An independent species of cestode of the genus Diphyllobothrium Cobbold, 1858, known only from the Pacific walrus, Odobenus rosmarus divergens Illiger, has been incorrectly designated Diphyllobothrium cordatum (Leuckart, 1863) in the literature since 1955. That cestode is described in this study as Diphyllobothrium fayi n. sp. on the basis of specimens obtained from walruses from the northern Bering Sea and the Arctic Ocean. It is distinguished readily from D. cordatum by its much larger strobila of different form and by a range of morphological characteristics of taxonomic significance in the reproductive organs. Comparisons were made with specimens of D. cordatum from the bearded seal, Erignathus barbatus (Erxleben), its typical host. Diphyllobothrium fayi has been recorded only from the Pacific walrus. Although that mammal feeds mainly on mollusks and other benthic invertebrates, records of cestodes from it suggest that fishes potentially harboring plerocercoids are frequently consumed.

The spiral intestines of 40 specimens of Urobatis halleri from the northern Gulf of California, Mexico, were examined for cestodes. Four new species, Rhinebothrium chollaensis n. sp., Rhinebothrium gravidum n. sp., Eutetrarhynchus cortezensis n. sp., and Prochristianella minima n. sp., are described. This is the first record of these 3 genera in the Gulf of California and the first report of Eutetrarhynchus in U. halleri.

Boliviana floridensis n. sp. (Apicomplexa: Eugregarinida: Gregarinidae) is described on the basis of morphology and life history in its natural host, the grasshopper Romalea microptera (Orthoptera: Romalidae) from south Florida, U.S.A. Trophozoites are slender with a globular epimerite. Protomerites are very broadly ovoid in early trophozoites, becoming deltoid in later stages. Deutomerites are deeply obovoid in immature trophozoites, becoming narrowly obdeltoid in mature trophozoites. Association is precocious, biassociative, and caudofrontal, with the satellite protomerite engulfing the posterior end of the primite deutomerite to form an interlock. Gametocysts are spherical with a conspicuous hyaline coat that dehisces through a single, short, and wide sporoduct. Oocysts are elliptoid. In the laboratory at ca. 28°C, the life cycle is completed in 18–20 d.

The freshwater fish leeches of North America are poorly studied taxonomically, and criteria for genus assignment, especially for the morphologically similar genera Piscicola and Cystobranchus, are based on the better-studied European fauna. In this study, we redescribe the internal anatomy of Cystobranchus virginicus and Piscicola salmositica from North America on the basis of serial sections. Cords of conducting tissue connecting the bursa to the ovisacs and accessory gland cells on the atrial cornu are present in both C. virginicus and P. salmositica. Presence or absence of accessory gland cells should not be used as a character to distinguish Piscicola from Cystobranchus. Piscicola is characterized by the presence of an external copulatory area and cords of conducting tissue arising from a ventral mass of vector tissue. Cystobranchus is characterized by the absence of an external copulatory area and the presence of cords of conducting tissue arising from the posterior portion of the bursa. These observations confirm the previous placement of Cystobranchus salmositicus.

Gonimosobdella klemmi n. gen., n. sp. parasitic on the caudal, pectoral, and anal fins of the stoneroller, Campostoma anomalum pullum, and largescale stoneroller, Campostoma oligolepis, in Arkansas and Missouri, U.S.A., and the redfin shiner, Lythrurus umbratilis, and red shiner, Cyprinella lutrensis, in Illinois, U.S.A, is described. Gonimosobdella n. gen. is characterized by having a wide, flat body, 2 pairs of eyes on the oral sucker, 3(5) annuli per segment, 11 pairs of pulsatile vesicles, segmental connections between the coelomic sinuses and the pulsatile vesicles, fused postceca with fenestrae, conducting tissue, accessory gland cells on the atrial cornua, greater than 6 pairs of testisacs, long ovisacs, but lacks mycetomes and intersegmental connections of the coelomic system. Gonimosobdella klemmi n. sp. displays the characteristics of the genus, is generally cream colored with transverse bands of black stellate chromatophores and small orange-pigment flecks, and has a mouthpore in the posterior half of the oral sucker, postceca fused with 4 fenestrae, 13 pairs of testisacs, and conducting tissue in the form of a single strand originating from the bursa that splits into 2 strands around the common oviduct and then anastomoses into a single mass posterior to the female pore.

