Molecular characterization of Sphaerospora molnari (Myxozoa), the agent of gill sphaerosporosis in common carp Cyprinus carpio carpio

Abstract

Sphaerospora molnari Lom, Dyková, Pavlásková and Grupcheva, 1983 often causes severe infections in the gills and skin of common carp fingerlings Cyprinus carpio carpio in Central Europe. Although most Sphaerospora spp. are coelozoic and affect the excretory system of fish, S. molnari develops mature spores in the epithelia of gill filaments, making it a rare representative of histozoic freshwater species within the genus. On the basis of a partial 18S rDNA sequence assigned as belonging to S. molnari, previous phylogenetic studies located the species within the Myxobolus clade. In the present study, S. molnari isolates from Hungary and the Czech Republic were characterized based on morphology, DNA sequence analysis and phylogenetic comparison. The obtained 3714 bp final consensus 18S rDNA sequence of the parasite showed several, sometimes extremely long inserts in the variable regions of the gene and differed considerably from the one published in GenBank in 2002. In situ hybridization confirmed the validity of the obtained DNA sequence and detected pre-sporogonic blood stages in the interstitium and blood vessels of the kidney. Phylogenetic analysis showed that S. molnari clusters within the Sphaerospora sensu stricto clade with a high support, revealing it as the first known histozoic member of the Sphaerospora subclade comprising parasites of freshwater fish.

Adaptive Radiation and Evolution Within the Myxozoa

“…This has led to erroneous results for PCR of samples with mixed myxozoan infections, which, in turn, led to misinterpretations of sphaerosporid evolutionary history. Corrected and additional molecular data have revealed Sphaerospora as separate myxosporean evolutionary lineage Eszterbauer et al 2013;Holzer et al 2013). However, there still appear to be a few cases of convergent evolution of myxosporeans with Sphaerospora myxospore morphotypes.…”

Specificity of Infection Sites in Vertebrate Hosts

“…The majority of known myxosporean species infect gills (Molnár 2002a), probably because this location serves as an easy option for spore release (Eszterbauer et al 2013). Myxosporean plasmodia might develop in or among gill lamellae, in gill filaments and inside the cartilaginous gill arch.…”

Ultrastructure and localisation of late-sporogonic developmental stages of Sphaerospora ranae (Myxosporea: Sphaerosporidae)

“…The round polar filament is a rare trait among myxozoans in general. In sphaerosporids it is documented in S. angulata, S. dykovae, S. galinae, S. molnari, S. ojiroveci, S. tincae Plehn, 1925and apparently S. ictaluri Hedrick, McDowell et groff, 1990(see Hamilton 1980, Lom et al 1982, Desser et al 1983, Lom et al 1985, Hedrick et al 1990, Kaup et al 1995, Dyková and Lom 1997, all of which parasitise freshwater fish and thus most probably belong to the Lineage B, as confirmed for S. angulata, S. molnari and S. dykovae (all three B1) , Eszterbauer et al 2013, Holzer et al 2013a. The H/S-shaped polar filament is known in both marine/ brackish and freshwater species, namely in S. epinepheli, S. sparidarum (both A), S. elegans, S. truttae (both B2), polysporoplasmid sphaerosporids S. sparis (B3) and S. mugilis (most probably B3) and S. ranae (B4) (Feist et al 1991, Supamattaya et al 1993, Mcgeorge et al 1994, Sitjà-Bobadilla and Alvarez-Pellitero 1995.…”

“…To avoid confusion, we would like to stress that species identinfications in these two papers changed in light of the demise of the genus Leptotheca Thélohan, 1895 (see gunter and Adlard 2010) and recent findings of Holzer et al (2013a) and Eszterbauer et al (2013). In fact, a new name S. dykovae was introduced for S. renicola Dyková et Lom, 1982 as a consequence of the transfer of mackerel parasite Sphaerospora renicola from the suppressed genus Leptotheca to Sphaerospora.…”