water habitats. Contracaecum rudolphii were found in stomachs of 454 birds (92.5%); the 46,244 nematodes included third- (L3) and fourth-stage larvae (L4), and sub-adult and adult females and males. The distribution of nematodes in the host population were highly aggregated. The occurrence of C. rudolphii was significantly dependent on the host's age and habitat, as well as on season; the proportion of development stages differed significantly depending on birds' age and season (the latter only in adult birds). The infrapopulations of C. rudolphii in the adult cormorants showed distinct density-dependent correlations: that is, as the infrapopulation size increased, the number of adult females C. rudolphii decreased, and the proportion of larvae and sub-adult females increased. A higher proportion of larvae and sub-adult females characterized the component population structure of the nematodes in the cormorant nestlings, compared with adult birds, probably because of immune system deficiency in the immature birds, coupled with the development of the nematode population. Seasonal changes in the C. rudolphii population, observed in the adult cormorants, were not related to seasonality of the L3 occurrence in food; instead, the changes are believed to have resulted from independent processes of elimination of the oldest nematodes and their replacement by larval stages that subsequently matured.     

Microtopography of Nippostrongylus brasiliensis (Nematoda: Heligmosomatidae): Parasitic larval stages and adults

Specimens of the rat hookworm, Nippostrongylus brasiliensis (Nematoda) were recovered from lungs (third- and fourth-stage larvae) and intestine (fourth-stage larvae and adults). The following features were studied in the different stages by scanning electron microscopy: cephalic structures, especially sense organs, synlophe, cervical region, and caudal part. The main differences between the third and fourth stages concerned the lip-like structures around the oral aperture, the appearance of the cephalic space with the presence of a cephalic cap in fourth-stage larvae, the pattern of longitudinal ridges, and sexual differentiation. Pore-like papillae, not seen in third-stage larvae, developed in later stages. Deirids were observed only in adults, and phasmids were poorly discerned. Some of these morphological features, such as the cephalic sense organ apertures and cuticle pores and micropores, can be observed only by scanning electron microscop y. The possible functions of these different structures and their relationship with the behavior of the worms during their life cycle are discussed. © 1993 Wiley-Liss, Inc.     

Body size evolution of oxyurid (Nematoda) parasites: the role of hosts

Studying the diversification of body size in a taxon of parasites allows comparison of patterns of variation observed in the parasites with patterns found in free-living organisms. The distributions of body size of oxyurid nematodes (obligate parasites of vertebrates and invertebrates) are lognormally right-skewed, except for male oxyurids in invertebrates which show left-skewed distributions. In these parasitic forms, speciose genera do not have the smallest body sizes. Parasite body size is positively correlated with host body size, the largest hosts possessing the largest parasites. This trend is shown to occur within one monophyletic group of oxyurids, those of Old World primates. Comparative methods are used to take account of the effects of phylogeny. The use of multiple linear regression on distance matrices allows measurements of the contribution of phylogeny to the evolution of body size of parasites. Evolution of body size in female pinworms of Old World primates appears to be dependent only on the body size of their hosts. The tendency of parasite body size to increase with host body size is discussed in the light of the evolution of life-history traits.     

Population biology of Camallanus oxycephalus Ward and Magath, 1916 (Nematoda: Camallanidae) in white bass in western Lake Erie.

The distribution and abundance of the nematode Camallanus oxycephalus infecting white bass, Morone chrysops, in western Lake Erie was studied for over 2 years. Infection was generally more frequent and of higher intensity in large fish. The frequency distributions of nematode abundance in all segments of the fish population followed the negative binomial distribution. The data show seasonal cycles in population structure, site selection, intensity of infection, maturation, and reproduction. Infection occurs during July and August with a resulting peak in population density; during late summer and autumn, mortality, probably density-dependent, reduces the population by 30 to 60%; surviving worms are eliminated at 1 year of age. Growth and development of female worms is arrested from November to April, then proceeds at a rapid rate until the worms release their larvae and die. This growth pattern is probably related to temperature but may also involve host hormone cycles. The dispersal period of the nematode coincides with the annual maximum density of the intermediate host, a cyclopoid copepod,and is interpreted as an adaptation which increases the probability of successful transmission. Because the number of larvae produced by each female worm is a function of body volume, natural selection has favored rapid spring growth and attainment of large body size relative to the male worm. Both seasonal timing in the life cycle and the number of larvae produced are important factors in determining the abundance of this and perhaps other parasites. Evidence is presented suggesting that fluctuations of environmental parameters may disrupt the timing of transmission and alter the distribution and abundance of the parasite. It is hypothesized that the magnitude of such changes in parasite abundance may be related to the complexity of the host-parasite system.     

