Nematodes of Proceratophrys ararype (Anura: Odontophrynidae), an endemic frog from the Araripe Plateau, northeastern Brazil

Abstract: Parasites are an important component of the global biomass, having significant roles in several regulatory mechanisms in the ecosystem. Parasitism is one of the most common ecological interactions on the planet. Studies have shown that the helminth fauna of only 8% of amphibian species in Brazil have been studied, and this percentage is lower for the Odontophrynidae family, with only four of the 50 species kown to occur in Brazil having been investigated. Here, we present the helminth fauna of Proceratophrys ararype, an anuran endemic to the “Brejo de Altitude” Chapada do Araripe (Araripe Plateau), northeastern Brazil. The infection parameters analyzed were prevalence, mean intensity of infection and mean abundance of parasites. We used the Pearson’s linear correlation coefficient to check the correlations between the abundance of the parasites with the snout-vent length (SVL) of hosts. To verify the degree of aggregation of parasites in hosts, we used the dispersion index. Out of 40 specimens examined, 19 specimens were infected with at least one parasite. The overall prevalence was 47.5% with a mean infection intensity of 18.93 ± 10.77. The endoparasitic community associated with P. ararype consisted of six species of parasites, with Falcaustra mascula having the highest prevalence (25%). Most parasites had a uniform dispersion index in the hosts and their abundance was unrelated to host size. Here, we also present a compilation of all parasites associated with host species of the genus Proceratophrys from South America. Overall, we found 23 species of parasites associated with five host species (P. ararype, P. appendiculata, P. boiei, P. cristiceps, P. mantiqueira). Of these, two species of parasites (Oswaldocruzia mazzai and Strongyloides sp.) represent new records for the genus Proceratophrys. Our results demonstrate the lack of studies on amphibian helminth fauna and fill an important knowledge gap on the diversity of parasites of Proceratophrys ararype, an endemic frog from the Araripe Plateau, northeastern Brazil.

摘要：寄生虫是全球生物量的重要组成部分，在生态系统多项调控机制中发挥关键作用。寄生现象是地球上最普遍的生态互作类型之一。研究表明，巴西仅8%的两栖动物物种的寄生蠕虫区系（helminth fauna）得到过研究，而齿蟾科（Odontophrynidae）的相关研究占比更低：该科在巴西已知的50个物种中，仅4种被开展过相关调查。
本研究报道了巴西东北部阿拉里皮高原（Araripe Plateau）的高地沼泽（Brejo de Altitude）区域特有无尾目物种短头蟾（Proceratophrys ararype）的寄生蠕虫区系。本次分析的感染参数包括感染率、平均感染强度与寄生虫平均丰度。我们采用皮尔逊线性相关系数（Pearson’s linear correlation coefficient）检验寄生虫丰度与宿主吻肛长（snout-vent length, SVL）的相关性；为验证寄生虫在宿主体内的聚集程度，使用了离散指数（dispersion index）。
本次共检查40号宿主标本，其中19号至少感染1种寄生虫，总感染率为47.5%，平均感染强度为18.93±10.77。与短头蟾相关的内寄生群落包含6种寄生虫，其中斧口线虫（Falcaustra mascula）的感染率最高（25%）。多数寄生虫在宿主体内呈现均匀的离散分布特征，且其丰度与宿主体型无相关性。
本研究同时整理了南美洲短头蟾属（Proceratophrys）所有宿主物种的相关寄生虫记录。经统计，目前共记录到与5种宿主（短头蟾P. ararype、P. appendiculata、P. boiei、P. cristiceps、P. mantiqueira）相关的23种寄生虫，其中奥斯瓦尔德克鲁兹线虫（Oswaldocruzia mazzai）和类圆线虫（Strongyloides sp.）为短头蟾属宿主的新记录寄生虫。
本研究结果凸显了两栖动物寄生蠕虫区系研究的匮乏，填补了巴西东北部阿拉里皮高原特有物种短头蟾的寄生多样性相关的重要知识空白。