Light microscope observations of a haplosporidian in Diporeia spp. amphipods from Lakes Michigan and Huron, USA, found that the parasite spore is operculate and measures 8.1 µm in length and 6.1 µm in width. Round to amorphous sporocysts averaging 23.6 µm were present throughout hemal sinuses of infected amphipods. The number of developing spores within a sporocyst was highly variable and spores were observed in various stages of development. Electron microscopy revealed a lid over the operculum of developing spores and documented spores with fairly large and extensive ornamentation. This is the first haplosporidian reported in Diporeia spp. amphipods and only the second haplosporidian from freshwater species.KEY WORDS: Parasite · Haplosporidian · Amphipod · Diporeia spp. · Great Lakes · Microscopy
Resale or republication not permitted without written consent of the publisherInter-Research 2009 · www.int-res.com Dis Aquat Org 83: [153][154][155][156][157] 2009 schizogony and maturation of spores were observed throughout the hemal sinuses of the host. Individual spores measured 8.1 µm in length (SE = 0.23) and 6.1 µm in width (SE = 0.16, n = 21). A hinged operculum was evident on individual, mature spores. A small projection was apparent on the posterior or abopercular end of several mature spores and thin filaments or extensions appeared to be present on a few mature spores.In what was presumed to be early stages of parasite development, sporonts contained numerous nuclei with small, dense endosomes (nucleoli). Parasite cytoplasm was granular and somewhat basophilic, and there was no obvious separation between nuclei in some early stage sporonts. It appears that sporoblasts developed with larger nuclei, some with acentric endosomes adjacent to the nuclear wall. Occasionally, small sporoblasts were seen individually or as sporonts with single nuclei (Fig. 2b). Sporonts were amorphous, oval or rounded in shape. Sporonts with developing sporoblasts had clear, semi-granular or granular cytoplasm.In sporoblasts that appeared more mature, the endosporoplasm was defined, dense and basophilic. In some, a translucent area was present between the endosporoplasm and spore wall (Fig. 2c). The endosporoplasm of some sporoblasts contained a secondary basophilic body. Some sporoblasts were ellipsoidal with a limiting membrane apparent and some had dense basophilic structures in the apex of the elliptical developing spore (Fig. 2d). Sporoblasts differentiated and matured into spores; a few maturing spores had what appeared to be a sculptured cell wall with a developing operculum.Some AFB-stained sporocysts had numerous round sporoblasts with knob-like projections; others had a prominent bar-shaped structure that extended 1.3 µm (SE = 0.10, n = 21) beyond the sporoplasm (Fig. 2e). The endosporoplasm of some younger spores (those that took up more AFB staining) appeared to be separating, whereas more mature spores (less staining) had a smaller AFB-positive body and faint internal structures or debris; mature spores w...