北京地区水霉科真菌季节性分布

本文报道北京地区水霉科(Saprolegniaceae)真菌季节性分布的调查、研究结果,发现影响水霉季节性分布的主要因素是水温的季节性变化。不同属、种具不同的季节性分布,而种的季节性分布与它们卵孢子的结构有关。

SEASONAL PERIODICITY OF SAPROLEGNIACEAE IN BEIJING DISTRICT

A study of the taxonomy and ecology of Saprolegniaceae in Beijing district, China, was conducted from February, 1980 to July, 1981. The present paper reports on the seasonal periodicity of Saprolegniaceae. The number of zoospores in the investigated water bodies varied with the changes in wate temperature, the maximum being in May (water temperature about 15—20℃) and the minimum in July and August (water temperature above 25℃). Our results showed that this was due to the change in water temperature caused by seasonal variation rather than the seasonal periodicity itself. On the ocher hand, the production of the zoospores was also influenced by the population of Lacustrin bacteria in water. Six genera and eleven species of Saprolegniaceae were identified. Among them, Achlya and Saprolegnia were the most frequently encountered genera throughout the whole year, followed by Aphanomyces and Dictyuchus which were isolated largely from spring to autumn, very rarely in winter. Calyptralegnia and Brevilegnia were occasionally found, only in soil. Achlya americana Humphrey, Saprolegnia ferax (Gruith.) Thuret and Achlya debaryana Humphrey were the most widely distributed species in this area. According to the structure of oospores, the species of Saprolegniaceae isolated could be divided into two groups. The first group, consisting of species characterized by centric and subcentric oospores, exhibited a marked seasonal periodicity and mainly occurred in winter and spring when water temperature ranged from 1℃ to 13℃; the second group, consisting of species forming eccentric oospores, showed no discernible periodicity and were found throughout the year when the temperature was from 1℃ to 27℃. The procedure used for the determination of the number of zoospores of saprolegniaceous fungi was briefly described and discussed. Althóugh, no technique was perfect for such quantitative study, we considered our method providing a close estimation of the occurrence of zoospores of Saprolegniaceae in water.