Key to Superfamilies of RHABDITIDA 1 Pseudolabia always absent; buccal capsule well developed, reduced or absent; oesophagus divided into muscular and glandular portions or muscular throughout; oesophageal glands uninucleate (except in Philonema and some species of Philometroides); larvae without cephalic hooks, tail generally long and pointed, usually with conspicuous phasmids containing broad cavities and prominent pores; parasitic in gut of cold-blooded vertebrates or other organs of all classes of vertebrates; intermediate hosts mostly copepods............................................................ (Suborder Camallanina)…2 - Head with small pseudolabia, sometimes rudimentary; buccal capsule usually an elongate, moderately sclerotized tube; mus- cular and glandular portions of oesophagus well differentiated; oesophageal glands multinucleate; larvae usually with cephalic hooks or spines and inconspicuous pore-like phasmids; parasitic in gut or tissues of all classes of vertebrates; intermediate hosts invertebrates other than copepods (except Gnathostomatoidea)......................... (Suborder Spirurina) ... 3 2 Buccal capsule well developed, orange-brown in colour; buccal cavity well developed; internal labial papillae tiny; parasitic in gut...................................................................................... Camallanoidea - Buccal capsule reduced or absent (except for Anguillicoloidea); if buccal cavity present then simple, rounded, not separated into two valves; internal labial papillae prominent; not usually parasitic in gut......................................3 3 Oviparous. Buccal capsule well developed. Oesophagus short, undivided. Sclerotized copulatory organs absent. Vulva func- tional. Parasites of swim bladder of eels........................................................Anguillicoloidea - Viviparous. Buccal capsule usually reduced or absent. Oesophagus divided into muscular and glandular portions or muscular throughout. Spicules, copulatory plate or sclerotized genital cone present. Anus and vulva in gravid worms sometimes atro- phied. Parasites of tissues, body cavity or closed cavities and organs of vertebrates..................... Dracunculoidea 4 Buccal capsule well cuticularized, elongate or short. Pseudolabia present or absent................................. 5 - Buccal capsule little cuticularized; two massive lateral trilobed pseudolabia present; inner face of each pseudolabium thick, generally folded into rounded tooth-like formations that fit into corresponding folds on adjacent pseudolabium; anterior extremity sometimes swollen into bulb; adults parasitic in fishes, reptiles and mammals, larvae in fishes Gnathostomatoidea 5 Pseudolabia practically absent; caudal alae absent.......................................................... 6 - Pseudolabia present; caudal alae present or absent.......................................................... 7 6 Buccal capsule variable, sometimes long and cylindrical; mouth opening hexagonal or oval; caudal papillae not arranged as in typical spirurid; vulva markedly anterior or posterior in position; adults parasitic in intestine of fishes......... Thelazioidea - Buccal capsule well cuticularized, never long and cylindrical; caudal alae present; caudal papillae arranged as in typical spiru- rid; vulva rarely markedly anterior or posterior in position; larvae parasitic in fishes, adults in higher vertebrates. Spiruroidea 7 Pseudolabia not covering entire cephalic surface, median lips still visible; four outer labial papillae often visible on lips; buccal cavity rarely long and cylindrical; cephalic cuticular ornamentation present or absent; adults parasitic in various organs of fishes................................................................................. Habronematoidea - Pseudolabia large, involving entire cephalic surface; outer labial papillae fused with cephalic papillae; buccal cavity generally elongated and cylindrical; cuticular cephalic ornamentation present; larvae parasitic in arthropods and fishes, adults in birds........................................................................................... Acuarioidea 8 Buccal cavity weakly developed; leaf crowns absent; bursa and often dorsal ray reduced; vulva at mid-body or posterior end; didelphic or monodelphic; viviparous or ovoviviparous; parasitic in the respiratory, cardiovascular and nervous systems of mammals............................................................................. Metastrongyloidea

Published as part of Arai, Hisao P. & Smith, John W., 2016, Guide to the Parasites of Fishes of Canada Part V: Nematoda, pp. 1-274 in Zootaxa 4185 (1) on pages 35-36, DOI: 10.11646/zootaxa.4185.1.1, http://zenodo.org/record/165530