Several environmental factors influencing the distribution of the freshwater polychaete,Manayunkia speciosa leidy

A coelomic myxozoan infection was detected in freshwater polychaetes, Manayunkia speciosa from the Klamath River, Oregon/California, a site enzootic for the myxozoan parasites Ceratomyxa shasta and Parvicapsula minibicornis. The tetractinomyxon type actinospores had a near-spherical spore body 7.9 x 7.1 microm, with 3 spherical, protruding polar capsules, no valve cell processes, and a binucleate sporoplasm. Parvicapsula minibicornis-specific primers Parvi1f and Parvi2r amplified DNA from infected polychaetes in a polymerase chain reaction (PCR) assay. The small subunit 18S rRNA gene of the spores was sequenced (GenBank DQ231038) and was a 99.7% match with the sequence for P. minibicornis myxospore stage in GenBank (AF201375). Chinook salmon (Oncorhynchus tshawytscha) exposed to a dose of 1,000 actinospores per fish tested PCR positive for P. minibicornis at 14 wk postinfection and presporogonic stages were detected in the kidney tubules by histology at 20 wk. This life cycle is 1 of only about 30 known from more than 1,350 myxozoan species, and only the second known from a freshwater polychaete.

We quantified microscale flow forces and their ability to entrain the freshwater polychaete, Manayunkia speciosa, the intermediate host for 2 myxozoan parasites (Ceratomyxa shasta and Parvicapsula minibicornis) that cause substantial mortalities in salmonid fishes in the Pacific Northwest. In a laboratory flume, we measured the shear stress associated with 2 mean flow velocities and 3 substrates and quantified associated dislodgement of polychaetes, evaluated survivorship of dislodged polychaetes, and observed behavioral responses of the polychaetes in response to increased flow. We used a generalized linear mixed model to estimate the probability of polychaete dislodgement for treatment combinations of velocity (mean flow velocity = 55 cm/s with a shear velocity = 3 cm/s, mean flow velocity = 140 cm/s with a shear velocity = 5 cm/s) and substrate type (depositional sediments and analogs of rock faces and the filamentous alga, Cladophora). Few polychaetes were dislodged at shear velocities <3 cm/s on any substrate. Above this level of shear, probability of dislodgement was strongly affected by both substrate type and velocity. After accounting for substrate, odds of dislodgement were 8× greater at the higher flow. After accounting for velocity, probability of dislodgement was greatest from fine sediments, intermediate from rock faces, and negligible from Cladophora. Survivorship of dislodged polychaetes was high. Polychaetes exhibited a variety of behaviors for avoiding increases in flow, including extrusion of mucus, burrowing into sediments, and movement to lower-flow microhabitats. Our findings suggest that polychaete populations probably exhibit high resilience to flow-mediated disturbances.

Freshwater polychaetes (Manayunkia speciosa) near the Detroit River, western Lake Erie: Abundance and life‐history characteristics

Manayunkia speciosa, a freshwater polychaete, is the invertebrate host of myxosporean parasites that negatively affect salmonid populations in the Pacific Northwest of the USA. Factors that drive the distribution of M. speciosa are not well understood, which constrains our understanding of disease dynamics and the development of management solutions. We described the distribution of M. speciosa at 3 sites on the Klamath River, California, based on 2-dimensional hydraulic models (2DHMs) and a generalized linear mixed model (GLMM). 2DHMs were built to explain hydraulic variation at each site and used to stratify biological sampling effort along depth–velocity gradients and by substrate class. We assessed the presence/absence of M. speciosa at 362 georeferenced locations in July 2012 and built GLMMs to describe relationships between hydraulic and substrate variables and the distribution of M. speciosa. The best-fitting GLMMs demonstrated that M. speciosa distributions were associated with depth–velocity conditions and substrate size during base discharge (area under the receiver operating characteristic curve [AUC] = 0.88) and at peak discharge (AUC = 0.86). We evaluated the GLMMs with an independent data set collected in July 2013 (n = 280) and found that the top models predicted the distribution of M. speciosa with a high degree of accuracy (AUC = 0.90). These results support the conclusion that the summer distribution of M. speciosa is related to observed hydraulic and substrate conditions during base discharge (summer) and modeled hydraulic and substrate conditions during peak discharge (late winter to early spring). These results may have implications for the use of flow manipulation as a disease management tool. These results also illustrate the importance of examining species distribution data in the context of temporally disconnected environmental factors and demonstrate how models can fulfill this need.

