A morphological, molecular and life cycle study of the capybara parasite Hippocrepis hippocrepis (Trematoda: Notocotylidae)

Hippocrepis hippocrepis is a notocotylid that has been widely reported in capybaras; however, the molluscs that act as intermediate hosts of this parasite remain unknown. Furthermore, there are currently no molecular data available for H. hippocrepis regarding its phylogenetic relationship with other members of the family Notocotylidae. In the present study, we collected monostome cercariae and adult parasites from the planorbid Biomphalaria straminea and in the large intestine of capybaras, respectively, from Belo Horizonte, Minas Gerais, Brazil. We subjected them to morphological and molecular (amplification and sequencing of partial regions of 28S and cox-1 genes) studies. Adult parasites collected from the capybaras were identified as H. hippocrepis and the sequences obtained for both molecular markers showed 100% similarity with monostome cercariae found in B. straminea. The sequences obtained for H. hippocrepis were compared with data available in public databases; analysis revealed this species differs from other notocotylids with available sequences (1.5–3.8% with respect to 28S and 11.4%–13.8% with respect to cox-1). On the phylogenetic analyses, H. hippocrepis appeared to be a distinct lineage in relation to other notocotylids. Some ecological aspects related to the infection of capybaras with H. hippocrepis are briefly discussed.Hippocrepis hippocrepis是一种背孔科（Notocotylidae）吸虫，此前已有多例在水豚（capybara）体内检出的报道，但该寄生虫的中间宿主软体动物类群至今仍未明确。此外，目前尚无关于H. hippocrepis与背孔科其他类群系统发育关系的分子数据。本研究于巴西米纳斯吉拉斯州贝洛奥里藏特市开展，分别从扁卷螺科（Planorbidae）的截形扁卷螺（Biomphalaria straminea）体内采集到单口尾蚴（monostome cercariae），并从水豚大肠内采集到该寄生虫的成虫。我们对样本进行了形态学与分子生物学分析，包括28S rRNA基因及cox-1基因部分区域的扩增与测序。经鉴定，从水豚体内采集的成虫为H. hippocrepis，且两种分子标记的序列均与截形扁卷螺体内检出的单口尾蚴序列完全一致（相似度达100%）。将H. hippocrepis的序列与公共数据库中的公开数据进行比对后发现，该物种与其他已获取序列的背孔科吸虫存在遗传差异：28S基因区域的序列差异为1.5%~3.8%，cox-1基因区域的序列差异为11.4%~13.8%。系统发育分析结果显示，H. hippocrepis相较于其他背孔科吸虫构成一个独立演化支系。本研究还对水豚感染H. hippocrepis的部分生态学特征进行了简要探讨。