ABSTRACT
Disseminated visceral coccidiosis (DVC) is a widely distributed intestinal and extraintestinal disease of cranes caused by eimeriid coccidia and has lethal pathogenicity to several crane species. Here, feces of 164 black-necked cranes collected in Dashanbao Black-necked Crane National Nature Reserve, China, were examined to determine the prevalence of coccidial oocysts. Of the 164 fecal samples, 76 (46.3%) were positive for oocysts of Eimeria, including E. gruis in 59 (35.9%), E. reichenowi in 52 (31.7%), and E. bosquei in 47 (28.7%) by microscopic observation. Sixty-eight (89.5%) of these positive samples included two or more morphologically identifiable species of Eimeria. The nearly full length 18S rRNA gene (18S rRNA; about 1.8 kb) and partial mitochondrial cytochrome c oxidase I gene (COX1; about 1.3 kb) from oocysts of each morphologically distinct species of Eimeria were amplified, sequenced, and analyzed. BLAST searches using these new 18S rRNA sequences for E. gruis, E. reichenowi, or E. bosquei showed the most similar sequences were those of E. gruis (98.7-99.7% identity), E. reichenowi (97.9-100% identity), or E. gruis (98.6-99.6% identity) isolated from different species of Grus. BLAST searches using the new COX1 sequences for the three species of Eimeria showed that no nucleotide sequences of Eimeria and Isospora coccidia in GenBank have more than 83.0% identity with these species. Identities among the new COX1 sequences were 91.8% for E. gruis and E. reichenowi, 94.5% for E. gruis and E. bosquei, and 91.3% for E. reichenowi and E. bosquei. Phylogenetic analysis based on 18S rRNA or COX1 sequences indicated that Eimeria spp. in black-necked cranes were clustered together with other previously identified Eimeria species from different cranes.
Subject(s)
Bird Diseases/epidemiology , Birds/parasitology , Coccidiosis/veterinary , Eimeria/genetics , Eimeria/isolation & purification , Animals , Bird Diseases/parasitology , China , Coccidiosis/epidemiology , Coccidiosis/parasitology , Feces/parasitology , Intestines/parasitology , Oocysts/classification , Phylogeny , PrevalenceSubject(s)
Life Cycle Stages , Parasitology/trends , Animals , Disease Vectors/classification , Echinococcus/classification , Humans , Malaria/parasitology , Malaria/transmission , Plasmodium/growth & development , Plasmodium/physiology , Societies, Scientific , Taenia/growth & development , Taenia/physiology , Taeniasis/parasitology , Trypanosoma/physiology , Trypanosomiasis, African/parasitology , Trypanosomiasis, African/transmissionABSTRACT
Sheep (Ovis aries) are intermediate hosts for at least six named species of Sarcocystis: S. tenella, S. arieticanis, S. gigantea, S. medusiformis, S. mihoensis, and S. microps. Here, only two species, S. tenella and S. arieticanis, were found in 79 of 86 sheep (91.9%) in Kunming, China, based on their morphological characteristics. Four genetic markers, i.e., 18S rRNA gene, 28S rRNA gene, mitochondrial cox1 gene, and ITS-1 region, were sequenced and characterized for the two species of Sarcocystis. Sequences of the three former markers for S. tenella shared high identities with those of S. capracanis in goats, i.e., 99.0%, 98.3%, and 93.6%, respectively; the same three marker sequences of S. arieticanis shared high identities with those of S. hircicanis in goats, i.e., 98.5%, 96.5%, and 92.5%, respectively. No sequences in GenBank were found to significantly resemble the ITS-1 regions of S. tenella and S. arieticanis. Identities of the four genetic markers for S. tenella and S. arieticanis were 96.3%, 95.4%, 82.5%, and 66.2%, respectively.
