A long term record of rotifers in Lake Kinneret (Israel) indicated that Keratella cochlearis is the most common zooplankter in it. Population dynamics parameters (“egg/female ratio” procedure) were combined with lim...A long term record of rotifers in Lake Kinneret (Israel) indicated that Keratella cochlearis is the most common zooplankter in it. Population dynamics parameters (“egg/female ratio” procedure) were combined with limnological data to analyze temporal fluctuations of K. cochlearis in the Kinneret ecosystem. Lake Kinneret is characterized by mesooligotrophic conditions. During the winter-spring period, when the lake is completely mixed and at low temperatures, water and nutrient inputs are maximal. The lake is stratified in the summer, with an oligotrophic epilimnion;at high temperatures, nutrient and water inputs are minimal. Since the early 1990’s, a decline in rainfall and water inputs and a reduction in Peridinium, coinciding with an ascending level of blue greens, were documented. K. cochlearis is affected by the water input regime, temperature, nutrient concentrations and the phytoplankton composition. The densities of individuals and egg bearing females are low in the summer and fall, and high during the late winter-spring, with E/F values being the highest during January-April. Population dynamics parameters were respectively similar. Regressions of densities of individuals and egg bearing females vs time (years) revealed a prominent long term decline.展开更多
美洲龟甲轮虫Keratella americana Carlin,1943年被认为主要分布在美洲地区,但陆续报告在其他地区有出现。2015年在对华南地区浮游动物调查时发现,星云湖、抚仙湖、百色水库及飞来峡水库中均出现该种类。检测了广西百色水库中龟甲轮虫...美洲龟甲轮虫Keratella americana Carlin,1943年被认为主要分布在美洲地区,但陆续报告在其他地区有出现。2015年在对华南地区浮游动物调查时发现,星云湖、抚仙湖、百色水库及飞来峡水库中均出现该种类。检测了广西百色水库中龟甲轮虫的COⅠ序列,与已知美洲龟甲轮虫序列相似度高达98%。中国该龟甲轮虫种群与墨西哥美洲龟甲轮虫种群间差异度为2%,进一步确定为美洲龟甲轮虫。文章描述了美洲龟甲轮虫形态及生境,使用扫描电镜法比较了美洲龟甲轮虫、螺形龟甲轮虫Keratella cochlearis(Gosse,1851)、热带龟甲轮虫Keratella tropica(Apstein,1907)及无棘龟甲轮虫Keratella tecta(Gosse,1851)的咀嚼器。美洲龟甲轮虫主要特点为:背甲长度远大于宽度,侧中棘刺短于侧棘刺,背甲中央最后一个板块未封闭,向后棘刺延伸。4种龟甲轮虫咀嚼器主要区别在于砧基的形状,美洲龟甲轮虫砧基比其他3种轮虫发达,螺形龟甲轮虫砧基似"T"形,热带龟甲轮虫砧基为扇形,无棘龟甲轮虫平直。种间的砧基存在明显差异,可作为热带地区龟甲轮属的分类依据。展开更多
文摘A long term record of rotifers in Lake Kinneret (Israel) indicated that Keratella cochlearis is the most common zooplankter in it. Population dynamics parameters (“egg/female ratio” procedure) were combined with limnological data to analyze temporal fluctuations of K. cochlearis in the Kinneret ecosystem. Lake Kinneret is characterized by mesooligotrophic conditions. During the winter-spring period, when the lake is completely mixed and at low temperatures, water and nutrient inputs are maximal. The lake is stratified in the summer, with an oligotrophic epilimnion;at high temperatures, nutrient and water inputs are minimal. Since the early 1990’s, a decline in rainfall and water inputs and a reduction in Peridinium, coinciding with an ascending level of blue greens, were documented. K. cochlearis is affected by the water input regime, temperature, nutrient concentrations and the phytoplankton composition. The densities of individuals and egg bearing females are low in the summer and fall, and high during the late winter-spring, with E/F values being the highest during January-April. Population dynamics parameters were respectively similar. Regressions of densities of individuals and egg bearing females vs time (years) revealed a prominent long term decline.
