Khawia japonensis ( Yamaguti, 1934 ) Hsü, 1935

Toma, Scholz, s, P, Gerardo & Leon, erez-Ponce de, 2021, Caryophyllidean tapeworms (Cestoda), Nearctic parasites of fish in Mexico, including description of a new species of Isoglaridacris and the first report of Khawia japonensis, an invasive parasite of common carp (Cyprinus carpio), International Journal for Parasitology: Parasites and Wildlife 15, pp. 70-78 : 76

6. Khawia japonensis ( Yamaguti, 1934) Hsü, 1935 Fig. 3

Synonyms: Caryophyllaeus japonensis Yamaguti (1934) ; Bothrioscolex japonensis ( Yamaguti, 1934) Szidat, 1937 ; Khawia iowensis Calentine et Ulmer, 1961 ; Khawia cyprini Li, 1964

Material studied: Seven specimens misidentified as Khawia sinensis Hsü, 1935 from Cyprinus carpio, Presa Francisco Zarco , Durango, Mexico, collected by David Hern´andez in June and November 2008 (CNHE 6515, 6516; IPCAS C-348) (see P´erez-Ponce de Le´on et al., 2010).

Type host: Cyprinus carpio Linnaeus ( Cypriniformes : Cyprinidae ).

Distribution in Mexico: Durango, Tamaulipas.

Morphological description: Yamaguti (1934 – as Caryophyllaeus japonensis ), Calentine and Ulmer (1961 – as K. iowensis ), Protasova et al. (1990), Scholz et al. (2001, 2011a).

Remarks

Tapeworms found by the present authors in common carp correspond in their morphology to K. japonensis as redescribed by Scholz et al. (2011a). All specimens were immature except a single worm bearing just two eggs in the uterus. The worms were 4.8–10.7 mm long and 0.64–1.23 mm wide at the level of the scolex or at the first third of the body. The scolex is cuneifimbriate, 0.64–1.01 mm wide ( Fig. 3A, B ). Anterior-most testes arranged in two longitudinal row, confluent more posteriorly; posterior-most testes anterior or anterolateral to the cirrus-sac ( Fig. 3A, C ). Anterior-most vitelline follicles begin at the same level as first testes and reach posteriorly as far as to the ovary, with a few follicles present lateral to the ovarian wings, but not continuous with postovarian follicles ( Fig. 3A, C ).

Khawia japonensis was described as Caryophyllaeus japonensis from the common carp, Cyprinus carpio , in Japan and occurred originally in East Asia ( Yamaguti 1934; Protasova et al., 1990; Scholz et al., 2001, 2011a). With the import of common carp throughout the world, the parasite was introduced to North America (described there as Khawia iowensis by Calentine and Ulmer, 1961) and more recently to Europe ( Scholz et al. 2011b, 2018).

Scholz et al. (2011a) considered K. japonensis to be a specific parasite of C. carpio , even though Hoffman (1999) reported non-cyprinid fishes such as bigmouth buffalo, Ictiobus cyprinellus , white sucker, Catostomus commersonii ( Cypriniformes : Catostomidae ), and black bullhead, Ameiurus melas (Rafinesque) ( Siluriformes : Ictaluridae ) as hosts of this parasite in North America. However, these fishes are apparently incidental hosts or other caryophyllidean tapeworms were misidentified.

In North America, K. japonensis occurs in Canada (Manitoba and Ontario) and USA (California, Illinois, Iowa, Kansas, Minnesota, Nebraska, North Dakota, Oklahoma, Oregon, South Dakota, Tennessee, Wisconsin – Scholz et al., 2018). The only previous record of K. japonensis (as K. iowensis ) from Mexico was listed in an Appendix 1 by P´erez-Ponce de Leon´and Choudhury (2005) from unspecified cyprinids from the Rio Grande basin in Mexico. However, no other details about this record were provided. The present specimens confirm the occurrence of K. japonensis in northern Mexico and most likely represent the southernmost record of the parasite (25.270833 S, 103.773056 W).

Khawia japonensis is distinguished from congeneric species, including Khawia sinensis , another parasite of common carp, by the shape of its body, with almost the same width throughout its length, a cuneifimbriate scolex slightly wider than the neck region, the first testes beginning very close posterior to the scolex, usually anterior to the first vitelline follicles ( Fig. 3A, B ), and a few vitelline follicles present lateral to the preovarian uterine loops, with a few isolated follicles lateral to the ovarian arms ( Fig. 3A, C ). Unlike K. sinensis , which is considerably larger (up to 12 cm) and has a wider distribution area ( Oros et al., 2009), the pathogenicity and veterinary importance of K. japonensis for cultured carp are not known.

Figures

Fig. 3. Khawia japonensis (Yamaguti, 1934) from Cyprinus carpio, Durango (CNHE 6516). A – total view, ventrally (median preovarian vitelline follicles omitted except for anterior-most follicles); B – anterior end; C – posterior end, ventrally. Abbreviations: cgp – common genital pore; cs – cirrus-sac; Mg – Mehlis’ gland; ov – ovary; povf – postovarian vitelline follicles; sd – sperm duct (vas deferens); sr – seminal receptacle; te – testes; ug – uterine glands; ut – uterus; va – vagina; vf – vitelline follicles.