Al-Jahdali M O, Hassanine R M El-Said
Biological Sciences Department, Rabigh-Faculty of Science and Arts, King Abdulaziz University, Rabigh, Saudi Arabia.
J Helminthol. 2012 Mar;86(1):85-94. doi: 10.1017/S0022149X11000095. Epub 2011 Mar 14.
In infrapopulations of helminth parasites, density-dependent effects, through some form of intra- and interspecific competition, play an important role in shaping and regulating the infrapopulations. The mechanisms responsible for these processes have often been observed in laboratory studies and rarely studied under natural conditions. Here, 24 natural infrapopulations (77-447 individuals) of the acanthocephalan Sclerocollum saudii Al-Jahdali, 2010 from the fish Siganus rivulatus consisted of cystacanths, newly excysted juveniles, immature and mature worms, distributed in a well-defined fundamental niche (anterior 60% of the intestine). Each of these stages exhibited a significantly different longitudinal distribution within this niche. In small infrapopulations, cystacanths and newly excysted juveniles were found in the sixth 10% of the intestine, immature worms in the fifth 10% and mature worms in the anterior 40% of the intestine. However, their proportions followed a clear ascending order in each infrapopulation, and the female-male ratios of both immature and mature worms were distinctly female-biased. In large infrapopulations, mature worms existed partially in the site of immature ones, where a differential mortality among immature females was constantly observed. However, the proportions of immature worms increased significantly and those of mature worms decreased significantly, the mean lengths of immature and mature females decreased dramatically and the female-male ratios were distinctly male-biased. The mean sizes of immature and mature males seemed stable through all infrapopulations. The distribution of mature males and females suggests intense male-male competition for access to females, and reveals that larger females are copulated prior to the smaller ones. The results are statistically significant and suggest that infrapopulation self-regulation is through density-dependent mechanisms, in which immature females may play a key role.
在蠕虫寄生虫的亚种群中，密度依赖效应通过某种形式的种内和种间竞争，在塑造和调节亚种群方面发挥着重要作用。这些过程的机制在实验室研究中经常被观察到，但在自然条件下很少被研究。在这里，从黄斑蓝子鱼中采集到24个自然亚种群（77 - 447个个体）的沙特硬棘吻虫（Sclerocollum saudii Al-Jahdali，2010），包括囊棘头体、新脱囊幼虫、未成熟和成熟的虫体，分布在一个明确界定的基础生态位（肠道前60%）内。这些阶段中的每一个在这个生态位内都表现出显著不同的纵向分布。在小亚种群中，囊棘头体和新脱囊幼虫位于肠道后10%，未成熟虫体位于肠道第五个10%，成熟虫体位于肠道前40%。然而，它们在每个亚种群中的比例遵循明显的上升顺序，未成熟和成熟虫体的雌雄比例均明显偏向雌性。在大亚种群中，成熟虫体部分存在于未成熟虫体的位置，在未成熟雌性中经常观察到不同的死亡率。然而，未成熟虫体的比例显著增加，成熟虫体的比例显著下降，未成熟和成熟雌性的平均长度大幅下降，雌雄比例明显偏向雄性。未成熟和成熟雄性的平均大小在所有亚种群中似乎稳定。成熟雄性和雌性的分布表明雄性之间为获得雌性而进行激烈竞争，并表明较大的雌性比较小的雌性先进行交配。结果具有统计学意义，表明亚种群的自我调节是通过密度依赖机制进行的，其中未成熟雌性可能起关键作用。
