Fish cestodes of the Karadag nature reserve and adjacent water areas of the Black Sea

The first data on marine fish parasites in Karadag nature reserve water area were published at the beginning of the 20th century. By the beginning of the 21st century, information on the fauna of cestodes in this area of the Black Sea included data on 19 species recorded in 24 fish species. However, taxonomy of this class of helminths has changed significantly over the last decade, and regional fauna needs to be revised. The aim of this work is to revise the species composition of fish cestodes in the water area of the Karadag nature reserve and adjacent areas on the basis of new data obtained and in accordance with current systematics of Cestoda. The material for this study was the collections of cestodes gathered by the staff of IBSS RAS Environmental Parasitology Department in the area of the Karadag nature reserve in different years, as well as our own collections of 1754 specimens of rays and teleosts of 53 species (2005–2018). The area studied is Black Sea coastal area from Meganom Cape to Ordzhonikidze village (southeastern part of Crimea), including various marine biotopes of the Karadag nature reserve. Voucher preparations of all types of cestodes used in this study were deposited in a subcollection of marine parasites of the World Ocean hydrobionts collection of IBSS RAS. Totally 20 cestode species were found in 17 fish species. Nine species, namely Progrillotia dasyatidis, Parachristianella trygonis, Dollfusiella aculeata, Rhinebothrium walga, Caulobothrium sp., Rhabdotobothrium sp., Acanthobothrium sp. 5, 7, and Anthocephaliidae gen. sp. 2., were reported for the common stingray Dasyatis pastinaca in the area under study for the first time. Cestodes belonging to the new species Acanthobothrium sp. 1, 2, 4 were found in the thornback ray Raja clavata. Of 19 species previously known in Karadag area, only 8 adult mature cestodes were recorded: “Bothriocephalus scorpii”, “B. gregarius”, Echinobothrium typus, Grillotia erinaceus, Prochristianella papillifer, Echeneibothrium variabile, Cairaeanthus ruhnkei, and C. healyae. In addition, larvae of the complex species “Scolex pleuronectis” were found in teleost fish. Larvae of cestode Progrillotia dasyatidis were found for the first time in the water area studied in 8 teleost fish species; this data contribute to the information on the participants in the life cycle of this helminth. Four cestode species, namely Hepatoxylon trichiuri larvae, Nybelinia lingualis larvae, Tetrarhynchobothrium tenuicolle, and Anthobothrium cornucopia, which were previously reported from this area, were not found in the present survey. Moreover, recent analysis of the occurrence and synonymy of species of orders Trypanorhyncha and Onchoproteocephalidea revealed that the previous identification of the cestodes in elasmobranchs as Grillotia (Christianella) minuta and Acanthobothrium coronatum, as well as identification of the cestodes in teleosts as Tentacularia sp. larvae, is incorrect due to the absence of their specific definitive hosts in the Black Sea. On the other hand, among representatives of Acanthobothrium spp. registered in D. pastinaca and R. clavata in Karadag water area, we found 7 morphologically different new taxa identified to the species level. The cestodes found belong to 6 orders: Bothriocephalidea, Diphyllidea, Trypanorhyncha, “Tetraphyllidea” relics, Rhinebothriidea, and Onchoproteocephalidea. The most species diversity of cestodes in both species of rays is registered among representatives of the orders Trypanorhyncha and Onchoproteocephalidea (5 species each), the least – in the orders Diphyllidea and “Tetraphyllidea” relics (1 species each). Thus, 12 species were added to the fauna of the cestodes parasitizing fish in Karadag area, and 8 of them are obviously representatives of new taxa.