Rhinoclemmysnema n. g. and three new species of nematodes of the family Atractidae (Cosmocercoidea), with notes on the helminth fauna of Rhinoclemmys pulcherrima (Testudines: Bataguridae) in Costa Rica.

Rhinoclemmysnema n. g. and three new species of atractid nematodes, namely, Atractis costaricaensis n. sp., Orientatractis asymmetrica n. sp. and Rhinoclemmysnema multilabiatum were recovered from the small and large intestine of Rhinoclemmys pulcherrima, the painted wood turtle in the Guanacaste Conservation Area, Costa Rica. The genera and three species are characterized by the features of the cephalic region and male tail. Neopolystoma fentoni (conjuctival sac) and Heronimus mollis (lungs) were also collected.

Description of Buckarootrema goodmani n. g., n. sp. (Digenea: Pronocephalidae), a parasite of the freshwater turtle Emydura macquarii (Gray, 1830) (Pleurodira: Chelidae) from Queensland, Australia, and a phylogenetic analysis of the genera of the Pronocephalidae Looss, 1902.

Buckarootrema goodmani n. g., n. sp. is described from the small intestine of the Murray turtle, Emydura macquarii (Gray, 1830), from the vicinity of Warwick, Queensland, Australia. The distinctive taxonomic features include the vitellarium, which consists of 2 compact masses directly anterior to and occasionally overlapping the testes; the uterus with extensive pre- and postovarian coils; intestinal ceca with small, medial diverticula that terminate anterior to or at the anterior margin of the testes; a comma-shaped cirrus sac with both internal and external seminal vesicles. Phylogenetic systematic analysis of the genera of the Pronocephalidae including Buckarootrema and Notopronocephalus, the only other genus of pronocephalids reported from Australian freshwater turtles, indicates that Buckarootrema is the sister taxon of Neopronocephalus and Notopronocephalus is the sister group of the rest of the Pronocephalinae.

Neopolystoma fentoni n. sp. (Monogenea: Polystomatidae) a parasite of the conjunctival sac of freshwater turtles in Costa Rica.

Neopolystoma fentoni n. sp. is described from the conjunctival sac of Kinosternon leucostomum (Duméril, Bibron, and Duméril 1851) and Rhinoclemmys pulcherrima (Gray 1855) from the Guanacaste Conservation Area in Costa Rica. The new species differs from all other species of Neopolystoma, except N. elizabethae Platt 2000 in possessing a circle of eight genital spines that are recurved and possess a crescent-shaped base. N. fentoni n. sp. differs from N. elizabethae in lacking cecal diverticula and in a number of morphometric criteria.

Helminth parasites of the western painted turtle, Chrysemys picta belli (Gray), including Neopolystoma elizabethae n. sp. (Monogenea: Polystomatidae), a parasite of the conjunctival sac.

Neopolystoma elizabethae n. sp. is described from the conjunctival sac of the western painted turtle Chrysemys picta belli (Gray), from the Upper Peninsula of Michigan. This is the first species found in this location from chelonians in North America. The new species differs from all other species of Neopolystoma in possessing a circle of 8 genital spines that are recurved and possess a crescent-shaped base. Eight additional species of helminths were found in the 5 turtles examined in this study. All are common parasites of North American freshwater turtles. An additional species of Monogenea (Polystomoidespauli) was found in the oral cavity. Four species of Digenea (Eustomos chelydrae, Allassostomoides chelydrae, Spirorchis kirki, and Spirorchis parvus) and 3 species of Nematoda (Spiroxys contorta, Serpinema trispinosus, and Amphibiocapillaria serpentina) were also found. The following are reported from Michigan for the first time: P. pauli, S. kirki, and A. serpentina.

Description and life-cycle of three new species of Dingularis n.g. (Digena: Plagiorchiida), parasites of Australian freshwater turtles.

Dingularus n.g. is proposed to accommodate three new species, D. anfracticirrus, D. pearsoni and D. megapharynx, within the Plagiorchiida. Dingularus is closely related to the Plagiorchiidae, despite the unusual excretory systems of the three species. Adult worms were parasitic in the intestines of freshwater turtles, Chelodina expansa (D. pearsoni and D. megapharynx) and Emydura macquarii (D. anfracticirrus), and appeared to be host-specific. The three species had similar, three-host, aquatic life-cycles and each life-cycle was followed experimentally. The planorbid snail Glyptophysa gibbosa served as the first intermediate host for each species. Tadpoles of Limnodynastes peronii and snails G. gibbosa and Austropeplea lessoni served as second intermediate hosts. Dingularus spp. eggs were fully embryonated and infective when laid. They remained viable for 2-3 months in water but did not hatch until eaten by G. gibbosa. Miracidia were stimulated in the stomach of the snail host but did not hatch until eggs passed into the intestine. Hatching occurred in only the anterior fifth of the intestine. Hatched miracidia were not passed with the snail faeces. The pre-patent period in the snail differed in each species: D. anfracticirrus 42 days, D. pearsoni 23 days and D. megapharynx 32 days.

