Plagiorhynchus (Plagiorhynchus) odhneri Lundström, 1942

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 : 79-81

Plagiorhynchus (Plagiorhynchus) odhneri Lundström, 1942

Material studied. [All labelled as P. crassicollis .] BMNH 1946.5.14.121-122, from small intestine of Charadrius hiaticula , Orkney Islands, Scotland, wet material (3 specimens); BMNH 1936.8.17.124-140 (1 immature female), from small intestine of C. hiaticula, Weymouth , Dorset, England, wet material; BMNH 1951.12.12.34, from small intestine of Haematopus ostralegus Linnaeus, Holy Island (adjacent to Isle of Arran), Scotland, wet material (1 specimen).

Description ( Fig. 2 )

Based on 1 male and 1 female specimen and 1 metasoma (female) from BMNH 1946.5.14.121-122.

Male. Length of trunk (deformed) 4.0. Proboscis cylindrical, situated at angle to trunk axis, 0.68 long, 0.15 wide. Proboscis armament consists of 20 longitudinal rows of 16-17 hooks per row. Length of first 9 (10) hooks – blade 32-42 µm, root 34-37 µm; length of next 3 hooks – blade 25-27 µm, root 25-34 µm; length of last 3 hooks – blade 22 µm, root 15-20 µm. Neck trapezoidal, 0.18 long, 0.13-0.22 wide. Proboscis receptacle 0.6 long, 0.2 wide. Lemnisci 1.3 (1.4) long, 0.1-0.11 wide. Testes not clearly seen; anterior testis at c. 1.12 from tip of proboscis receptacle. Length of cement glands c.0.80.

Female. Trunk elliptical, oval to fusiform, 4.4-5.6 long, 1.9-2.2 wide. Proboscis cylindrical, situated at angle to trunk axis, 0.76 long, 0.19 wide. Proboscis armament consists of 17 longitudinal rows of 15-16 hooks per row. Length of first 9 (10) hooks – blade 37-49 µm, root indistinct; length of next 2-3 hooks – blade 29-32 µm, root indistinct; remaining 4 hooks could not be measured. Neck withdrawn. Proboscis re- ceptacle and lemnisci indistinct. Genital pore at 0.2 from end of trunk. Eggs elongateoval, shuttle-shaped, with polar prolongations, 93-115 × 20-39 µm.

Additional data. Based on 1 immature specimen from C. hiaticula and 1 specimen from Haematopus ostralegus . Trunk of immature specimen 3.6 long, 1.4 wide. Proboscis cylindrical, situated at angle to trunk axis, 0.76 long, 0.17 wide. Proboscis armament consists of 18 longitudinal rows of 15-16 hooks in each row. Length of first 9-10 hooks – blade 36-43 µm, root 39-44 µm; length of next 2-3 hooks – blade 27-32 µm, root 27-39 µm; length of last 3 hooks 22-27 µm, root 20 µm (for hooks XIV-XV). Trunk of female specimen c.4.0 long, 1.55 wide. Proboscis 0.8 long, 0.15 wide.

Remarks. Lundström (1942) described this species from Haematopus ostralegus in Sweden. Golvan (1956) considered it to be a variety of P. crassicollis and later ( Golvan 1960) as a subspecies. In the taxonomic arrangement of the nominotypical subgenus of Plagiorhynchus proposed by Schmidt and Kuntz (1966) and Amin (1985), this species is missing. According to other authors ( Petrochenko 1958; Yamaguti 1963; Khokhlova 1986; Golvan 1994), P. odhneri is a valid species. Lisitsina (1992) redescribed it on the basis of specimens from Charadrius dubius Scopoli and C. alexandrinus L. in the Ukraine.

Unfortunately, the type material of this species was not available for re-examination during the course of the present study. The studied specimens were identified as P. odhneri mainly on the basis of the proboscis armature (especially with regard to the number of hooks in each longitudinal row). The armature (17-20 longitudinal rows of 15-17 hooks) recorded in the present study is within the limits of variation reported by Lundström (1942) in the original description (18-19 longitudinal rows of 14-18 hooks) and by Lisitsina (1992) (18-22 longitudinal rows of 15-19 hooks).

In comparison with the previous descriptions ( Lundström 1942; Lisitsina 1992), I found some differences. These mainly concern the shape and measurements of the trunk. The present specimens possess an almost oval trunk (only the female metasoma is spindle-shaped) with measurements of 4.0 ×? (male) and 4.4-5.6 × 1.9-2.2 mm (female) versus an almost spindle-shaped trunk measuring 5.0-8.4 × 0.8-1.7 (male) and 9.0-11.0 × 1.7-2.4 mm (female), as described by Lundström (1942), and an almost cylindrical trunk measuring 3.57-6.58 × 0.96-1.58 (male) and 8.76-12.53 × 1.10-1.23 mm (female), according to Lisitsina (1992). With regard to these characters, our specimens are close to P. crassicollis (see above), as described by Lühe (1911), with an oval trunk and measurements of 5.0 × 1.6-1.8 (male) and 7.0 × 3.0 mm (female).

In addition, the proboscis of our worms is shorter, i.e. 0.68 (male) and 0.76-0.8 mm (female) compared with 0.8 (male) and 0.9-1.1 mm (female) as recorded by Lundström (1942). However, it is longer than the proboscis of P. crassicollis (0.6 mm) ( Lühe 1911). Lisitsina (1992) reported wider limits of variation for this character (0.68-1.23 mm in both sexes), and our specimens fit within this morphometric range. More abundant material is needed to assess the variation within P. odhneri and to confirm its validity.

P. odhneri has previously been reported from Charadrius hiaticula and Haematopus ostralegus in the United Kingdom ( Williams 1961; Threlfall 1963). Other records are from charadriiform birds in Sweden, Russia (White Sea coast), the Ukraine and Bulgaria ( Lundström 1942; Belopol’skaya 1983; Lisitsina 1992; Hansson 1997; Dimitrova et al. 2000).

Figures

Fig. 2. Plagiorhynchus (Plagiorhynchus) odhneri Lundström, 1942. A. Female, general view. B. Female, anterior end of trunk. C. Female, posterior end of trunk with terminal genital tract. D. Male, anterior end of trunk. E. Female, longitudinal row of hooks (lateral view). Scale-bars: A, 1.0 mm; B, C, D, 0.2 mm; E, 0.1 mm.