Contracaecum Railliet & Henry, 1912

Ramallo, Geraldine, Cancino, Fabiana, Ruiz, Ana Lía & Ailán-Choke, Lorena Gisela, 2020, Gastrointestinal nematodes of freshwater fish from Pilcomayo River, Argentina including description of a new species of Procamallanus (Spirocamallanus), Zootaxa 4810 (3), pp. 468-480 : 475-476

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).