Hysterothylacium reliquens (Norris & Overstreet, 1975) Deardorff & Overstreet, 1981

Arai, Hisao P. & Smith, John W., 2016, Guide to the Parasites of Fishes of Canada Part V: Nematoda, Zootaxa 4185 (1), pp. 1-274 : 145

Hysterothylacium reliquens (Norris & Overstreet, 1975) Deardorff & Overstreet, 1981

Synonym: Thynnascaris reliquens Norris & Overstreet, 1975

Description (after Deardorff & Overstreet 1981). With characteristics of the genus. Body reaching greatest width near midbody. Cuticle with inconspicuous annulations and minute lateral alae. Alae become more apparent at levels behind rectum. Lips approximately equal in size, all longer than wide; flanges constricted near middle of lip; pulp pedunculated. Interlabia with height equal to or slightly greater than width at base. Interlabial grooves absent ( Fig. 83 A). Preventriculus 11–13% of body length. Ventriculus narrower than widest level of preventriculus. Usually longer than broad; ventricular appendix departing without angulation from posterior portion of ventriculus. Nerve ring located at anterior 16–28% of preventriculus. Excretory pore at or immediately posterior to level of nerve ring. Tail with spined conical mucron.

Males: body 25–40 long by 0.5–0.9 wide. Preventriculus 3.3–4.5, ventriculus 0.141–300, ventricular appendix 1.2–1.7, and intestinal caecum 0.315–598 long. Spicules 1.7–2.4 long, relative length varies: spicule ratio 1:0.6– 1.3. Caudal papillae 27 to 33 pairs: 23 to 29 pre–cloacal pairs, four to five post–cloacal pairs with 3rd pair from tail end doubled; para-anal papillae lacking. Distinct medio-ventral organ, papillated. Tail reflexed ventrad, 0.123– 0.185 long, including multispinous process ( Fig. 83 B).

Females: body 21–44 long by 0.5–1.1 wide. Preventriculus 2.9–5.0, ventriculus 0.142–0.286, ventricular appendix 1.0–2.9, and intestinal caecum 0.394–0.788 long. Vulva without protruding lips, opens 6.5–17.0 from anterior end. Ovaries rarely extend beyond anterior level of vulva. Tail 0.370–0.574 long, including multispinous process ( Fig. 83 C).

Site: stomach

Host: Xiphias gladius

Distribution: Atlantic

Record: Hogans et al. 1983

Figures

FIGURE 83. Hysterothylacium reliquens (Norris & Overstreet, 1975) Deardorff & Overstreet, 1981. A. head, lips, ventral view showing interlabium (il); B. male, posterior end showing caudal papillae, lateral view; C. multispinous process on tail tip, lateral view. (Redrawn from Deardorff & Overstreet 1981)