No abstract

Using a long-term demographic data set, we estimated the separate effects of demographic and environmental stochasticity in the growth rate of the great tit population in Wytham Wood, United Kingdom. Assuming logistic density regulation, both the demographic (sigma2d = 0.569) and environmental (sigma2e = 0.0793) variance, with interactions included, were significantly greater than zero. The estimates of the demographic variance seemed to be relatively insensitive to the length of the study period, whereas reliable estimates of the environmental variance required long time series (at least 15 yr of data). The demographic variance decreased significantly with increasing population density. These estimates are used in a quantitative analysis of the demographic factors affecting the risk of extinction of this population. The very long expected time to extinction of this population (approximately 10(19) yr) was related to a relatively large population size (>/=120 pairs during the study period). However, for a given population size, the expected time to extinction was sensitive to both variation in population growth rate and environmental stochasticity. Furthermore, the form of the density regulation strongly affected the expected time to extinction. Time to extinction decreased when the maximum density regulation approached K. This suggests that estimates of viability of small populations should be given both with and without inclusion of density dependence.

Trypanosoma danilewskyi Laveran & Mesnil, 1904 caused anemia In goldfish Carassius auratus. The severity of the anemia was associated with high parasitemia. At least 2 factors are responsible for the anemia; (1) hemolysin: a secretory/excretory product of living trypanosomes which lyses red blood cells (rbc) in the absence of antibody (in vitro study) and (2) hemodllution (in vivo study). No significant hernolysis was detected when rbc were added to sonicated trypanosomes. The hernolysis and hemodilution were correlated with numbers of parasites. Secretion/excretion of hernolysin by living trypanosomes was associated with declining pH in the lncubat~on medium but the pH itself was not involved in hernolysis.

214 taxa under 21 genera of desmids have been described and illustrated from Bangladesh, of which 3 species and 8 varieties are new to science.

Trypanosoma danilewskyi is pathogenic to goldfish, Carassius auratus; the number that survived an infection was related to the size of inoculum, i.e., the mortality was low when the inoculum was small. Most fish that had prior exposure(s) to the parasite survived subsequent homologous challenge(s) and were protected for at least 89 days. The immunity was nonsterile as low numbers of parasites were detected in the blood of some recovered fish. Intraperitoneal injection of corticosteroid in recovered fish significantly increased the number of trypanosomes in peripheral blood of some fish. Although most recovered fish were protected from challenge, a few died from high parasitemia after challenge.