Epizootiology of Eustrongylides ignotus in Florida: transmission and development of larvae in intermediate hosts

Under laboratory conditions, 2 modes of transmission of Eustrongylides ignotus (Nematoda: Dioctophymatoidea) to fish were identified. Eastern mosquitofish (Gambusia holbrooki) became infected after ingestion of either eggs of E. ignotus containing first-stage larvae or aquatic oligochaetes (Limnodrilus hoffmeisteri) containing third-stage larvae of E. ignotus. After removal from the uterus of gravid E. ignotus females and incubation for 17-28 days, depending on temperature, it was found that parasite eggs contained first-stage larvae that were infective to fish and oligochaetes. Larvae developed to the third stage in oligochaetes and were infective to fish 35-77 days postinfection (PI) and when fed to fish, developed to the fourth stage between 127 and 184 days PI. Eggs containing first-stage larvae fed directly to fish developed to the fourth stage between 84 and 105 days PI. The amount of time for development from the undifferentiated egg to the fourth-stage larva was 78-156 days shorter when fish ingested eggs containing first-stage larvae than when fish ingested oligochaetes containing third-stage larvae. Three species of large piscivorous fish, including black crappie (Pomoxis nigromaculatus), largemouth bass (Micropterus salmoides), and warmouth (Lepomis gulosus), were fed mosquitofish containing fourth-stage larvae. At necropsy, live E. ignotus larvae were recovered from all 3 species. Several fish had multiple infections after ingesting > 1 larva, indicating that bioaccumulation of the parasite in the food chain may occur.     

Population and infection dynamics of Daubaylia potomaca (Nematoda: Rhabditida) in Helisoma anceps

Daubaylia potomaca is an unusual parasite for several reasons. Specifically, it has a direct life cycle in which it uses a planorbid snail, Helisoma anceps , as the definitive host. In addition, adult females have been shown to be both the infective stage and the only stage documented to be shed from a live, infected host. Finally, adults, juveniles, and eggs have been observed in all tissues and blood spaces of the host, suggesting the parasite consumes and actively migrates through host tissue. The present study examined the population and infection dynamics of D. potomaca in Mallard Lake, a 4.9-ha public access pond in the Piedmont region of North Carolina. In particular, the study examined the role of seasonality on the prevalence and mean intensity of infection of D. potomaca in the snail host. Data collected from August 2008 to October 2009 suggest that prevalence and mean intensity were inversely related in the spring and fall. Prevalence in fall 2008 was 10.3% but increased to 47.3% in spring 2009. Conversely, intensity was high in fall 2008 at 52.4 ± 8.9 worms/infected host but dropped to 3.1 ± 0.3 worms/infected host in spring 2009. During the same time, the parasites within the snails went from highly aggregated populations in the fall to a less aggregated distribution in the spring. It is hypothesized that D. potomaca induces mortality of the snail hosts during the winter, followed by a rapid recruitment event of the nematodes by the snail population after torpor.     

Epizootiology of Eustrongylides ignotus in Florida: distribution,density, and natural infections in intermediate hosts

A total of 63,451 fish, representing 39 species, was collected from 176 foraging sites used by ciconiiform wading birds in peninsular Florida (USA) and examined for larvae of Eustrongylides ignotus. Infected fish were identified from 30 (17%) of the sites, all of which had been altered by human disturbance such as removal of sediment to construct ditches and dikes, improve water flow, or increase storage capacity and had a history of receiving anthropogenic nutrients such as sewage effluent, urban runoff, or agricultural runoff. The mosquitofish (Gambusia holbrooki) and several species of sunfish (Centrarchidae) were the most important intermediate hosts. Infected fish were not collected at any of the unaltered sites. A total of 10,508 oligochaetes (representing 36 species) was identified from 22 sites that had fish infected with E. ignotus and 36 sites where no infected fish were collected. None of the oligochaetes was infected with larvae of E. ignotus. Immature tubificids without hair setae (probably Limnodrilus sp.), Dero digitata, and L. hoffmeisteri were the most abundant oligochaetes at sites where infected fish occurred, making up 78% of the total collected. Compared to unaltered sites, altered sites were characterized by higher mean densities of fish and oligochaetes; surface waters with decreased dissolved oxygen and increased total nitrogen, total phosphorus, and chlorophyll-a; sediments with higher soil oxygen demand and total phosphorus; larger grain sizes; and higher percentage emergent vegetation and grasses.     

