Hysterothylacium amoyense ( Hsü, 1933 ), Hsu, 1933

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 : 56-59

Hysterothylacium amoyense ( Hsü, 1933) ( Figs. 1 , 2 )

Synonyms: Contracaecum amoyensis Hsü, 1933

Contracaecum amoyense ( Hsü, 1933) Hsü, 1934

Contracaecum muraenesoxin Luo, 1999

Hysterothylacium muraenesoxin ( Luo, 1999) Li, Xu & Zhang, 2006

Host: Muraenesox cinereus (Försskal) ( Anguilliformes : Muraenesocidae )

Site of infection: Intestine

Locality: Shidao Island (₁₂₂° ₂₆ʹ ₄₂ʹʹ Ε﹔ ³₆° ₅₂ʹ ₅₇ʹʹ Ν), Yellow Sea, Shandong Province, China

Prevalence and intensity of infection: 33.3% (1 out of 3 fishes) were infected with intensity of 2 specimens.

Voucher specimens: 1 male (HBNU-0713), 1 female (HBNU-0714)

Additional specimens examined: 5 males and 5 females collected from Zhoushan Islands, East China Sea, China deposited in the Institute of Zoology, Chinese Academy of Sciences; 1 male and 1 female of paratypes of H. muraenesoxin from Amoy, Taiwan Strait, China deposited in the Parasitology Research Laboratory, Xiamen University.

General: Medium to large sized, whitish nematodes, with finely transversely striated cuticle. Lateral alae absent. Anterior end with 3 lips, approximately equal in size, with deep postlabial grooves and prominent membranous flanges, broadest at posterior middle of lips. Proximal part of each lip with four lobes. Dorsal lip with 2 lateral double papillae; subventral lips each with one amphid, one single papillae and one double papillae. Interlabia triangular, well developed, about 2/5 length of lips. Oesophagus long, slightly broader posteriorly. Nerve ring encircling oesophagus between 1/4–1/5 of its length. Ventriculus almost spherical, approximately as wide as oesophagus. Ventricular appendix narrow, much longer than intestinal caecum. Excretory pore slightly posterior to nerve ring. Rectum hyaline, tube-shaped, surrounded by 3 large, unicellular rectal glands. Tail conical, relatively short, tip of male and female tail covered with numerous nodular protuberances.

Male: Body length 37.8 mm (based on one male from the Yellow Sea), 37.0– 43.2 mm (based on 5 males from the East China Sea), maximum width 530 (537–742). Dorsal lip 123 (134–194) long, 125 (117–185) wide. Interlabia 68 (59–77) long, 97 (81–102) wide. Oesophagus 2.14 mm (1.94–2.53 mm) long, 5.7% (5.2– 5.5%) of body length, 240 (233–262) wide. Nerve ring 600 (504–633) and excretory pore 640 (563–669) from anterior extremity. Ventriculus 190 (146–252) long by 210 (146–272) wide. Ventricular appendix 3.26 mm (3.21–3.69 mm) long by 87 (78–98) wide. Intestinal caecum160 (146–175) long, 7.5% (7.5–7.9%) of oesophagus length; 110 (89–122) wide. Ratio of intestinal caecum to ventricular appendix 1: 20.4 (1: 20.7–21.9).

Ejaculatory duct 1.65 mm (1.67–2.52 mm) long, 4.4% (4.3–5.8%) of body length. Spicules slender and equal in length, 680 (582–1019) long, 41.2 % (35.3–42.4%) of ejaculatory duct, 1.8% (1.6–2.4%) of body length. Gubernaculum absent. Tail 240 (175–245) long; tail tip 39 (29–49) long, with nodular protuberances. Caudal papillae arranged as follows: 22 (19–25) pairs of preanal papillae, 3 pairs of paranal papillae and 6 (6–7) pairs of postanal papillae (the fifth pair double).

Female: Body length 56.8 mm (based on one female from the Yellow Sea), 58.2–62.3 mm (based on 5 females from the East China Sea), maximum width 580 (675–712). Dorsal lip 125 (145–194) long, 128 (133– 194) wide. Interlabia 87 (89–97) long, 130 (153–172) wide. Oesophagus 3.50 mm (2.72–4.27 mm) long, 6.2% (4.9–7.0%) of body length, 250 (274–283) wide. Nerve ring 680 (660–854) and excretory pore 710 (728–912) from anterior extremity. Ventriculus 270 (191–292) long by 240 (213–276) wide. Ventricular appendix 3.88 mm (4.46–5.63 mm) long by 97 (92–107) wide. Intestinal caecum180 (194–272) long, 5.1% (4.8–6.4%) of oesophagus length; 130 (128–143) wide. Ratio of intestinal caecum to ventricular appendix 1: 21.6 (1: 20.7– 23.0). Tail length 390 (485–563); tail tip 49 (49–68) long, covered with nodular protuberances in its posterior half. Vulva slit-like, without salient lips, located equatorially, 53.2% (49.2–54.3%) from anterior end. Vagina muscular, directed posteriorly. Uteri opposed. Eggs embryonated, oval, 44 (45–63) long by 39(41–57) wide.

Remarks: Hsü (1933) described Contracaecum amoyensis Hsü, 1933 in Muraenesox cinereus from Amoy, Taiwan Strait, China. Later, this author corrected the specific name to Contracaecum amoyense (see Hsü, 1934), which was finally transferred to the genus Hysterothylacium by Deardorff and Overstreet (1980). The morphometric characteristics of the specimens collected from the Yellow Sea and East China Sea in our study are in agreement with the original description of H. amoyense . However, in the original description of this species, Hsü (1933) reported eight pairs of postanal papillae, but in our material we observed only 6–7 pairs. Notwithstanding, SEM study showed that the fifth pair of papillae are double which could be considered as two single papillae under light microscopy.

Luo (1999) described a new species using light microscopy from the intestine of M. cinereus (type host), Trichiurus haumela and Synodus variegates , named it Contracaecum muraenesoxin Luo, 1999 . Li et al. (2006) transferred this species to the genus Hysterothylacium . However, the major characters of H. muraenesoxin and H. amoyense including body length, lip shape, esophagus length, intestinal caecum and ventricular appendage proportions, spicule length, position of vulva, number of postanal papillae and tail morphology are very similar (see Table 1). Moreover, both H. muraenesoxin and H. amoyense were found in the same host species M. cinereus from the same locality (see Table 1). Unfortunately, H. muraenesoxin was not compared with H. amoyense in the original description of Luo (1999). Therefore, we considered H. muraenesoxin as junior synonymy of H. amoyense ( Hsü, 1933) .

Figures

FIGURE 1. Hysterothylacium amoyense (Hsü, 1933). A, cephalic end of female, lateral view; B, cephalic end of female, dorsal view; C, posterior end of male, lateral view; D, anterior part of male, ventral view; E, posterior end of male, lateral view; F, posterior end of female, lateral view; Scale bars in mm.

FIGURE 2. Scanning electron micrographs of Hysterothylacium amoyense (Hsü, 1933). A, B, cephalic extremity of male, apical view; C, cephalic extremity of male, lateral view; D, dorsal lip; E, subventral lip; F, posterior end of male; G, postcloacal papillae; H, tip of female tail; I, tip of male tail; J, paracloacal papillae (arrows); K, posterior end of female, lateral view; L, anterior end of male, lateral view; i, interlabium; d, double papillae; s, single papillae; pd, postcloacal double papillae.