Revision of Leptorhynchoides thecatus (Acanthocephala: Illiosentidae), with morphometric analysis and description of six new species.

Six new species of Leptorhynchoides from the southeastern United States are described. These new species were once part of the Leptorhynchoides thecatus complex of species that was previously recognized on the basis of DNA sequence data. Multivariate morphometric analysis including discriminant function analysis and decision tree analysis indicated that each of the species is morphologically distinct. Both analyses classified more than 90% of specimens correctly and most misclassifications occurred between members of 2 pairs of species that are morphologically similar. The most discriminating continuous characters were: trunk length, number of longitudinal rows of hooks, length of the longest hook, and testes width. Hook asymmetry and missing hooks on the proboscis were also important taxonomic characters. The discriminant function and the decision tree generated from the data were used to classify new specimens, yielding a 96% and 84% correct classification rate, respectively. The new taxonomic designations account for much of the previously recognized variability in host use, habitat use, and development as determined by survey data. With the addition of these 6 new taxa, 10 species currently are recognized within the genus.

A history of the Journal of Parasitology.

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.

A description of mature Oncicola venezuelensis (Acanthocephala: Oligacanthorhynchidae) from a feral house cat in the U. S. Virgin Islands.

A road-killed feral house cat from the U.S. Virgin Islands was parasitized by 87 acanthocephalans of the species Oncicola venezuelensis Marteau, 1977. The finding allowed for the documentation of a suitable definitive host for the species in the Virgin Islands and permits a more comprehensive description of the species, including the first of fully mature adults and completely formed eggs. Sexually mature males from the cat were 6.5-8.4 (8.0) mm long; gravid females were 13.2-18.3 (15.5) mm long. Fully formed eggs dissected from the trunk of females were 67-72 (69) µm long by 43-50 (47) µm wide. The life cycle of O. venezuelensis in the Virgin Islands is now apparent, i.e., termites serve as intermediate hosts, lizards and birds as paratenic hosts, and domestic cats as definitive hosts. Extra-intestinal infections in mongooses are likely incidental.

Acanthocephala from amphibians in China with the description of a new species of Pseudoacanthocephalus (Echinorhynchida).

Amphibians of 24 species were surveyed for acanthocephalans in 4 nature reserves in 2 Chinese provinces during 2004­2006. Pseudoacanthocephalus bufonis (Echinorhynchida) occurred in both nature reserves in Guangxi Province. In the Jing Xi County Provincial Nature Reserve, P. bufonis infected 36 of 62 amphibians at a mean intensity of 9.9. Less than 250 km away, at Shiwandashan National Nature Reserve, 5 of 20 amphibians were infected at a mean intensity of 6.2. Pseudoacanthocephalus bufonis was not found in either of the reserves in Guizhou Province. In the Kuan Kuoshui Nature Reserve, 9 of 28 amphibians were parasitized at a mean intensity of 2.0 by a previously undescribed species of Pseudoacanthocephalus , and no acanthocephalan occurred in a small sample of 2 toads at Dashahe Nature Reserve. The new species, Pseudoacanthocephalus reesei n. sp., differs from all others in the genus by typically having 14 longitudinal rows of 4 hooks, each of which is much longer than corresponding hooks of any other species of the genus. The length of proboscis hooks increases from the apex to the base of the proboscis, further distinguishing the new species from all but Pseudoacanthocephalus nguyenthileae .

Virulence of Corynosoma constrictum (Acanthocephala: Polymorphidae) in Hyalella azteca (Amphipoda) throughout parasite ontogeny.

Development and growth of parasites depend on resources provided by the host and the parasite's ability to use them. Identifying specific costs incurred by the host provides insight for assessment of parasite energy budgets, which differ among taxa and ontogenetic stages. Data from this study were analyzed using an accelerated failure-time model with intensity as a covariate. Results indicated significantly reduced survival of amphipods, Hyalella azteca, infected with the acanthocephalan Corynosoma constrictum compared with uninfected controls. Male and female amphipod survivorship and infection intensity did not differ; however, amphipods with high-intensity infections (> 16 larvae) died earlier compared with amphipods with low-intensity infections (< 3 larvae). The majority of infected amphipods died between 12 and 24 days postexposure, a period of rapid larval development. It is hypothesized that host death may be due either to an increase in overall larval nutritional demands or to parasite-mediated depletion of a specific host substance. Results from this study suggest that developing C. constrictum satisfies energy requirements by depriving amphipod hosts of resources normally used for somatic growth and maintenance.

