Collection and morphological characterization of Gyrodactylus Once at the laboratory, the external body surfaces, fins, and gills of cyprinid hosts were checked for the presence of gyrodactylid parasites using an MST130 stereoscopic microscope. When present, parasite specimens were removed using surgical needles and mounted on slides with a mixture of glycerine and ammonium picrate (GAP) [59]. Monogenean specimens were studied morphologically considering a total of 23 morphological characters, of which four, seven, and one corresponded to the hamuli (also termed anchors), and the ventral and dorsal bars, respectively, and eight and two characters corresponded to the marginal hooks and male copulatory organ (MCO), respectively. The terminology for the haptoral sclerites and the method of measurements follow those of Malmberg [58], Pugachev et al. [78], and Kritsky and Thatcher [50]. Gyrodactylus species were identified using original descriptions available thus far (see the result sections for references). Measurements (given in micrometers as the mean followed by the range and the number of measurements (n) in parentheses) and photographs were taken using an Olympus BX51 phase-contrast microscope and Olympus Stream Image Analysis v. 1.9.3 software (Olympus, Tokyo, Japan). Drawings of the haptoral sclerotized parts were made on flattened specimens using an Olympus BX51 microscope equipped with a drawing tube and edited with a graphic tablet compatible with Adobe Illustrator CS 6 v. 16.0.0 and Adobe Photoshop v. 13.0 (Adobe Systems Inc., San Jose, CA, USA). Prevalence and intensity of infection were calculated according to Bush et al. [8]. Voucher material was deposited in the Helminthological Collection of the Institute of Parasitology, the Biology Centre of the Academy of Sciences of the Czech Republic, České Budějovice (IPCAS) under the accession numbers (see Results section).

Published as part of Rahmouni, Chahrazed, Seifertová, Mária, Bean, Megan G. & Šimková, Andrea, 2024, Intraspecific variation in Gyrodactylus mediotorus and G. crysoleucas (Gyrodactylidae) from Nearctic shiners (Leuciscidae): evidence for ongoing speciation, host-switching, and parasite translocation, pp. 1-14 in Parasite (Paris, France) (Paris, France) 31 (29) on page 3, DOI: 10.1051/parasite/2024023, http://zenodo.org/record/12524595