Rhabdias sphaerocephala Goodey, 1924

KUZMIN, YURIY, 2013, Review of Rhabdiasidae (Nematoda) from the Holarctic, Zootaxa 3639 (1), pp. 1-76 : 51-52

Rhabdias sphaerocephala Goodey, 1924

( Fig. 27 )

Host: Bufo bufo ( Amphibia: Anura : Bufonidae ).

Site: lungs.

Distribution: Western Palaearctic.

Description. Adult hermaphrodites. Head end spherical, tail end tapered. Body length 8.87 (6.37–12.35) mm, maximum width 354 (284–448). Body cuticle swollen, with irregular folds. Spherical swelling of cuticle present on head end. This anterior swelling sufficiently wider and distinctly separated from the rest of body cuticle. Oral opening round. Six lips prominent, lateral lips situated farther from oral opening than submedian ones. Vestibulum reduced. Buccal capsule cup-like, 14 (10–16) deep and 21 (14–24) wide. Oesophagus with prominent dilation at middle of muscular part. Oesophagus length 689 (622–755) (8.1 [5.4–10.7] % of body length). Oesophagus width: 62 (54–70) at anterior end, 80 (64–90) at middle of muscular part, 68 (60–84) at middle of glandular part; bulb 113 (90–134) wide. Nerve ring at 198 (174–216) from anterior end of oesophagus (28.8 [25.3–33.3] % of oesophagus length). Intestine wide, its anterior end usually wider than posterior bulb of oesophagus. Rectum thick-walled. Vulva situated at 5.05 (3.77–7.2) mm from anterior end (57.3 [49.5–67.0] % of total length). Vulva lips reduced. Eggs numerous, most eggs containing fully developed larvae. Egg size 98–129 × 53–72 (after Hartwich 1975). Tail conical, 280 (207–382) long (3.2 [2.6–4.0] % of body length).

Subadult hermaphrodites lacking the anterior swelling of cuticle. Body length 3.20 (2.21–4.17) mm, maximum width 92 (72–126). Body cuticle thin and smooth. Buccal capsule 14.6 (14–16) deep and 20 wide. Oesophagus 545 (506–606) long (17.4 [13.5–22.9] % of body length). Oesophagus width: 42 (38–48) at anterior end, 47 (44–52) at the middle of muscular part, 40 (36–48) at the middle of glandular part; bulb width 59 (52–68). Nerve ring at 209 (191–224) from anterior end of oesophagus (38.3 [35.6–41.3] % of oesophagus length). Intestine thin-walled. Vulva at 1.99 (1.34–2.52) mm from anterior end (62.2 [59.6–64.3] % of total length). Vulva lips distinct. Uteri tubular. Eggs absent. Tail conical, elongated, 141 (124–166) long (4.5 [3.9–5.6] % of body length).

Biology (after Kuzmin 1997). Life cycle is of rhabdiasoid type. Free-living females usually had 2 or 4 eggs in uteri, less frequently 1 or 3 eggs. Up to 4 larvae developed inside each female. Matricidal hatching was not observed to be obligatory and some number of larvae developed from oviposited eggs. Infected larvae readily penetrated the skin of experimental hosts, B. bufo and P. fuscus . In the latter host, however, the development of hermaphrodites was arrested on the subadult stage. The arrested worms were found in subcutaneous tissues and abdominal muscles.

Remarks: the species was described from B. bufo in England ( Goodey, 1924 b) and then found in the same host in Germany, Ukraine and Eastern Russia ( Hartwich 1975; Kharchenko 1991; Kuzmin 1997). The records from Central and South America were proved to be erroneous ( Kuzmin et al. 2007).

Material studied: about 100 specimens ( SIZK, MNHN), of which 22 gravid and 14 subgravid specimens were measured .

References: Goodey (1924 b), Hartwich (1975), Kharchenko (1991), Kuzmin (1997).

Figures

FIGURE 27. R. sphaerocephala. A—anterior part of body, lateral view; B—head end, apical view; C—head end of subgravid specimen, lateral view; D—tail end, lateral view. Scale bars: A, D—0.2 mm; B, C—0.1 mm.