Mawsonascaris zhoui, Li & Xu & Zhang, 2012

Li, Liang, Xu, Zhen & Zhang, Lu-Ping, 2012, A new species of the genus Mawsonascaris Sprent, 1990 (Nematoda: Ascaridida) from Glaucostegus granulatus (Cuvier) (Rajiformes: Rhinobatidae) in the Taiwan Strait, with remarks on the systematic status of Raphidascaroides myliobatum Yin & Zhang, 1983, Journal of Natural History 46 (21 - 22), pp. 1307-1319 : 1308-1313

Mawsonascaris zhoui sp. nov.

( Figures 1A–K , 2 , 3A–I )

Type host

Glaucostegus granulatus (Cuvier) (Rajiformes: Rhinobatidae ).

Site of infection

Stomach.

Prevalence and intensity of infection

50.0% (one out of two fishes) were infected with intensity of 32 specimens. Type locality

Taiwan Strait, off Xiamen (118 ◦ 04 ′ E; 24 ◦ 26 ′ N), Fujian Province , China.

Type specimens

Holotype: male (HBNU–F1132), allotype: female (HBNU–F1133), paratypes: eight males, 22 females (HBNU–F1134).

Etymology

The species is named for Dr Hong-Zhang Zhou, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.

Description

Medium to large sized, whitish nematodes. Males usually smaller and more slender than females. Cuticle with fine, transverse striations. Maximum width of body at region just posterior to oesophagus. Anterior end with three prominent lips ( Figure 2A–C ), approximately equal in size; lateral membranous flanges prominent, the labial pulp possessing finger-like lobe extending into lateral membranous flanges ( Figure 1B–D ). Distal part of each lip with small, obtusely triangular, medioapical notch ( Figure 2F ). Prominent dentigerous ridges present along anterior border of lips and anterior edge of flanges ( Figure 3B, C ). Dorsal lip with two lateral double papillae at approximately anterior 1 / 3 of its length ( Figures 1B , 2E ); ventrolateral lips each with one double papilla, one small single papilla and amphid ( Figures 1C , 2D ). Interlabia triangular, well developed, about 2 / 5 length of lips ( Figures 1D , 3A ). Cervical alae absent. Oesophagus muscular, very long, distinctly broader posteriorly. Nerve ring encircling oesophagus between first and second sixths of its length ( Figure 1A ). Ventriculus oval, clearly demarcated from oesophagus and intestine, slightly wider than posterior part of oesophagus. Intestinal caecum and ventricular appendix absent. Excretory pore just posterior to nerve ring. Ventral, longitudinal stockade-like ornamentation of cuticle well developed in both sexes ( Figure 3F, H ), beginning at short distance before first pair of precloacal papillae. Narrow caudal alae ending at base of tail tip. Tail of both sexes conical, with a sharply pointed tip ( Figures 1E, F , 2G–I , 3D, E ).

Male (based on nine mature specimens). Body 22.1–33.2 (28.6) mm long, maximum width 490–784 (670). Dorsal and ventrolateral lips almost equal in size, 147–196 (180) long, 137–206 (176) wide. Interlabia 69–98 (81.7) long. Oesophagus 1.86–2.65 (2.32) mm long, 294–323 (310) in maximum width, representing 7.97–8.43 (8.11)% of body length (BL). Nerve ring and excretory pore 588–735 (653) and 617–833 (712), respectively, from anterior extremity. Ventriculus 196–265 (235) long by 196–343 (278) wide. Posterior end of body curved ventrally. Ejaculatory duct 1.86–2.45 (2.16) mm long. Spicules slender, alate, distinctively unequal, ending in sharp point; left spicule 3.33–5.00 (4.38) mm long, representing 179–222 (202)% of ejaculatory duct (ED) and 15.1–15.7 (15.3)% of BL; right spicule 1.57–2.35 (2.09) mm long, representing 84.4–109 (96.4)% of ejaculatory duct (ED) and 7.08–7.71 (7.30)% of BL ( Figure 1I ). Gubernaculum present, banana-shaped, 147–206 (183) long ( Figure 1H ). Caudal papillae 16–17 pairs in total, arranged as follows: 10–11 pairs of precloacal papillae, one pair of paracloacal double papillae and five pairs of postcloacal papillae ( Figures 1E, J , 2G–I , 3H ). A single, median precloacal volcaniform papilla present ( Figure 3I ). Tail 127–176 (150) long.

