Gyrodactylus molweni, Christison & Vaughan & Shinn & Hansen, 2021

Christison, Kevin W., Vaughan, David B., Shinn, Andrew P. & Hansen, Haakon, 2021, Gyrodactylus molweni sp. n. (Monogenea: Gyrodactylidae) from Chelon richardsonii (Smith, 1846) (Mugilidae) from Table Bay, South Africa, International Journal for Parasitology: Parasites and Wildlife 15, pp. 87-94 : 89-91

3.1. Gyrodactylus molweni sp. n.

Type-host: Chelon richardsonii (Smith, 1846)

Site of infection: Skin and fins.

Type locality: Victoria and Alfred Waterfront , Table Bay Harbour , Cape Town, South Africa

(- 33.905571 ◦ S, 18.420845 ◦ E)

Environmental parameters on collection: Dissolved oxygen = 75.9%,/ 6.3 mg /L, temperature = 13.8 ◦ C, salinity = 35.8‰, and pH = 7.97.

DNA reference sequences: A 985 bp DNA reference sequence covering the 18S (12 bp), ITS 1 (381 bp), 5.8S (157 bp), ITS 2 (393 bp) and partial 28S (42bp) are deposited in GenBank under accession number FJ040182.

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Type material: The holotype ( NHMUK 2021.4.15.1) and two paratypes ( NHMUK 2021.4.15.2-3) are deposited in the Parasitic Worms collection of the Natural History Museum , London. Further paratypes are deposited in the South African Museum, Cape Town, South Africa ( SAMCT A093740-44 ) and in the Helminthological collection of the Institute of Parasitology, Ceske ˇ´Budˇejovice Czech Republic ( IPCAS M-757 ) .

ZooBank registration: The Life Science identifier for Gyrodactylus molweni sp. n. is urn:lsid:zoobank.org:act:2DCFE189-46BD-4E74-8A81-59532D4422C1 .

Etymology: Named for the general greeting ‘ molo ’ (single person), ‘ molweni ’ or ‘ molweni nonke ’ (multiple people) in the local African Xhosa language. The name is proposed as a salutation to the parasites found on this commercially important native species of fish.

Description ( Figs. 1–3 )

Coverslip-flattened specimens 257.2 ± 19.1 (227–282, n = 25) long,

72.3 ± 8.00 (63–86, n = 25) wide at the level of the uterus. Intestinal crura extend to the posterior end of uterus when the uterus is occupied with a well-developed embryo; when the uterus is empty, the crura extend as far as the testis. Haptor approximately circular 52.9 ± 3.6 (48–61, n = 25) long, 47.5 ± 5.3 (39–59, n = 25) wide. The pharyngeal bulb measures 21.6 ± 5.5 (15–30, n = 12) long × 25.5 ± 4.8 (19–33, n = 12) wide across the anterior bulb; 22.2 ± 3.8 (18–28, n = 12) long × 25.3 ± 6.5 (18–32, n = 12) wide across the posterior bulb. Male copulatory organ (MCO) spherical positioned posterior to the posterior pharyngeal bulb. MCO bulb diameter 11.7 ± 0.4 (11–12, n = 4). MCO armature consists of one principal spine and four smaller spines arranged in a single row, the outer two larger than the central pair. Hamulus total length 45.3 ± 2.1 (42–48, n = 24); hamulus shaft length 31.7 ± 2.5 (27–38, n = 24); proximal shaft width 7.6 ± 1.5 (5–11, n = 24); point length 22.4 ± 1.4 (19–24, n = 24). Hamulus aperture 16.0 ± 1.4 (13–19, n = 24); outer aperture angle 33.3 ± 2.2 ◦ (29–37 ◦, n = 24);

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inner aperture angle 38.9 ± 3.1 ◦ (33–44 ◦, n = 24). Hamulus distal shaft width 3.8 ± 0.5 (3–5, n = 24); root length 13.8 ± 2.4 (10–19, n = 24). Dorsal bar simple, 1.9 ± 0.3 (1–3, n = 16) wide by 17.5 ± 2.2 (14–21, n = 16) long. Ventral bar with conspicuous bilateral processes 33.4 ± 2.6 (29–39, n = 23) long, 25.2 ± 1.5 (22–28, n = 24) wide; ventral bar process to mid-length 11.4 ± 0.6 (10–13, n = 24); ventral bar median length 5.7 ± 0.4 (5–7, n = 25); ventral bar processes 8.5 ± 1.0 (6–10, n = 24) long; ventral bar membrane rhomboid, 16.1 ± 1.5 (13–20, n = 23) long. Total length of marginal hooks 20.1 ± 1.3 (17–22, n = 16); marginal hook shaft 16.0 ± 1.2 (13–18, n = 16) long; marginal hook sickle proper 4.6 ± 0.3 (4–5, n = 21) long with sickle proximal width 3.8 ± 0.3 (3–4, n = 21); toe length 1.4 ± 0.3 (1–2, n = 21); sickle distal width 2.7 ± 0.3 (2–3, n = 21); sickle aperture 3.6 ± 0.4 (3–5, n = 21); instep/arch height 0.6 ± 0.1 (0.4–0.8, n = 18).

Figures

Fig. 1. Gyrodactylus molweni sp. n. A. The haptoral central hook complex of hamuli (ham), dorsal (db) and ventral (vb) bars. B. Hamulus. C. Ventral bar (vb) which for this species bears large ventral bar processes (vbp) and a rhomboid-shaped ventral bar membrane (vbm). D. Male copulatory organ bearing a single principal spine (ps) and then a single row of four small spines, the outer two larger than the central pair. E. Marginal hook. Scale Bars = 10 μm.

Fig. 2. Light micrographs of the attachment hooks of Gyrodactylus molweni sp. n. A. The haptoral central hook complex of hamuli, and ventral bar. B. Hamulus. C. Marginal hook. Scale Bars = 10 μm.

Fig. 3. Comparison of the marginal hook sickle of Gyrodactylus molweni sp. n. (dotted outline) with those of Gyrodactylus species described from various mullet species and with a number of closely related species. Each pair of marginal hook sickles are aligned by their inner curved faces. A. G. molweni sp. n.; B. G. arcuatus Bychowsky, 1933 (drawn from a scanning electron micrograph of liberated hooks from specimens parasitizing Gasterosteus aculeatus L.); C. G. arcuatoides Huyse, Malmberg and Volckaert, 2004 (redrawn from Huyse et al., 2004); D. G. branchialis Huyse, Malmberg and Volckaert, 2004 (redrawn from Huyse et al., 2004); E. G. flavescensis Huyse, Malmberg and Volckaert, 2004 (redrawn from Huyse et al., 2004); F. G. gondae Huyse, Malmberg and Volckaert, 2004 (redrawn from Huyse et al., 2004); G. G. mugelus Rawson, 1973 (redrawn from Rawson, 1973); and, H. G. zhukovi Ling, 1963 (redrawn from Miroshnichenko and Maltsev, 1998).