Alexandra M. Shapiro

Morphological and molecular characterization of a new microsporidian species from the predatory mite Metaseiulus occidentalis (Nesbitt) (Acari, Phytoseiidae).

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 microm and one with a longer polar filament (8-9 coils) that measured 3.14 x 1.77 microm. 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.

Development of the Insect Pathogenic Alga Helicosporidium

ABSTRACT. This study examined the morphogenesis and replication dynamics of the different life stages (cysts, filamentous cells, vegetative cells) of Helicosporidium sp., a non‐photosynthetic, entomopathogenic alga. The isolate (SjHe) used originated from an infected black fly larva. Filamentous cell transformation into vegetative cells and autosporulation during vegetative cell replication were observed under controlled in vitro conditions. The transformation process was initiated by a partial swelling of the filamentous cell along with the reorganization of the nuclear material. Two subsequent nuclear and cell divisions resulted in the release of 4 rod‐shaped daughter cells, which divided into oval to spherical vegetative cells. These underwent several cycles of autosporogenic cell division. Multiple‐passaged vegetative cell cultures formed non‐motile, adherent cell clusters (palmelloid colonies). Vegetative replication dynamics were also observed in 2 experimental noctuid hosts, Spodoptera exigua and Helicoverpa zea. The average density of helicosporidial cells produced per microliter hemolymph exceeded cell concentrations obtained in vitro by 15‐ and 46‐fold in S. exigua and H. zea, respectively. Cyst morphogenesis was only observed in the hemolymph, whereas no cysts differentiated at various in vitro conditions.

A newly discovered baculovirus induces reflex bleeding in the butterfly Heliconius himera (Nymphalidae: Heliconiinae).

Heliconius himera (Nymphalidae: Heliconiinae) and other members of the subfamily Heliconiinae constitute some of the most frequently purchased organisms for butterfly exhibitions. Detailed life table data, including information on affiliated diseases, is lacking for many butterflies including H. himera. During the summer 2002, a greenhouse colony of H. himera in its fifth generation, began to show signs of a disease that gradually decimated the colony. At this time, larvae possessed abnormally thickened, bent cuticular spines. Incidental contact of these larvae with forceps or needles and/or with conspecifics stimulated a pronounced reflex bleeding (Cuernot, 1896) from the cuticular spines in sick larvae (Fig. 1). When mechanical stimulation ceased, a portion of the exuded droplets was siphoned back into the spines. It should be noted that reflex bleeding is not observed in healthy larvae. Throughout the progression of the disease, H. himera larvae displayed this reflex bleeding with emitted drops often being deposited on leaves. During the final stages of the disease, the larvae moved very slowly and ceased feeding. Immobile larvae