Description and life-cycle of Thrinascotrema brisbanica n. g., n. sp. (Digenea: Plagiorchiida), a parasite of the freshwater turtle Elseya latisternum from Australia, and the erection of the family Thrinascotrematidae.

A new genus and species, Thrinascotrema brisbanica, is proposed to accommodate a plagiorchiidan trematode parasitic in the stomach of the freshwater turtle Elseya latisternum. The distinctive taxonomic features of the parasite are the shape and extent of the excretory bladder, and the stenostomate arrangement of the excretory collecting ducts in the adult, cercaria and metacercaria together with a cercarial protonephridial formula of 2¿(12 + 12 + 12) + (12 + 12 + 12)¿. The life-cycle is three- host and aquatic. The pulmonate snail Glyptophysa gibbosa served as both a first and second intermediate host and tadpoles of Limnodynastes peronii, Adelotus brevis and Bufo marinus, and the snail Austropeplea lessoni also served as second intermediate hosts. Eggs were fully embryonated and infective when laid, but did not hatch until eaten by the snail. Cercariae first emerged 55 days after infection at 24-28 degrees C. They were sluggish swimmers and survived for about 48 hr. They attached firmly to the skin of snails and tadpoles on contact and began to penetrate the skin after a short exploratory migration. Metacercariae survived in snails and tadpoles for at least 3 months. It is concluded that Thrinascotrema is best placed within a new family, the Thrinascotrematidae (Digenea: Plagiorchiida), based on the unusual morphology of the excretory system.

Redescription of Hapalotrema mistroides (Monticelli, 1896) and Hapalotrema synorchis Luhman, 1935 (Digenea: Spirorchidae), with comments on other species in the genus.

Hapalotrema mistroides (Monticelli, 1896) Stiles and Hassall, 1908 and Hapalotrema synorchis Luhman, 1935 are redescribed using specimens from the loggerhead turtle. Caretta caretta (L.). The redescription of H. mistroides is based on specimens collected by Looss and described as Hapalotrema constrictum Leared, 1862 and renamed Hapalotrema loossi Price, 1934, which is now considered a junior synonym of H. mistroides. Hapalotrema orientalis Takeuti, 1942 is considered a junior synonym of Hapalotrema synorchis. The redescriptions are consistent with the originals but provide an unreported range of variation while adding new information about the reproductive systems. Reexamination of Hapalotrema dorsopora Dailey, Fast, and Balazs, 1993 confirms the presence of a reproductive system typical for the genus and the absence of a dorsal genital pore; therefore, H. dorsopora is reduced to a junior synonym of Hapalotrema mehrai Rao, 1976. Four valid species of Hapalotrema are recognized: H. mistroides. H. synorchis, H. postorchis, and H. mehrai, and a key to the species is provided.

Evolution of the schistosomes (Digenea: Schistosomatoidea): the origin of dioecy and colonization of the venous system.

Trematodes of the family Schistosomatidae are considered venous system specialists whose sister group is the vascular system generalists (Spirorchidae) of turtles. Colonization of homeotherms by vascular trematodes required precision egg laying near the conduit for egg passage to the external environment and avoidance of pathogenesis that might result in the premature death of the host. Evolution of dioecy from the hermaphroditic condition may have proceeded through androdioecy in which hermaphrodites were specialized for precision egg placement in the vascular system and larger adults became functional males. The evolution of nuclear genes suppressing female function along with cytoplasmic genes suppressing male function could then have resulted in the origin of dioecious, dimorphic populations. Schistosomes compensated for the reduction in potential reproductive partners by (1) increased overdispersion in the vertebrate host, (2) reduced egg hatching time in the external environment, (3) formation of permanent pairs mimicking the hermaphroditic condition, (4) increased longevity in the definitive host, and (5) increased fecundity. Colonization of the venous system was necessitated by (1) evolutionary radiation into terrestrial vertebrates and (2) the increased immunopathology associated with the high, constant body temperature of homeothermic vertebrates. The immune response to spirorchid and schistosome eggs appears to be qualitatively similar in their respective hosts. The arterial dwelling spirorchids release eggs in the direction of blood flow, resulting in a wide dissemination of eggs within the host. The lower body temperature of poikilotherms accompanied by the seasonal nature of the immune response in these hosts would result in a quantitatively reduced pathogenesis. Hosts that did succumb to the infection would most likely die in water, where eggs could be released by predation, scavengers, or decomposition and develop successfully. Colonization of the venous system by schistosomes would require precision egg placement because eggs are released against blood flow. Eggs are sequestered within the portal system of homeotherms, thus restricting egg dispersal and resulting pathogenesis to less sensitive organs. A significant number of eggs may escape into the external environment before a heavily infected host is incapacitated by, or dies from, the infection.

