Bighorn sheep, a new host record for Parelaphostrongylus odocoilei (Nematoda: Protostrongylidae)

Larval nematodes with a dorsal spine on the tail were recovered from fecal samples of California bighorn sheep (Ovis canadensis californiana) in northeastern Washington State, USA. The identity of these dorsal-spined larvae (DSL) was established by single-strand conformation polymorphism (SSCP) analyses of a partial fragment of the first internal transcribed spacer of the ribosomal DNA. The SSCP profiles of individual DSL from bighorn sheep were compared with those of DSL of five protostrongylid species (Parelaphostrongylus andersoni, P odocoilei, P. tenuis, Elaphostrongylus rangiferi, and Muellerius capillaris) but were identical to only those of P. odocoilei. This study represents the first confirmed identification of P. odocoilei in bighorn sheep.     

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.     

Dall's sheep horn growth and harvest management in the Mackenzie Mountains,Northwest Territories,Canada

Across most of their native North American range, the horns of mountain sheep (Ovis spp.) males are getting smaller, a pattern attributed to selective hunting pressure. We measured the horns of 755 Dall's sheep males (Ovis dalli dalli) in the southern Mackenzie Mountains, Northwest Territories, between 2002 and 2017. For each male, we measured the circumference and length of each annulus for the right horn and calculated horn volume for each year. We examined changes in horn size in 4 different outfitter areas, using age at harvest as a covariate. Hunting pressure across years in the study area was consistently low, and this population did not experience the decline in horn size observed in several other mountain sheep populations in Canada. Over the 16-year period, the average horn volume of harvested males was stable and even increased in 1 outfitter area. Local management of Dall's sheep delivered independently by the guide outfitters in the Mackenzie Mountains appears to contribute to maintaining a population of males that has not been adversely affected by strong selective hunting pressure. The resilience of this management strategy may be challenged by environmental changes associated with rapid warming in northern mountain environments.     

Parelaphostrongylus odocoilei (Nematoda: Protostrongylidae) and a protostrongylid nematode in woodland caribou (Rangifer tarandus caribou) of Alberta, Canada

Two size-groups of dorsal-spined, first-stage, nematode larvae were found in feces of woodland caribou, Rangifer tarandus caribou (Gmelin), in Alberta from 1976-1982. Larvae from caribou feces in northeastern Alberta were 451 +/- 17 micrograms in length, while those from west-central Alberta were 362 +/- 18 micrograms in length. Larvae collected from west-central Alberta developed to the infective stage, experimentally, in the terrestrial gastropod Triodopsis multilineata (Say) and were infective to captive mule deer fawns, Odocoileus H. hemionus (Rafinesque). Adult nematodes, identified as Parelaphostrongylus odocoilei (Hobmaier and Hobmaier, 1934), were recovered from the skeletal muscles of the mule deer.     

Geographic distribution of the muscle-dwelling nematode Parelaphostrongylus odocoilei in North America, using molecular identification of first-stage larvae

Molecular identification of dorsal-spined larvae (DSL) from fecal samples indicates that the protostrongylid parasite Parelaphostrongylus odocoilei occupies a broader geographic range in western North America than has been previously reported. We analyzed 2,124 fecal samples at 29 locations from thinhorn sheep (Ovis dalli dalli and O. d. stonei), bighorn sheep (Ovis canadensis canadensis and O. c. californiana), mountain goats (Oreamnos americanus), woodland caribou (Rangifer tarandus caribou), mule deer (Odocoileus hemionus hemionus), and black-tailed deer (O. h. columbianus). The DSL were recovered from populations of thinhorn sheep south, but not north, of the Arctic Circle, and they were not recovered from any of the bighorn sheep populations that we examined. In total, DSL were recovered from 20 locations in the United States and Canada (Alaska, Yukon Territory, Northwest Territories, British Columbia, Alberta, and California). The DSL were identified as P. odocoilei by comparing sequences of the second internal transcribed spacer (ITS2) region of ribosomal RNA among 9 protostrongylid species validated by adult comparative morphology. The ITS2 sequences were markedly different between Parelaphostrongylus and other protostrongylid genera. Smaller fixed differences served as diagnostic markers for the 3 species of Parelaphostrongylus. The ITS2 sequences (n = 60) of P. odocoilei were strongly conserved across its broad geographic range from California to Alaska. Polymorphism at 5 nucleotide positions was consistent with multiple copies of the ITS2 within individual specimens of P. odocoilei. This work combines extensive fecal surveys, comparative morphology, and molecular diagnostic techniques to describe comprehensively the host associations and geographic distribution of a parasitic helminth.     

