Haemoprotozoans infecting near-shore catsharks (Elasmobranchii: Scyliorhinidae) off the Western Cape

Abstract

Little is known on blood parasites or haemoprotozoans (haemogregarines and trypanosomes) infecting elasmobranchs worldwide, and knowledge on these parasites in South African cartilaginous fishes is even more limited. Even though haemoprotozoans have been reported infecting two scyliorhinid species off the coast of the Western Cape of South Africa, only one of these has been formally described, Trypanosoma haploblephari Yeld and Smit, 2006 (Trypanosomatida: Trypanosomatidae). Furthermore, descriptions are based entirely on morphology of peripheral blood stages of these parasites. At microscopy level, the available characters that may be used to differentiate parasite species and, even in some cases, genera, are limited, and as such morphological characteristics alone cannot be relied upon. Additionally, some species of Trypanosoma Gruby, 1943 are known for pleomorphism (having more than one form), which limits the use of morphological characters for differentiation even further. Over the last decade, there has been increased effort to use molecular characteristics in the description and differentiation of haemoprotozoans to genus and species levels. However, until recently, this effort has been largely focused on the haemoprotozoans of other vertebrate groups (mammals, birds, reptiles, and amphibians). With these groups, the combination of both morphological and molecular characteristics has greatly aided in determining the phylogenetic placements, thus the identity and taxonomy of these parasites, which in turn has aided in assessing their biodiversity. Haematophagous vectors such as leeches (for both trypanosomes and haemogregarines) and gnathiid isopods (for some haemogregarines) have been implicated in the transmission of these parasites. Within the framework of this project, we assessed the species diversity of haemoprotozoans infecting near-shore scyliorhinids off the Western Cape. This study aimed to provide both morphological descriptions and molecular characterisation of these parasites, aiding in formal descriptions, phylogenetic placement and thus taxonomic identity, which will assist in determining their biodiversity in these catsharks from this region. Four shark species were targeted including the dark shyshark Haploblepharus pictus (Müller and Henle), the puffadder shyshark Haploblepharus edwardsii (Schinz), pyjama catshark Poroderma africanum (Gmelin) and the leopard catshark Poroderma pantherinum (Müller and Henle). Blood collected was used for both the preparation of blood smears, to study morphology (presence, identity and parasitaemia of haemoprotozoans), and a volume fixed in 70% ethanol for molecular work. A subset of samples (those with high parasitaemias) was selected for molecular and phylogenetic analysis. Of the 98 shark individuals screened, 45 (96 %) of H. pictus, 13 (100 %) of H. edwardsii, 15 (63 %) of P. africanum and 14 (100 %) of P. pantherinum were infected with trypanosomes. While the individuals of H. pictus and H. edwardsii were parasitised by a trypanosome identifying morphologically with T. haploblephari, individuals of P. africanum and P. pantherinum were parasitised by an unknown morphotype of Trypanosoma.