Subject(s)
Sarcocystis/isolation & purification , Sarcocystosis/veterinary , Sheep Diseases/parasitology , Animals , China/epidemiology , DNA, Protozoan/chemistry , DNA, Protozoan/isolation & purification , DNA, Ribosomal Spacer/genetics , Electron Transport Complex IV/genetics , Genetic Markers , Microscopy, Electron, Transmission/veterinary , Mitochondria/enzymology , Muscles/parasitology , Phylogeny , Prevalence , RNA, Ribosomal, 18S/genetics , RNA, Ribosomal, 28S/genetics , Sarcocystis/classification , Sarcocystis/genetics , Sarcocystis/ultrastructure , Sarcocystosis/epidemiology , Sarcocystosis/parasitology , Sheep , Sheep Diseases/epidemiologyABSTRACT
Rapid losses of biodiversity due to the changing landscape have spurred increased interest in the role of species diversity and disease risk. A leading hypothesis for the importance of biodiversity in disease reduction is the dilution effect, which suggests that increasing species diversity within a system decreases the risk of disease among the organisms inhabiting it. The role of species diversity in trematode infection was investigated using field studies from sites across the U.S. to examine the impact of snail diversity in the infection dynamics of both first and second intermediate larval stages of Echinostoma spp. parasites. The prevalence of Echinostoma spp. sporocysts/rediae infection was not affected by increases in snail diversity, but significant negative correlations in metacercariae prevalence and intensity with snail diversity were observed. Additionally, varying effectiveness of the diluting hosts was found, i.e., snail species that were incompatible first intermediate hosts for Echinostoma spp. were more successful at diluting the echinostome parasites in the focal species, while H. trivolvis, a snail species that can harbor the first intermediate larval stages, amplified infection. These findings have important implications not only on the role of species diversity in reducing disease risk, but the success of the parasites in completing their life cycles and maintaining their abundance within an aquatic system.
Subject(s)
Biodiversity , Echinostoma/physiology , Snails/classification , Snails/genetics , Animals , Host-Parasite Interactions , LarvaABSTRACT
Water buffalo (Bubalus bubalis) is the intermediate host for at least four species of Sarcocystis: S. fusiformis, S. buffalonis, S. levinei, and S. sinensis/S. dubeyi. Here, a new species, Sarcocystis dehongensis, is reported in 51 of 756 (6.7%) water buffaloes in China. By light microscopy, the cysts of S. dehongensis were macroscopic, up to 18.5 mm long and 95 µm in diameter; 4.9-11.9 µm villous protrusions extended beyond the sarcocyst wall. Using transmission electron microscopy, the sarcocyst wall had lancet- or leaf-like protrusions in longitudinal section, but the cross section showed that the protrusions appeared as mushroom-like in shape with a core of tightly packed microtubules, similar to "type 24." BLAST searches revealed that S. dehongensis shared the most similarities with the 18S rDNA sequence of S. hardangeri (92.4%) and mitochondrial cox1 gene sequence of S. ovalis (81.0%), whereas no sequences in GenBank were found to be significantly similar to the ITS-1 region of S. dehongensis. A phylogenetic analysis based on 18S rDNA and mitochondrial cox1 gene sequences suggested that S. dehongensis was closely related to Sarcocystis species from cervids that employ corvids as definitive hosts.
Subject(s)
Buffaloes/parasitology , Sarcocystis/classification , Sarcocystosis/veterinary , Animals , China , DNA, Mitochondrial/chemistry , DNA, Ribosomal/chemical synthesis , DNA, Ribosomal/genetics , Microscopy, Electron, Transmission/veterinary , Phylogeny , RNA, Ribosomal, 18S/genetics , Sarcocystis/genetics , Sarcocystis/isolation & purification , Sarcocystis/ultrastructure , Sarcocystosis/parasitologyABSTRACT
Williamson's mouse deer, Tuagulus williamsoni (Kloss), is one of the smallest ungulates among tragulid species found in northern Thailand, and Yunnan Province, China. Here we describe Sarcocystis menglaensis n. sp., infecting two of 14 (14.3%) Williamson's mouse deer from south-western China. By light microscopy, sarcocysts of S. menglaensis are microscopic, up to 2,170 µm in length, and have a striated sarcocyst wall with 1.5-3.6 µm long palisade-like protrusions. Transmission electron microscopy observations revealed that sarcocyst wall is of "type 10f", and has numerous villar protrusions folded over the cyst wall. The villar protrusions contained microtubules dispersed throughout the protrusions. Phylogenetic analysis based on 18S rDNA and mitochondrial cox1 gene sequences indicated that S. menglaensis shared a close affinity with species of Sarcocystis Lankester, 1982 from ruminants, which utilise felids as definitive hosts.