The actinosporean life stage of Ceratomyxa shasta, a myxozoan parasite of salmonids, and the annelid worm that serves as its alternate host were identified in laboratory transmission experiments and their roles were confirmed using molecular techniques. Infection by the parasite occurred in susceptible fish that were either exposed to or force fed the freshwater polychaete, Manayunkia speciosa, infected with the actinosporean. These observations were confirmed using the polymerase chain reaction with primers designed from the C. shasta 18S rDNA sequence. DNA was amplified from polychaetes harboring the actinosporean that caused infection in the fish but not from uninfected polychaetes. Amplified DNA from an infected polychaete was sequenced and its homology with the 18S rDNA sequence of C. shasta spores verified the proposed life cycle. Ultrastructural examination of the actinosporean in the polychaete showed developmental stages in the epidermis rather than within the intestinal epithelium as described for other myxozoans. The methods described will be useful in identifying alternate hosts and morphologically diverse life stages in the complex life cycles of other myxosporea and in understanding the relationships between these parasites and their hosts.

Molecular evidence of undescribed Ceratonova sp. (Cnidaria: Myxosporea) in the freshwater polychaete, Manayunkia speciosa, from western Lake Erie

Ribosomal DNA identification of Nosema/Vairimorpha in freshwater polychaete, Manayunkia speciosa, from Oregon/California and the Laurentian Great Lakes

The myxozoan parasite Ceratomyxa shasta is a significant pathogen of juvenile Chinook salmon Oncorhynchus tshawytscha in the Klamath River, California, USA. This parasite requires 2 hosts to complete its life cycle: a freshwater polychaete (Manayunkia speciosa) and a salmonid. The complex life cycle and large geographic area where infection occurs make it difficult to monitor and manage ceratomyxosis. We present a model for ceratomyxosis-induced mortality in O. tshawytscha, from which parameters important to the persistence of C. shasta are identified. We also experimentally quantify specific parameters from the model and identify a mortality threshold (a critical parameter), by naturally exposing native O. tshawytscha to C. shasta in the Klamath River. The average percent mortality that resulted from these experimental challenges ranged from 2.5 to 98.5% over an exposure dose of 4.4 to 612 x 10(6) parasites. This experiment identified a non-linear mortality threshold of 7.7 +/- 2.1 x 10(4) actinospores fish(-1) for Chinook salmon from the Iron Gate Hatchery on the Klamath River. Below this threshold no mortality occurred and above it mortality increased dramatically, thus providing a target by which to reduce parasitism in emigrating juvenile O. tshawytscha.

Two new localities are reported for the fresh-water polychaete worm Manayunkia speciosa. Details of the two lakes from the investigations in the summers of 1961, 1963 and 1964 are given. A short summing up of the various Manayunkia species is presented, viz. M. speciosa Leidy 1858, M. aestuarina (Bourne) 1883, M. baicalensis (Nusbaum) 1901, M. caspicaAnnenkova 1920, and M. brasiliensisBanse 1956. The opinion of Zenkevich (1935) and Kozhov (1963) that the genus may be rather old is accepted, but it is emphasized that other theories must rest, until much more is known about the various species.

