Distribution of Myxobolus cerebralis in Salmonid Fishes in Montana

Abstract

Over an approximately 2-year period, 20,974 fish (trout and other salmonid species) from 230 separate waters (creeks, rivers, lakes, reservoirs, ponds, hatcheries, and irrigation ditches) within 21 of the 22 major drainages in Montana were examined for Myxobolus cerebralis. Nine of the major river drainages have waters containing infected fish: Beaverhead, Big Hole, Blackfoot, Clark Fork above the Bitterroot River, Flathead below the south fork of the Flathead River, Jefferson, Madison, Missouri above the Marias River, and Yellowstone above the Bighorn River. The Beaverhead, Clark Fork above the Bitterroot River, Jefferson, Madison, and Missouri above the Marias River have the greatest number of waters containing fish infected with M. cerebralis. Comparisons of infection levels (number of pooled samples that contain fish infected with M. cerebralis) between species among these drainages show significantly lower levels of infection in brown trout Salmo trutta and rainbow trout Oncorhynchus mykiss in the Missouri above the Marias River drainage and significantly higher levels of infection of rainbow trout in the Jefferson. Comparisons of differences in infection levels between drainages among species show that, in the Beaverhead, Clark Fork above the Bitterroot River, and Madison, infection levels in brown trout are significantly higher than in rainbow trout. This is partially attributed to losses of juvenile rainbow trout because of M. cerebralis infection, leading to biased samples. Histopathologic studies showed lesions were consistently less severe in brown trout than other species and occurred in a different location (gill arches versus ventral calvarium). In six of the nine affected drainages (Beaverhead, Blackfoot, Clark Fork above the Bitterroot River, Flathead below the South Fork, Jefferson, and Madison), infected fish were found at or near the time that intensive sampling was initiated in the spring of 1995. In the three remaining affected drainages (Missouri above the Marias River, Yellowstone above the Bighorn River, and the Big Hole), infected fish were not identified until at least 15 months after the initiation of widespread testing. This indicates that in the first six drainages listed above, the infection was well established prior to 1995 but spread into the last three drainages in the ensuing months. Methods of transmission and the sources of infection are unknown, although the absence of infected fish in state, private, and federal hatcheries in Montana indicates hatchery fish from these sources are not likely to be responsible.     

Is intraspecific variation in diet and morphology related to environmental gradients? Exploring Liem's paradox in a cichlid fish

Interspecific studies have demonstrated that trophic morphology and ecology are not always tightly matched: a phenomenon rarely reported at the intraspecific level. In the present study, we explored relationships among diet, morphology and the environment in a widespread cichlid fish, Astatoreochromis alluaudi (Pellegrin 1904), from 6 sites in southern Uganda to test for evidence of eco-morphological matching at the interdemic level. Previous studies of Astatoreochromis alluaudi have demonstrated developmental plasticity in trophic morphology in response to diet: a mollusk diet produces specimens with large pharyngeal jaws and muscles, whereas a soft-food diet produces smaller pharyngeal jaws and corresponding changes in musculature. Sites were chosen to maximize variability in environmental variables that might directly or indirectly affect trophic morphology. We found significant differences in pharyngeal jaw and muscle morphology among populations. Similarly, we found differences in diets among sites: mollusks were found in the stomachs of fish from only 2 populations sampled, despite the presence of mollusks in 5 of the 6 sites. Although trophic morphology did match the observed diet in 2 sites, diet did not correlate with either morphology or environmental variables across sites, nor were environmental variables correlated with morphological variation among sites. These results suggest that mismatch can occur among different populations of a single species for reasons such as seasonality in resources, developmental plasticity and/or complex indirect interactions. Intraspecific mechanisms should be further studied in order to better understand the complex relationships between morphological specialization and ecological generalization.     