Microhabitat specificity of Macracanthorhynchus ingens (Acanthocephala: Oligacanthorhynchidae) in the small intestine of raccoons (Procyon lotor) was investigated. Twenty-nine of 43 raccoons necropsied from Ossabaw Island, Georgia, U.S.A., were infected with 1–767 M. ingens. Macracanthorhynchus ingens occurred in the anterior 19 of 20 intestinal segments; however, over 71% of 1,481 total worms collected occurred in segments 4–9 of raccoon intestines. Worm location did not differ between sexes, among size classes, or between reproductive states (gravid vs. nongravid). Levin's standardized niche breadths for individual infrapopulations were significantly smaller than niche breadths calculated from a null model assuming random site selection. Observed niche breadths reached an asymptote at between 25 and 50 worms/raccoon. In addition, worms were observed attached to each other in segments 5–10 of the most heavily infected raccoon. These data suggest that M. ingens exhibits preferential site selection and that roughly the second quarter of the intestine encompasses the preferred habitat of M. ingens in raccoons.

Growth of the polyopisthocotylid monogenean Metamicrocotyla macracantha was studied in relation to the size of its host, the striped mullet Mugil cephalus. Forty-nine adult monogeneans were collected; total length, body length, haptor length, and clamp widths were measured and compared with host total length. Although no significant correlation between these size parameters of M. macracantha and that of the host was found, the haptor of the worm was found to reach a maximum length while its body continued to elongate. Such a growth pattern may be indicative of a less-efficient haptor resulting in the unique coiling behavior of M. macracantha.

Examination of 30 Virginia opossums (Didelphis virginiana) from south-central Connecticut revealed the presence of 7 species of gastrointestinal helminths: the nematodes Capillaria sp., Cruzia americana, and Physaloptera turgida; the trematodes Brachylaima virginiana, Brachylaima didelphis, and Didelphodiplostomum variabile; and the cestode Mesocestoides sp. All represent geographic distribution records for Connecticut.

Forty-two rodents, representing 3 murid species (Mus musculus, Peromyscus maniculatus, and Rattus rattus), were collected from 3 sites: Metztitlán, San Cristóbal, and Rancho Santa Elena in Hidalgo, Mexico, and examined for parasites. In all, 13 species of helminths were collected: 10 nematode taxa (Syphacia obvelata, Syphacia muris, Syphacia peromysci, Aspiculuris sp., Gongylonema sp., Trichuris muris, Trichinella sp., Nippostrongylus brasiliensis, Capillaria gastrica, and Carolinensis carolinensis) and 3 cestode taxa (Rodentolepis nana, Taenia taeniaeformis, and Taenia sp.). Nippostrongylus brasiliensis was most prevalent. Aspiculuris sp. was the most intense and abundant, followed by R. nana. All species collected are new geographic distribution records for Hidalgo.

House mice, Mus musculus, are reservoirs of zoonotic pathogens and parasites, but most consumers assume mice sold by pet stores are disease- and parasite free. We purchased 30 frozen mice from 15 pet stores in South Carolina and examined them for ectoparasites. All mice were infested with 1 or more of the following ectoparasites: unidentified Acaridae, Liponyssoides sanguineus, Myocoptes musculinus, Myobia musculi, Ornithonyssus bacoti, Polyplax serrata, or Radfordia affinis. Both L. sanguineus and O. bacoti are vectors of zoonotic pathogens. The presence of ectoparasites on commercially available mice implies that other pets could be infested with ectoparasites.

Nine bats, 3 Tadarida brasiliensis mexicana, and 6 Myotis californicus, collected from 2 locations in Northern California between September 1968 and April 1969 were found to harbor 4 species of digeneans: Plagiorchis vespertelionis, Paralecithodendrium carlsbadensis, Paralecithodendrium transversum, and Paralecithodendrium Swansoni. These findings represent new locality records for all and a new host record for P. transversum.

A total of 1,294 goodeid fish representing 35 species collected from 51 localities in Mexico was examined for adult intestinal helminths. Sampling was conducted between September 2001 and December 2004. Ten helminth species were collected (4 digeneans, 2 cestodes, and 4 nematodes). Allocreadium lobatum and Proteocephalus longicollis are reported for the first time in Mexico. The geographic and host range of Allocreadium mexicanum is extended to include new host species within Goodeinae in the Mezquital basin. Margotrema bravoae was found mainly in the Lerma-Santiago River basin and sparsely in the Balsas River, and Margotrema guillerminae was only found in the Western basins related to the Mesa Central. Proteocephalus longicollis was found in 1 host and 1 location. Rhabdochona lichtenfelsi was the most prevalent and abundant helminth in collections from the freshwater basins of Lerma-Santiago and Pánuco river systems. It is considered as the only nematode species of goodeids endemic to both basins. Rhabdochona ahuehuellensis was found mainly in the Balsas, in the Western Basins supposed to have been formerly related in geological time to the Balsas, and in the Panuco basin. Margotrema bravoae, M. guillerminae, R. ahuehuellensis, and R. lichtenfelsi are considered to be the core species of the helminth communities of Goodeinae. Two exotic helminths, Bothriocephalus acheilognathi and Pseudocapillaria tomentosa, are reported from new hosts and locations. Overall, 29 new host and 48 new locality records are reported for endohelminths of goodeid fishes in Mexico. Distribution of Margotrema spp. is congruent with a vicariant origin that closely mirrors the phylogeny of the Goodeidae whereas Rhabdochona spp. does not, indicating it has multiple host and biogeographical origins within the Americas.

