Merogonic Stages Research Articles

Observations on an apicomplexan microparasite from the pericardic body of Ciona intestinalis L. (Protochordata)

Summary Specimens of the ascidia Ciona intestinalis L. collected in the Gulf of Naples showed the occurrence within the pericardic body of a microorganism characterized by sporogonial plasmodia and complex sporulation stages. An ultrastructural study revealed several sporonts and plasmodia. The latter showed asynchronous merogonic stages, characterized by merozoites budding at their periphery. These stages were abundant and aggregated at the periphery of the pericardic body among haematic cells, cell debris and other host degenerative material. The merogonic plasmodia had a coccidian-like structure and were the most frequent stages observed in the C. intestinalis pericardic bodies. The microorganism was considered as parasitic and represents a possible re-discovery of Cardiosporidium cionae , a sporozoan described early this century from the same host. Infection by the microparasite appeared implicated in the origin of the pericardic body, considered as an host response to infection.

Redescription of Glugea caulleryi, a microsporidian parasite of the greater sand‐eel, Hyperoplus lanceolatus (Le Sauvage), (Teleostei: Ammodytidae), as Microgemma caulleryi comb. nov.

A detailed study of a microsporidian parasite detected in the liver of the greater sand-eel, Hyperoplus lanceolatus (Le Sauvage), is reported. The parasite, originally described as Glugea caulleryi, invades hepatocytes, inducing xenoma formation and marked hypertrophy of the host-cell nucleus. Macroscopically, the infection is characterized by the presence of fibrous whitish structures of about 5 mm in length, each containing several xenomas. The final merogonic stages are rounded plasmodia, about 5 μm in length, which divide by plasmotomy. Meronts are characterized by the abundant membranous structures present in their cytoplasm. It was not possible to characterize the transition from merogonic to sporogonic plasmodia. During sporogony, the parasite remains in direct contact with the host-cell cytoplasm and sporonts produce uninucleate sporoblasts by exogenous budding. The spores are ovoid and uninucleate with a mean size of 1.2 x 2.6 μm, a polar tube coiled between seven and nine times and only a laminar-type polaroplast. In view of these characteristics, it is proposed that this species should be transferred to the genus Microgemma, with the name Microgemma caulleryi comb. nov.

Ultrastructural features of cystic and merogonic stages of Hepatozoon sipedon (Apicomplexa: Adeleorina) in northern leopard frogs (Rana pipiens) and northern water snakes (Nerodia sipedon) from Ontario, Canada.

The cystic and merogonic stages of the haemogregarine Hepatozoon sipedon, infecting Northern water snakes (Nerodia sipedon sipedon) and Northern leopard frogs (Rana pipiens), respectively, in Ontario, Canada, were investigated by transmission electron microscopy. Cysts, which were observed in the liver of Northern leopard frogs (Rana pipiens) after these anurans ingested mosquitoes (Culex pipiens) containing oocysts of the parasite, harboured two cystozoites, each of which contained a large crystalloid inclusion anterior to the nucleus. Two types of meronts were observed in snakes that were fed the liver of infected frogs. Macromeronts, which matured in endothelial cells of the liver approximately 16 d after snakes ingested infected frogs, contained about 50 large macromerozoites. Macromerozoites emerged from macromeronts, entered the bloodstream of the snake, and reinfected endothelial cells. Micromeronts, which matured about 34 d post-inoculation, contained about 150 micromerozoites that infected erythrocytes and transformed into gamonts. The ultrastructural features of micromeronts and macromeronts differed only slightly: immature macromeronts and macromerozoites contained numerous amylopectin and lipid inclusions, whereas immature micromeronts and micromerozoites did not contain amylopectin inclusions and featured fewer, smaller lipid inclusions. A comparison of cystic stages among Hepatozoon species in different groups of vertebrates is presented with respect to their structure and evolutionary significance.