Purification of first-stage larvae of Elaphostrongylus cervi (Nematoda: Protostrongylidae) from feces

Parasites are often found in a milieu that requires extensive preparation and labor-intensive cleaning before they are suitable for use in analytical procedures. Application of modern techniques in immunology and molecular biology demands pure yields of parasites. To purify first-stage (L1) larvae of Elaphostrongylus cervi, fecal suspensions from an infected red deer were processed by the Baermann method and embedded in a gel matrix with the objective of selectively trapping fecal debris. About half the number (50.9%) of embedded larvae migrated out of the gel within a 24-hr period and were collected as clean parasite suspensions, virtually free from fecal debris. The numbers of L1 emigrating from gels were inversely proportional to the fecal debris content and the thickness of the gel. Removal of fecal debris from Baermann fluid by sieving prior to gel embedment enhanced the yield of pure L1.     

Parelaphostrongylus andersoni (Nematoda: Protostrongylidae) in white-tailed deer from Michigan

Dorsal-spined larvae in fecal samples from free-ranging white-tailed deer (Odocoileus virginianus) in Michigan and Pennsylvania were used as a source of larvae to infect a hand-raised white-tailed deer fawn. The fawn receive 200 third-stage larvae and passed dorsal-spined larvae in feces 66 days later. Muscleworm (Parelaphostrongylus andersoni), and meningeal worm (Parelaphostrongylus tenuis) were recovered at necropsy. Two white-tailed deer and seven wapiti (Cervus elaphus) exposed to larvae of the source from Pennsylvania harbored only P. tenuis. This is the first report of P. andersoni in the midwestern United States and extends the known range of this muscleworm in free-ranging white-tailed deer. Concurrent infections of P. andersoni and P. tenuis have not been established previously in experimentally infected fawns.     

Development and pathogenesis of Parelaphostrongylus odocoilei (nematoda: protostrongylidae) in experimentally infected thinhorn sheep (Ovis dalli )

Recently, the protostrongylid nematode Parelaphostrongylus odocoilei has been reported in a new host species, thinhorn sheep (Ovis dalli). For the first time, we completed the life cycle of P. odocoilei in three Stone's sheep (O. dalli stonei) and two thinhorn hybrids (O. dalli stonei x O. dalli dalli), each infected with 200 third-stage larvae from slugs (Deroceras laeve). The prepatent period ranged from 68 days to 74 days, and shedding of first-stage larvae (L1) peaked at >10,000 L1 per gram of feces between 90 and 110 days postinfection. A total of 75, 27, and 14 adult P. odocoilei were recovered from skeletal muscles of three Stone's sheep. Starting in the prepatent period, all infected sheep lost weight and developed peripheral eosinophilia. At 2 wk before patency, two thinhorn hybrids developed neurologic signs (hind end ataxia, loss of conscious proprioception, and hyperesthesia) that resolved at patency. Eosinophilic pleocytosis and antibody to Parelaphostrongylus spp. were detected in the cerebrospinal fluid of the affected sheep, suggesting that the migration route of the "muscleworm" P. odocoilei may involve the central nervous system. Twenty days after treatment with ivermectin, neurologic signs recurred and larval shedding ceased in one infected thinhorn hybrid, whereas multiple treatments transiently suppressed but did not eliminate larval shedding in the other. During patency, two Stone's sheep with numerous eggs and larvae of P. odocoilei in the lungs died of respiratory failure following anesthesia or exertion. Parelaphostrongylus odocoilei has widespread geographic distribution, high prevalence, the possibility of causing neurologic and respiratory disease, resistance to treatment, and may constitute a significant emerging disease risk for thinhorn sheep.     

A re-evaluation of the phylogeny of Parelaphostrongylus Boev & Schulz, 1950 (Nematoda: Protostrongylidae)

The phylogeny of the genus Parelaphostrongylus was reconstructed using Elaphostrongylus rangiferi as an outgroup. Parelaphostrongylus is monophyletic and divided into two clades, one containing the meningeal worm, P. tenuis of white-tailed deer, and the other consisting of two muscle-inhabiting forms, P. andersoni and P. odocoilei of white-tailed and mule deer, respectively. Differences in biological features, including tissue migration route and prepatent period, are mapped onto the cladogram and discussed. Phylogenetic relationships among the host group, the Cervidae, are reviewed. It is suggested that E. rangiferi evolved in a Palaearctic cervid. Parelaphostrongylus probably co-speciated with Nearctic deer, Odocoileus spp. Host-switching from O. virginianus may explain the widespread occurrence of P. andersoni in Rangifer in North America.     

