Beĭer T V, Sidorenko N V
Parazitologiia. 1993 Jul-Aug;27(4):309-19.
Suckling rats were used as a model host for our previous EM studies of the endogenous development of Cryptosporidium parvum isolated from spontaneously infected calves (Beĭer e. a., 1990; Beĭer, Sidorenko, 1990). In the course of repeated infections it was noticed that the oocysts discharged by the recipient host (rat) were obviously larger than those in the donor's (calf's) isolates. Keeping in mind the presumable taxonomic significance of coccidian oocysts as a constant and rather reliable tool for species discrimination we made a comparative quantitative and statistical analysis of the mean values of oocysts of C. parvum, originating from several sources (table 2): a random human isolate (N 1), several random isolates from spontaneously infected calves (N 2-5), isolates from calves (N 6-8) used as the infecting material for suckling rats, and fecal samples from the experimentally infected rats (N 9-15). The results obtained have shown that the oocysts discharged by rats (N 9-15) were larger that those of calf origin (N 6-8), with the differences being statistically significant with 95% confidence. Besides, within the same host (rat) at least two oocyst groups were distinguished (N 9-11 and 12-15, resp.) whose differences in mean values also appeared statistically significant. The larger oocysts displayed differences in morphology bearing distinct walls which were never observed either in the donor isolates or in the smaller population of the recipient oocysts. The established differences in oocyst dimensions lay presumably within the frames of the normal reaction of C. parvum and other Cryptosporidium species, due to biological peculiarities of unusual life cycles of these unique coccidia: their homoxenous (i.e. confined to one host body only) development is combined with polyxeny (i.e. a wide host specificity that involves the number of host species representing different environmental conditions). The parasite's ability to change its functional morphology and size may appear some kind of preadaption to the number of varying conditions met by these polyxenous coccidia. This and other relevant assumptions are discussed in the paper.
在我们之前的电子显微镜研究中，使用乳鼠作为模型宿主，研究从自然感染的犊牛中分离出的微小隐孢子虫的内源性发育情况（Beĭer等人，1990年；Beĭer，Sidorenko，1990年）。在反复感染过程中，注意到受体宿主（大鼠）排出的卵囊明显大于供体（犊牛）分离株中的卵囊。考虑到球虫类卵囊作为物种鉴别中一种恒定且相当可靠的工具可能具有的分类学意义，我们对来自多个来源的微小隐孢子虫卵囊的平均值进行了比较定量和统计分析（表2）：一份随机的人类分离株（N 1）、几份从自然感染的犊牛中随机分离出的分离株（N 2 - 5）、用作乳鼠感染材料的犊牛分离株（N 6 - 8）以及实验感染大鼠的粪便样本（N 9 - 15）。所获得的结果表明，大鼠排出的卵囊（N 9 - 15）比犊牛来源的卵囊（N 6 - 8）更大，差异在95%置信水平上具有统计学意义。此外，在同一宿主（大鼠）内至少区分出了两组卵囊（分别为N 9 - 11和12 - 15），其平均值差异也具有统计学意义。较大的卵囊在形态上存在差异，具有明显的壁，这在供体分离株或受体卵囊的较小群体中均未观察到。卵囊尺寸的既定差异可能处于微小隐孢子虫和其他隐孢子虫物种正常反应的范围内，这是由于这些独特球虫不寻常生命周期的生物学特性所致：它们的同宿主发育（即仅局限于一个宿主体内）与多宿主性（即广泛的宿主特异性，涉及代表不同环境条件的多种宿主物种）相结合。寄生虫改变其功能形态和大小的能力可能表现为对这些多宿主球虫所遇到的多种不同条件的某种预适应。本文讨论了这一观点及其他相关假设。
