Hysterothylacium fabri ( Rudolphi, 1819 )

Li, Liang, Xu, Zhen & Zhang, Luping, 2008, Redescription of three species of Hysterothylacium (Nematoda: Anisakidae) from marine fishes from the Yellow Sea, China, with the synonymy of Hysterothylacium muraenesoxin (Luo, 1999), Zootaxa 1878, pp. 55-67 : 59-61

Hysterothylacium fabri ( Rudolphi, 1819) ( Figs. 3 , 4 )

Synonyms: Ascaris fabri Rudolphi, 1819 Ascaris biuncinata Molin, 1858

Contracaecum fabri ( Rudolphi, 1819) Baylis, 1923

Host: Trachurus japonicus (Temminck & Schlegel) , Argyrosomus argentatus (Houttuyn) , Astroconger myriaster (Brevoort) , Chelidonichthys kumu (Cuvier)

Site of infection: Intestine

Locality: Shidao Island (122° 26’ 42’’ E; 36° 52’ 57’’ N), Yellow Sea, Shandong Province, China

Prevalence and intensity of infection: 33.3% (1 infected / 3 examined), 3 specimens of Trachurus japonicus ; 3.3% (2 infected / 60 examined), 2–5 (3.5) specimens of Argyrosomus argentatus ; 3.0% (1 infected / 33 examined), 3 specimens of Astroconger myriaster ; 3.5% (2 infected / 58 examined), 1–4 (2.5) specimens of Chelidonichthys kumu .

Voucher specimens: 5 females (HBNU-0712)

General: Small to medium sized, whitish nematodes with finely transversely striated cuticle. Lateral alae very narrow, extending from short distance behind the base of subventral lips to caudal region. Anterior end with 3 lips, approximately equal in size, with narrow lateral flanges and inconspicuous postlabial grooves. Proximal part of each lip without conspicuous lobes. Dorsal lip with 2 lateral double papillae; Subventral lips each with one amphid, one single papillae and one double papillae. Interlabia very small, about 1/3 length of lips. Oesophagus short, slightly broader posteriorly. Nerve ring encircling oesophagus between 1/3–1/4 of its length. Excretory pore slightly posterior to nerve ring. Ventriculus almost spherical, approximately as wide as oesophagus. Ventricular appendix narrow, much longer than intestinal caecum. Tail conical, relatively short, tip of female tail covered by numerous spines.

Female (based on 5 gravid specimens): Body 11.2–30.2 (20.7) mm long, 170–490 (320) maximum width. Dorsal lip 29–59 (46) long, 24–37 (35) wide. Interlabia 12–25 (18) long, 19–34 (27) wide. Oesophagus 0.83–1.89 (1.18) mm long, 4.3–7.4 (5.9) % of body length. Nerve ring 360–530 (440) and excretory pore 390–530 (450) from anterior extremity. Ventriculus 87–240 (150) long by 58–190 (120) wide. Ventricular appendix 1.14–2.23 (1.59) mm long, 118–137 (128) % of oesophagus length. Intestinal caecum 120–390 (210) long, 13.3–29.6 (18.4) % of oesophagus length. Ratio of intestinal caecum to ventricular appendix 1: 3.7–10.9 (1: 8.6). Tail length 110–270 (180), tail tip 29–49 (37) long, with numerous spines. Vulva slit-like, without salient lips, located pre-equatorially, 20.4–20.6 (20.5) % from anterior end. Vagina muscular, directed posteriorly. Uteri opposed. Eggs unembryonated, oval, 28–32 (29) long by 25–30 (27) wide.

Remarks: Hysterothylacium fabri is a scarcely studied anisakid species, not previously described from SEM micrographs, which has been found in many Mediterranean fish species ( Nikolaeva and Naidenova, 1964; Petter and Radujkovic, 1986; Sánchez et al., 2003). Petter and Maillard (1987) redescribed H. fabri from Uranoscopus scaber from the Mediterranean Sea using light microscopy. The morphometry of our specimens agree well with Petter & Maillard’s redescriptions in lip morphology, interlabial shape, origin of lateral alae, position of excretory pore, oesophagus length, ratio of ventricular appendage and intestinal caecum, and shape of the female tail. Therefore, we have not hesitated to make the identification. However, Sánchez et al. (2003) suggested that H. fabri represents a species complex comprising at least three sibling species parasitizing Mediterranean fish species based on isoenzyme electrophoresis and RAPD methods. Whether this is also the case for H. fabri from Chinese marine fishes is not clear. This species is recorded from China for the first time.

Figures

FIGURE 3. Hysterothylacium fabri (Rudolphi, 1819). A, anterior part of female, lateral view; B, cephalic end of female, dorsal view; C, cephalic end of female, lateral view; D, cephalic end of female, ventral view; E, tip of female tail; Scale bars in mm.

FIGURE 4. Scanning electron micrographs of Hysterothylacium fabri (Rudolphi, 1819). A, cephalic end of female, lateral view; B, cephalic extremity, lateral view; C, cephalic extremity, apical view; D, subventral lip; E, dorsal lip; F, posterior end of female, lateral view; G, tip of female tail; a, lateral alae; i, interlabium; d, double papillae; s, single papillae; am, amphid.