Gyrodactylus crysoleucas Mizelle and Kritsky, 1967

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, Parasite (Paris, France) 31 (29), pp. 1-14 : 5-6

Gyrodactylus crysoleucas Mizelle and Kritsky, 1967

( Figures 1A–1B )

Previous records: golden shiner, N. crysoleucas, Rooney Pond , 17 miles east of Sacramento, California, USA [ 65]; captive N. crysoleucas , private baitfish, Minnesota [ 55], both in the USA.

Present study: blacktail shiner, C. venusta , West Mud Creek, Neches River, Texas, USA

Site of infection: fins

Prevalence and intensity of infection: 2.9%, a single infected host out of 34 investigated, two Gyrodactylus specimen on a single infected host.

Voucher: IPCAS M- 795

Host GenBank accession number: cyt- b: PP314044– PP314045

Parasite GenBank accession numbers: 18S rDNA: PP309996; ITS: PP309998

Morphology: Haptor subcircular, anchor base with folds, tips curved inward, total length 51.6 (51.2–51.9; n = 2); shaft slightly bowed, length 39.6 (39–40.3; n = 2); point curved and elongate, length 22.9 (22.5–23.4; n = 2); root relatively short, tapered, length 14.3 (13.1–15.5; n = 2). Ventral bar with short, blunt lateral processes extending out of bar, total length 23.1 (23–23.2; n = 2), total width 22.9 (22.7–23.1; n = 2), lateral processes length 2 (1.5–2.5; n = 2), distance between tips 22.4 (21.5–23.3; n = 2), median width 5.3 (5.2–5.3; n = 2), membrane (shield) almost trapezoid tapering posteriorly and extending almost 1/2 of length of anchor shaft, no striations or ridges were observed, length 15 (13.8–16.2; n = 2), width at the insertion 12.8 (12.3–13.4; n = 4). Dorsal bar straight with projections near each end, attenuated ends inserted into terminal plates, total length 21.9 (19.4–24.4; n = 2), width at midpoint 2.5 (2.2–2.7; n = 2). Marginal hooks total length 25.6 (25.1– 26.1; n = 2); sickle foot noticeable with downward globose heel, prominent triangular toe, conspicuous shelf; sickle proper almost as thick as toe base, shaft length 5.2 (4.9–5.5; n = 2); sickle length to shaft attachment 3.5 (3.4–3.5; n = 2); sickle proximal width 2.9 (2.6–3.2; n = 2); sickle distal width 3.7 (3.6–3.8; n = 2); point relatively thin and slightly curved, length 1.5 (1.3–1.8; n = 2); filament loop extending about 1/2 of handle length, length 8.9 (8.3–9.5; n = 2); handle length 20.8 (19.9–21.6; n = 2). MCO not found.

Considering the original study by Mizelle and Kritsky [ 65], our specimens presented relatively (i) shorter anchors (51.2–51.9 µm in this study vs. 55–61 µm in the original description), and (ii) a shorter ventral bar (23–23.2 µm in this study vs. 25–32 µm in the original description). The shape of the marginal hooks was similar with a downward heel and prominent finger-like toe and shelf, but with a slightly thinner shaft of the sickle proper in the case of our specimens. Photographs published by Leis et al. [ 55] provided more details about the morphology of the haptoral sclerotized structures of G. crysoleucas and indicated that our specimens parasitizing C. venusta sampled in its natural southcentral range and those found on cultured N. crysoleucas in Minnesota were of a similar shape, and that measurements of the hard parts mostly overlapped.

Figures

Figure 1. Photomicrographs (A) and line drawings (B) of Gyrodactylus crysoleucas from the blacktail shiner, Cyprinella venusta.