Hindlimb bone maturation during postnatal life in the Greater Rhea (Rhea americana,Aves, Palaeognathae): Implications for palaeobiological and zooarchaeological interpretations

The objective of this study was to study the morphological pattern of bone maturation of the hindlimb bones of Rhea americana and find out how it can affect bone morphology after a taphonomic process. Juvenile specimens (n = 10) ranging from one month old to eight months old were studied. For comparison, bones from adults and juveniles from museum specimens (n = 4 and n = 6, respectively) were studied. In fresh bones, ossification centres were identified in the proximal and distal epiphyses of the tibiotarsi and in the proximal epiphysis of the tarsometatarsi, whereas the distal region of the femora and tarsometatarsi showed abundance of cartilage. The development and extension of the ossification centres of the tibiotarsi were different. In the proximal epiphysis, the centre presented less development with respect to the distal epiphysis. In the dry tibiotarsi, the proximal centre was absent and the distal one was well preserved. Both the fresh and dry juvenile tarsometatarsi presented unfused metatarsals and bulkier and wider aspect than the adult ones. The dry femora presented a noticeable excavation between condyles, whereas the dry tarsometatarsi showed the absence of the proximal epiphysis. The femora, tibiotarsi and tarsometatarsi possessed different traits of immaturity, which differentially affect the morphology of the preserved bones during a taphonomic process.     

Morphological and genetic analysis of Vietnamese Sus scrofa bones for evidence of pig domestication

In the present study, we used morphological and genetic analyzes to distinguish bones of domestic boars from those of wild boars. We analyzed 65 Sus bones (cranium, mandible and teeth) stored in three research institutes in Vietnam and in a village in Vietnam. Based on comparison of bucco‐lingual measurements of mandibular parts, the 58 specimens were morphologically classified into two size groups: a large bone group and a small bone group. Analysis of 572‐bp mitochondrial DNA (mtDNA) sequences indicated that the large bones had genetic links to wild boar lineage including Ryukyu, Taiwan and Korean wild boars, and that the small bone group was closely related to East Asian domestic pigs. The phylogenetic analysis and parsimonious networks constructed among mtDNA haplotypes belonging to Ryukyu wild boar lineage showed that the Ryukyu wild boar is closely related to the Vietnamese wild boars, and uniquely miniaturized on their islands after the Ryukyu archipelago became isolated from the Asian continent.     

Magnetic resonance imaging‐detected adaptation and pathology in the distal condyles of the third metacarpus,associated with lateral condylar fracture in Thoroughbred racehorses

Reasons for performing the study: Lateral condylar (LC) fractures of the third metacarpus (McIII) are a common reason for euthanasia in racehorses, and may be the result of repetitive overloading or cumulative pathological change. Magnetic resonance imaging (MRI) allows monitoring of bone and cartilage to detect pathological and adaptive changes that may be precursors of fracture. Objectives: To describe bone and cartilage MRI features in the distal condyles of McIII of Thoroughbred racehorses, with and without condylar fracture. Hypotheses: 1) A greater degree of bone and cartilage adaptation or pathology will be seen in fractured McIIIs compared with their respective contralateral McIIIs. 2) Contralateral McIIIs will have a greater degree of bone and cartilage adaptation or pathology than McIIIs from control horses that did not sustain a LC fracture. Methods: The McIIIs from 96 horses subjected to euthanasia at racecourses were divided into 3 groups: Group 1: nonfractured bones from horses without LC fracture; Group 2: nonfractured bones from horses with unilateral LC fracture; and Group 3: fractured bones from horses with unilateral LC fracture. The MR images were examined and graded for bone and cartilage changes. Results: Nine percent of Group 1 (n = 9) and 11% of Group 2 bones (n = 5) had incomplete LC fractures. Focal palmar necrosis was most frequently detected in bones from Group 1 (12%) compared with Groups 2 (9%) and 3 (4%). The prevalence of bone and/or cartilage abnormalities tended to increase from Group 1 to Group 2 to Group 3. Conclusions: Magnetic resonance imaging is able to detect cartilage and bone changes that may be associated with LC fracture. There was no significant difference in bone/cartilage changes between bones from Groups 1 and 2, despite increased pathology in Group 2 bones. Potential relevance: Periodic monitoring of bone and/or cartilage changes in distal McIII of Thoroughbred racehorses may help to prevent catastrophic LC fractures.     