Subject(s)
Deer/parasitology , Phylogeny , Sarcocystis/classification , Animals , China , Electron Transport Complex IV/genetics , Microscopy, Electron, Transmission , RNA, Ribosomal, 18S/genetics , Sarcocystis/genetics , Sarcocystis/ultrastructure , Species SpecificityABSTRACT
Digenetic trematodes have complex life cycles involving multiple hosts and free-living larval stages. Some species have 2 lar-val stages that infect snails, with miracidia and cercariae using these molluscs as first and second intermediate hosts, respec-tively. Although both larval stages may infect the same snail species, this is accomplished using different chemical cues and may be influenced by different biotic and abiotic factors. Significant differences in the infection patterns of these parasitic stages regarding host size and density were observed in 2 separate field studies. The prevalence of sporocysts/rediae and mean abundance of Echinostoma spp. metacercariae infection were positively correlated with host size, while the prevalence of Echinostoma spp. cercariae infection was positively correlated with host density across 5 different pulmonate snail species. Larger snails within a given species tend to be older and the increased exposure time may be responsible for the positive correlations with host size. Additionally, infection by miracidia in more vagile snail hosts was influenced by trematode species richness at a sample site, which may be attributed to increased encounter rate as a result of increased movement by the snail hosts. Echinostoma spp. metacercariae prevalence was influenced by host density, possibly due to high abundances of larval clones and their response to more generalized chemical cues attributed to low host specificity by cercariae. Although they can infect the same gastropod hosts, miracidia and cercariae infection are dependent on different factors at both the individual and population level of their snail hosts.
Subject(s)
Trematoda/physiology , Trematode Infections/transmission , Animals , Disease Reservoirs , Lakes , Larva/physiology , Ponds , Snails/parasitology , Species Specificity , Trematoda/genetics , Trematode Infections/parasitology , United StatesSubject(s)
Nobel Prize , Parasitology , History, 20th Century , History, 21st Century , Northern Ireland , Parasitology/history , Sweden , United StatesABSTRACT
The microhabitats in which hosts live can potentially influence the ability and success of parasites in finding and infecting these hosts. The infection dynamics of both digenetic trematode parasites and a nematode parasite (Daubaylia potomaca) infecting a pulmonate snail, Helisoma anceps , were observed in a small North Carolina lake using 3 different classifications of substratum type based on percent coverage by leaves and debris. There were no differences in snail site occupancy or density between substratum types, but small-scale differences in microhabitat impacted parasite prevalence and intensity in their gastropod hosts. Snails inhabiting substrata covered in more leaf litter and debris had a lower prevalence and intensity of infection by all of the trematode species and life stages when compared to H. anceps inhabiting other substrata types, while only the intensity of infection was impacted in D. potomaca infections. These findings emphasize the importance of microhabitat, specifically its physical components, in influencing parasite infection in intermediate hosts and that small-scale differences may significantly affect the patterns of infection.
Subject(s)
Ecosystem , Rhabditoidea/physiology , Snails/parasitology , Trematoda/physiology , Animals , Geologic Sediments , Host-Parasite Interactions , Lakes , North Carolina , Snails/growth & developmentABSTRACT
Numerous species of Sarcocystis have been reported from wild ruminants, but none has been from Williamson's mouse deer (Tuagulus williamsoni). Here, we describe a new species, Sarcocystis tuagulusi, infecting five of 12 Williamson's mouse deer from southwest China. Mature sarcocysts are microscopic, up to 2280-µm long. The sarcocyst wall had 8.2-µm long villar protrusions, type 24. Using transmission electron microscopy, the protrusions on sarcocysts appeared as elongated, lancet- or leaf-like shapes in longitudinal sections; in contrast, the cross-sections revealed mushroom-shaped protrusions. In the core of the protrusion, a bundle of microtubules penetrated diagonally into a ground substance along the longitudinal axis. A phyogenetic analysis based on 18S rRNA and cox1 sequences suggested S. tuagulusi is closely related to Sarcocystis species from ruminants that employ felids as definitive hosts.
