Plagiorhynchus (Plagiorhynchus) charadrii ( Yamaguti, 1939 )

Dimitrova, Zlatka, 2009, Acanthocephalans of the nominotypical subgenus of Plagiorhynchus (Plagiorhynchidae) from charadriiform birds in the collection of the Natural History Museum, London, with a key to the species of the subgenus, ZooKeys 6 (6), pp. 75-90 : 82-83

Plagiorhynchus (Plagiorhynchus) charadrii ( Yamaguti, 1939)

Van Cleave & Williams, 1951

Material studied. BMNH 1965.931-937, from the small intestine of Charadrius alexandrinus nihonensis Deignan, Pescadore Islands , Taiwan, whole-mount of 2 specimens (1 slide).

Description ( Fig. 3 )

Based on 2 male specimens.

Males. Trunk elongate, almost cylindrical but tapering both anteriorly and posteriorly, 3.7-4.0 long, 0.9-1.1 wide. Numerous amoeba-shaped hypodermal nuclei. Proboscis cylindrical (in both specimens invaginated to different degrees, i.e. anterior third in first specimen and anterior two-thirds in other), c.0.93-0.95 long, 0.23 wide. Proboscis armament consists of 18 longitudinal rows of 12-13 hooks (anterior hooks invaginated) (in 1 specimen). Most of hooks with posteriorly directed roots; only pos- teriormost 4 (3) hooks spiniform with short apophyses. Length of first 8 (9) hooks – blade 52-59 µm, root 29-49 µm; length of last 4 (3) spiniform hooks – 42-52 (54) µm, root 12-22 µm. Neck short, c.0.13 long, 0.25 wide. Proboscis receptacle doublewalled, 1.5 long, 0.26 wide. Lemnisci band-shaped, c.1.5 long, c.0.05 wide (only 1 measured). Testes spherical, 0.26-0.32 long, 0.23-0.35 wide, situated in tandem in middle of trunk, at c.0.06 from one another; anterior testis 0.14 from tip of proboscis receptacle. Cement glands 6 in number, tubular, arranged in 2 groups of 3; longest cement gland of first group (1.70 long) present immediately posterior to anterior testis; remaining 2 cement glands slightly further posterior, 1.44 and 1.01 long; 2 of cement glands of second group present posterior to hind testis, 1.35 long, with remaining cement gland slightly further posterior, 1.03 long. Genital bursa (everted in 1 specimen) 0.55 long, 0.45 wide.

Remarks. Despite the partial invagination of the proboscis, we identified these specimens as Plagiorhychus charadrii based on the number of the longitudinal rows and morphometric data from both the hooks (especially the posterior three or four hooks) and of some internal organs (testes and cement glands). When comparing the present morphometric data with those from published descriptions ( Yamaguti 1939; Johnston and Edmonds 1947; Schmidt and Kuntz 1966; Belopol’skaya 1983; Amin et al. 1999; Dimitrova et al. 1999), we did not find significant differences, although differences in the maximum length of the hook blade are apparent. Regarding the latter feature, the studied specimens are most similar to the descriptions given by Yamaguti (1939), Schmidt and Kuntz (1966) and Dimitrova et al. (1999), i.e. 60-63 versus 59 µm in present specimens. However, Johnston and Edmonds (1947) and Belopol’skaya (1983) reported smaller lengths for the hooks, i.e. 29 and 54 µm, respectively.

This species was described from Charadrius dubius curonicus Gmelin in Japan ( Yamaguti 1939) and later recorded, mainly from charadriiform birds, in the Australian Region (Australian mainland and Tasmania) ( Johnston and Edmonds 1947; Amin et al. 1999; Smales 2002, 2003), the Palaeotropical Region ( Taiwan and the Pescadore Islands) ( Schmidt and Kuntz 1966; Amin et al. 1999), the Palaearctic Region ( Japan, Russian Far East, Kazakhstan, the Ukraine and Bulgaria) ( Lisitsina 1992; Amin et al. 1999; Dimitrova et al. 1999; Araki 2003), the Oceanic Region (Hawaii) ( Amin et al. 1999) and the Neotropical Region ( Belize) ( Canaris and Kinsella 2001).

Figures

Fig. 3. Plagiorhynchus (Plagiorhynchus) charadrii (Yamaguti, 1939). A. Male, general view. B. Proboscis. C. Longitudinal rows of hooks (lateral view) and some posterior hooks (frontal view). Scale-bars: A, 1.0 mm; B, 0.2 mm; C, 0.1 mm.