The Life Cycle of Ceratomyxa shasta, a Myxosporean Parasite of Salmonids, Requires a Freshwater Polychaete as an Alternate Host

Abstract

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.

Distribution and abundance of the salmonid parasite Parvicapsula minibicornis (Myxozoa) in the Klamath River basin (Oregon-California, USA)

“…The discovery that the freshwater polychaete Manayunkia speciosa serves as the invertebrate host for the myxosporeans Parvicapsula minibicornis and Ceratomyxa shasta (Bartholomew et al 1997) provides an explanation for the overlapping geographic distribution of these salmonid parasites. P. minibicornis was originally described from adult and juvenile salmon from the Fraser River, British Columbia, Canada (Kent et al 1997) and subsequently from the Columbia River basin, Washington/Oregon/Idaho, USA (Jones et al 2004).…”

Polymerase Chain Reaction and Indirect Fluorescent Antibody Technique for the Detection of Kudoa amamiensis (Multivalvulida: Myxozoa) in Yellowtail Seriola quinqueradiata.

“…These methods will be employed not only for the diagnostic purposes, but also in the studies of life-cycles of myxosporeans. Andree et al (1997), Bartholomew et al (1997) and Anderson et al (2000) successfully performed the 18SrDNA analysis, and united alternate actinosporean and myxosporean stages on the molecular basis.…”

Ultrastructural localisation of carbohydrates in four myxosporean parasites

“…Those found in the spore surface or in polar filaments could be involved in the invasion and dispersion within the hosts, including a putative invertebrate intermediate host, if the complex life cycle demonstrated for some fresh water myxosporean parasites (Wolf & Markiw, 1984;Bartholomew et al, 1997;Lin et al, 1999) takes also place in these marine myxosporoses. Different membrane and humoral lectins have been demonstrated in invertebrates (Vasta & Ahmed, 1996), and some of them are involved in host-pathogen interactions (Penland & Boucias, 1992;Welburn & Maudlin, 1999).…”