Subject(s)
Deer , Sarcocystis/isolation & purification , Sarcocystosis/veterinary , Animals , China/epidemiology , Gene Expression Regulation, Enzymologic , Mice , Microscopy, Electron, Transmission , Phylogeny , RNA, Protozoan/genetics , RNA, Ribosomal, 18S/genetics , Sarcocystis/classification , Sarcocystosis/epidemiology , Sarcocystosis/parasitologyABSTRACT
Auto-infection is a life history strategy used by many parasitic organisms, including digenetic trematodes. The process of autoinfection most frequently involves the transfer of a life cycle stage of the parasite from one site to another inside the same host, usually accompanied by morphological transformation. Moreover, among trematodes, the stage being transferred may also move from one host to another in completing the life cycle, i.e., an indirect cycle. Echinostoma spp. parasites offer the opportunity to study auto-infection because they utilize gastropods as both first and second intermediate hosts. Rejection of a null model predicting independent infection of first and second intermediate larval stages coupled with the presence of rediae being the best predictor of metacercariae prevalence and intensity suggests that auto-infection by Echinostoma spp. cercariae is occurring in their molluscan hosts. Shell length was also found to be a significant predictor of metacercariae intensity in the snails hosts, but this is most likely attributed to larger snails being more commonly infected with Echinostoma spp. rediae as opposed to an increased likelihood of cercariae infection. Auto-infection as a life history strategy increases transmission success of the parasite, but may also have negative consequences for the parasite that necessitate auto-infection coupled with the release of cercariae to maximize transmission success and host survival.
Subject(s)
Echinostoma/isolation & purification , Echinostoma/physiology , Echinostomiasis/veterinary , Snails/parasitology , Animals , Cercaria/isolation & purification , Echinostomiasis/parasitology , Life Cycle StagesABSTRACT
In 1984, work on the parasite population and community ecology in the pulmonate snail, Helisoma anceps , was initiated in Charlie's Pond (North Carolina). Similar research on Physa gyrina was started in 1986. When study in the pond began in 1984, 8 species of larval trematodes were being shed from Hel. anceps. By far, the dominant species was Halipegus occidualis , with prevalences generally â¼60%, except during midsummer, when older snails were dying. For the other 7 trematode species being shed, prevalences were consistently less than 4%. By 2006, 18 species had been identified in Hel. anceps at one time or another. In 1986, Hal. eccentricus was discovered in P. gyrina , with a prevalence of â¼49%. Through 2006, 7 trematodes were found to be shedding cercariae from P. gyrina . Halipegus eccentricus disappeared from the pond in 1998. From March through November of 2012 and 2013, 1,292 Hel. anceps and 716 P. gyrina were collected, using collection protocols that were identical to those used from 1984 through 2006. In 2012, 5 trematode species, including Hal. occidualis, were present in Hel. anceps at one time or another. During the last part of the 2012 collecting season cercariae of just 2 species were being shed from Hel. anceps (and 1 from P. gyrina ). In 2013, only cercariae of Haematoloechus longiplexus and Uvulifer ambloplitis were observed from Hel. anceps. The latter species was lost by 2014, and an echinostome was present (2.1%); a single snail was infected with Haem. longiplexus. Four species were being shed from P. gyrina , i.e., Echinoparyphium sp. (7.9%), Glypthelmins sp. (1.5%), Plagiorchis sp. (4.9%), and Posthodiplostomum sp. (7.4%). Rarefaction curves were generated for Hel. anceps shedding in 1984, 1988, 1989, 2002, 2006, and August of 2014. The data clearly indicate that species diversity was constantly declining over the 31-yr period. We did not include P. gyrina in the analysis since data for this snail species were not acquired until 1991-1992. At present, we have no definitive explanation for the decrease in diversity, although circumstantial evidence suggests that it might be related to periodic declines in water level that negatively affected the colonization and maintenance of emergent vegetation within the pond.
