Henry Hong

The life history, ultrastructure, and experimental transmission of Hepatozoon catesbianae n. comb., an apicomplexan parasite of the bullfrog, Rana catesbeiana and the mosquito, Culex territans in Algonquin Park, Ontario.

Gametogenesis and sporogonic development of a haemogregarine parasite of bullfrogs (Rana catesbeiana) was observed in cells of the Malpighian tubules of laboratory-reared Culex territans that had fed on naturally infected bullfrogs. Mature oocysts, which varied considerably in size, were multisporocystic with ellipsoidal sporocysts that contained 4 sporozoites. Sporogonic development was completed in about 20 days. Mature meronts were observed in the liver and merozoites in erythrocytes of laboratory-reared bullfrogs that had been fed sporocysts 19 days previously. Similar attempts to infect laboratory-reared green and northern leopard frogs experimentally were unsuccessful, suggesting rather narrow specificity for this parasite in ranids. Gametogenesis and sporogonic stages of this parasite were ultrastructurally similar to those described for Hepatozoon species. The parasite appears to be transmitted directly between bullfrogs and mosquitoes in the study area where Cx. territans feeds avidly on bullfrogs, which in turn were observed to naturally ingest these mosquitoes. Based on data presented in this study and the earlier description by Stebbins in 1903, the haemogregarine parasite of bullfrogs was designated as a new combination, Hepatozoon catesbianae.

INTRAERYTHROCYTIC DEVELOPMENT OF SPECIES OF HEPATOZOON INFECTING RANID FROGS: EVIDENCE FOR CONVERGENCE OF LIFE CYCLE CHARACTERISTICS AMONG APICOMPLEXANS

Intraerythrocytic development of the adeleorin apicomplexans Hepatozoon clamatae and Hepatozoon catesbianae were investigated in the bullfrog, Rana catesbeiana, the green frog, Rana clamitans melanota, and the Northern leopard frog, Rana pipiens. Merozoites emerging from hepatic meronts penetrated erythrocytes and underwent 1–3 rounds of binary fission to produce 2–8 merozoites. Following their release from infected erythrocytes, individual merozoites entered new cells and transformed into gamonts. Although this is the first report of intraerythrocytic development for a fully described species of Hepatozoon, a phylogenetic reanalysis of 11 species of Hepatozoon, 6 species representative of the 5 other hemogregarine taxa, 2 species of dactylosomatids, and 2 species of piroplasms, indicates that asexual reproduction of parasites within blood cells of vertebrates has arisen at least 3 times in the apicomplexan lineage that includes adeleorins and piroplasms. This method of asexual development, which is also observed in species of hemospororin genera such as Plasmodium, is discussed in the context of the evolution of apicomplexan life cycles. In addition to supporting the paraphyly of the genus Hepatozoon determined in an earlier study, this phylogenetic analysis featured a monophyletic group, consisting of the sister taxa Hemolivia and Karyolysus, that was the sister group to a clade consisting of the more derived hemogregarines, the dactylosomatids, and the piroplasms.

Association of SPARC (osteonectin, BM-40) with extracellular and intracellular components of the ciliated surface ectoderm of Xenopus embryos

SPARC (Secreted Protein, Acidic, Rich in Cysteine) was detected by immunohistochemistry in the sensorial layer of the bilayered embryonic epidermis of Xenopus laevis during neurulation, when a subset of the sensorial cells are selected to differentiate into ciliated cell precursors. After the ciliated cells had intercalated into the outer layer and had undergone ciliogenesis, intense SPARC immunostaining was associated with the cilia and remained associated with the cilia throughout their persistence on the epidermis. Circumferential SPARC immunostaining was also detected at the interface between surface epithelial cells. Animal cap explants indicated that the embryonic activation of SPARC expression in the dorsal ectoderm does not require signaling from factors secreted by the underlying mesoderm. Immunoelectron microscopy revealed that SPARC is intimately associated with the 9 + 2 microtubule arrays of cilia. Our data indicate that SPARC plays a role in the development and function of the surface ciliated epidermis of Xenopus embryos. We propose that the counter-adhesive activity of SPARC facilitates the intercalation of ciliary cell precursors to the surface epithelial layer, where its Ca(2+)-binding abilities promote cell-cell adhesion. Based on its association with ciliary microtubule arrays, we also propose that intracellular SPARC may play a role in regulating ciliary beat frequency and polarity.

