Molecular characterization of Myxobolus catmrigalae (Myxosporea: Myxobolidae) infecting the gill lamellae of carp Cirrhinus mrigala (Hamilton).

The present study attempted sequencing the 18S rRNA gene of Myxobolus catmrigalae infecting the gill lamellae of carp, Cirrhinus mrigala and compared its genetic homology and phylogenetic characteristics with 18S rRNA genes of other Myxobolus spp. The infected fish had up to 3 small, creamy white plasmodia per gill filament with 30-50 spores each. The spore size was 17.90 ± 0.70 × 7.40 ± 0.40 μm. The sporoplasm contained two large nuclei of size 0.57 ± 0.09 μm and no iodinophilous vacuole. The DNA sequence of M. catmrigalae was clustered phylogenetically with other Myxobolus spp. infecting the gills of cyprinids available in GenBank, which showed 77-87 % homogeneity. On the phylogenetic tree, M. catmrigalae (KC933944) was clustered with M. pavlovskii (HM991164) infecting the gill lamellae of silver carp, Hypophthalmichthys molitrix . The species most closely related to M. catmrigalae in GenBank was M. pavlovskii (AF507973) infecting the gill lamellae of big head carp, Aristichthys nobilis with 87 % homogeneity. This is the first report on molecular characterization of gill lamellae infecting M. catmrigalae.