Two new species of Uterotrema (Digenea: Spirorchidae) parasitic in Emydura krefftii (Testudines: Chelidae) from Australia.

Two new species of Uterotrema (Digenea: Spirorchidae) are described from Emydura krefftii in northern Queensland, Australia. Both new species are smaller than the only previously described member of the genus and possess an oral sucker/ventral sucker ratio > 1. Uterotrema burnsi n. sp. possesses a thin, elongate uterus that is 25% of the total body length. The uterus of Uterotrema kreffti n. sp. is shorter, and it possesses vitellaria and a vitelline reservoir, neither of which were reported in the type species. Although reported here as distinct species they may represent a single species that sequentially changes reproductive roles during development in the definitive host.

Postmortem migration of Hymenolepis diminuta (Cestoidea: Cyclophyllidea) in the laboratory rat.

Postmortem migration is of considerable concern in surveys and studies of parasite ecology where accurate estimates of parasite location is crucial. Yet, there is no quantitative information documenting this phenomenon. Twenty-seven Sprague-Dawley rats were each inoculated with 5 cysticercoids of Hymenolepis diminuta. Four weeks postinfection, 15 rats were killed by cervical dislocation. The small intestines of 3 rats were removed immediately and fast frozen. Additional groups of 3 rats each (experimentals) were processed at intervals of 30, 60, 120, and 240 min after death (AD). Four additional groups of 3 rats (controls) were killed and processed at 30, 60, 120, and 240 min in order to assess changes due to circadian movement. Changes in the position of the scolex and biomass (dry weight) were assessed as a proportion of small intestine length for the following criteria: anterior, median, and posterior location. The only significant within-group difference was an anterior shift in median biomass in the experimental group. Between-group differences were not evident at 30 min. Significant posterior shifts were found in anterior and median scolex position of the experimentals at 120 and 240 min AD, respectively. Median and posterior biomass shifted significantly anteriorly at 60 and 120 min AD in the experimental group, respectively, and worm range was significantly reduced in the experimentals at 120 min AD. There appears to be a 30-min period following host death in which H. diminuta does not change its position within the rat small intestine.

Uterotrema Australispinosa n. gen., n. sp. (Digenea: Spirorchidae), a parasite of a freshwater turtle Emydura macquarii from southern Queensland, Australia.

Uterotrema australispinosa n. gen., n. sp. from the heart of the Murray River turtle Emydura macquarii (Pleurodira: Chelidae) is distinguished from other members of the Spirorchidae by the presence of a voluminous uterus; a single, lobed testis occupying the posterior quarter of the body; linear rows of 5-6 spines arranged along the lateral margins of the hindbody from the posterior rim of the acetabulum to the posterior end of the body; and the posterior end ventrally curved with a dorsal cluster of spines near the terminal end. This is the first report of a spirorchid from a member of the family Chelidae and from Australia.

A phylogenetic and biogeographic analysis of the genera of Spirorchinae (Digenea: Spirorchidae) parasitic in freshwater turtles.

Cladistic analysis of the freshwater genera of Spirorchinae (Schistosomatoidea: Spirorchidae sensu Yamaguti, 1971) plus Haematotrema Stunkard, 1923, and Aphanospirorchis Platt, 1990, was completed. The Spirorchinae were considered monophyletic based on synapomorphies of the esophagus. Three lineages, Spirhapalum (Europe/Asia), Plasmiorchis+Hemiorchis (India), and Spirorchis + Henotosoma + Haematotrema + Aphanospirorchis (North America), were identified. Nelsen consensus analysis was used as the basis for recognizing 3 valid monophyletic genera: Spirhapalum, Plasmiorchis, and Spirorchis. Hapalotrematinae sensu Smith, 1972 (e.g., Hapalorhynchus/Coeuritrema), is considered the most plesiomorphic group of spirorchids. Freshwater representatives of the hapalotrematines have been reported from 7 of 12 extant turtle families, including the relatively primitive Pelomedusidae (Pleurodira) and exhibit a worldwide distribution. It is hypothesized that this group arose in the early Triassic period, prior to the breakup of Pangea. Thus, it represents a primitive lineage that was present during the diversification of turtle lineages in the mid-Mesozoic era. Spirorchinae arose later (late Cretaceous period) as a Laurasian component parasitic in the more recent pond turtles (Emydidae + Bataguridae). Species of Spirhapalum retained a relatively plesiomorphic distribution, and they are found in emydids (Europe) and batagurids (Asia). Species of Spirorchis arose and diversified with North America emydids following the separation of North America and Europe in the late Cretaceous or early Tertiary periods. Species of Plasmiorchis are hypothesized to be derived from Asian ancestors that accompanied the colonization of India by Asian batagurids during the early Tertiary period. The presence of Spirorchis species in snapping turtles (Chelydridae/North America) and of Plasmiorchis species in Indian soft-shelled turtle (Trionychidae) are considered independent colonization events.

