Stephen C. Ayala

A population of Pasmodium colmbiense sp. n. in the iguanid lizard, Anolis Auratus.

Plasmodium colombiense sp. n. is described from 274 naturally infected Anolis auratus from western Colombia. Host blood pictures, parasitemia, parasite structure, infection states, and host population dynamics are correlated. Local epidemics occur, but in contrast to temperate zone species there is little regional synchronization. Active infections occur year-around, being somewhat more common in dry seasons; however, chronic infections predominate. Mature schizonts have 3 to 14, usually 6, 8, or 10 merozoites, reduced to 4 to 6 in chronic infections. Gametocytes are round to oblong, measuring 6 by 5 mu, and the pigment in microgametocytes occurs in a single peripheral vacuole. Parasitemia averaged 2.5% and seldom surpassed 20 to 30%. Infections cause significant anemia, and parasites in active infections are most common in immature erythrocytes. Host response is similar to avian or primate infections, including erythropoiesis, phagocytosis, and interference with parasite growth.

Isospora manchacensis n. sp., an intranuclear coccidian from the Louisiana ground skink, Scincella lateralis (Say, 1823) (Lacertilia: Scincidae)

Isospora manchacensis n. sp. is described from ground skinks, Scincella lateralis (Say, 1823) from Louisiana. Overall prevalence at 6 sites near Lake Ponchartrain was 43.1% (59/137) and ranged from 8% (1/13) to as high as 60% (6/10). Endogenous stages develop inside the nuclei of epithelial cells in the small intestine. Infected hypertrophic nuclei migrate from the basal lamina of the host cell to the luminal striated border. Oocysts in freshly passed fecal pellets usually contain a single contracted sporont that divides to form 2 sporoblasts. These undergo a brief pyramid stage followed by sporulation within 45-50 hr. Sporulated oocysts have a single-layered wall and measure 25.0 X 22.6 (20.0-28.9 X 18.6-26.0) micron. The lemon-shaped sporocysts measure 12.8 X 10.2 (11.1-15.2 X 9.0-11.0) micron and contain a Steida body, a spherical to oval substeida body, and a dispersed, granular sporocyst residuum. Prepatent periods in skinks fed 700 and 1,400 oocysts ranged from 24 to 32 days. Experimentally infected skinks produced large numbers of oocysts continuously during the 3-4 wk they were monitored after the onset of patency, but exhibited no signs of disease. Experimental doses of 200 oocysts failed to produce infections in skinks monitored for as long as 7 wk.

TWO NEW TRYPANOSOMES FROM NORTH AMERICAN SNAKES

Trypanosoma thamnophis from Thamnophis sirtalis in eastern Canada is the only previously known trypanosome from a North American snake. Trypanosoma yaegeri n. sp. and Trypanosoma hydrae n. sp. are described here from a cottonmouth Agkistrodon piscivorus leucostoma and a broad-banded watersnake Nerodia fasciata confluens, respectively, from southern Louisiana. Trypanosoma hydrae easily infects other colubrid snakes, but not cottonmouths, turtles, or the lizard Anolis carolinensis. There are only a few scattered records of try- panosome infections in Nearctic reptiles, with two named species from lizards, one from turtles, and one from snakes. We describe here two new trypanosomes found in swamp dwelling snakes from Louisianas Mississippi River delta region, and summarize the earlier observations on try- panosomes of North American reptiles (Table I), with some revised host identifications.

Plasmodium pessoai sp. n. from Two Costa Rican Snakes

A unique malaria parasite species was found in 1/1 Spilotes pullatus (Colubridae) and 1/70 Lachesis muta (Crotalidae) from the moist Atlantic lowland forests of eastern Costa Rica. It is distinguished by small, sausage-shaped gametocytes (x 10.4 by 4.6 mu), growing schizonts that often contain a noticeable digestive vacuole with the contents partially visible, and striking spherical or bouquet-shaped segmenters whose precise merozoite numbers are difficult to discern (about 22-32) because of an intensely staining magenta or rose-colored substance in the matrix of the surrounding vacuole.