Ultrastructure and development of Microsporidium ovoideum (Thélohan, 1895) Sprague, 1977, a microspohdian parasite of the red band fish ( Cepola macrophthalma L) : Redescription of the organism and reassignment to the genus Microgemma, ralphs & matthews 1986

Summary A study of the ultrastructure and life cycle of Microsporidium ovoideum , a hepatic parasite of Cepola macrophthalma , has been carried out. This parasite caused xenomas up to 1–2 mm, which consisted of a hypertrophic cell, filled with different stages of the parasite and rests of the host cell organelles, which had a pychnotic hypertrophic nucleus. Merogonic stages consisted of round multinucleate plasmodia that divided by plasmotomy or exogenous budding, and were not enclosed by any membrane. Sporogonic plasmodia divided by exogenous budding to produce sporoblast mother cells which after a binary fission become sporoblasts. Sporogony occurs in direct contact with host cytoplasm. The spores, which are ovoid and uninucleate, show a posterior vacuole in the posterior third of the spore and an isofilar polar filament with 6–8 coils. The characteristic features permit a reassignation of this microsporidium into the genus Microgemma and give a new combination: Microgemma ovoidea .

Life cycles, morphological characteristics, and host specificity of Hepatozoon species infecting eastern garter snakes from Ontario

The life cycles of species of Hepatozoon that occur naturally in eastern garter snakes, Thamnophis sirtalis sirtalis, were studied in the mosquito Culex pipiens in various amphibians, including northern leopard frogs, bullfrogs, gray treefrogs, American toads, and blue-spotted salamanders, and in natricine snakes, including northern water snakes and northern brown snakes. Morphological features of the oocysts of two forms of Hepatozoon from various widely separated regions of Ontario differed with respect to the number of sporozoites per sporocyst and the diameter and shape of the oocyst. However, morphological and morphometric differences were not apparent in the cystic or merogonic stages in the vertebrate hosts. Cystic stages of these haemogregarines were found in the liver of all four species of anurans, but not in salamanders. These forms were transmitted experimentally to garter, water, and brown snakes, with gamonts appearing in erythrocytes 45 days after the snakes were fed infected anurans. A comparison of these forms of Hepatozoon with previously named species of ophidian haemogregarines from North America indicates that there are at least two, and likely more, species of Hepatozoon in Ontario.

Eimerian infection in the gut of the tube-nosed gobyProterorhinus marmoratus (Pallas) of the River Danube

A mixed infection with twoEimeria species,E. credintsi Moshu, 1992 andE. marmorata n. sp., was found in the gut of the tube-nosed goby of the River Danube basin. Sporulated oocysts ofE. credintsi and unsporulated and semisporulated oocysts ofE. marmorata were found freely in the gut lumen. Sporocysts ofE. credintsi open at the cap-like end, releasing sporozoites through a funnel-shaped opening. Sporocysts ofE. marmorata open at the tapered end, forming a fissure alongside the suture reaching up to half the length of the sporocysts. In histological preparations, both species were found in the intestinal epithelium. Merogonic and sporogonic stages ofE. credintsi and gamogonic and sporogonic stages ofE. marmorata were detected in the epithelium of the anterior part of the gut.

Ultrastructure and development of Agmasoma penaei (Microspora, Thelohaniidae) found in Penaeus notialis (Crustacea, Decapoda, Penaeidae) from senegal

Summary The microsporidium Agmasoma penaei is found in the shrimp Penaeus notialis from Senegal. It attacks the gonads, hepatopancreas, heart, intestine, nervous system and the muscles forming white cysts (xenomas). It is partly responsible for high mortality in Senegal shrimp farming. Its merogonic stages are diplokaryotic and in direct contact with the cytoplasm of the host cell. All sporogonic stages have unpaired nuclei. The sporogony is usually octosporoblastic. Sporoblasts and spores are contained within a sporophorous vesicle. The formation of sporoblasts does not occur by budding. The sporoblasts are segragated by fragments of plasma membrane within the sporogonial plasmodium. Synaptonemal complexes are apparently absent. The spores have an anisofilar polar filament and a polaroplast with a finely lamellar anterior region and a vesicular posterior part.

