Molecular diagnostic based on 18S rDNA and supplemental taxonomic data of the cnidarian coelozoic Ceratomyxa (Cnidaria, Myxosporea) and comments on the intraspecific morphological variation

Ceratomyxa amazonensis is a cnidarian myxosporean originally described with strongly arcuate crescent-shaped myxospores, absence of vegetative stages and infecting Symphysodon discus , an important Amazonian ornamental fish in the aquarium industry. As part long-term investigation concerning myxosporeans that infect spp. from different rivers Amazon Basin, thirty specimens S. collected Unini River were examined. Plasmodial therefrom found freely floating bile gall bladders eighteen fish. Mature myxospores slightly crescent-shaped, measuring 4.72 ± 0.1 (4.52–4.81) μm length, 24.2 0.4 (23.9–25.3) thickness polar capsules 2.31 (2.29–2.33) length 2.15 (2.13–2.17) width. Strong morphological differences observed between newly isolated obtained previously C. ; however, molecular assessment, based on 18S rDNA, revealed high similarity (99.91%), only single nucleotide base change. This study provides new data, expanding original description species discussion myxospore-morphology context intraspecific plasticity.