Aznar F J, Balbuena J A, Bush A O, Raga J A
Department of Animal Biology, University of Valencia, Valencia, Spain.
J Parasitol. 1997 Feb;83(1):13-8.
The linear habitat selection of 4 sequential maturity stages (1, 2, 3, and 4) of the trematode Hadwenius pontoporiae in the intestines of 26 South American dolphins Pontoporia blanvillei was investigated. The franciscana is a suitable host for H. pontoporiae because all 26 hosts were infected, the infrapopulations being composed mostly of gravid (stage 4) worms. Most trematodes were found in the first third of the intestine. The niches of the maturity stages decreased from stage 1 to 4. Gravid worms favored the most anterior part of the duodenum, whereas stages 1, 2, and 3 occurred more posteriorly in every host. The distributions of the maturity stages showed a narrow site fidelity and were ordered following the developmental sequence. The positions of stages 2, 3, and 4 covaried positively when the effect of intensity was controlled. All this evidence suggests that H. pontoporiae undergoes an anteriad ontogenetic migration from the posterior to the most anterior duodenum. At high intensities, the distribution of stages 2, 3, and 4 expanded and shifted posteriorly. According to the maturity structure of H. pontoporiae at the infrapopulation level, it is proposed that there might be more developing worms at high intensities, and, therefore, the expansion and shift might result, at least partly, from the presence of more migrating worms along the fundamental niche of H. pontoporiae. Other Hadwenius species show a similar general pattern of distribution to H. pontoporiae. This raises the possibility that the habitat selection behavior of H. pontoporiae may be due to the inheritance of prior phylogenetic constraints.
对26只南美拉河豚（Pontoporia blanvillei）肠道内的庞氏哈德吸虫（Hadwenius pontoporiae）4个连续成熟阶段（1、2、3和4期）的线性栖息地选择进行了研究。拉河豚是庞氏哈德吸虫的适宜宿主，因为所有26只宿主均被感染，感染群体主要由成熟（4期）虫体组成。大多数吸虫发现于肠道前三分之一处。成熟阶段的生态位从1期到4期逐渐减小。成熟虫体偏好十二指肠最前端，而1、2和3期在每个宿主体内分布更靠后。成熟阶段的分布显示出狭窄的位点保真度，并按照发育顺序排列。在控制感染强度的影响后，2、3和4期的位置呈正协变。所有这些证据表明，庞氏哈德吸虫在个体发育过程中经历了从十二指肠后部向前部的迁移。在高强度感染时，2、3和4期的分布范围扩大并向后移动。根据感染群体水平上庞氏哈德吸虫的成熟结构，推测在高强度感染时可能有更多发育中的虫体，因此，这种分布范围的扩大和移动可能至少部分是由于沿着庞氏哈德吸虫基础生态位有更多迁移虫体的存在。其他哈德吸虫物种显示出与庞氏哈德吸虫相似的总体分布模式。这增加了庞氏哈德吸虫栖息地选择行为可能是由于先前系统发育限制的遗传的可能性。