The occurrence of 6 species of helminth parasites (Clinostomum complanatum, Diplostomidae gen. sp., Posthodiplostomum minimum, Bothriocephalus acheilognathi, Glossocercus sp., Contracaecum sp.) is reported from 7 species of freshwater fishes (Chirostoma jordani, Astyanax mexicanus, Herichthys labridens, Oreochromis niloticus niloticus, Abramis brama, Cyprinus carpio carpio, and Poeciliopsis gracilis) in Metztitlán Lake (Laguna de Metztitlán), Reserva de la Biosfera Barranca de Metztitlán, Hidalgo, Mexico. Fish were collected between July 2002 and June 2003. The helminth fauna of H. labridens, an endangered species of Cichlidae, is described for the first time. Migratory birds of the families Ardeidae and Phalacrocoracidae appear to play an important role in the helminth species composition of fishes from Metztitlán Lake. All helminth species represent new records for this federally protected area of Hidalgo.

Single-species and dual infections of Bolbophorus damnificus and a second cryptic species of Bolbophorus were distinguished in marsh rams-horn snails, Planorbella trivolvis, from aquaculture ponds in Mississippi, U.S.A. The cercariae of both B. damnificus and Bolbophorus sp. are described and distinguished using differences in body length, tail stem length, intestinal primordia, and integument spine patterns.

Young-of-the-year paddlefish, Polyodon spathula (Polyodontidae), from Lewis and Clark Lake, an impoundment of the Missouri River in Nebraska, U.S.A., were surveyed for parasites. In 2001 and 2002, 28 and 48 fish were examined for parasites, respectively. Only the nematode Rhabdochona decaturensis infected fish collected in 2001, but 8 parasite taxa (R. decaturensis, Spinitectus sp., Camallanus sp., Contracaecum sp., Marsipometra sp., Diclybothrium hamulatum, Ergasilus elongatus, and 1 unidentified leech) infected fish collected in 2002. Rhabdochona decaturensis was the most common parasite, occurring in 21.4% of fish in 2001 and 79.2% of fish in 2002. Prevalence of other parasite species infecting fish from 2002 was 33% or less. The helminth community of young-of-the-year paddlefish in both years was dominated by nematodes. This study is the first report on parasites of young-of-the-year paddlefish and documents a new host record for R. decaturensis.

Examination of coelomic cavities of 22,508 chaetognaths revealed the presence of 19 hemiurid metacercariae representing 3 genera as follows: Brachyphallus sp. from Serratosagitta serratodentata, Ectenurus sp. from Parasagitta friderici, and Lecithochirium sp. from Flaccisagitta enflata, S. serratodentata, Sagitta bipunctata, and Sagitta helenae. Samples were collected along the Mexican coast of the Caribbean Sea from 50 m depth to surface during February, March, May, and August 1991. Overall prevalence and mean infection intensity were 0.084% and 1.0, respectively. Serratosagitta serratodentata and S. helenae represent new host records for hemiurids.

Helminths from Eumeces latiscutatus (n = 17) and Takydromus tachydromoides (n = 34) from Japan are reported. Two species of Nematoda, Kurilonema markovi and Meteterakis japonica, and 1 taxon of Acanthocephala, cystacanths of Centrorhynchus sp., were found in E. latiscutatus; 1 species of Digenea, Plagiorchis taiwanensis, and 2 species of Nematoda, K. markovi and Oswaldocruzia filiformis, were found in T. tachydromoides. Oswaldocruzia yezoensis is proposed as a synonym of Oswaldocruzia filiformis. Takydromus tachydromoides represents a new host record for P. taiwanensis and Japan is a new locality record.

Leeches were sampled from 2 turtle species, Chelodina burrungandjii and Emydura australis, from 9 rivers spanning the Kimberley Plateau of Western Australia, Australia. Placobdelloides octostriata was collected from both turtle taxa across the Kimberley Plateau, and Bogobdella diversa was collected from a single specimen of E. australis in the Fitzroy River, the westernmost catchment of the sample area. Relative prevalence of P. octostriata was influenced by host behavior, with a 10-fold difference in prevalence on the sit-wait predator C. burrungandjii (37.4–42.2%) in comparison with the more actively swimming E. australis (1.3–3.7%). The prevalence of parasitism was not substantially different between sites for each species. These are new host and locality records for Euhirudinea in Australia.