ORIGINAL ARTICLE: Fish bones – a highly available calcium source for growing pigs

In general, there is a lack of scientific documentation of nutritional value of marine by‐products. The bone fraction from fish has been regarded as waste. Due to the high mineral content of fish bones, this material can be well suitable as a natural calcium source. In the present study, apparent calcium absorption of different fish bone sources was tested using growing pigs. The experimental diets consisted of boiled salmon frames, or salmon, saithe or cod bones treated with enzymes. Calcium carbonate (CaCO₃) was used as control. The experimental diets were formulated to contain 0.7% total calcium of which the added calcium source to be tested contributed about 71% (study 1) and 86% (study 2). Except for the calcium and phosphorus sources, the animals received similar basal diets. Apparent calcium digestibility coefficient was calculated using yttrium as indicator (both studies) and was based on complete collection of faeces and urine (study 2). The experimental design was parallel and cross‐over in study 1 and study 2, respectively. In study 1, piglets getting salmon bone treated with enzymes had significantly higher calcium absorption than piglets getting boiled fish bone or calcium carbonate. Therefore, in the second study only enzymatically treated fish bones were included. The higher calcium absorption from enzymatically treated salmon bone was also found in study 2, but this time not significant. Calcium from boiled salmon bones in study I, and from enzymatically treated saithe and cod bones in study II were absorbed as well as the calcium carbonate control. The results indicate that fish bones may be a useful and well absorbed calcium source. Due to the high mineral content of the bone fraction, salmon bones can be well suitable as a natural calcium and phosphorus source in, for example, food, feed or as supplement.     

Ichthyophoniasis: An Emerging Disease of Chinook Salmon in the Yukon River

Abstract

Before 1985, Ichthyophonus was unreported among Pacific salmon Oncorhynchus spp. from the Yukon River; now it infects more than 40% of returning adult Chinook salmon O. tshawytscha. Overall infection prevalence reached about 45% in the Yukon River and about 30% in the Tanana River between 1999 and 2003. Mean infection prevalence was greater in females than males in the main-stem Yukon River during each of the 5 years of the study, but the infection prevalence in males increased each year until the difference was no longer significant. Clinical signs of ichthyophoniasis (presence of visible punctate white lesions in internal organs) were least at the mouth of the Yukon River (～10%) but increased to 29% when fish reached the middle Yukon River and was 22% at the upper Tanana River. However, clinical signs increased each year from 7% in 1999 to 27% in 2003 at the mouth of the river. As fish approached the upper reaches of the Yukon River (Canada) and the spawning areas of the Chena and Salcha rivers (Alaska), infection prevalence dropped significantly to less than 15% in females on the Yukon River and less than 10% for both sexes in the Chena and Salcha rivers, presumably because of mortality among infected prespawn fish. Age was not a factor in infection prevalence, nor was the position of fish within the run. The source of infection was not determined, but Ichthyophonus was not found in 400 Pacific herring Clupea pallasi from the Bering Sea or in 120 outmigrating juvenile Chinook salmon from two drainages in Alaska and Canada. Freshwater burbot Lota lota from the middle Yukon River were subclinically infected with Ichthyophonus, but the origin and relationship of this agent to the Chinook salmon isolate is unknown.     

Prevalence and Pathogenicity of a Heterophyid Trematode Infecting the Gills of an Endangered Fish,the Fountain Darter,in Two Central Texas Spring-Fed Rivers

Abstract

Gills of 194 fountain darters Etheostoma fonticola collected from the Comal River in Texas from May 1997 through May 1998 were found to be parasitized with 8–1,524 metacercarial cysts of a heterophyid trematode tentatively identified as Centrocestus formosanus. The intensity of infection varied among three sites on the Comal River. In contrast, of 130 darters from the nearby San Marcos River that were examined, only 4 (3%) were infected, and these had 1–2 cysts per fish. Of 2,279 Melanoides tuberculata snails from the Comal River that were examined, 139 (6.1%) were infected with the trematode. Only 1 snail in 2,241 from the San Marcos River that were examined was infected. The presence of metacercariae in darters was associated with flared opercula, shortened or thickened gill filaments, epithelial hyperplasia, and engorged lamellae. The normal cartilage support of the filaments was distorted and displaced, leading to severe deformities of filament structure. Gill damage was severe and possibly life threatening for the darters with more than 800 cysts per fish (9% of examined fish). We suspect that fountain darter deaths were caused by the parasite in the Comal River during this study.     

