Morphological description and molecular identification ofMyxobolus dajiangensisn. sp. (Myxozoa: Myxobolidae) from the gill ofCyprinus carpioin southwest China

Abstract

BackgroundMyxosporean diversity is a hot topic since they are difficult to accurately identify and classify. ManyMyxobolusparasites have been named asMyxobolus koibecause of their similar morphological features with the species originally reported. However, the distinctions in fine morphological features, host specificity, and molecular data have given rise to the attention of researchers.MethodsThe classical morphometric and histological methods were used to describe theMyxobolus dajiangensisn. sp. in morphology. The common techniques in modern molecular biology and the methods of phylogenetic analyses were combined to identify the species.ResultsPlasmodia of interlamellar-vascular type were found in the vascular network of gill lamellae. Mature myxospores ofM. dajiangensisn. sp. were elongated and pyriform from the frontal view. The myxospores were 14.8 ± 0.4 (13.9–15.6) µm in length, 8.0 ± 0.5 (7.2–9.1) µm in width, and 5.5 µm in thickness. The two polar capsules were pyriform and slightly different in length. The length of the larger polar capsules was 8.0 ± 0.4 (7.1–8.8) µm, and it was 7.4 ± 0.4 (6.1–8.0) µm for the smaller ones. The width of both polar capsules was 2.5 ± 0.2 (2.0–3.2) µm. The polar filaments within the polar capsules were each coiled nine to 11 turns. Comparative analysis of both the morphological and molecular data between the present speices and other similar species revealed that the present species is a novel species,Myxobolus dajiangensisn. sp. Also,M. koi(FJ710800) was misidentified and the congener withM. dajiangensisn. sp., depending on the secondary structures of SSU rRNA and phylogenetic analysis. Moreover, the cryptic species existed in theM. koiparasites.