First record of a 'fish' blood fluke (Digenea: Aporocotylidae) from a marine mammal: n. sp.

We describe the first known blood fluke from a marine mammal, the dugong, (Sirenia: Dugongidae), which represents a new species of aporocotylid, n. sp. (Digenea: Aporocotylidae). Eggs presumed to be of blood flukes have been previously reported from dugongs. This exciting discovery raises questions regarding evolution and host-switching in the Aporocotylidae, which prior to this study were only known to infect actinopterygian and chondrichthyan fishes. The new species has male and female genital pores opening on the right side of the body, with the male genital pore opening posterior to the entire reproductive system and the testis is extra-caecal. The uterus is highly convoluted, and the ovary is irregularly lobate. These features, together with the size and number of the tegumental spines per row, easily distinguish the new species from the most similar congeners Holzer et al., 2008, Yamaguti, 1970, Bullard and Overstreet, 2004, Cribb et al., 2000, Yong et al., 2016, and Bullard and Overstreet, 2004, all of which infect actinopterygian fishes. Given that is the most diverse and least host-specific of the marine aporoctoylid genera, it seems credible that a successful host-switch has occurred from an actinopterygian to . Further sampling of sirenians and other marine mammals is warranted to gain a more comprehensive understanding of the evolutionary biology and biodiversity of the blood flukes (superfamily Schistosomatoidea Stiles and Hassall, 1898), but presents a substantial challenge with respect to their conservation status and large size.