Female (based on 23 gravid specimens). Body 32.0–53.2 (43.4) mm long, maximum width 735–980 (837). Dorsal and ventrolateral lips almost equal in size, 186–245 (208) long, 196–245 (218) wide. Interlabia 88–117 (100) long. Oesophagus 3.38–3.82 (3.63) mm long, 304–412 (355) in maximum width, representing 7.11–10.6 (8.36)% of BL. Nerve ring 637–784 (715) and excretory pore 735–882 (804), respectively, from anterior extremity. Ventriculus 284–343 (308) long by 343–392 (355) wide. Vulva slitlike, situated in anterior region of body, 12.6–16.3 (13.5) mm from anterior extremity, at 25.1–42.4 (31.1)% of BL. Vagina weakly muscular, directed posteriorly. Undivided uterus not clearly demarcated from vagina, extending posteriorly to the level of the rectum ( Figure 1G ). Eggs small, suboval to almost rounded, 20–39 (31.4) long by 20–29 (27.4) wide ( Figure 1K ). Tail 323–519 (459) long. Phasmids well developed, at about two thirds distance from anus to tip of tail ( Figure 3D, E, G ).

Remarks

Mawsonascaris zhoui sp. nov. is similar to M. australis ( Johnston & Mawson, 1943) from Urolophus testaceus (Müller & Henle) (now Trygonoptera testacea Müller & Henle ) (Rajiformes: Urolophidae ), Rhynchobatus djiddensis (Forsskål) (Rajiformes: Rhinobatidae ), Aptychotrema banksii (Müller & Henle) (now Aptychotrema rostrata (Shaw)) (Rajiformes: Rhinobatidae ), Taeniura lymma (Forsskål) (Rajiformes: Dasyatidae ) and Rhinobatos batillum Whitley (now Glaucostegus typus Anonymous [Bennett]) (Rajiformes: Rhinobatidae ) from Australian waters and M. myliobatum ( Yin & Zhang, 1983) from Myliobatis tobijei Bleeker (Rajiformes: Myliobatidae ) from Chinese waters in lacking an intestinal caecum. Mawsonascaris zhoui sp. nov. is different from M. myliobatum by having fewer caudal papillae (16–17 pairs in the new species versus 26–28 pairs in the latter). The new species also differs from M. australis in having a different number and arrangement of caudal papillae (10–11 pairs of precloacal, one pair of paracloacal and five pairs of postcloacal in the former versus eight pairs of precloacal, two pairs of paracloacal and four pairs of postcloacal in the latter) and the presence of a single, median precloacal volcaniform papilla.

Figures

Figure 1. Mawsonascaris zhoui sp. nov. (A) Anterior part of female body, lateral view; (B) cephalic extremity of female, dorsal view; (C) cephalic extremity of female, lateral view; (D) cephalic extremity of female, ventral view; (E) caudal region of male, lateral view;

Figure 2. Scanning electron micrographs of Mawsonascaris zhoui sp. nov. (A) Cephalic extremity of male, apical view; (B) cephalic extremity of male, lateral view; (C) cephalic extremity of male, subventral view; (D) ventrolateral lip; (E) dorsal lip; (F) apical part of ventrolateral lip, showing obtusely triangular medioapical notch; (G) caudal region of male, ventral view (arrow – median precloacal volcaniform papilla); (H) caudal region of male, lateral view (arrows – postanal papillae); (I) caudal region of male, lateral view (arrow – paranal double papillae).

Figure 3. Scanning electron micrographs of Mawsonascaris zhoui sp. nov. (A) Cephalic extremity of female, lateral view; (B) dentigerous ridges of lips of female, apical view; (C) dentigerous ridges of lips of male (arrow), lateral view; (D) posterior end of female, ventral view (arrows – phasmids); (E) posterior end of female, lateral view (arrow – phasmid); (F) longitudinal stockade-like ornamentation of cuticle of female; (G) phasmid of female; (H) precloacal papilla and longitudinal stockade-like ornamentation of cuticle of male; (I) median precloacal volcaniform papilla.