Metacercarial Distribution of Centrocestus formosanus among Fish Hosts in the Guadalupe River Drainage of Texas

Abstract

We examined the gills of wild fish collected from central Texas for Centrocestus formosanus metacercariae to determine whether this temperature-restricted parasite had invaded the thermally dynamic Guadalupe River via an introduced population in its thermally stable tributary, the Comal River. We collected fish from three sites in the Guadalupe River near its confluence with the Comal River (upstream, at, and downstream) and one site in the Comal River. Centrocestus formosanus infected 14 of the 25 species examined (56.0%) and 171 of the individual fish (27.1%). Several of the infected fish represent new host records for the parasite, and two are listed as species of special concern by the state of Texas. Mean metacercarial intensities varied from 8 to 616 among species, and the highest recorded intensity was greater than 800 in two Guadalupe roundnose minnow Dionda nigrotaeniata. Among the 24 species examined from the Guadalupe River, 11 (45.8%) were infected with C. formosanus. Thorough surveys at the study sites yielded no living specimens of the first obligate intermediate snail host (red-rim melania Melanoides tuberculatus), which must be present to perpetuate the parasite. Thus, the infections were probably due to drifting cercariae that had been shed into the water column upstream of the study area in the Comal River. We therefore investigated spatial patterns in cercarial acquisition using caged fish to determine whether drifting cercariae were present in the water column at the study sites. Of 57 uninfected blacktail shiners Cyprinella venusta exposed to Guadalupe River water downstream from and at the confluence, 52 (91.2%) became infected with C. formosanus metacercariae at a mean rate of 4 metacercariae/d. This finding extends the known geographic range of this invasive exotic parasite and is the first report of the life cycle being advanced in the fish assemblage of a thermally variable temperate stream in the USA.

Received October 18, 2010; accepted April 7, 2011     

Sex-related differences of bone properties of pelvic limb and bone metabolism indices in 14-month-old ostriches (Struthio camelus)

1. Sex-related differences of long pelvic limb bones and serum bone metabolism indices were evaluated in 14-month-old female (N = 7) and male (N = 7) ostriches of similar body weights.

2. Densitometric parameters of femur, tibia and tarsometatarsus were determined using quantitative computed tomography (volumetric bone mineral density, calcium hydroxyapatite density and mean volumetric bone mineral density) and dual energy X-ray absorptiometry (bone mineral density and bone mineral content) methods. Geometrical parameters such as cortical bone area, cross-sectional area, second moment of inertia, mean relative wall thickness and cortical index were determined in the midshaft of bones. Mechanical properties of bones (maximum elastic strength and ultimate strength) were evaluated using three-point bending test. Serum concentrations of free amino acids, osteocalcin, N-terminal propeptide of type I procollagen, C-terminal telopeptides of type II collagen and total antioxidative capacity were also determined.

3. Bone weight and relative bone weight of all bones were significantly higher in males than in females. Significantly lower values of trabecular bone mineral density and calcium hydroxyapatite density were found in the trabecular bone of tibia in males. The highest number of the sex-related differences was observed in the tarsometatarsus where bone length, bone mineral content, cortical bone area, cross-sectional area and ultimate strength were higher in males. Serum concentrations of taurine, hydroxyproline, valine and isoleucine were significantly higher in males.

4. Higher loading of the tarsometatarsus in comparison to femur and tibia may be an important factor interacting with sex hormones in regulation of bone formation and mineralisation processes. Sex-related differences of bone properties were associated with increased serum concentration of selected amino acids in males.     