X-irradiation of Eimeria tenella oocysts provides direct evidence that sporozoite invasion and early schizont development induce a protective immune response(s)

Sporulated oocysts of the protozoan parasite Eimeria tenella were attenuated by exposure to various doses of X-radiation to inhibit intracellular replication and thus determine whether sporozoites alone can induce a protective immune response. Exposure to doses greater than 15-kilorads had a significant effect on development, as indicated by the absence of oocyst production in chickens infected with parasites treated with 20 or 30 kilorads of radiation. Infection with nonirradiated or 15-kilorad-exposed parasites led to either normal or reduced oocyst shedding. Equivalent protection was afforded chickens inoculated with a minimum immunizing dose of either nonirradiated or 20-kilorad-irradiated E. tenella oocysts. Immunofluorescence staining of cecal tissue from chickens inoculated with 10(7) nonirradiated or 20- or 30-kilorad-irradiated oocysts with stage-specific monoclonal antibodies showed no significant difference in sporozoite invasion between treatment groups. Normal merogonic development was observed at appropriate times (48, 60, 72, and 96 h) postinfection in chickens inoculated with nonirradiated oocysts. In contrast, irradiated parasites exhibited minimal merogonic development at 48 h postinfection. Furthermore, no merogonic stages were observed at times of otherwise peak merozoite development (60, 72, and 96 h) in cecal tissue from chickens inoculated with irradiated parasites. Infection of chicken cells with irradiated or nonirradiated parasites in vitro corroborated these findings and indicate that events early after sporozoite invasion induce a protective immune response against this parasite.

Ultrastructural observations on merogonic and gamogonic stages of Goussia carpelli (Apicomplexa, Coccidia) in experimentally infected common carp Cyprinus carpio

Ultrastructural features of merogonic and gamogonic stages of Goussia carpelli, a coccidian parasite of carp are described. The parasite developed along lines often found in eimerian parasites in the apical portion of intestinal epithelial cells. After laboratory infection, merogonic stages were found at days 2 to 7 post exposure (PE). Meronts gave rise to 12 to 20 merozoites by endomerogony. Gamogonic stages occurred between days 7 and 9 PE. Young macrögamonts developed in parasitophorous vacuoles with narrow spaces. Differentiations of the macrogamont's surface or the parasitophorous vacuole membrane that could be regarded as "feeding organelles" were not observed. Young oocysts were surrounded by an envelope composed of three layers and contained large clusters of electron dense material.

Developmental stages of Cyclospora talpae in the liver and bile duct of the mole (Talpa europaea)

The completed life-cycle of Cyclospora talpae, an extra-intestinal coccidian (Apicomplexa) of the liver of the mole (Talpa europaea), is reported. Oocysts sporulated within 12-14 days at room temperature (20-22 degrees C). Both macro- and microgametocytes developed independently within the nucleus of epithelial cells lining the bile duct as demonstrated by both light and electron microscopy. Merogony was seen in the mononuclear cells in the capillary sinusoids of the liver. Merozoites showed the typical ultrastructural features of the Apicomplexa. The life-cycle of C. talpae and the ultrastructure of the gametogonic and merogonic stages are reported; the ultrastructure of the merozoites is reported as the first description of this stage for the genus Cyclospora.

Nosema jirivavrai n.sp. (Microsporea; Protozoa) from the leech Batracobdella picta in Ontario

A new microsporidian species was described from the muscle and connective tissue of the glossophoniid leech Batracobdella picta. Subepithelial xenomas contained sporonts, sporoblasts, and spores. Merogonic stages were not observed. All sporogonic stages were diplokaryotic. Mature spores were ovoid, 3.0–3.6 × 1.8–2.2 μm. The spore wall was 190–240 nm thick, with a distinct exospore, endospore, and underlying plasmalemma. The polar filament had 12–13 coils and measured 105 nm in diameter. The angle of tilt of the anterior coils of the filament to the vertical axis of the spore was about 63°. This newly discovered parasite was named Nosema jirivavrai.

PULMONARY LESIONS IN DISSEMINATED VISCERAL COCCIDIOSIS OF SANDHILL AND WHOOPING CRANES

Fifty cranes, consisting of 46 sandhill (Grus canadensis) and four whooping cranes (Grus americana), were studied. Eighteen sandhill cranes and the four whooping cranes were naturally infected with disseminated visceral coccidiosis (DVC). The remaining sandhill cranes were chicks experimentally infected with oocysts of Eimeria reichenowi and/or E. gruis; five chicks served as controls. There were no clinical signs attributed to respiratory infection. Necropsy of naturally infected adult birds revealed nodules in many organs, including the lung, air sacs, trachea and nares. Artificially infected sandhill cranes and the whooping crane chicks that died from DVC had congestion and consolidated areas in the lung with frothy fluid in the airways. Grossly visible nodules were observed from 10 days postinoculation. Granulomatous pneumonia and tracheitis were observed with light microscopy. Lesions were associated with merogonic and gametogonic stages of eimerian coccidia. Granulomas and granulomatous foci contained parasitized large mononuclear cells. Merogonic stages were seen in lymphoid cells by ultrastructural examination. Oocysts were observed in the trachea and bronchial mucosa and admixed with exudate in the airways, indicating that crane eimerians can complete their life cycle at these sites. Of the few eimeriid coccidia that have extraintestinal stages of development in birds and mammals, only the species in cranes complete their life cycle in both the digestive and respiratory tracts.

