A New Species of the Acanthocephalan Genus Polymorphus and Notes on the Status of the Name Profilicollis

Abstract

In 1931, A. Meyer introduced the name Profilicollis into the acanthocephalan literature for a generic concept based on two species previously described as Filicollis botulus Van Cleave, 1916, and F. arcticus Van Cleave, 1920. Witenberg in 1932 (p. 260) regarded Profilicollis as a synonym of Polymorphus. Since 1931, the present writer has been engaged in a restudy of the species assigned to Profilicollis and of numerous undescribed forms from birds as well as the known species of Polymorphus. When the name Profilicollis was first proposed, the distinctive features of its included species seemed so obvious that the writer felt impelled to accept the concept as valid, even after Witenberg expressed belief that Profilicollis is a direct synonym of Polymlorphus. The relatively long, slender neck seemed clearly to differentiate the species from Polymiorphus. Coupled with this was the observation that the concentric embryonic membranes of Profilicollis stood in contrast with embryos of Polyimorphus which characteristically possess polar prolongations of the middle membrane. A reexamination of the original material on which Filicollis arcticus was based showed that among the embryos with strictly concentric membranes there were a few having polar prolongations. With the intergrading of these characters, this presumed generic distinction vanished, leaving length of neck as the only possible means of differentiating Polymorphus and Profilicollis. As a relative character this was found inadequate as a generic criterion. Numerous collections gave evidences supporting this decision, for intermediate forms were frequently encountered in this study. The only solution seemed to lie in the reduction of Profilicollis to a direct synonym of Polymnorphus. Preliminary attention was directed to this synonymy in a brief abstract published in 1937 (Van Cleave, 1937: 563). By this decision Profilicollis botulus (Van Cleave, 1916) becomes Polynmorphus botulus (Van Cleave, 1916) and Profilicollis arcticus (Van Cleave, 1920) becomes Polymorphus arcticus (Van Cleave, 1920). In the second section of his monograph, Meyer (1933: 529) gave tacit acknowledgment of the inability to separate Profilicollis and Polymorphius, for when he prepared a key to the genera of Acanthocephala he Received for publication, September 26, 1938. * Contributions from the Zoological Laboratory of the University of Illinois, No. 524. 129