Macro‐anatomical and morphometric studies of the hindlimb of grasscutter (Thryonomys swinderianus,Temminck‐1827)

The hindlimb of the grasscutter (Thryonomys swinderianus, Temminck‐1827) was studied using 12 adult (≥6 months) rats of either sex with the mean weights of 1.42 ± 0.20 kg and 0.82 ± 0.13 kg for buck (n = 6) and doe (n = 6), respectively (p < .05). Characteristics of the bones were studied by gross observation after their preparation. Measurements of different segments of the hindlimb were also taken, giving a total average length of 31.80 cm. Correlation coefficients between length of bone and weight of rats were positive (p < .05) in bucks for all bone segments, except the pes (p > .05), whereas those in does were all non‐significant (p > .05), with significant sexual dimorphism in the relationships. The average total number of bones in the hindlimb was 92, with no apparent sexual dimorphism. The bones of the hindlimb revealed important differences and similarities in morphology with those of other rodents. The Os coxae presented a relatively large obturator foramen, formed by the ramus of the ischium and shaft of the pubis. The femur had a body and two extremities with a prominent head, well‐defined neck and trochanter. The fibula, a slender bone with triangular‐shaped proximal extremity, ran down the length of tibia with proximal attachment (via cartilage) and distal fusion, leaving an extensive interosseus space. The pes revealed eight tarsals and four metatarsals; each of the metatarsals showed three phalanges.     

Skull of the grey heron (Ardea cinerea): Detailed investigation of the orbital region

The skull of the grey heron (Ardea cinerea) was examined with an emphasis on describing the orbital region. In the young (circa sixteen to seventeen days old) heron, the frontal bone (os frontale) and nasal bone (os nasale) comprised separate paired bones, connected by sutures (sutura interfrontalis, sutura internasalis and sutura frontonasalis plana). In adult animals, the relationship between these bones was different: the left and right frontal bone and the left and right nasal bone had grown together, and the frontal bone and nasal bone had fused into a common frontonasal bone (os frontonasale). In the ectethmoid bone (os ectethmoidale), the main components comprised of the orbital and antorbital part of the ectethmoid plate (lamina ectethmoidalis orbitalis et antorbitalis), the lateral process (processus lateralis ectethmoidalis) and the tubercle (tuberculum ectethmoidalis); the left and right ectethmoid plates were fused together to form the ectethmoid sinus (sinus ectethmoidalis) between them. In the young heron, the anatomical and functional link between the frontal and lacrimal bones did not exist yet, nor did the osseous frame of the ectethmoid‐lacrimal complex. Further research into the young heron skulls is needed. This article provides novel insights into the grey heron's orbital region.     

Mild exercise early in life produces changes in bone size and strength but not density in proximal phalangeal, third metacarpal and third carpal bones of foals

Exercise or lack of it in early life affects chondro-osseous development. Two groups of horses were used to investigate the effects of age and exercise regimen on bone parameters of diaphyseal, metaphyseal, epiphyseal and cuboidal bones of the distal limb of Thoroughbreds. One group had exercised only spontaneously from an early age at pasture (PASTEX group), while the other group of horses were exposed to a 30% greater workload through additional defined exercise (CONDEX). Longitudinal data from peripheral quantitative computed tomography (pQCT) were obtained from eight scan sites of the left forelimb (proximal phalangeal (P_p; 1 site), third metacarpal (Mc3; six sites) and third carpal (C₃; one site) bones) of 32 Thoroughbred foals scanned five times from ∼3 weeks to 17 months of age. The primary outcome measures were bone mineral content (BMC), bone area (BA), and periosteal circumference (Peri C) in diaphyseal bone, with cortical thickness (CortTh), volumetric bone mineral density (BMD_v) and a bone strength index (SSI) also being analysed.At the P_p site within the model there was a significant effect (P = 0.00–0.025) of conditioning exercise increasing bone parameters, except endosteal circumference (Endo C) and BMD_v. The BMC, BA, and SSI of P_p were significantly greater in the CONDEX than PASTEX groups at 12 and 17 months (P = 0.015–0.042) and CortTh at 17 months (P = 0.033). At the M55 site of Mc3 BMC, BA and SSI (P = 0.02–0.04), and at the M33 site, SSI (P = 0.05) were higher in the CONDEX than PASTEX group. The adaptive responses, consistent with diaphyseal strengthening, were more marked in the diaphysis of P_p than Mc3. In the Mc3, metaphysis, trabecular BMD_v was less in the CONDEX than PASTEX group, associated with greater bone mineral accretion in the outer cortical-sub-cortical bone in the CONDEX group. There were no significant between-group differences in any epiphyseal or cuboidal bone parameter. Although the early imposed exercise regimen was not intensive, it had significant effects on diaphyseal bone strength, through change in size but not bone density.     