Reproductive,behavioral, and endocrine characteristics of the Dall's sheep (Ovis dalli dalli)

Failed interspecific embryo transfer between Dall's sheep (Ovis dalli dalli) and domestic ewes (Ovis aries), and a paucity of physiological data available for the Dall's sheep, provided incentive for developing a reproductive database in Dall's sheep. Urine samples were collected on a regular basis from a captive herd of Dall's sheep during the breeding to lambing interval over a 3 year period. To provide comparative endocrine data during pregnancy, samples also were collected during a single gestation period from five Suffolk ewes. All urine samples were analyzed for pregnanediol-3-glucuronide (PdG) and estrone conjugates (EC). Behavioral observations from Dall's sheep were made each year during the rut and lambing periods to calculate estrous cycle and gestation lengths. Placentas from Dall's sheep (n = 20) and Suffolk ewes (n = 10) were collected, the total number of cotyledons counted, and the length, width, area, and weight of eight cotyledons/horn from each placenta calculated. Endocrine and behavioral results indicated that the Dall's sheep is seasonally polyestrous and monovulatory, with a mean estrous cycle length of 18.2 ± 0.3 days, a mean luteal phase of 11.8 ± 0.5 days, and an average gestation length of 171.6 ± 0.9 days. While hormonal patterns for pregnancy generally were similar between the two species, there was a pronounced difference in the magnitude of hormone concentrations, particularly PdG, and an absence of a marked preparturition EC rise in domestic sheep. Cotyledon numbers, weight, and area were smaller (P < 0.05) in the Dall's sheep, compared to Suffolk ewes. These data suggest that unsuccessful interspecies embryo transfer attempts may have been due to failed fetal/maternal communications resulting from hormonal and/or placental differences. © 1996 Wiley-Liss, Inc.     

Muscleworms, Parelaphostrongylus andersoni (Nematoda: Protostrongylidae), discovered in Columbia white-tailed deer from Oregon and Washington: implications for biogeography and host associations

Parelaphostrongylus andersoni is considered a characteristic nematode infecting white-tailed deer (Odocoileus virginianus). Host and geographic distribution for this parasite, however, remain poorly defined in the region of western North America. Fecal samples collected from Columbia white-tailed deer (O. v. leucurus) in a restricted range endemic to Oregon and Washington, USA, were examined for dorsal-spined larvae characteristic of many protostrongylid nematodes. Multilocus DNA sequence data (internal transcribed spacer 2 and cytochrome c oxidase subunit 1) established the identity and a new record for P. andersoni in a subspecies of white-tailed deer previously unrecognized as hosts. Populations of P. andersoni are now recognized along the basin of the lower Columbia River in Oregon and Washington and from south-central Oregon on the North Umpqua River. Current data indicate a potentially broad zone of sympatry for P. andersoni and Parelaphostrongylus odocoilei in the western region of North America, although these elaphostrongylines seem to be segregated, respectively, in white-tailed deer or in black-tailed and mule deer (Odocoileus hemionus) at temperate latitudes. The geographic range for P. andersoni in white-tailed deer is extended substantially to the west of the currently defined limit in North America, and we confirm an apparently extensive range for this elpahostrongyline. These observations are explored in the broader context of host and geographic associations for P. andersoni and related elaphostrongylines in North American cervids.     

Scale-bearing Chrysophyceae (Mallomonadaceae and Paraphysomonadaceae) from Mackenzie Delta area lakes, Northwest Territories, Canada

Scale-bearing Chrysophyceae have been examined by means of light, scanning electron, and transmission electron microscopy. Samples were taken from nine arctic lakes in the Mackenzie Delta area of the Northwest Territories, Canada. Seventeen species of the genera Chrysosphaerella, Mallomonas, Paraphysomonas, Spiniferomonas and Synura have been identified. Included in these species are seven species previously unreported from northern Canada and one species reported only in North America. The composition of the chrysophycean flora from the Mackenzie Delta area lakes is compared with that of arctic lakes in the Saqvaqjuac area, Hudson Bay (N.W.T.), Alaskan lakes, and Greenland lakes.     

Variations in silk gland morphology among sawfiy larvae (Hymenoptera: Symphyta)

An account is given of the occurrence of different types of secretory cell and storage reservoir in the larvae of 45 species of Symphyta.     

