Diel Division Cycle and Growth Rates of Synechococcus in Lakes Huron and Michigan1

A clone of Synechococcus isolated from Lake Huron and natural populations of Synechococcus from lakes Huron and Michigan were studied in 1989 to examine the diel division cycle and to provide estimates of the in situ growth rate based on the frequency of dividing cells (FDC) method. Cultured populations of Synechococcus exhibited a consistent diel division pattern with a midday/afternoon (1100–1800 h) peak in the percent of dividing cells. The maximum percent of dividing cells varied among cultures (8-27%) and was related to the growth rate. A small fraction of dividing cells (3-5%) remained throughout the dark period, suggesting that some cells were arrested in the doublet stage prior to division. The duration of division (t_d) ranged from 2.6-4.9 h, with a 3.7 h mean for cultures with growth rates ≥0.34 d⁻¹ but increased to 8 h at a lower growth rate of 0.20 d⁻¹. The diel division pattern for natural populations was very similar to the laboratory clone; an afternoon peak (1400-2100 h) in dividing cells and a small fraction of dividing cells (2-5%) remained during the dark period. The maximum percent of dividing cells for natural populations ranged from 6-10%. In situ growth rates, determined from the FDC and assuming a constant t_d of 3.7 h, ranged from 0.30-0.42 d⁻¹. The FDC method may provide accurate estimates of in situ growth, particularly in environments where the growth rate is >0.34 d⁻¹, but in lakes Huron and Michigan where growth rates can be lower and t_d values may increase, FDC-growth rates must be viewed with caution.     

Trypanosoma congolense: isolation and purification.

Yields of Trypanosoma congolense grown in rats may be increased by placing the rats in a 37 °C environment for 1 hr prior to sacrifice. A further increase in the number of parasites recovered per rat may be achieved by replacement of blood removed by a lactated Ringer's solution with 5% glucose as the rat is being bled from the abdominal aorta. The Ringer's solution serves to maintain intravascular volume during the bleeding procedure and thereby prevents premature cardiac arrest. Erythrocytes in infected blood may be then lysed by raising and rapidly lowering the osmolarity of the blood. This permits separation of the trypanosomes from 95% of the erythrocytes by differential centrifugation. The remaining blood cell contamination may then be removed on a small DEAE-cellulose column. The purified trypanosomes are motile, infective, and intact as judged by electron microscopy. More than 10¹⁰ purified T. congolense can be obtained from three adult rats by these methods.     

Prevalence of Toxoplasma gondii antibodies in nine populations of dairy goats: compared titers using modified direct agglutination and indirect hemagglutination

In a convenience survey of dairy goats on 9 farms in Tennessee, Kentucky, and Georgia, 54 of 99 females were positive for antibodies to Toxoplasma gondii as measured by the indirect hemagglutination test (IHA). Two of 9 males were also positive. Positive goats were found on all farms. The percentage of positive does increased from 55% to 65% when the sera were titered a second time by modified direct agglutination (MDAT). This difference was not statistically significant, indicating that both IHA and MDAT are reliable epidemiological tools.     

Biological Basis of Saki (Pithecia) Folk Species Recognized by the Matses Indians of Amazonian Perú

The Matses Indians of northeastern Perú recognize two linguistically labeled folk species of saki monkeys (Cebidae: Pithecia) that are said to be morphologically distinguishable, to prefer different habitats, and to be noninterbreeding. Because the systematic literature recognizes only one biological taxon of Pithecia in the area inhabited by the Matses, their folk taxonomy suggests either the presence of a previously undescribed species or a hitherto undocumented range extension. All known species of Pithecia are currently thought to be allopatric, so both possibilities are of interest. We obtained blood samples and anatomical voucher material from hunters' kills in order to test the biological basis for the Matses folk taxonomy of sakis. Molecular and morphological analyses of the collected material indicate that both Matses folk species correspond to one effectively panmictic population of Pithecia monachus. Overdifferentiation in folk classification systems, whereby one biological species is represented by two or more nonsynonymous folk species names, is a potentially widespread source of error that should be considered by researchers using local informants for primate field studies. In addition to resolving a folk-taxonomic enigma, our study provides the first quantitative analyses of local (within-population) morphological and molecular variation in this little-known platyrrhine genus.