Gastrointestinal nematodes of freshwater fish from Pilcomayo River, Argentina including description of a new species of Procamallanus (Spirocamallanus) Author Ramallo, Geraldine Author Cancino, Fabiana Instituto de Vertebrados, Fundación Miguel Lillo, Miguel Lillo 251, (4000) San Miguel de Tucumán, Argentina. Author Ruiz, Ana Lía Facultad de Ciencias Naturales e I. M. Lillo, Universidad Nacional de Tucumán. Miguel Lillo 205. (4000) San Miguel de Tucumán, Argentina. Author Ailán-Choke, Lorena Gisela Instituto para el Estudio de la Biodiversidad de Invertebrados, Facultad de Ciencias Naturales, Universidad Nacional de Salta, Av. Bolivia 5150, (4400) Salta, Argentina. & Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina text Zootaxa 2020 2020-07-13 4810 3 468 480 journal article 10.11646/zootaxa.4810.3.4 1175-5326 3943945 9832DCB8-9460-4A8F-93A4-6F552442B7CC Genus Contracaecum Railliet & Henry, 1912 Hosts: Pimelodus albicans (CI-FML#2472). Locality: Misión La Paz , Pilcomayo River , Rivadavia Department , Province of Salta ( 22º22’10”S- 62º32’14”W ) Site of infection: free or encapsulated in abdominal cavity, mesenteries, intestine or liver. Quantitative descriptors: Table I. Deposition of voucher specimen: CH-N-FML#7769: host: Pseudoplatystoma corruscans (CI-FML #2720); CH-N-FML#7770: host: Sorubim lima (CI-FML#2767); CH-N-FML#7771: host: Hoplias misionera (CI-FML #2471 (98)); CH-N-FML#7772: host: Pimelodus albicans (CI-FML#2472); CH-N-FML#7785: host: Pygocentrus nattereri (CI-FML #2749); General description (based on six specimens). Whitish nematodes, medium to large size. Cuticle with transversal striations. Head end rounded, bearing small ventral cuticular tooth. Three lips present, one dorsal and two ventrolateral. Between the last two is observed a cuticular tooth 0.01±0.00 (0.01) length and behind it the excretory pore. Each subventral lip has a papilla and two dorsal lip. Total body 18.13±1.2 (16.30–20.35) length; body 0.72±0.1 (0.60–0.85) width. Nerve ring-anterior end 0.30±0.005 (0.30– 0.31). Esophagus narrow 2.07±0.07 (1.95– 2.18) length; ventriculus small and rounded, 0.11±0.01 (0.10– 0.13) length and 0.10±0.01 (0.09- 0.11) wide; Ventricular appendix 0.50±0.10 (0.40–0. 51) length. Intestine brownish, dark. Intestinal caecum very long, 1.44±0.06 (1.33–1.50) length; extending anteriorly almost to nerve ring. Rectum short, three small rectal glands present. Tail conical, 0.13±0.02 (0.12– 0.17).