Haemogregarina sp. (Apicomplexa: Adeleorina) from the geckoTarentola annularis in the Sudan: fine structure and life-cycle trials

The ubiquitous gecko Tarentola annularis in the area around Khartoum, Sudan, was found to be infected with Haemogregarina sp., with merogonic stages in its pulmonary endothelial cells and gamonts in its erythrocytes. The fine structure of Haemogregarina meronts, merozoites and gamonts revealed great conformity with the micromorphology of similar stages of other apicomplexan parasites. The unsuccessful transmission of Haemogregarina gamonts to the mosquitoes Aedes aegypti, Culex quinquefasciatus and Anopheles stephensi is also reported.

Goussia girellae n. sp. (Apicomplexa: Eimeriorina) in the opaleye, Girella nigricans.

Goussia girellae n. sp. is described from the opaleye fish, Girella nigricans. Merogonic stages were observed in the apices of intestinal epithelial cells, in the lamina propria, and in extra-intestinal sites including liver, gills, and spleen. Gamonts were observed in the intestinal epithelial cells. Only unsporulated oocysts were detected in the intestine, and sporulation occurred when feces containing oocysts were incubated for 48 h in seawater at 21 degrees C. Oocysts are elongated (24.8 x 14.7 micron) with a wall about 200 nm thick and have no residuum, micropyle, or polar granule. Sporocysts are ellipsoid (8.5 x 4.5 micron), have a thin two-layered wall approximately 30 nm thick, and consist of two valves joined by a suture. Although moribund opaleye were also infected with Gyrodactylus sp., Cryptobia sp., Cardicola sp., and epitheliocystis organisms (chlamydia), all fish were heavily infected with G. girellae and morbidity was thus attributed to the coccidium.

Light and Electron Microscopic Observations on the Intraerythrocytic Development of Babesiosoma stableri (Apicomplexa, Dactylosomatidae) in Frogs from Algonquin Park, Ontario1

ABSTRACT. The intraerythrocytic development and ultrastructure of Babesiosoma stableri Schmittner & McGhee, 1961 are described from Rana catesbeiana and Rana septentrionalis from Algonquin Park, Ontario. Morphometric and chronological observations on B. stableri in an experimentally infected Rana pipiens support the hypothesis that two successive types of merogonic cycles occur within the erythrocytes of infected frogs; the first cycle gives rise to the second and the second cycle produces merozoites destined to become gamonts. Merozoites, meronts, and gamonts are described by light and electron microscopy. Merozoites are typically coccidian and have a trilaminate pellicle with micropores, approximately 40 sub‐pellicular microtubules, an apical and posterior polar ring, a conoid with two accessory rings and a pair of intra‐conoidal microtubules, three rhoptries and numerous micronemes, and a nucleus with a nucleolus and a paranuclear Golgi body. The gamonts are larger than merogonic stages and are isogamous. They have approximately 55 sub‐pellicular microtubules and large stores of amylopectin. These observations indicate that the genus Babesiosoma should be transferred from the Family Haemohormidiidae (Piroplasmida, Piroplasmia) to the Family Dactylosomatidae (Eucoccidiida, Coccidia).

Haemogregarina pseudemydis n. sp. (Apicomplexa: Haemogregarinidae) and Pirhemocyton chelonarum n. sp. in turtles from Louisiana.

SYNOPSIS. The blood of each of 95 turtles (8 species) collected from southeastern Louisiana was infected with some or all of the merogonic stages and gametocyte stage of Haemogregarina pseudemydis n. sp. Five species of turtles harbored Pirhemocyton chelonarum n. sp. Turtle Haemogregarina and Pirhemocyton are locality records for Louisiana. Pirhemocyton is reported for the first time in turtles and in the continental U.S.A.