Subject(s)
Ponds/parasitology , Rana clamitans/parasitology , Snails/parasitology , Trematoda/growth & development , Animals , Biodiversity , Droughts , Magnoliopsida/growth & development , North Carolina , Snails/growth & development , Snails/physiology , Trematoda/classification , Trematoda/physiology , Typhaceae/growth & developmentABSTRACT
The infection patterns of parasites are often tied to host behavior. Although most studies have investigated definitive hosts and their parasites, intermediate host behavior may play a role in shaping the distribution and accumulation of parasites, particularly the larval stages. In an attempt to answer this question, more than 4,500 pulmonate snails were collected from 11 states in the mid-Atlantic and Midwestern United States in the summer of 2012. These snails were necropsied and echinostome metecercariae were commonly observed infecting the snails as 2(nd) intermediate hosts (20.0%). The snails included species of 3 genera with distinct differences in the infection patterns of Echinostoma spp. metacercariae among them. Physa spp. (comprising of P. acuta and P. gyrina) snails exhibited a significantly higher prevalence of infection (23.5%) than both Lymnaea columella (11.6%) and Helisoma spp. (comprising of H. anceps and H. trivolvis) (14.2%; P < 0.05), with no difference in prevalence observed between the latter 2 genera (P > 0.05). The intensity of metacercariae within the snail hosts was significantly different between the 3 genera (P < 0.05), with L. columella having the highest intensity (24.3 ± 5.6), followed by Physa spp. (15.2 ± 1.5) and Helisoma spp. (5.0 ± 0.9). Differences in prevalence and intensity were also observed when the different snail families co-habited the same body of water. The disparities in infection patterns are likely due to distinct differences in the behavioral and feeding ecology of the snail hosts.
Subject(s)
Echinostoma/isolation & purification , Snails/parasitology , Animals , Ecology , Host-Parasite Interactions , Larva , Metacercariae , Prevalence , Seasons , United StatesABSTRACT
Fifty-six oriental voles, Eothenomys miletus (Thomas), were collected in Anning prefecture of Yunnan Province (China) between March 2012 and December 2013 and examined for the presence of sarcocysts. Sarcosysts of a new species, Sarcocystis eothenomysi n. sp., were found in 14 out of 56 E. miletus (25%); they possessed a striated cyst wall, c.1-2 µm thick. Under transmission electron microscopy the cysts of S. eothenomysi exhibited numerous small, irregular protrusions, which may appear T-shaped in some sections. A phylogenetic analysis based on 18S rRNA gene sequences indicated that S. eothenomysi shares closest affinity with those species of Sarcocystis Lankester, 1982, which use cobra or viperid snakes as definitive hosts. We therefore, hypothesise that a venomous snake may serve as the definitive host for S. eothenomysi. This is the first species of Sarcocystis reported from Eothenomys spp.
Subject(s)
Phylogeny , Sarcocystis/classification , Animals , Arvicolinae/parasitology , China , Microscopy, Electron, Transmission , RNA, Ribosomal, 18S/genetics , Sarcocystis/genetics , Sarcocystis/ultrastructure , Species SpecificityABSTRACT
The present issue is Number 1 of Volume 100, The Journal of Parasitology. All 6 numbers of this, our Centennial Volume, are dedicated to those in the past who have contributed in any manner to the Journal's success as a national and international broker for parasitology. Our essay on the history of the Journal is divided into 3 parts. The first extends from 1914 to 1932, i.e., 'the beginning', when Henry Baldwin Ward was Editor and owned the Journal. The 'middle years' continue from 1933, when Ward gave the Journal to the American Society of Parasitologists, to 1961. The 'current period' carries on from 1961 to the present, our Centennial year. Obviously, we cannot provide a great many specific details for each era, but we have made an effort to identify some of the events, issues, and people that have played a significant role in our Journal's history.
Subject(s)
Parasitology/history , Periodicals as Topic/history , History, 20th Century , History, 21st Century , Societies, Scientific/history , United StatesABSTRACT
Daubaylia potomaca is a nematode parasite that exhibits an unusual direct life cycle in planorbid snails in which adult females are the infective stage, after being shed from a definitive host. The present study examined the shedding patterns of this nematode to determine what cues or mechanisms might lead to the parasite leaving its host. A correlation was found between host death and the frequency and number of D. potomaca shed, suggesting that the nematodes can detect that the host is dying and may leave in search of a new host. Furthermore, elevated intensities of D. potomaca in the snail induce shedding earlier, suggesting that competition for space and resources may also play a role in the shedding patterns of the nematode, but not when time to death is controlled. Finally, nematodes shed a longer time before host death were significantly longer and more likely to be gravid than those shed as time to snail death approached, implying that the nematode reaching maturity or being inseminated might also be cues for D. potomaca to leave its snail host. In summary, the shedding patterns of D. potomaca appear to be a complex mix of host death detection, competition, and nematode maturation.
