Kenneth H. Nicholls

In 1961, the testate amoeba Nebela kivuense Gauthier-Lièvre et Thomas, 1961 was described for the first and only time from an area near Lake Edward in the Democratic Republic of the Congo (at 0.002° N Latitude). The lack of recent reports of this species, despite exhaustive surveys of the testate amoebae fauna of the major continents of the world, suggested that N. kivuense was a rare species perhaps endemic to a small, local equatorial region of the African continent. This paper reports its rediscovery from two wetland-conifer forest ecosystems in southern Ontario, Canada (at 44° N Latitude), thus changing dramatically our previous perception of its very restricted global distribution. This has implications for the idea held by many students of biogeography that there is a special category of microscopic protists that contains truly rare species and their rarity, perhaps together with specific habitat requirements and tolerances, limits opportunities for dispersal around the world. The N. kivuense story is a clear example of the dangers of inferring endemism from rarity.

Several Ontario (Canada) populations of the “heliozoan-like” protist Belonocystis Rainer, 1968 were studied to help elucidate the taxonomic position of this genus relative to other rhizarian protists with fine pseudopodia. The Ontario material presently includes two distinct species – B. tubistella Rainer and B. quadrangularis n. sp., described here as a new species based on cell morphology and microstructure of the spiny investiture encasing its cell. The organic nature of the spiny structures of both species has been confirmed by their dissolution in 6% sodium hypochlorite solution. Median cell diameters of B. tubistella and B. quadrangularis were 10.5 μm and 7 μm, respectively. As revealed by transmission electron microscopy, the spine bases in B. tubistella consisted of a complex structure of four curved ribs interconnected by a membranous sheet replete with closely-appressed, large circular to elliptical pores, while in B. quadrangularis the spine bases consisted of a simple four-cornered “pyramid” of struts that supported the main shaft of the spine. These findings strengthen the status of the genus Belonocystis and it placement outside the realm of the Centrohelida and Rotosphaerida.
 

Zoelucasa sablensis n. gen et n. sp. is a small heterotrophic fl agellate housed within a pyriform lorica of relatively large imbricate, circular siliceous scales. It was found in near-shore benthic sand/seawater samples of both the Pacific and Atlantic Oceans (west and east coasts of Canada; salinity = 32–33 ppt). The median length and width of the lorica was 18 and 11 μm, respectively (n = 29). This taxon lacks chloroplasts and swims with a slow zig-zag motion controlled by a short (5–7 μm long), anteriorly-directed flagellum and a longer trailing flagellum, 15–20 μm in length. Its classification within the phylum Cercozoa (most likely, Class Imbricatea) is tentative, as there are no known morphological homologues (discoidal, overlapping siliceous plate-scales forming a test or lorica enclosing a heterotrophic flagellate). Further study of cultured and wild material, including a search for other possible non-flagellate (e.g. amoeboid?) life history stages, TEM examination of cell sections, and rDNA sequencing will most certainly provide more opportunities for a justifi able classifi cation, possibly including a new Order.