Taphonomy of the middle Cambrian (Drumian) Ravens Throat River Lagerstätte,Rockslide Formation,Mackenzie Mountains,Northwest Territories,Canada

The Middle Cambrian (series 3, Drumian, Bolaspidella Biozone) Ravens Throat River Lagerstätte in the Rockslide Formation of the Mackenzie Mountains, northwestern Canada, contains a Burgess Shale‐type biota of similar age to the Wheeler and Marjum formations of Utah. The Rockslide Formation is a unit of deep‐water, mixed carbonate and siliciclastic facies deposited in a slope setting on the present‐day northwestern margin of Laurentia. At the fossil‐bearing locality, the unit is about 175 m thick and the lower part onlaps a fault scarp cutting lower Cambrian sandstones. It consists of a succession of shale, laminated to thin‐bedded lime mudstone, debris‐flow breccias, minor calcareous sandstone, greenish‐coloured calcareous mudstone and dolomitic siltstone, overlain by shallow‐water dolostones of the Broken Skull Formation, which indicates an overall progradational sequence. Two ~1‐m‐thick units of greenish calcareous mudstone in the upper part exhibit soft‐bodied preservation, yielding a biota dominated by bivalved arthropods and macrophytic algae, along with hyoliths and trilobites. It represents a low‐diversity in situ community. Most of the fossils occur in the lower unit, and only the more robust components are preserved. Branching burrows are present under the carapaces of some arthropods, and common millimetre‐sized disruptions of laminae are interpreted as bioturbation. The fossiliferous planar‐laminated calcareous mudstone consists of chlorite, illite, quartz silt, calcite and dolomite and is an anomalous facies in the succession. It was deposited via hemipelagic fallout of a mixture of platform‐derived and terrestrial mud. Geochemical analysis and trace‐element proxies indicate oxic bottom waters that only occasionally might have become dysoxic. Productivity in the water column was dominated by cyanobacteria. Fragments of microbial mats are common as carbonaceous seams. Complete decay of soft tissues was interrupted due to the specific sediment composition, providing support for the role of clay minerals, possibly chlorite, in the taphonomic process.     

Circulation of parasites among fishes from lakes in the Caribou Mountains,Alberta, Canada

Circulation of 24 macroparasite species among 12 species of fish was evaluated within samples of hosts collected from 9 lakes on an isolated plateau in northern Alberta, Canada. Twenty-seven parasite taxa (24 species plus the larval stages of Triaenophorus crassus, T. stizostedionis, and Raphidascaris acus) had the potential to be circulated among hosts. Sixteen parasite taxa were recovered from a single host species within a lake. Of the 11 remaining nonspecialist taxa, 4 were larval stages that matured in fish or birds and 7 were adults. Eight of the 11 cases of circulation among hosts involved lake whitefish, and this host was involved in the transmission of 5 species to piscivorous fishes. Despite evidence for the circulation of 7 taxa among the 4 species of sympatric Salmonidae, 60-99% of all worms were recovered from just 1 species of host. These results indicated that approximately 60% of the parasite taxa that infected fish in these lakes were absolute host specialists. The remaining 40% of parasite taxa had restricted host ranges, with most examples of parasite circulation limited to the 2 species of sympatric coregonid.     

The cephalic morphology of the Gondwanan key taxon Hackeriella (Coleorrhyncha,Hemiptera)

External and internal head structures of Coleorrhyncha, a key-taxon within the Hemiptera, are described in detail and documented using modern techniques. The main focus is on Hackeriella veitchi, but two additional representatives of the Gondwanan relict group were also examined, and also head structures of Enicocephalidae, a member of a potentially basal heteropteran lineage. Features were compared to those documented in literature for the Sternorrhyncha, Auchenorrhyncha, and Heteroptera. Coleorrhyncha are characterized by highly modified head structures and correspondingly an entire series of autapomorphies, such as for instance a strongly flattened head capsule with fenestrations. However, they also display features that are likely plesiomorphic compared to members of other hemipteran groups. These include the almost complete tentorium and the lack of the gula. The sistergroup relationship between Coleorrhyncha and Heteroptera is well supported by cephalic features. Potential synapomorphies are the presence of a distinct mandibular sulcus, the reduced number of antennomeres, the absence of clasping organs in the labial groove, coiled accessory salivary ducts, the presence of a small cervical muscle M1a (M. pronotopostoccipitalis medialis), the presence of a second mandibular promotor M14 (M. zygomaticus mandibulae), the presence of M28 (M. verticopharyngalis), and M30 (M. frontobuccalis posterior).