Fried B, Schmidt K A, Sorensen R E
Department of Biology. Lafayette College, Easton, Pennsylvania 18042, USA.
J Parasitol. 1997 Apr;83(2):251-4.
In vivo and ectopic encystment of the cercariae of Echinostoma revolutum from Lymnaea elodes snails in Indiana and chemical excystation of the metacercariae were studied. In vivo encystment occurred in adults of Biomphalaria glabrata and Helisoma trivolvis (Colorado strain) snails and in neonatal and juvenile L. elodes snails. These results were expected because 37-collar-spined Echinostoma species show broad specificity in their second intermediate gastropod hosts. Encysted metacercariae of E. revolutum and Echinostoma trivolvis removed from experimentally infected snails and treated in a trypsin-bile salts excystation medium at 39 C showed 30.3% excystation for the former and 55.7% for the latter at 4 hr. The ducts and openings of the paraesophageal glands of excysted metacercariae of E. revolutum from cysts formed in snails did not stain with neutral red. Abnormal ectopic cysts with distorted outer walls and granular inner walls were obtained within 48 hr of placing E. revolutum cercariae in Locke's 1:1 plus 1% dextrose. These metacercariae excysted rapidly in the excystation medium and their paraesophageal gland ducts and openings stained with neutral red. Differences in ectopic encystment and chemical excystation in vitro can be used to distinguish these closely related species in the E. revolutum complex.
研究了来自印第安纳州伊乐螺（Lymnaea elodes）的卷棘口吸虫（Echinostoma revolutum）尾蚴在体内和异位的包囊形成以及后尾蚴的化学脱囊。体内包囊形成发生在光滑双脐螺（Biomphalaria glabrata）和三色膀胱螺（Helisoma trivolvis，科罗拉多品系）的成体以及新生和幼年伊乐螺中。这些结果在意料之中，因为具37个领棘的棘口吸虫物种在其第二中间宿主腹足纲动物中表现出广泛的特异性。从实验感染的螺中取出的卷棘口吸虫和三带棘口吸虫（Echinostoma trivolvis）的包囊后尾蚴，在39℃的胰蛋白酶 - 胆盐脱囊培养基中处理，4小时时前者的脱囊率为30.3%，后者为55.7%。在螺中形成的囊肿内取出的卷棘口吸虫脱囊后尾蚴的食管旁腺导管和开口不着中性红。将卷棘口吸虫尾蚴置于洛克氏1:1加1%葡萄糖溶液中48小时内可获得外壁扭曲和内壁呈颗粒状的异常异位囊肿。这些后尾蚴在脱囊培养基中迅速脱囊，其食管旁腺导管和开口着中性红。异位包囊形成和体外化学脱囊的差异可用于区分卷棘口吸虫复合体中这些密切相关的物种。
