FIGURE 8 in Review of Rhabdiasidae (Nematoda) from the Holarctic

FIGURE 8. Schematic shape and position of the circumoral structures (papillae, lips, pseudolabia) in various species of Rhabdiasidae. A—assumed ancestral arrangement of lips and papillae; B—two lateral groups of lips observed in Rhabdias spp. parasitizing snakes; C—lateral and submedian lips similar in shape and size, submedian lips situated closer to the oral opening than lateral ones (R. bufonis, R. ambystomae); D—submedian lips flattened, lateral lips reduced, all lips and papillae arranged in circle surrounding oral opening (Entomelas spp.); E—submedian lips close to oral opening, lateral lips transformed into low, rounded pseudolabia (R. sphaerocephala, R. joaquinensis, R. ranae); F—lateral pseudolabia large, elevated, submedian lips reduced (R. bakeri, R. americanus, R. tarichae); G—lips and papillae indistinct, only lateral pseudolabia present (R. bicornis).