流溪河水库中瘤棘砂壳虫的摄食食物种类研究

有壳变形虫是一些单细胞的,异养的,自由生活的,生活在由有机颗粒,石英啥,硅质的矿物质等以规则的顺序组成的外壳中的原生动物^1],广泛分布于世界各地^2],水生砂壳虫是其典型代表^3]。据报道砂壳虫摄食水中的微小颗粒以及轮虫,甚至是大型的浮游生物^4]。因而砂壳虫可能是水体中连接经典食物链和微型食物链的关键浮游生物。为了系统地研究砂壳虫的摄食行为的特点,在流溪河水库水体中进行了两年的野外监测并结合室内活体观察。瘤棘砂壳虫最初发现于贵州,杨军等人于2004年重新描述了该种类并给予系统地形态学和壳元素组成研究^5],是流溪河水库该属的一个优势种类。瘤棘砂壳在流溪河水库中于晚春出现,秋季消失,种群在夏季达到峰值。据活体观察,该种类属肉食性,其摄食浮游生物主要是轮虫,包括胶鞘轮虫,独角聚花轮虫(个体),螺形龟甲轮虫,红多肢轮虫(死亡个体),奇异六腕轮虫(死亡个体),对棘异尾轮虫(死亡个体),以及无节幼体(死亡个体)。瘤棘砂壳虫2006年出现于5月~10月,丰度范围为1.2~25.88ind.·L^-1,2007年丰度范围为0.2~11.2 ind.·L^-1。螺形龟甲轮虫和红多肢轮虫的丰度范围分别为0.2~101.2ind.·L^-1,0.1~45.71ind.·L^-1。胶鞘轮虫和独角聚花轮虫的丰度范围分别为0.02~11.4ind.·L^-1,0~26 ind.·L^-1,并且都是在夏季达到峰值。胶鞘轮虫和独角聚花轮虫由于身体柔软、游泳速度不快,是易被瘤棘砂壳虫摄食的轮虫。独角聚花轮虫在自然水体中有集群行为,能够抵御肉食动物的捕食,因为在自然水体中被摄食的几率较小。而其它的轮虫如龟甲轮虫,红多肢轮虫,由于外壳硬,游泳速度快,瘤棘砂壳虫对它们的捕食成功率很低。瘤棘砂壳虫主要依靠伪足进行摄食活动和爬行,其摄食行为和机制应该得到进一步的研究。

Food selectity of Difflugia tuberspinifera in Liuxihe Reservoir,South China

Lobose Testate Amoeba Difflugia, a worldwide distributed genus with its remarkable size and prey species, are critical plankters which link the classic food chain to the microral loop in the water column. To recognise its prey species and its predation mechanism, a field study, including statistical study and direct live observation was carried from May, 2006 to December, 2007 in Liuxihe Reservoir, Guangdong Province, with several coexisting Difflugia, and D. tuberspinifera as the dominant species in the water column. Both live observation and fixed samples from fields indicated that soft body rotifers, such as Collotheca sp. and Conochilus dossuarius are preferred food for D. tuberspinifera, but C. dossuariu might not be captured easily by D. tuberspinifera because of the colonying behavior. Keratella cochlearis can also be successfully handled by D. tuberspinifera by tearing up the strong lorica. However, the handling time was much longer than the soft body rotifers which might prevent it from been frequently caught. D. tuberspinifera might have direct trophic cascade effect toward Collotheca in the water body.