Geographic analysis of host use, development, and habitat use of an acanthocephalan species, Leptorhynchoides thecatus.

Leptorhynchoides thecatus (Linton, 1891), an acanthocephalan parasite of freshwater fishes, varies in host use, development, and habitat use throughout North America. Spatial structure of these characteristics was examined from data extracted from the literature. Geographic patterns were inferred from point comparisons using correllograms and then tested with Moran's I statistic for global and local significance, and visually from regional means within major river drainages. Species of Micropterus Lacepède, 1802 (black basses) were common hosts in most regions, except the Lower Mississippi and South Atlantic regions where species of Lepomis Rafinesque, 1819 (sunfishes) were common hosts. Development, described as the proportions of adults relative to cystacanths (extraintestinal juveniles), decreased with latitude. Habitat use of L. thecatus showed marked geographic patterns. Leptorhynchoides thecatus occurred in the intestine of sunfishes in the South Atlantic and Lower Mississippi regions, in the ceca in fish of all species included in the study in the Missouri and Texas-Gulf regions, and both in ceca and intestines in fish of all species in northern regions. Leptorhynchoides thecatus showed geographic patterning within the variable traits across the range of the species. These patterns may be the result of ecological factors or of genetic differences that might indicate L. thecatus comprises multiple cryptic species.

Cystacanths of Oncicola venezuelensis (Acanthocephala: Oligacanthorhynchidae) in Caribbean termites and various paratenic hosts in the U.S. Virgin Islands.

Cystacanths of Oncicola venezuelensis (Acanthocephala: Oligacanthorhynchidae) were discovered in the hemocoel of Caribbean termites (Nasutitermes acajutlae) on St. Thomas and St. John islands in the U.S. Virgin Islands. In addition to occurring in the insect intermediate host, cystacanths were present in subcutaneous nodules of lizards (Anolis cristatellus and Anolis stratulus), in the greater omentum of small Indian mongooses (Herpestes auropunctatus), and embedded in mesenteries of pearly-eyed thrashers (Margarops fuscatus). These vertebrates likely are paratenic hosts, although a definitive host in the Virgin Islands is yet to be discovered. Cystacanths from intermediate and paratenic hosts agree fully with the original description of proboscis armature, including size and shape of hooks and their roots, of the species. Qualitative features of developing and growing structures agree with the original description of the species, but the sizes are smaller.

First sequenced mitochondrial genome from the phylum Acanthocephala (Leptorhynchoides thecatus) and its phylogenetic position within Metazoa.

The complete sequence of the mitochondrial genome of Leptorhynchoides thecatus (Acanthocephala) was determined, and a phylogenetic analysis was carried out to determine its placement within Metazoa. The genome is circular, 13,888 bp, and contains at least 36 of the 37 genes typically found in animal mitochondrial genomes. The genes for the large and small ribosomal RNA subunits are shorter than those of most metazoans, and the structures of most of the tRNA genes are atypical. There are two significant noncoding regions (377 and 294 bp), which are the best candidates for a control region; however, these regions do not appear similar to any of the control regions of other animals studied to date. The amino acid and nucleotide sequences of the protein coding genes of L. thecatus and 25 other metazoan taxa were used in both maximum likelihood and maximum parsimony phylogenetic analyses. Results indicate that among taxa with available mitochondrial genome sequences, Platyhelminthes is the closest relative to L. thecatus, which together are the sister taxon of Nematoda; however, long branches and/or base composition bias could be responsible for this result. The monophyly of Ecdysozoa, molting organisms, was not supported by any of the analyses. This study represents the first mitochondrial genome of an acanthocephalan to be sequenced and will allow further studies of systematics, population genetics, and genome evolution.

The behavioral response of amphipods harboring Corynosoma constrictum (Acanthocephala) to various components of light.