Subject(s)
Rhabditida/physiology , Snails/parasitology , Animals , Female , Host-Pathogen Interactions , Lakes , Linear Models , Male , North Carolina , Rhabditida/anatomy & histology , Sex FactorsABSTRACT
Hemophagocytic syndrome is a rare disease that is often fatal, despite treatment. An immunocompetent patient was presented with fever, hepatosplenomegaly, cytopenias, hypertriglyceridemia, hypofibrinogenemia, and hyperferritinemia, which conformed to a hemophagocytic syndrome diagnosis. Despite broad antibiotic treatment, the patient's clinical condition rapidly deteriorated and he died within 8 days of admission. Blood cultures and a serology test were negative; however, based on morphological characteristics, tissue cysts Toxoplasma gondii were found in the bone marrow. Based on polymerase chain reaction analysis, identity of the parasite was confirmed. Although very rare, T. gondii-associated hemophagocytic syndrome should be suspected in the case of cytopenia or multiorgan failure symptoms. To our knowledge, this is the first fatal toxoplasmosis case reported from China.
Subject(s)
DNA, Protozoan/isolation & purification , Lymphohistiocytosis, Hemophagocytic/diagnosis , Toxoplasmosis/diagnosis , Adult , Aminoglycosides/therapeutic use , Asian People , Bone Marrow , Cefoperazone/therapeutic use , China , Fatal Outcome , Humans , Lymphohistiocytosis, Hemophagocytic/etiology , Lymphohistiocytosis, Hemophagocytic/parasitology , Male , Penicillanic Acid/analogs & derivatives , Penicillanic Acid/therapeutic use , Seroepidemiologic Studies , Tazobactam , Toxoplasma/isolation & purification , Toxoplasmosis/complicationsABSTRACT
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.
Subject(s)
Life Cycle Stages/physiology , Rhabditida/physiology , Snails/parasitology , Animals , Female , Fresh Water , Host-Parasite Interactions , Male , North Carolina , Rhabditida/anatomy & histology , Rhabditida/growth & development , SeasonsABSTRACT
Many biotic interactions can affect the prevalence and intensity of parasite infections in aquatic snails. Historically, these studies have centered on interactions between trematode parasites or between trematodes and other organisms. The present investigation focuses on the nematode parasite Daubaylia potomaca and its interactions with a commensal, Chaetogaster limnaei limnaei , and a variety of trematode species. It was found that the presence of C. l. limnaei indirectly increased the mean intensity of D. potomaca infections, apparently by acting as a restraint for various trematode parasites, particularly the rediae of Echinostoma sp. In turn, Echinostoma sp. rediae adversely affected the mean intensity of D. potomaca by their consumption of both juvenile and adult nematodes present in tissues of the snail. These organisms not only belong to 3 different phyla but occupy distinct trophic levels as well. The complex interactions among these 3 organisms in the snail host provide an excellent example of biotic interactions influencing the infection dynamics of parasites in aquatic snails.
Subject(s)
Echinostoma/physiology , Nematoda/physiology , Oligochaeta/physiology , Snails/parasitology , Algorithms , Animals , Fresh Water , Host-Parasite Interactions , North Carolina , Random Allocation , Trematoda/physiologyABSTRACT
Daubaylia potomaca is a parasitic nematode that exhibits a direct life cycle using planorbid snails as their only host. Within the snail host Helisoma anceps , all developmental stages of the parasite are present at any given time. The nematode has an unusual life cycle, with the adult female being the infective stage rather than the third-stage larvae (L(3)), as is commonly the case in many other parasitic nematode life cycles. In addition, length analysis showed that L(1) and L(2) were not present in tissues, suggesting that larvae hatch from eggs as the L(3). Previous studies by other investigators show that adult females abandon Biomphalaria glabrata at some point between 3 and 9 days of host death; in the present study, adult female D. potomaca leave H. anceps up to 59 days (and a mean of 14.8 days) before host death. This observation indicates a striking physiological difference between an experimental and a natural host for the parasite.