Disease Susceptibility of Hatchery Snake River Spring–Summer Chinook Salmon with Different Juvenile Migration Histories in the Columbia River

Abstract

Various methods have been developed to mitigate the effects of dams on juvenile Pacific salmon Oncorhynchus spp. migrating to the Pacific Ocean through the Columbia River basin. In this study, we examined the health of hatchery Snake River spring and summer Chinook salmon relative to two mitigating strategies: dam bypass and transportation (e.g., barging). The health of out-migrants was assessed in terms of the difference in the incidence of mortality among fish, categorically grouped into no-bypass, bypass, and transportation life histories, in response to challenge with the marine pathogen Listonella anguillarum during seawater holding. These three life histories were defined as follows: (1) fish that were not detected at any of the juvenile bypass systems above Bonneville Dam were classified as having a no-bypass life history; (2) fish that were detected at one or more juvenile bypass systems above Bonneville Dam were classified as having a bypass life history; and (3) fish that were barged were classified as having the transportation life history. Barged fish were found to be less susceptible to L. anguillarum than in-river fish—whether bypassed or not—which suggests that transportation may help mitigate the adverse health effects of the hydropower system of the Columbia River basin on Snake River spring–summer Chinook salmon. The findings of this study are not necessarily transferable to other out-migrant stocks in the Columbia River basin, given that only one evolutionarily significant unit, that is, Snake River spring–summer Chinook salmon, was used in this study.     

Bone development of suckling piglets after prenatal,neonatal or perinatal treatment with dexamethasone

In mammals, the release from growth‐inhibiting conditions results in catch‐up growth. To investigate animal evidence for whether prenatal dexamethasone (DEX) treatment leads to the development of growth restriction especially reduced mineralization of skeleton, and release from it leads to the phenomenon of catch‐up, piglets were prenatally exposed to DEX (3.0 mg/sow per day^?2) during the last 24 days of prenatal life and tested further in two different ways: discontinued at birth and continued administration of DEX (0.5 mg/kg day^?2) to piglets through 30 days of neonatal life. Using dual energy X‐ray absorptiometry methods, bone mineral density (BMD) and bone mineral content (BMC) were measured. The three‐point bending test was applied to determine the mechanical properties of the bones. Furthermore, geometric properties of the bones were assessed. Serum concentration of osteocalcin (OC) was determined. Histomorphological analysis of the ribs was also performed. The consequences of neonate DEX treatment and in utero DEX exposure were reflected in a dramatic decrease of BMD, BMC and blood serum OC concentration and geometric parameters of piglets’ bones. Prenatal action of DEX during the last 24 days of pregnancy resulted in continued neonatal modification of bone tissues, thus diminishing bone quality, and negatively influenced structural development and mechanical properties, finally increasing the risk of fractures of ribs and limb bones. Prenatal DEX treatment limited to the last 24 days of foetal life did not reduce the term birth weight and the growth of suckling piglets followed up to 30 days of neonatal life, and catch‐up in bone mineralization did not occur.     

Macro-Anatomical Investigations on the Skeletons of Porcupine (Hystrix cristata). Part III: Skeleton axiale

The aim of this study was to investigate the axial skeleton of two porcupines (Hystrix cristata). The important features of the skull, observed in this study are as follows: The zygomatic process of frontal bone (os fron-tale) was found to be rudimentary, and the infraorbital foramen (for. infraorbitale) was very large. The zygomatic bone (os zygomaticum) has two processes (frontal and temporal) and the zygomatic arch (arcus zygomaticum) was composed of three bones. The dental formulae were 2 (I 1/1, C 0/0, P 1/1, M 3/3) = 20. The angular process (Proc. angularis) of mandible is well developed. The vertebral formula was found as C₇, T₁₅, L₄, S₄, Ca₁₂. All of cervical vertebrae had the transverse foramen (for. transversarium). The first eleven spinous processes (proc. spinosus) of thoracic vertebrae were caudally-sloped, the twelfth as the anticlin vertebrae and the last three were directed cranially. Hemal arches (or ossa arcus hemalis) were presented as separate bones which articulate with the ventral surfaces of the caudal ends of the bodies of the second, third and fourth caudal vertebrae.     

