Guide to the Parasites of Fishes of Canada Part V: Nematoda Author Arai, Hisao P. Author Smith, John W. text Zootaxa 2016 4185 1 1 274 journal article 10.11646/zootaxa.4185.1.1 11620862-ddcf-4c01-b0d9-32867e03d74b 1175-5326 165530 0D054EDD-9CDC-4D16-A8B2-F1EBBDAD6E09 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). 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) 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