Many studies have shown that photic behavior of amphipods is subject to parasitic manipulation. However, all these investigations have focused on but one property of light (i.e., intensity). This study investigated the possibility that variable wavelength sensitivity, as a potentially important component of amphipod ecology, is subject to parasitic manipulation. The photic behavior of freshwater amphipods Hyalella azteca, infected with the duck acanthocephalan Corynosoma constrictum, was tested. The phototactic responses of infected and uninfected amphipods to various wavelengths in the visible spectrum were compared, and to delineate the effects of intensity and wavelength on behavior, the preferences of amphipods for environments characterized by various combinations of light intensity and wavelength were determined. Response to blue light (400-450 nm) was little affected by infection. Amphipod response to higher red region wavelengths (600-700 nm) was altered by infection. Infected amphipods were significantly less responsive to green region light (500-550 nm), which could lead to increased wandering throughout the water column, thereby facilitating increased parasite transmission through increased predation risk. This study reinforces the subtlety with which parasites can alter their host's behavior, presumably resulting in an increased probability of being transmitted from the intermediate host to a definitive host.

Postcyclic transmission and its effect on the distribution of Paulisentis missouriensis (Acanthocephala) in the definitive host Semotilus atromaculatus.

The relationship of fish age class to parasitism by Paulisentis missouriensis was determined by sampling at least 29 creek chubs, Semotilus atromaculatus, from Easly Creek, Richardson County, Nebraska, every month from February 1996 to March 1997. In general, mean abundance and prevalence of the acanthocephalans increased with the age or length of chubs. It is unlikely that this distribution is explained by increased consumption of intermediate hosts by older, larger fish or by predatory fish acquiring parasites from paratenic hosts. The intermediate host for P. missouriensis is the cyclopoid copepod Acanthocyclops robustus, and creek chubs do not consume more microscopic crustaceans as they age or grow. Instead, the percentage of fish in the diet of creek chubs increases. Furthermore, P. missouriensis apparently does not use paratenic hosts. In laboratory infections, P. missouriensis survived predation of its original definitive host and transferred to the predator. Postcyclically transmitted P. missouriensis survived at least 14 days in the intestine of creek chubs, where they localized around the first flexure beyond the stomach. All stages of development of both sexes were transferred successfully. Postcyclic transmission is a plausible explanation, in some cases, for the greater worm burden frequently observed in older, larger hosts and for the occurrence in top carnivores of parasites not known to have paratenic hosts. This method of transmission appears to result in distribution of acanthocephalans to groups of animals that otherwise would be inaccessible.

Effect of cystacanth body size on adult success.

Laboratory-reared cystacanths of Leptorhynchoides thecatus (Acanthocephala: Rhadinorhynchidae) were used to study the effect of cystacanth size on adult success and the factors that influence cystacanth size within the intermediate host. To assess how host size and intensity of infection influence cystacanth size, infected amphipods (Hyalella azteca) were measured, and sex, length, and width of cystacanths were determined. After a subset of cystacanths was measured, small- and large-size classes of cystacanths were designated. To determine how cystacanth size relates to adult size, green sunfish (Lepomis cyanellus) were fed 10 large or small cystacanths. Fish were dissected 6 wk after infection, and worms were removed. After adult worms were permanently mounted on slides, their length and width were measured. Intensity of infection and amphipod size significantly influenced cystacanth size in that large amphipods harbored larger cystacanths than did small amphipods and heavy infections produced smaller cystacanths than did light infections. Adult worms from the small and large cystacanth-size classes showed no significant difference in size; however, large cystacanths had a significantly higher establishment and survival than did small cystacanths: 40% of large worms and 14% of small worms were recovered. The results of this study indicate that host size and host sharing influence cystacanth size and that cystacanth size is an important factor in determining adult success.

Acanthocephalans from crabs in the southeastern U.S., with the first intermediate hosts known for Arhythmorhynchus frassoni and Hexaglandula corynosoma.