Lethal osteogenesis imperfecta and skin fragility in newborn New Zealand Romney lambs

Osteogenesis imperfecta and skin fragility occurred in about 50 New Zealand Romney lambs born in a flock of 450 ewes. Affected lambs had soft bones and multiple intrauterine bone fractures. Long bones had a thickened diaphysis with almost complete absence of a medullary cavity. Other consistent gross findings were moderate brachynathia inferior, subcutaneous oedema, marked joint laxity, dark blue sclera and small pink teeth. Histopathologic and ultrastructural changes were consistent with a defect in collagen production by fibroblasts. DNA finger-printing was used to identify which of the five rams used in the flock was carrying the genetic defect. The disease was inherited as an autosomal dominant trait and was considered to be a new mutation in the testicular germ cell lines of this ram.     

Predicted Redistribution of Ceratomyxa shasta Genotypes with Salmonid Passage in the Deschutes River,Oregon

Abstract

A series of dams on the Deschutes River, Oregon, act as migration barriers that segregate the river system into upper and lower basins. Proposed fish passage between basins would reunite populations of native potamodromous fish and allow anadromous fish of Deschutes River origin access to the upper basin. We assessed the potential redistribution of host-species-specific genotypes (O, I, II, III) of the myxozoan parasite Ceratomyxa shasta that could occur with fish passage and examined the influence of nonnative fish on genotype composition. To determine the present distribution of the parasite genotypes, we exposed eight salmonid species—three native and five stocked for sport fishing—in present and predicted anadromous salmonid habitats. We monitored fish for infection by C. shasta and sequenced a section of the parasite ribosomal DNA gene from fish and water samples to determine parasite genotype. Genotype O was present in both upper and lower basins and detected only in steelhead Oncorhynchus mykiss. Genotype I was spatially limited to the lower basin, isolated predominately from Chinook salmon O. tshawytscha, and lethal for this species only. Genotype II was detected in both basins and in multiple species, but only as a minor component of the infection. Genotype III was also present in both basins, had a wide host range, and caused mortality in native steelhead and multiple nonnative species. Atlantic salmon Salmo salar and kokanee O. nerka were the least susceptible to infection by any genotype of C. shasta. Our findings confirmed the host-specific patterns of C. shasta infections and indicated that passage of Chinook salmon would probably spread genotype I into the upper Deschutes River basin, but with little risk to native salmonid populations.

Received April 20, 2012; accepted July 19, 2012     

Clinical and Pathological Effects of the Polyopisthocotylean Monogenean,Gamacallum macroura in White Bass

Abstract

An aquaculture research facility experienced high mortality rates in white bass Morone chrysops associated with a monogenean infestation of the gills, but not in striped bass Morone saxatilis in the same facility. All mortalities had pale gills. Monogeneans, identified as Gamacallum macroura (MacCallum and MacCallum 1913) Unnithan 1971, were found on the gills. Pale-gilled and healthy white bass were selected with no particular attention to condition for venipuncture and euthanasia for postmortem examination, including parasite counts from gills. The median packed cell volume (PCV) of fish with gill pallor was 12.5% (range 9–37%) while PVC of fish with more normal color was 30% (27–33%). Association between the PCV and gill pallor score was statistically significant, as was the association between PCV and the number of monogeneans found on the gills of each fish. Median estimated white blood cell count of fish with gill pallor, at 12.05 × 10^3/μL (range 3.8–24.7), was significantly lower than of apparently healthy fish: 24.7 × 10³/μL (17.3–31.5). Histopathology of the gill arches of pale-gilled fish revealed multifocal moderate to severe branchitis, focal areas of dilated hyperplastic lamellae occluded by fibrin, and monogeneans attached to the lamellae. Fish that were apparently healthy had grossly similar histologic lesions, but at lower frequency and severity.

Received May 27, 2011; accepted July 12, 2012