山美水库两种入侵罗非鱼繁殖生物学比较

为比较山美水库两种入侵齐氏罗非鱼(Coptodon zillii)和伽利略罗非鱼(Sarotherodon galilaeus)种群的繁殖生物学特征,于2021年3—10月份在山美水库逐月采样,分析了繁殖时间、性比、绝对繁殖力、相对繁殖力和成熟卵径等特征。结果表明,两种罗非鱼均于4月份开始繁殖,齐氏罗非鱼繁殖高峰为7月, 10月结束繁殖;伽利略罗非鱼繁殖高峰为6月, 9月结束繁殖。齐氏罗非鱼平均绝对繁殖力为(4009.85±1305.69)粒、平均体重相对繁殖力为(67.32±15.63)粒/g、平均体长相对繁殖力为(31.31±5.03)粒/mm;伽利略罗非鱼平均绝对繁殖力为(1701.85±591.29)粒、平均体重相对繁殖力为(6.46±0.87)粒/g、平均体长相对繁殖力为(8.22±2.33)粒/mm;齐氏罗非鱼的绝对繁殖力、体重相对繁殖力和体长相对繁殖力均显著高于伽利略罗非鱼,平均成熟卵径则显著小于伽利略罗非鱼。齐氏罗非鱼和伽利略罗非鱼繁殖群体的雌雄性比分别为1.59和1.83,两个种群的雌雄性比无显著差异,但均显著偏离1﹕1。研究表明两种共同入侵的罗非鱼种群具有不同的繁殖...     

A NEW METHOD FOR THE GENERATION AND USE OF FOCUSED ULTRASOUND IN EXPERIMENTAL BIOLOGY

1. An efficient generator of focused ultrasound has been designed, built, and successfully operated. 2. The generator has been used to produce focal heating in the centers of paraffin blocks, and in a similar manner, focal areas of destruction were obtained deep in fresh liver tissue with minimal effects at the surface and no effects on the intervening tissue. 3. In animals, focused ultrasound of high intensity produced local cerebral changes as inferred from behavior disabilities and as demonstrated at autopsy. This local brain effect was achieved through intervening scalp, skull, and meninges. The resulting behavior disabilities disappeared in from 2 to 16 hours. 4. To date, it has not been possible to produce such brain changes without incidental injury to the skin and subcutaneous tissue lying at the base of the cone of radiation. 5. Improvements in generation and application of the focused supersonic beam are suggested whereby it should be possible to increase still further the focal effects in the brain, with a corresponding decrease or elimination of complicating surface injury.     

THE BIOLOGY OF THE MOURNING CHAT IN WINTER QUARTERS

Mourning Chats ( Enanthe lugens in the Helwan area in Lower Egypt winter along the lower spurs of the mountains. Each bird occupies a separate territory from which it excludes other Mourning Chats, and wherein it sings.
"Winter" song is most energetic in the months of July to October; at this season the main singing hours are in the early morning and early evening. In the period November to February song is less frequent, and is most often heard in the late afternoon.
In the hot weather of the autumn the birds select perches in shade during the mid-day hours.
Evidence is advanced that there is a measure of interspecific territorial competition between Mourning Chats, Hooded Chats ( Enanthe monacha and White-tailed Chats ( Enanthe leucopyga. The possible relevance of this interspecific territorial practice to the hypothesis of the "food value" of territory is discussed.