Fish tapeworms (Cestoda) in the molecular era: achievements, gaps and prospects

Abstract

The tapeworms of fishes (Chondrichthyes and Actinopterygii) account one-third (1670 from around 5000) of the total tapeworm (Platyhelminthes: Cestoda) species diversity. In total 1186 species from 9 orders occur as adults in elasmobranchs (sharks, rays and chimaeras), and 484 species from 8 orders mature in ray-finned fishes (referred to here as teleosts). Teleost tapeworms are dominated by freshwater species (78%), but only 3% of elasmobranch tapeworms are known from freshwater rays of South America and Asia (Borneo). In the last 2 decades, vast progress has been made in understanding species diversity, host associations and interrelationships among fish tapeworms. In total, 172 new species have been described since 2017 (149 from elasmobranchs and 23 from teleosts; invalidly described taxa are not included, especially those from the Oriental region). Molecular data, however, largely limited to a few molecular markers (mainly 28S rDNA, but also 18S and cox1), are available for about 40% of fish tapeworm species. They allowed us to significantly improve our understanding of their interrelationships, including proposals of a new, more natural classification at the higher-taxonomy level (orders and families) as well as at the lower-taxonomy level (genera). In this review, we summarize the main advances and provide perspectives for future research.

Fish parasites (special issue)

“…The tapeworms of fishes (Chondrichthyes and Actinopterygii) account for one-third of the total cestode species diversity, with more than 500 new species described since 2000. In their review, Tomáš Scholz and Roman Kuchta from the Czech Republic mapped extraordinary progress made in our understanding of the species diversity, host associations and interrelationships among fish tapeworms in the last 2 decades (Scholz and Kuchta, 2022). They pinpoint the importance of molecular data that have helped to significantly improve our knowledge of tapeworm interrelationships, which led to the proposal of several new orders, and host associations, i.e.…”

Molecular Diversity of the Genus Plagiorchis Lühe, 1899 in Snail Hosts of Central Europe with Evidence of New Lineages

“…It plays a crucial role in maintaining ecological processes, promoting interactions among species and contributing to the overall health and adaptability of ecosystems [1]. While research on understanding the biodiversity of free-living organisms has been ongoing for decades, even centuries [2], our understanding of the actual diversity of parasites has only recently begun to unfold thanks to rapid advances in genetic data (e.g., [3][4][5][6][7][8]). Despite the generally negative perception of parasites, largely justified by their potential harm to human and animal health, elucidating the true diversity of parasites is extremely important for several reasons.…”