Distribution and abundance of freshwater polychaetes, Manayunkia speciosa (Polychaeta), in the Great Lakes with a 70-year case history for western Lake Erie

Ceratomyxa shasta is a myxozoan parasite identified as a contributor to salmon mortality in the Klamath River, USA. The parasite has a complex life cycle involving a freshwater polychaete, Manayunkia speciosa and a salmonid. As part of ongoing research on how environmental parameters influence parasite establishment and replication, we designed a laboratory experiment to examine the effect of water flow (velocity) on completion of the C. shasta infectious cycle. The experiment tested the effect of two water velocities, 0.05 and 0.01 m s(-1), on survival and infection of M. speciosa as well as transmission to susceptible rainbow trout and comparatively resistant Klamath River Chinook salmon. The faster water velocity facilitated the greatest polychaete densities, but the lowest polychaete infection prevalence. Rainbow trout became infected in all treatments, but at the slower velocity had a shorter mean day to death, indicating a higher infectious dose. Infection was not detected in Chinook salmon even at a dose estimated to be as high as 80,000 actinospores per fish. The higher water velocity resulted in lower C. shasta infection prevalence in M. speciosa and decreased infection severity in fish. Another outcome of our experiment is the description of a system for maintaining and infecting M. speciosa in the laboratory.

The freshwater polychaete,Manayunkia speciosa Leidy, is reported from the Schuylkill River in southeastern Pennsylvania for the first time near the type-locality since 1858. This polychaete appears to have a wide range of tolerance for environmental parameters such as dissolved oxygen content (1.8 to 14.0 ppm), depth (0.3 to 16.0 m), pH (6.8 to 8.8), and water temperature (2.8 to 28.3 C). An environmental factor which may limit its distribution is the requirement for fine particulate material in the substrate for the construction of the tube in which it lives.

The freshwater polychaete Manayunkia speciosa serves as the obligate intermediate host for the myxosporean parasites Ceratomyxa shasta and Parvicapsula minibicornis, which adversely affect the survival and freshwater production of juvenile salmon in the Klamath River and elsewhere in the Pacific Northwest USA. Scant information on the life history of the polychaete and inability to maintain individuals in culture has hindered development of management strategies to control disease outbreaks in Klamath River salmon. Through trial-and error- manipulations of food and water sources, culture environments and water velocities, we established conditions that allowed us to maintain M. speciosa in culture over a 10-mo period. In lab culture, eggs and young were brooded within the maternal tube for a 6–8 wk period during which 5 developmental stages were distinguished. Peak egg production occurred in late spring-early summer, with each female brooding up to 35 offspring. Juveniles left the maternal tube at a length of approximately 1 mm, and became reproductively mature in late December to early January at a length of approximately 2 mm. Duration of survival in lab culture, coupled with the absence of adult polychaetes in preserved river samples that were collected in mid-summer, suggests that M. speciosa has an approximately annual generation time.

A survey for Manayunkia speciosa, the freshwater polychaete host for the myxozoan parasite Ceratomyxa shasta, was conducted from 2003 to 2005 as part of an integrated study of the epizootiology of ceratomyxosis in Klamath River salmonids. Substrata samples (n = 257) were collected in a variety of habitats from Klamath Lake to the mouth of the Klamath River to document occurrence and relative abundance of the polychaete by habitat type and to estimate the prevalence of C. shasta within selected polychaete populations. Populations of M. specios a were identified throughout the Klamath River within pools (51.6%), eddy-pools (47.0%), and runs (40.0%). Large populations of M. speciosa were consistently found at the inflow to the main-stem reservoirs where densities were correlated with distance from the inflow into the reservoir. Using polymerase chain reaction assay and composite samples, 12 of 71 populations identified were tested for C. shasta, revealing a mean infection prevalence of 0.27%. An area of elevated infection prevalence (4.9 and 8.3%) was identified with 2 populations below a barrier to salmonid migration, which explains the high infectious spore densities demonstrated in concurrent studies and observations of C. shasta-induced mortality in Klamath River fall Chinook salmon (Oncorhynchus tshawytscha).