Molecular characterization of the progenetic metacercariae Crocodilicola pseudostoma parasitizing Rhamdia quelen (Siluriformes, Heptapteridae) in Brazil

Abstract The trematodes have developed several adaptations and strategies to complete their life cycle in the intermediate host, without even reaching the definitive host. Thus, metacercariae through progeny can produce viable eggs by self-fertilization in the second intermediate host. We analyzed 30 specimens of Rhamdia quelen Quoy & Gaimard 1824 (Siluriformes, Heptapteridae) collected in the Jacaré-Pepira River, Ibitinga. Among the specimens analyzed, only one host was parasitized by the progenetic metacercariae of Crocodilicola pseudostoma Willemoes-Suhm 1870 (Digenea: Proterodiplostomidae) presenting prevalence of 3.3%, mean intensity of 68.0 ± 12.4 and mean abundance of 2.3 ± 0.4. This is the first record of progenesis in the metacercariae of C. pseudostoma in the Jacaré-Pepira River, as well as the first partial sequence of COI gene obtained from this species in Brazil.

摘要：吸虫纲物种演化出多种适应性机制与生存策略，可在无需侵染终末宿主的情况下，于中间宿主体内完成生活史周期。其中，幼生殖囊蚴可通过幼体生殖途径，在第二中间宿主体内经自体受精产生具有活力的虫卵。本研究对采自巴西伊比廷加市雅卡雷-佩皮拉河的30份昆兰油鲶（*Rhamdia quelen* Quoy & Gaimard, 1824；鲇形目（Siluriformes），盾皮鲶科（Heptapteridae））标本开展寄生虫感染检测。结果显示，仅1份宿主标本被伪口鳄形吸虫（*Crocodilicola pseudostoma* Willemoes-Suhm, 1870；复殖纲（Digenea），前双穴科（Proterodiplostomidae））的幼生殖囊蚴感染，其感染率为3.3%，平均感染强度为68.0±12.4，平均感染丰度为2.3±0.4。本研究为雅卡雷-佩皮拉河流域伪口鳄形吸虫囊蚴幼体生殖现象的首次记录，同时也是巴西境内首次获取该物种的细胞色素氧化酶亚基I（Cytochrome Oxidase Subunit I，COI）基因部分序列。