Nybelinia surmenicola, Okada in Dollfus, 1929

Katahira, Hirotaka, Shirakawa, Hokuto & Nagasawa, Kazuya, 2014, Five Trophically-transmitted Parasites from Adult Arctic Lampreys Lethenteron camtschaticum (Petromyzontiformes: Petromyzontidae): Biological Indicators of the Host’s Marine Life as a Predator, Species Diversity 19, pp. 157-165 : 161

Nybelinia surmenicola (Okada in Dollfus, 1929) ( Trypanorhyncha : Tentaculariidae ) ( Fig. 1C–D )

Description. Ten plerocercoids (NSMT–Pl 6137, 6138a, b) examined. Scolex 7,400 –10,475 (9,335) long, with maximum width in bothridial region 2,900 –3,800 (3,295) and at muscular rings 2,675 –3,375 (3,048). Bothridia extending along 3,800 –4,700 (4,198) of anterior region of scolex. Velm 1,700 –4,500 (3,538) long. Strobila 2,700 –5,950 (4,665) long. Tentacles 2,220 –2,600 (2,440) long, with maximum width in basal region 100–183 (153), in metabasal region 80–143 (121) (n =9), and in apical region 75–115 (96) (n =4). Tentacular armature homeoacanthous-homeomorphous; minimum length of basal hook 17–23 (20.2), with root 15–20 (18.4), maximum length of metabasal hook 32–44 (40.4) (n =9), with root 28–38 (32.8), and maximum length of apical hook 42–48 (44) (n =4), with root 22–29 (25). Number of half spiral rows of hook in basal part 8–9, in metabasal part 8–9 (n =9), and in apical part 7–8 (n =4). Tentacle sheath 4,000 –4,825 (4,405)×50–140 (93) in length and width. Muscular rings in base of tentacle sheath. Bulbs 1,030 –1,330 (1,170)×300–460 (363) in length and width.

Remarks. The homeoacanthous-homeomorphous hook arrangements and the tight spacing of the hooks is the specific characters of N. surmenicola (see Palm 2004). This species resembles Nybelinia sakanariae Palm, 1999 but can be discriminated from it by the larger scolex of more than 4,000 µm in length ( Palm 2004). The present specimens are therefore considered to be conspecific with N. surmenicola .

This cestode is widely distributed in the North Pacific ( Palm 2004), with a complex life-cycle that includes euphausiid crustaceans as intermediate hosts, squid and teleosts as paratenic hosts, and the salmon shark Lamna ditropis Hubbs and Follett, 1947 as the definitive host ( Shimazu 1975a,b, 1999). The Japanese common squid Todarodes pacificus (Steenstrup, 1880) and gadid fishes are frequently and heavily infected with N. surmenicola in Japanese waters ( Nagasawa 1993a,b).

Figures

Fig. 1. Endoparasites from adult Arctic lampreys Lethenteron camtschaticum (Tilesius, 1811) from the Ishikari River, Hokkaido. A, Brachyphallus crenatus (Rudolphi, 1802); B, Lecithaster gibbosus (Rudolphi, 1802); C, Nybelinia surmenicola (Okada in Dollfus, 1929); D, metabasal armature of a tentacle of N. surmenicola; E, tetraphyllidean plerocercoid; F, male specimen of Bolbosoma sp.; G, female specimen of Bolbosoma sp. Scale bars: A–B, 500µm; C, E–G, 2mm; D, 50µm.