A Gallbladder Ceratomyxidae (Myxozoa: Bivalvulida) Parasite Described In Pimelodella cristata (Müller & Troschel, 1848) From the Eastern Amazon

The Myxozoa class is characterized by parasites that have valves joined by a suture line and polar capsules containing eversible spiral filamento and this class is considered an obligate parasite. The genus Ceratomyxa has approximately 300 species described in fish, both marine and freshwater fish, mainly infecting the gallbladder, but also occurring in the urinary bladder. This study describes a new species of Ceratomyxa in the Amazon region for Pimelodella cristata. For these analyses, the fish were desensitized by means of a medullary section with the aid of a sharp metallic instrument. With the fish desensitized, the entire body surface was examined under a binocular stereoscopic microscope. The gallbladder fragments were collected and fixed in Davidson for histological analyses and in ethanol for molecular analyses. This parasite was found in the host's gallbladder, with elongated spores in a decreasing shape in sutural view, measuring 1.64 ± 0.6 μm in length and 17.13 ± 2.6 μm in width. The polar capsules had a spherical shape of equal size and measured 1.36 ± 0.17 μm in length and 0.9 ± 0.05 μm in width, and each polar capsule contained 4 to 5 turns. Morphological and phylogenetic analyzes denote that this is a new species of the genus Ceratomyxa.