Rhabdias fuscovenosa ( Railliet, 1899 ) Goodey, 1924

KUZMIN, YURIY, 2013, Review of Rhabdiasidae (Nematoda) from the Holarctic, Zootaxa 3639 (1), pp. 1-76 : 39-41

Rhabdias fuscovenosa ( Railliet, 1899) Goodey, 1924 sensu lato

( Fig. 19 C, D )

Synonyms: Ascaris humilis Leidy, 1856 ; Angiostoma fuscovenosa Railliet, 1899 ; Strongylurus catanensis Rizzo, 1902 ; Rhabdias ophidia Goodey, 1924 ; Rhabdias annulosa Hsu, 1933 ; Rhabdias vellardi Pereira, 1927 sensu Harwood, 1932 .

Hosts. In Palaearctic: Natrix natrix (type host), N. tessellata , N. maura , Elaphe dione, E. quatuorlineata , Dolichophis jugularis , ( Reptilia: Serpentes: Colubridae ), Eryx tataricus (Boidae) (occasionally infected in laboratory), Vipera berus , V. ammodytes , V. ursinii , Gloydius halys (Viperidae) .

In Nearctic: Heterodon platirhinos , Lampropeltis triangulum , Nerodia cyclopion , N. erythrogaster , N. fasciata , N. rhombifera , N. sipedon , Opheodrys vernalis , Regina septemvittata , Storeria dekayi , S. occipitomaculata , Thamnophis ordinoides , T. proximus , T. sauritus , T. sirtalis , Virginia striatula ( Reptilia: Serpentes: Colubridae ).

Site: anterior part of lung.

Distribution: Holarctic.

Description. 1. Specimens from Palaearctic. Comparatively small species. Body length 3.60 (2.21–4.24) mm, maximum width 128 (100–199). Body cuticle thin, transversely striated. Sometimes striation indistinct or prominent only in anterior and posterior parts. Six lips arranged in two lateral groups. Oral opening round. Buccal capsule funnel-shaped or cup-like, 9 (7–10) deep and 14 (11–17) wide. Oesophagus club-shaped, 241 (216–274) long (6.9 [5.6–10.5] % of body length). Bulb width 50 (40–70). Nerve ring at 125 (91–149) from anterior end of oesophagus (52.1 [42.3–62.1] % of oesophagus length). Excretory glands somewhat shorter than oesophagus. Intestine with prominent lumen, often reddish or brown in posterior half. Rectum prominently sclerotised. Vulva at 1.59 (1.10–1.98) mm from anterior end (44.3 [35.6–50] % of general length). Vulva lips distinct. Eggs not numerous, numbering 13 (3–30) in both uteri, containing embryos on early cleavage stages. Egg size 77–82 × 44– 50 (after Sharpilo 1976). Tail conical, elongated, 175 (100–224) long (4.9 [2.7–6.9] % of body length). Tail end tapered.

2. Measurements of specimens from Nearctic (16 specimens from Thamnophis sirtalis, Reelfoot Lake , Tennessee, U.S.A.). Body length 3.21 (2.75–3.47) mm, maximum width 154 (130–173). Buccal capsule 6 (5–7) long, 14 (12–15) wide. Length of oesophagus 245 (222–266) or 7.7 (6.8–8.4) % of body length. Oesophageal bulb 54 (47–62) wide. Nerve ring at 129 (111–154) from anterior end of oesophagus (52.6 (45.0–61.0) % of oesophagus length). Distance from anterior end to vulva 1.51 (1.32–1.70) mm, or 47.1 (44.3–49.3) % of body length. Tail 207 (179–229) long 6.5 (5.2–7.5) % of body length .

Biology. Life cycle is of strongyloid type. Embryos in eggs of hermaphrodite generation complete their development during the passage of eggs through the host intestine. About 96 % of larvae in cultures develop directly. Homogonic infective larvae are rhabditoid. In the gonochoristic generation, males predominate with average ratio 2.7:1. Females with up to 10 eggs in both uteri. Matricidal hatching was observed, however, a part of eggs were oviposited by females. Laboratory infection of snakes per os resulted in successful development of parasitic stages. Parasitic larvae migrated from the oesophagus and continued development under connective tissues surrounding lung.

Remarks. Material investigated from Nearctic and Palaearctic showed no obvious morphological differences. Moreover, both forms are almost identical in peculiarities of their life cycles ( Chu 1936 b; Kuzmin 1993). However, molecular studies (Tkach, unpublished) proved that R. fuscovenosa from North America is a different species. That is why the species described herein is designated as R. fuscovenosa s.l. until further studies allow to separate forms from Nearctic and Palaearctic into two or more valid species.

Material studied. Palaearctic: several hundreds of specimens from various hosts (SIZK, MNHN, USNPC); 64 specimens (SIZK) were measured, of which 27 originated from N. natrix (10 from Buriatiya, Russia; 10 from Ukraine, 7 from Italy), 10 from N. maura ( France) , 10 from D. jugularis ( Azerbaijan) , 5 from C. austriaca ( Ukraine) , 2 from E. tataricus (laboratory), 7 from V. ursinii ( Ukraine) , 1 from V. berus ( Ukraine) , 2 from E. quatuorlineata ( Ukraine) . Nearctic: 16 specimens from Thamnophis sirtalis (SIZK) .

References (main): Railliet (1899), Goodey (1924 a), Harwood (1932), Chu (1936 a, b), Reiber et al. (1940), Gibson and Rabalais (1973), Hartwich (1975), Sharpilo (1976), Baker (1978), Fontenot and Font (1996), Kuzmin et al. (2003).

Figures

FIGURE 19. R. eustreptos: A—anterior part of body, lateral view; B—tail end, lateral view. R. fuscovenosa: C—anterior part of body, lateral view; D—tail end, lateral view. Scale bars: 0.1 mm.