Changes in Host and Parasite-Derived Cellular and Extracellular Matrix Components in Developing Cysts of Myxobolus pendula (Myxozoa)

Abstract Cysts of Myxobolus pendula from the gill arch of creek chub (Semotilus atromaculatus) were examined at various stages of development using light and electron microscopy. The subepithelial host connective tissue underwent dramatic changes, including degradation and remodelling of collagen and vascularisation, in response to the infection. Inflammatory cells lay in a fluid-filled space beneath the hosts connective tissue and surrounded a distinctive parasite-derived matrix, composed of collagen fibril bundles embedded in cellular processes of the underlying secretory cells. This collagen matrix was resistant to degradation and invasion by leukocytes. Secretion of a matrix by M. pendula as a structural support, and a protective barrier against the host inflammatory cells is a novel observation for cyst-forming Myxosporea.

Ultrastructure of the development of a species ofEncephalitozoon cultured from the eye of an AIDS patient

Human fibroblast cell cultures inoculated with microsporidia-infected corneal scrapings from an AIDS patient were fixed in situ and examined by scanning and transmission electron microscopy. The parasite grew prolifically and all developmental stages were observed. Meronts underwent binary fission and the daughter cells transformed into clongate, chain-like sporonts that eventually separated into sporoblasts. The formation of components of the mature spores is described. The parasite, a species ofEncephalitozoon, underwent development both in the cytoplasm and within a parasitophorous vacuole, distinguishing it from the morphologically similar speciesE. cuniculi andE. hellem, both of which have been described from lesions in the human eye and have been reported to develop exclusively within a parasitophorous vacuole.

Allozyme comparison of three Trypanosoma species (Kinetoplastida: Trypanosomatidae) of toads and frogs by starch-gel electrophoresis.

Six metabolic enzymes, glucose-6-phosphate dehydrogenase, glucosephosphate isomerase, isocitrate dehydrogenase, malate dehydrogenase, phosphoglucomutase, and purine nucleoside phosphorylase, from clonal isolates of 3 presumptive species of Trypanosoma (T. fallisi, T. ranarum, and T. rotatorium) from 3 anuran hosts (Bufo americanus, Rana clamitans, and Rana catesbeiana) were compared using starch-gel electrophoresis. Although bands were shared among the different zymodemes of isolates of the same host genus, low genetic polymorphism of the enzyme loci was observed with few apparent shared bands between samples isolated from frogs and toads. A distance value calculated between toad and frog trypanosome isolates suggests the likelihood of long-time separation of species. Cluster analysis based on overall similarity distinguished the trypanosomes of toads and frogs as separate taxa, suggesting that host specificity and observed morphological differences are consistent with heritable allozyme differences.

MORPHOLOGY, ULTRASTRUCTURE AND TAXONOMIC STATUS OFTODDIA SP. IN NORTHERN WATER SNAKES(NERODIA SIPEDON SIPEDON) FROM ONTARIO, CANADA

Inclusions characteristic of an infection caused by Toddia sp. were found in the erythrocytes and erythroblasts of 15 of 26 northern water snakes (Nerodia sipedon sipedon) collected near Kingston, Ontario, Canada. Erythrocytes contained translucent inclusions, small acidophilic bodies, and square-shaped crystalloid structures. Erythrocytes infected with Toddia sp. were more rounded than uninfected erythrocytes and had pycnotic nuclei. We observed icosahedral virus particles measuring 195 to 210 nm formed from a membrane-bounded viral assembly site in the cytoplasm of the host erythrocyte. As a result of the viral identity of this parasite, we recommend that the etiologic agent of Toddia sp. infections from this and other species of North American snakes be renamed Snake Erythrocytic Virus.

An ultrastructural study of Brugerolleia algonquinensis gen. nov., sp. nov. (Diplomonadina; Diplomonadida), a flagellate parasite in the blood of frogs from Ontario, Canada

A diplomonad flagellate found in the blood of frogs in Algonquin Park, Ontario is described by light and electron microscopy. Based on comparisons to earlier ultrastructural descriptions of various diplomonads, this flagellate warrants separate generic status and is consequently named Brugerolleia algonquinensis gen. nov., sp. nov. This organism measures 8.4 × 3.2 μm with the following features: paired reniform nuclei with kinetids arranged in binary axial symmetry; 3 pairs of flagella emerging from the anteriad and a pair of posteriorly directed recurrent flagella which emerge through fibrillar funnel-like structures; dimpled terminus; direct fibres posterior to the nuclei that recurve near the posterior end of the organism; concentric layers of endoplasmic reticulum; absence of mitochondria, Golgi bodies and caudal spike. The systematic position of this new genus is discussed with respect to the other diplomonads. Brugerolleia gen. nov. appears to have arisen between Octomitus spp. and Giardia spp. in the evolutionary scheme proposed by Brugerolle.