Plagiorhynchus (Plagiorhynchus) crassicollis (Villot, 1875) Lühe, 1911

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 : 76-79

Plagiorhynchus (Plagiorhynchus) crassicollis (Villot, 1875) Lühe, 1911

Syn. Plagiorhynchus lanceolatus (von Linstow, 1876) Lühe, 1911

Material studied. BMNH 1928.2 .17.91, from small intestine of Charadrius hiaticula L., Great Britain (detailed locality data not known), whole-mount of 2 specimens (1 slide) (material listed by Baylis, 1928) ; BMNH 1936.8.17.124-140, from small intestine of C. hiaticula, Weymouth , Dorset, England, wet material (material listed by Baylis 1939) .

Description ( Fig. 1 )

Based on 10 male and 12 female specimens from Charadrius dubius, Weymouth , Dorset, England (BMNH 1936.8.17.124-140).

General. Trunk elliptical, almost ovoid, narrowing posteriorly. Transverse vessels of lacunar system form dense reticulum of large polygons. Proboscis cylindrical, situated at angle to axis of trunk. Proboscis armament consists of 19-20 longitudinal rows of 13-14 (12) hooks; first 8 (9) hooks longest, next 2 smaller and last 3 hooks smallest; all hooks with posteriorly directed roots. Neck short (partly or completely withdrawn in some specimens), trapezoidal. Proboscis receptacle doublewalled. Lemnisci band-shaped (bifurcate in single specimen), longer than proboscis receptacle.

Male. Trunk 2.4-5.2 long, 1.0-1.64 wide. Proboscis (completely everted in only 2 specimens) 0.56-0.62 long, 0.16 wide. Length of first 8 hooks – blade 32-42 µm, root 32-44 µm; length of next 2 hooks – blade 29 µm, root 25-32 µm; length of last 3 hooks – 25-27 (29) µm, root 13-22 µm. Neck (in 2 specimens) c.0.1 long. Proboscis receptacle 0.70-0.95 long and 0.16-0.25 wide. Lemnisci 1.0-2.6 long, 0.09-0.15 wide. Testes oval to spherical, 0.30-0.80 long, 0.23-0.41 wide, situated in tandem and slightly overlapping one another, in middle region of trunk. Cement glands 6 in number, of different lengths, 0.30-0.95 long, situated immediately posterior to hind testis. Duct of cement glands 0.35-0.65 long. Genital bursa (everted in single specimen) 0.25 long, 0.30 wide.

Female. Trunk 2.64-7.0 long, 1.21-2.9 wide. Proboscis (completely everted in only 2 specimens) 0.66-0.7 long, 0.17-0.19 wide. Length of first 8 (9) hooks – blade 37-44 (49) µm, root 34-54 µm; length of next 2 hooks – blade 34-39 µm, root 27-39 µm; length of last 3 hooks blade – 17-29 µm, root 15-27 µm. Neck 0.15-0.17 long. Proboscis receptacle 0.72-1.1 long, 0.24-0.27 wide. Lemnisci 1.0-1.9 long, 0.1-0.13 wide. Female genital tract c.1.2-1.45 long. Vagina provided with 2 sphincters. Genital pore slightly subterminal, at 0.06-0.12 from posterior end of trunk. Fully-developed eggs were observed in 4 specimens (5.1-7.0 long). Eggs elongate-oval, shuttle-shaped, with polar prolongations, 91-134 (135) × 25-42 µm.

Additional data. (based on 2 male specimens from C. hiaticula , BMNH 1928.2.17.91). Trunk 4.0- 4.7 in length, 1.4-1.55 wide. Proboscis 0.48-0.5 long. Proboscis armament consists of 20 longitudinal rows of 11-12 hooks in each row. Measurements and morphology of hooks are similar to material from Dorset. Neck very short (40-63 µm long). Testes spherical, 0.60-0.65 long, 0.75-0.87 wide. Cement glands 0.55-1.0 long.

Remarks. There are only a few descriptions of this species ( Lühe 1911; Petrochenko 1958; Belopol’skaya 1983; del Valle and Coy Otero 1990). Only female specimens were described by Petrochenko (1958) from Phalaropus lobatus (L.) [= P. hyperboreus (L.)] in Kazakhstan. Compared to previous descriptions of the same species ( Lühe 1911; Belopol’skaya 1983), the specimens from Kazakhstan differ in the shape and the length of the trunk (elongate-cylindrical and 17 mm long versus oval and c. 7 mm long), the shape of the proboscis (oval versus cylindrical) and the number of longitudinal rows of hooks (16 longitudinal rows of hooks versus 18-20). In addition, there are differences in the dimensions of the eggs: 84 × 16 µm ( Petrochenko 1958) versus 110 × 49 µm ( Lühe 1911). Consequently, it seems likely that the specimens from Kazakhstan described by Petrochenko (1958) belong to another species.

Del Valle and Coy Otero (1990) reported P. crassicollis from Charadrius wilsonia wilsonia Ord in Cuba. According to their description, the armature of the proboscis consists of 18 longitudinal rows of 10-11 hooks per row. However, judging by the drawing of the proboscis (figure 1c in del Valle and Coy Otero 1990), the number of hooks per row is at least 18.

Comparing the morphometric data of the present specimens with the descriptions of Lühe (1911) and Belopol’skaya (1983), there are several differences. The maximum number of hooks per longitudinal row in the specimens studied is greater, i.e. 11-14 versus 11-12 ( Lühe 1911) or 13 ( Belopol’skaya 1983). The male specimens among our material (see ‘Additional data’ above) are in close accordance with the description of Lühe (1911); however, they have a smaller proboscis, i.e. 0.48-0.50 versus 0.60 mm. A difference in the females relates to the size of eggs, which are larger in our specimens, i.e. 91-134 × 25-42 µm compared to 110 × 49 µm ( Lühe 1911) and 88-102 × 27-34 µm ( del Valle and Coy Otero 1990).

One immature female from the same host specimen (Dorset material) possesses a longer proboscis (0.76 mm) and a greater number of hooks per row (15-16). According to these characters, we consider it as belonging to Plagiorhynchus odhneri Lundström, 1942 (see ‘Additional data’ for P. odhneri ).

P. (P.) crassicollis was previously reported from Charadrius hiaticula (= Aegialitis hiaticula ) in the United Kingdom ( Baylis 1928, 1939), once apparently in a mixed infection with P. odhneri (see below). It is mainly a parasite of charadriiform birds throughout the western Palaearctic [( Germany, France, Sweden, Switzerland, Ukraine, Russia (the White and Baltic Sea coasts)] ( Lühe 1911; Belopol’skaya 1983; Hansson 1997; Reimer 2002; Gibson 2004). There are also occasional records from the Nearctic [ Greenland ( Hansson 1997)] and Neotropical [ Cuba ( del Valle and Coy Otero 1990)] Regions.

Figures

Fig. 1. Plagiorhynchus (Plagiorhynchus) crassicollis (Villot, 1875). A-D (material from Dorset): A. Male, general view. B. Male, anterior end of trunk. C. Male, longitudinal row of hooks (lateral view). D. Eggs. E-G (material from unknown locality, in Great Britain): E. Male, general view. F. Male, anterior end of trunk. G. Male, longitudinal row of hooks (lateral view). Scale-bars: A, E, 1.0 mm; B, F, 0.2 mm; C, D, G, 0.1 mm.