The Nematodes Parasitic in the Gizzard of Birds: A Study in Morphological Convergence

Abstract

1. The structure of the head in the families Acuariidae and Habronematidae is described. It is established that the first is characterized by the cephalic papillae being on the pseudo-labia and all the cephalic elaborations being modifications of the pseudolabia and by paired structures arising dorsally and ventrally from the inner surfaces of the pseudo-labia. The second family is characterized by the presence of large, single labia, dorsally and ventrally, which cany the cephalic papillae.2. The family Acuariidae contains three groups, accepted as subfamilies. Acuariinae: characterized by long cordons produced by the development posteriorly of both the inner pseudo-labial flanges and the edges of the pseudo-labia; Seuratiinae: characterized by a cephalic cap developed largely from the outer surface of the head posterior to the pseudo-labia; Schistorophorinae: characterized by the presence of various lobes or helmet-like modifications derived from the inner surface of the pseudo-labia.