Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/7/2002
Publication Date: 6/19/2002
Citation: BECNEL, J.J., JEYAPRAKASH, A., HOY, M.A., SHAPIRO, A.M. MORPHOLOGICAL AND MOLECULAR CHARACTERIZATION OF A NEW MICROSPORIDIAN SPECIES FROM THE PREDATORY MITE METASEIULUS OCCIDENTALIS (NESBITT) (ACARI, PHYTOSEIIDAE). JOURNAL OF INVERTEBRATE PATHOLOGY. 2002. v.79. p.163-172. Interpretive Summary: Naturally occurring protozoan parasites (Microsporidia) of arthropods are under study to evaluate these disease-causing organisms as biological control agents and to determine their impact on beneficial arthropods. Microsporidian parasites are known to cause mortality in mass-produced beneficial mites worldwide, but fundamental knowledge of their life cycles, ,modes of transmission, and methods for identification is incomplete. This investigation by scientists at the Center for Medical, Agricultural, and Veterinary Entomology and at the University of Florida in Gainesville, Florida was made to examine and describe a new microsporidian pathogen of predaceous mites that are mass produced and released to control spider mites in various agroecosystems. New information obtained from this study contributes to our basic understanding of these pathogens and will assist producers in the diagnosis and elimination of microsporidia infections in beneficial predaceous mites.
Technical Abstract: A new microsporidian species is described from the predatory mite Metaseiulus (formerly Typhlodromus or Galendromus) occidentalis (Nesbitt) (Acari, Phytoseiidae). The ultrastructure of this new species is presented together with the first molecular characterization for a microsporidium of mites. All stages of this new microsporidium are haplokaryotic and develop in direct contact with the host cell cytoplasm. Sporogony is disporoblastic and spores are formed in eggs, immature stages and adults of M. occidentalis. There are two morphological classes of spores, one with a short polar filament (3-5 coils) that measured 2.53 x 1.68 micrometer and one with a longer polar filament (8-9 coils) that measured 3.14 x 1.77 micrometer. Horizontal transmission of this new species occurs by cannibalism of eggs and other stages and perhaps involves the spores with the long polar filament. Spores with the short polar filament may play a role in autoinfection and vertical (transovarial) transmission that is highly efficient in transferring the microsporidium from adults to progeny. Analysis of the small subunit ribosomal DNA indicated that this species from M. occidentalis is most closely related to the Nosema/Vairimorpha clade of microsporidia. A conflict between the morphological and molecular data is discussed. The species is compared to previously described microsporidia of arachnids resulting in creation of Oligosporidium occidentalis n. sp. in the family Unikaryonidae.