Bionomics of larvae of Parelaphostrongylus odocoilei (Nematoda: Protostrongylidae) in experimentally infected gastropod intermediate hosts

Parelaphostrongylus odocoilei is a protostrongylid parasite that has recently been recognized at several locations in sub-Arctic, but not Arctic, North America. We investigated factors that may determine the distribution of P. odocoilei, including suitable gastropod intermediate hosts, temperature requirements for larval development in gastropods, and larval emergence facilitating overwinter transmission. We collected and experimentally infected gastropods from a site in the sub-Arctic where P. odocoilei is at the northern limit of its distribution. Deroceras laeve, Catinella sp., and Euconulus cf fulvus, but not members of the Pupillidae, were suitable intermediate hosts. We describe bionomics of larvae of P. odocoilei in D. laeve and Catinella sp. Infective larvae emerged from all slugs (D. laeve) and 60% of Catinella sp. snails, and emergence from D. laeve was intensity dependent. Emerged infective larvae survived up to 6 mo under conditions approximating that of the subnivean environment. In D. laeve, there was a direct relationship between temperature and development rate of larvae of P. odocoilei. Larvae of P. odocoilei did not develop to infective stage below the theoretical threshold (8.5 C), and required a minimum of 163 degree days to complete development. These developmental parameters can be incorporated into a model to predict larval development in the field. Knowledge of the factors influencing larval bionomics provides the foundation for predicting temporal and spatial patterns of parasite distribution, abundance, and transmission.     

Subcellular localization of zinc in experimentally polluted tubifex tubifex (Annelida,Oligochaeta)

• 1.1. Localization of Zn (+ ⁶⁵Zn) has been examined within twelve subcellular fractions (derived from discontinuous sucrose gradients) of preincubated T. tubifex.
• 2.2. Zn was principally associated with the pellet (28% of total) and lowest density fraction (14%).
• 3.3. Pellet ultrastructure is composed of chloragosomes and epicuticle. Pellet Zn is localized within chloragosomes, X-ray microanalysis showing chloragosomal Zn concentration to exceed epiculticular Zn by a factor of thirty.
• 4.4. Biochemical and ultrastructural studies demonstrate that Zn is not appreciably bound to other cell constituents.
• 5.5. Chloragosomal localization of internalized Zn indicates a capacity for detoxification.

     

Population analysis in mass cultures of Tubifex tubifex

Mass cultures of Tubifex tubifex from Lake Orta were kept in the lab at 20 °C starting with different initial densities (10, 45, 86, 161 ind · jar^–1), with the aim of evaluating the effect of density on population numbers and on population parameters. The results show that density mainly controls fecundity, growth, maturation and ovigeration rates. Growth rates and mean number of eggs laid/ovigerous (R₀) are inversely related to density, but generation time appears to be directly related. Very low or very high initial densities display, at different times of the culture history, efficient density controls. Intermediate N₀ seem to bring about situations of bad control, easily leading to numerical overshoots. A possible implementation of a population dynamics model (Bonomi & Di Cola, 1980), originally used for laboratory observations on T. tubifex cohorts was considered, including some density control functions derived from our observations on cohort and mass cultures in some transfer rates and in fecundity rate.     

Pseudostertagia bullosa (Nematoda: Trichostrongyloidea) in artiodactyl hosts from North America: redescription and comments on systematics

A relationship for Pseudostertagia bullosa within the trichostrongyloids has been enigmatic or unresolved. Studies of the synlophe in males and females of P. bullosa revealed a tapering system anterior to the deirids and a pattern of parallel ridges extending to near the caudal extremity in both lateral and median fields. Structurally, the synlophe differs considerably from that seen among the Cooperiinae and exhibits homoplasy with respect to ridge systems among some Ostertagiinae. Other structural characters due to symplesiomorphy, homoplasy or because they represent autapomorphies do not serve to reveal the putative relationships for P. bullosa with other trichostrongyloids. Although somewhat equivocal, the 2-2-1 pattern of the bursa and position of rays 2 and 3 suggest an association with the Cooperinae, as postulated by Durette-Desset and others. Pseudostertagia bullosa appears to be a species that has survived in the pronghorn, Antilocapra americana, a relictual pecoran artiodactyl that occurs in xeric regions of western North America; pronghorn are the sole remnant of the late Tertiary radiation for Antilocapridae across North America. Pseudostertagia bullosa may occur in mixed infections with a number of ostertagiines in the abomasa of mule deer (Odocoileus hemionus) and domestic sheep (Ovis aries) in regions of sympatry for pronghorn and these artiodactyl hosts.