Ultrastructural features of the apical complex, pellicle, and membranes investing the gamonts of Haemogregarina magna (Apicomplexa: Adeleina)

Mature gamonts of Haemogregarina magna lie within a type of parasitophorous vacuole (Pv) apparently unique to the haemogregarines. The cytoplasm of infected erythrocytes was separated from the parasite by two Pv membranes. An additional membrane, coated on both sides with electron-dense material, closely invested the gamonts. The apical complex of the gamonts includes a conoid, two preconoidal rings, and an elaborate polar ring complex. The latter consisted of the polar ring and approximately 78 posteriorly directed, radially arranged, "tine-like" structures which fuse as they merge anteriorly into the polar ring. Freeze fracture replicas demonstrated that the pellicle of gamonts of H. magna was structurally similar to that of other apicomplexans. The closely apposed inner membranes of the pellicle formed plates which were arranged into strips along the long axis of the gamont. Calculations indicated that 13 such strips are found around the circumference of the gamonts with about six subpellicular microtubules associated with the inner surface of each strip. Gamonts of H. magna share many structural similarities with the kinetes, ookinetes, and sporokinetes of other apicomplexans. We propose that the conoid and polar ring complex are fundamental features of all apicomplexan "kinetes."     

Haematological observations on a hibernating tuatara,Sphenodon punctatus

Abstract

Quantitative and biochemical observations were made on the peripheral blood of a hibernating female tuatara. The packed red cell volume (haematocrit) was 30%. There were about 260 000 erythrocytes and 5000 leucocytes per mm³ blood. Lymphocytes and neutrophils were the predominant leucocytes, followed by monocytes, eosinophils, and basophils. Haemoglobin, plasma protein, glucose, sodium, potassium, cholesterol, and triglyceride levels were determined. These haematological data are compared with data from the same animal obtained during the active summer period.     

Descriptions and phylogenetic systematics of Myxobolus spp. from cyprinids in Algonquin Park, Ontario

Eight species of Myxobolus were collected from four species of cyprinids in Algonquin Park, Ontario. On the basis of spore morphology, five of these species are described as new and two are redescribed. The evolutionary relationships among these eight species were studied using partial small subunit ribosomal DNA (ssu-rDNA) sequence data. The resulting cladograms, which were highly resolved and with strongly supported relationships, allowed for the evaluation of spore morphology, host specificity, and tissue tropism, criteria traditionally used in species identification. These criteria, recently criticized for creating artificial rather than natural taxonomic groupings, were evaluated for their reliability in the systematics of the species examined. The data showed that distantly related species often infect the same host and tissue, and that closely related species often occur in different hosts. Morphologically similar species are more closely related to each other and the taxonomy based on spore morphology is consistent with the relationships depicted in the phylogenies. These results suggest that spore morphology is better than host specificity and tissue tropism as a species character, as well as for determining evolutionary relationships among the species of Myxobolus examined.     

Encapsulation of Myxobolus pendula (Myxosporidia) by epithelioid cells of its cyprinid host Semotilus atromaculatus

Spores of Myxobolus pendula develop within the cores of complex cysts on the gill arch of creek chub Semotilus atromaculatus. Adjacent to, and surrounding, the spores are concentric layers of stratified interdigitating cells, whose nature was examined by transmission electron microscopy and by immunohistochemical and molecular biological techniques. In situ hybridization data using parasite-derived ribosomal DNA as a probe indicate that infection leads to the encapsulation of developing plasmodia by host immune cells that form an epithelioid granuloma. Epithelioid cell-cell adhesion is effected by desmosomes anchored intracellularly to cytokeratin intermediate filaments. High levels of alkaline phosphatase activity are associated with regions of cellular interdigitation. The granuloma may serve to limit the spread of the parasite to surrounding tissues but does not appear to inhibit diffusion of oxygen and nutrients to the developing spores.     

Observations on the role of simuliids and culicids in the transmission of avian and anuran trypanosomes

Although Trypanosoma rotatorium undergoes transformation and prolific multiplication in the mid and hindgut of Culex territans, several attempts to experimentally infect laboratory-reared, Rana pipiens by different routes were unsuccessful. Trypanosoma avium undergoes a similar pattern of development in the gut of Simulium rugglesi. Experimental infections of T. avium in ducklings indicates that S. rugglesi serves as an intermediate host and probably as an active and passive vector of the parasite in nature.     

Metal accumulation in two contiguous eutrophic peri-urban lakes,Chivero and Manyame,Zimbabwe

Concentrations of aluminium, cadmium, chromium, cobalt, copper, iron, lead, nickel and zinc were determined in surface water, benthic sediments, and the gills, liver and stomach muscle tissues of Oreochromis niloticus and Clarias gariepinus in peri-urban lakes Chivero and Manyame, Zimbabwe. Five sites were sampled in each lake once per month in November 2015, February, May, August and November 2016. Pollution load index detected no metal contamination, whereas the geo-accumulation index reflected heavy to extreme sediment pollution, with Fe, Cd, Zn, Cr, Ni and Cu present in both lakes. Significant spatial temporal variations were detected for Al, Cr, Cu and Pb across sites within and between the two lakes. High Fe, Al and Cr concentrations in water and sediments in lakes Chivero and Manyame derive from geogenic background sources in addition to anthropogenic loads and intensity. Elevated concentrations of Al, Pb, Cu, Cd, Fe and Zn detected in gills, liver and stomach tissue of catfish corroborate concentrations in water and sediments, and pose the highest ecological and health risk for hydrobionts in lakes Chivero and Manyame. Contiguity of peri-urban lakes exposes them to similar threats, necessitating creative water management strategies, which ensure ecological continuity.