title: Light and electron microscopy of the spore of Myxobolus heckelii n. sp. (Myxozoa), parasite from the Brazilian fish Centromochlus heckelii (Teleostei, Auchenipteridae).
abstract: A myxosporean parasitizing the gill filaments of the freshwater teleost fish Centromochlus heckelii collected in the Tocantins River (Lower Amazonian Region, Brazil) is described using light and electron microscopy. This parasite produces spherical to ellipsoidal cyst-like plasmodia up to 250 mum in diameter, with a thick wall strengthened by several stratified juxtaposed crossed collagen layers, whose thickness varies according to the number of the layers. Several compressed fibroblasts are observed among the collagen fibrils. Deposits of spherical dense material are scattered at the internal periphery of the cysts. Plasmodia and different developmental stages, including immature and mature spores, filled the central region of the cysts. The spore body is ellipsoidal in valvar view and biconvex in sutural view. It is formed by two equal-sized and symmetric valves measuring 12.7 microm long (12.2-13.1) (n=50), 6.6 microm wide (6.3-6.9) (n=25), and 4.0 microm (3.7-4.4) (n=20) thick. A thin layer formed by fine and anastomosed microfibrils is observed at the spore surface. Two equal, elongated pyriform polar capsules measure 2.9 microm (2.7-3.3) x 1.7 microm (1.4-2.0) (n=25), each containing four or five oblique polar filament coils. The binucleated sporoplasm contains numerous spherical sporoplasmosomes, glycogen particles, and a large vacuole with fine granular matrix. Based on the morphological and ultrastructural differences and specificity of the host, we describe this isolate as a new myxosporidian, Myxobolus heckelii n. sp. (Myxozoa, Myxosporea).
authors.affiliation: Department of Cell Biology, Institute of Biomedical Sciences (ICBAS/UP), University of Porto, Porto P-4099-003, Portugal. azevedoc@icbas.up.pt
authors.forename: Carlos
authors.initials: C
authors.lastname: Azevedo
authors.forename: Graça
authors.initials: G
authors.lastname: Casal
authors.forename: Patrícia
authors.initials: P
authors.lastname: Matos
authors.forename: Iris
authors.initials: I
authors.lastname: Ferreira
authors.forename: Edílson
authors.initials: E
authors.lastname: Matos
mesh_terms: D000818:Animals; D001938:Brazil; D002397:Catfishes / Q000469:parasitology*; D024022:Fibrillar Collagens / Q000648:ultrastructure; D005347:Fibroblasts / Q000648:ultrastructure; D005393:Fish Diseases / Q000469:parasitology*; D005618:Fresh Water / Q000469:parasitology; D006790:Host-Parasite Interactions; D046529:Microscopy, Electron, Transmission; D055766:Myxobolus / Q000145:classification / Q000502:physiology / Q000648:ultrastructure*; D013045:Species Specificity; D033761:Spores, Protozoan / Q000648:ultrastructure*
chemical_list: D024022:Fibrillar Collagens