de León Rodrigo Ponce, Vera Bárbara Berón, Volonterio Odile
Sección Zoología de Invertebrados, Facultad de Ciencias, Universidad de la República, Uruguay, c/ Iguá 4225, Montevideo 11400, Uruguay.
J Parasitol. 2015 Aug;101(4):424-8. doi: 10.1645/GE-2363.1. Epub 2015 Apr 14.
The genus Temnocephala is endemic to the Neotropical region. Temnocephala mexicana and Temnocephala chilensis are the only 2 temnocephalans whose known distribution ranges extend to the south beyond Parallel 40°S. No Temnocephala species has ever been recorded from the extensive area between Parallel 43°S and the southern end of the South American continent, which makes the study of the southern limit of the distribution of the genus a topic of great interest. The southernmost report corresponds to T. chilensis from the Telsen River, Chubut Province, Argentina. In March 2000, several temnocephalans were found on the freshwater anomuran crustacean Aegla neuquensis from the same locality; the specimens were identified as belonging to a new species, which is described here. This species is characterized by possessing an unusually thin-walled, narrow zone that has the appearance of a deep groove connecting the introvert to the shaft of the penial stylet; an introvert with 36 longitudinal rows of spines, each bearing 6-8 spines that are progressively smaller towards the distal end; a distal end of the introvert with a very thin, sclerotized wall without spines; a seminal vesicle that opens sub-polarly into the contractile vesicle; a pair of paranephrocytes at the level of the pharynx and a second pair at the level of the anterior portion of the anterior testes, and eggs with very long stalks. On the basis of their overall morphology, host preference, and geographical distribution, T. chilensis and the new species are closely related, so a diagnostic key for the southern species of Temnocephala is also included. The type locality of the new species is in the southern limit of the known distribution area of T. chilensis, so after this work there are 2 known species marking the southern limit of the distribution of the genus.
头吻虫属是新热带区特有的。墨西哥头吻虫和智利头吻虫是仅有的2种已知分布范围向南延伸至南纬40°以南的头吻虫。在南纬43°与南美大陆南端之间的广袤区域，从未有过头吻虫属物种的记录，这使得对头吻虫属分布南界的研究成为一个极具吸引力的课题。最南端的记录是来自阿根廷丘布特省特尔森河的智利头吻虫。2000年3月，在同一地点的淡水异形甲壳动物新内克河阿埃格螺上发现了几只头吻虫；这些标本被鉴定为属于一个新物种，在此进行描述。该物种的特征在于拥有一个异常薄壁、狭窄的区域，其外观像一条深沟，将阴茎鞘的内翻部分与轴连接起来；内翻部分有36排纵向排列的刺，每排有6 - 8根刺，向远端逐渐变小；内翻部分的远端有一层非常薄的、硬化的壁，没有刺；精囊亚极地开口于收缩囊；咽部水平有一对副肾细胞，在前睾丸前部水平有第二对副肾细胞，以及带有很长柄的卵。根据它们的整体形态、宿主偏好和地理分布，智利头吻虫和新物种密切相关，因此还包括了头吻虫属南部物种的鉴别检索表。新物种的模式产地在智利头吻虫已知分布区域的南界，所以这项工作之后有2个已知物种标志着头吻虫属分布的南界。
