Small Subunit Ribosomal RNA Sequences Unite Alternate Actinosporean and Myxosporean Stages of Myxobolus cerebralis the Causative Agent of Whirling Disease in Salmonid Fish

Abstract

The alternating myxosporean and actinosporean stages of the myxozoan parasite Myxobolus cerebralis (Hofer 1903) from its salmonid fish and aquatic oligochaete hosts, respectively, were compared for sequence homology of the small subunit (18s) ribosomal RNA genes. A 99.8% similarity between the sequences of these two stages was substantially greater than that of M . cerebralis compared to two other Myxobolus sp. from salmonid fish. Our results are the first molecular evidence confirming the alternating stages initially described by Wolf and Markiw [25] for the life cycle of M . cerebralis but found in two different taxonomic classes (Myxosporea and Actinosporea) are indeed forms of the same organism. Sequencing of rRNA genes of the actinosporean stage followed by development of specific primers for DNA amplification of the myxosporean stage, as in our study, should be applied to solve other myxozoan life cycles. Additionally, these approaches will in the future provide useful diagnostic reagents for the detection and study of this important group of fish pathogens.Supplementary key words. Myxozoa, triactinomyxon, fish, whirling disease. VER 1,200 myxozoans have been described as parasites of 0 fish [12] but many of their characteristics, including mul-M .

A nested polymerase chain reaction for the detection of genomic DNA of Myxobolus cerebralis in rainbow trout Oncorhynchus mykiss

“…(1989). The 18s rDNA sequencing and alignments of sequences were performed as described previously (Andree et al 1997). The 1700 bp fragment of the 18s rDNA from Myxobolus neurobius, M. insidiosus, M. arcticus, and M. squamalis was amplified using primers MX5 and MX3.…”

“…DNA extractions, sequencing, and alignments of rDNA. DNA extractions were carried out as described for myxosporeans (Andree 1997). DNA isolation from whole tissue and from transformant bacterial cells was performed as described by Sambrook et al.…”

“…Earlier work in our laboratory sequencing the 18s rRNA gene of Myxobolus cerebralis provided the essential elements for the development of this DNAbased diagnostic test (Andree et al 1997). To establish the practicality of such an approach for standard testing of fish stocks we developed and evaluated a PCR test ir!…”

Identification and characterization of one novel type of Triactinospomyxon with short spore axis

“…Although there is no generally accepted baseline of genetic distance that allow the distinction between species boundaries, several studies have indicated that the divergence is well within the value (<2%) determined for same species isolates from different hosts or geographic locations (Hallett et al 2004;Whipps and Kent 2006;Yokoyama et al 2006;Urawa et al 2009). An interspecific pairwise comparison for 1,700 bp of 18S rDNA sequences from ten Myxobolus species indicated a 71.9-97.7% similarity (Andree et al 1997). This novel type spore does not correspond to any of the triactinomyxon already sequenced, and the closest relatives found were the Triactinomyxon types identified by Hallett et al (2005), with low similarity (80.33%) in their 18S rDNA sequences, suggesting it is a novel type.…”

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.…”