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 Cystoopsis acipenseris Wagner, 1867 Description (after Moravec 2001 ). Head rounded in both sexes. Mouth opening triangular, surrounded by ring mound with 10 small teeth. Four small cephalic papillae, and pair of lateral amphids. Anterior muscular portion of oesophagus well developed, posterior glandular portion comprising two longitudinal rows of stichocytes ( Fig. 17 A). Intestine in both sexes ends blindly. Males: body cylindrical, both ends rounded, 2.10 – 3.00 long, 0.017 – 0.024 wide. Cuticle with fine cuticular tubercles. Muscular oesophagus 0.27 – 0.28 long, glandular one 0.70 – 0.73 long. Nerve ring encircles muscular oesophagus slightly behind its proximal end. Testis convoluted, filling entire body-cavity. Spicule fine, moderately sclerotized, 0.23 – 0.26 long. Spicular sheath present ( Fig. 17 B). Females: anterior body region thread-like 2.48 – 2.74 long, posterior globular region 5.0 – 6.0 in diameter ( Fig. 17 C). Anterior cuticle with transverse rings of minute tubercles. Muscular oesophagus 0.54 – 0.57 long, glandular one 1.09 – 1.18 long. Oesophago-intestinal junction in anterior body region. Intestine continues into posterior globular region ending blindly as a sac 2.0 – 2.5 wide. Nerve ring 0.48 – 0.52 from anterior end. Vulva 0.080 – 0.120 from anterior end ( Fig.17 A). Muscular vagina passes through thread-like body region. Uterine coils, ovary and oesophagus fill body-cavity in posterior body region. Uterus contains many eggs at different stages of development, mature ones containing formed larvae. Mature eggs thin-walled with smooth surface, barrel-shaped with polar plugs, 0.063 – 0.068 x 0.021 – 0.025 ( Fig. 17 D). Site: subcutaneous Host: Acipenser transmontanus (1, 2) Distribution: British Columbia Records: 1. Margolis & McDonald 1986 ; 2. McDonald et al. 1989