Gastropod intermediate hosts of Parelaphostrongylus tenuis (Nematoda: Metastrongyloidea) from northwestern Indiana.

Thirteen species of terrestrial gastropods from the Kingsbury State Fish and Wildlife Area, Indiana, were examined for the presence of third-stage larvae (L3s) of the meningeal worm, Parelaphostrongylus tenuis, during the summers of 1987 and 1988. Three (Deroceras laeve, Discus cronkhitei, and unidentified species of Cochlicopa [= Cionella]) were infected. Prevalence of infection was low, 1.1% and 2.7% in 1987 and 1988, respectively. The highest prevalence was 5.5% in Cochlicopa spp.; however, most of the larvae from this host were recently molted second-stage larvae (L2s). Attempts to identify foci of infection based on vegetation cover, soil pH, and replaceable calcium levels in the soil were unsuccessful. This is the first report of P. tenuis from Indiana.

The relationship of park maintenance and accessibility to dogs to the presence of Toxocara spp. ova in the soil.

Three parks in St. Joseph/Benton Harbor, Michigan were examined for the presence of Toxocara spp. ova in the soil. Nineteen per cent (22/114) of the samples contained ova, and mean density (eggs/5 g soil) was 0.73. The density of two samples, collected at the base of playground equipment in one park, was greater than 2.1, which is considered sufficient for human infection. Subjective assessments of park maintenance and accessibility to dogs were not good indicators of the presence of Toxocara spp. ova.

An examination of the prepatent period and the absence of a crowding effect in Angiostrongylus cantonensis in laboratory rats.

The effects of the size of the infective inoculum on the prepatent period and the effect of crowding on body volume were examined in populations of Angiostrongylus cantonensis (Metastrongyloidea: Angiostrongylidae) in the laboratory rat. Groups of five rats were infected with 5, 10, 20 and 40 L3 of A. cantonensis, respectively. The prepatent period was determined by examination of faeces using a modified Baermann technique. The prepatent period ranged from 37 to 45 days and was best described by a negative logarithmic curve (y = 51.21 + x-3.838). Based on developmental data in the literature, it is suggested that 37 days represents the minimum prepatent period for A. cantonensis in this host. Worm population showed a significant, positive increase with inoculum size, yet there was no relationship between worm volume and population size in females and a slight, but significant, increase in worm volume and population size in males from rats necropsied 76-84 days post-infection. It is concluded that crowding is likely to have little effect on worm size in rats naturally infected with A. cantonensis.

Survey for heartworm, Dirofilaria immitis, and Dipetalonema reconditum (Nematoda:Filarioidea) in dogs from Virginia and North Carolina.

Random-source dogs (n = 100) in Virginia and North Carolina were surveyed for the microfilariae of Dirofilaria immitis. Microscopic examination of fresh thin-films and modified Knott preparations were made. Dirofilaria immitis and Dipetalonema reconditum were found in 19% and 6% of the animals, respectively. There was no animal that harbored both species. Prevalence was significantly higher in North Carolina (28.6%) than in Virginia (13.6%) (P less than 0.025). Mean PCV was significantly lower (P less than 0.005) in infected vs noninfected animals.

A redescription and neotype designation for Parelaphostrongylus odocoilei (Nematoda: Metastronglyoidea).

Parelaphostrongylus odocoilei is redescribed from worms collected from the type host (Odocoileus hemionus columbianus) in California, as well as material from experimentally infected mule deer (O. h. heminus) in Alberta. A single male specimen from the California material is designated as the neotype of P. odocoilei, the type species of Parelaphostrongylus. The male copulatory structures of the 3 species of Parelaphostrongylus (P. tenuis, P. anderscni, and P. odocoilei) are reviewed and a key for the identification of males is provided.