Cystacanths of Hexaglandula corynosoma were discovered in the fiddler crabs Uca spinicarpa and Uca rapax collected in Mississippi and Florida. Adults were present in yellow-crowned night herons, Nyctanassa violacea, collected in Florida. Cystacanths are very similar to adults, varying only in size and state of development. This is the first record of H. corynosoma from the United States and the first record of an intermediate host for any species of the genus. Cystacanths of Arhythmorhynchus frassoni were present in U. rapax from Florida. The proboscis size, shape, and armature of the cystacanths are identical to those of adults from clapper rails (Rallus longirostris) collected in several southeastern states. This is the first report of an intermediate host for A. frassoni. Profilicollis altmani cystacanths were collected from mole crabs (Emerita talpoida) at Atlantic Beach, North Carolina. These specimens, together with adults obtained from shore birds in Louisiana and Mississippi, are consistent with the view that P. altmani, Profilicollis kenti, and Profilicollis texensis are synonyms, with P. altmani having nomenclatural priority.

Corynosoma magdaleni in gray seals from the Gulf of Bothnia, with emended descriptions of Corynosoma strumosum and Corynosoma magdaleni.

Because of the likelihood that Corynosoma magdaleni Montreuil, 1958. has been confused with C. strumosum (Rudolphi, 1802) in reports of parasites from seals and to clarify its distribution in the Baltic Sea, acanthocephalans from 26 young gray seals from the southwestern Finnish archipelago (western Baltic Sea) were examined. All harbored C. semerme (Forssell. 1904). In addition to C. semerme, 12 had both C. strumosum and C. magdaleni, 3 had only C. strumosum, and 9 had only C. magdaleni. Most anatomical structures of C. strumosum are similar to, but larger than, those of C. magdaleni. The most conspicuous differences are the longer and more robust trunk of C. strumosum, the routinely longer proboscis (mean, 653 vs. 476 microm) and larger proboscis hook (mean, 69 vs. 58 microm) of C. strumosum, and the greater extent of ventral trunk spines (mean, 61 vs. 47%) in C. magdaleni. In addition, C. strumosum consistently possesses 18 longitudinal rows of proboscis hooks, whereas C. magdaleni has 17-23, with 20 being the usual number by far. In seals aged 3.6 mo, on average, C. strumosum was more prevalent and abundant than was C. magdaleni, whereas in seals of age 2.0-3.0 mo the reverse was true, with C. strumosum being nearly absent. These differences might reveal the age-dependent food habits of the very young seals. No site segregation was found between C. strumosum and C. magdaleni in the small intestine, but they clearly segregated from C. semerme, which occurred mainly in the cecum, large intestine, and rectum. All species matured equally well in gray seals, with 62, 67, and 53% of the C. magdaleni, C. strumosum, and C. semerme, respectively, comprising gravid worms (possessing eggs with fully formed acanthors).

Presomal morphology and development of Prosthorhynchus formosus, Prosthenorchis elegans, and Moniliformis dubius (Acanthocephala).

Larvae removed at one-day intervals from laboratory infected intermediate hosts provided material for a comparative study of presomal development in Prosthorhynchus formosus (Van Cleave, '18) Travassos, '26, Prosthenorchis elegans (Diesing, 1851) Travassos, '15, and Moniliformis dubius Meyer, '33. Acanthellae begin development soon after entering intermediate hosts' hemocoels, and by the 18th day all three species possess three nuclear masses representing primordia of the proboscis, proboscis receptacle and ganglion, and trunk musculature and genitalia. Presomal development of P. formosus and P. elegans results in structures concurring with morphology of other adult palaeacanthocephalans and archiacanthocephalans. Development of M. dubius, however, differs from that of other archiacanthocephalans in that the muscular receptacle wall lines the entire surface of the nonmuscular sheath, failing to form a ventral cleft characteristic of other archiacanthocephalans. Unlike receptacle protrusor muscles of other archiacanthocephalan species, those of M. dubius spiral around the receptacle as they extend posteriad to attach individually to a pouchlike, muscular thickening at the receptacle's base. These protrusor muscles are distinct from the receptacle wall, as attested by their development alongside neck retractor muscles, not from the receptacle primordium, and the manner in which they are left to trail behind the receptacle when it is drawn anteriorly into the proboscis during larval development. The proboscis receptacle of M. dubius should not be thought of as being double-walled, as envisioned by previous workers.