Authors
G Oosthuizen3; A A Acosta2; N J Smit1; B C Schaeffner1; 1 North-West University Water Research Group, South Africa; 2 Water Research Group, Unit for Environmental Sciences and Management, North-West University, Potchefstroom, South Africa; 3 North West University, South Africa Discussion
Trypanorhynch cestodes resemble the most species-rich order infecting elasmobranchs. During a recent parasitological investigation of the spotted skate (Raja straeleni Poll) off the south coast of the Western Cape (South Africa), an unidentified species of Grillotia Guiart, 1927 was discovered (among several other unidentified species belonging to different cestode orders). After thorough examination using morphological and molecular approaches, the description of a species new to science was provided (published in Parasitology International, 2021, doi: 10.1016/j.parint.2021.102307). Grillotia sasciae is the first species of the genus from southern African waters and, interestingly, the first record of the order Trypanorhyncha from the spotted skate. Numerous trypanorhynch cestodes have been described worldwide, however, only 11 species have been reported from South Africa. Most of the Grillotia species from the Atlantic Ocean were reported from the northern Atlantic while fewer reports were recorded from the southwestern Atlantic off the coast of Argentina. Observation of a single host species and detecting a so far hidden biodiversity aspect illustrates the possibility of finding additional species infecting elasmobranchs in the southern Atlantic, and, particularly, the waters off southern Africa. It also illustrates the current lack of knowledge on marine parasites of elasmobranchs in general. Among this group of apex predators, batoid rays have been particularly neglected in scientific sampling endeavors. In the global framework of biodiversity science, the new South African species found within a single host species resembles only the tip of the iceberg when considering the cestode diversity that still awaits scientific discovery. In these times of decreasing host populations and continuous increase in extinction risk for many, particularly near-shore and endemic elasmobranch species, it becomes of utmost importance to incorporate parasite species together with their threatened host species in future conservation programs. This new approach to future conservation agendas is further supported by the fact that the majority of threatened parasite species may in fact be lost before they were even discovered. 
