Resurrection of Southwellina Witenberg, 1932, with a Description of Southwellina dimorpha sp. n., and a Key to Genera in Polymorphidae (Acanthocephala)

Abstract

The family Polymorphidae is briefly discussed, and a key to its genera is presented. The subfamilies Polymorphinae Meyer, 1931, and Corynosomatinae Petrochenko, 1956, are suppressed. Southwellina Witenberg, 1932, is considered valid and is redefined. It contains S. hispida (Van Cleave, 1925), S. macracanthus (Ward et Winter, 1952) comb. n., and S. dimorpha sp. n. The new species was found as juveniles in crayfish, Procambarus clarkii, in Louisiana, and as adults in white ibis, Eudocimus albus, in Florida. It differs from other species in its sexual dimorphism, the female having large hooks and 1 field of trunk spines, and the male having smaller hooks and 2 fields of trunk spines. The following species are considered synonyms of S. hispida: Arhythmorhynchus duocinctus Chandler, 1935; A. fuscus Harada, 1939; Polymorphus ardeae Belopolskaia, 1958; and Hemiechinosoma ponticum Petrochenko et Smogorjevskaia, 1962. Skrjabinorhynchus Petrochenko, 1956, is suppressed and its species are recombined as Arhythmorhynchus capellae (Yamaguti, 1935) comb. n., and Arhythmorhynchus eroliae (Yamaguti, 1939) comb. n. The resulting homonym, A. capellae Schmidt, 1963, is renamed Arhythmorhynchus jeffreyi nom. n. The family Polymorphidae Meyer, 1931, is a homogeneous assemblage of species, most of which are parasites of aquatic birds and mammals. Distinction between species is usually difficult, and between genera even more so. When first proposed, most genera were based on one or a few species. Each genus had some distinctive characteristics which readily separated it from other genera. But as more species were discovered, differences between genera became less apparent; today very slight distinctions are used to separate them. For example, Corynosoma differs from Polymorphus only in possessing genital spines, and in some species the spines are on only one sex. Efforts by Petrochenko (1956) and Yamaguti (1963) to divide the family into the subfamilies Polymorphinae Meyer, 1931, and Corynosomatinae Petrochenko, 1956, resulted in placing genera as obviously closely related as Polymorphus and Corynosoma in different subfamilies. As this is less than useful, I cannot accept these subfamilies as valid. The discovery of a new species in this family has stimulated me to review the status of these related genera. It could be logically argued that all species in this family belong to a single genus. On the basis of similarity of form, embryology, and biology they are obviously genetically similar. However, for a Received for publication 13 October 1972. classification to be workable it must help distinguish between species groups in the most convenient manner possible. Therefore, I have taken a more liberal approach and recognize nin genera, which can be diagnosed by the following key. Key to genera in Polymorphidae Meyer, 1931 (Syn. Filicollidae Petrochenko, 1956) la. Cement glands kidney-shaped. Proboscis of adult female greatly swollen, with hooks restricted to short, radially arranged rows on anterior surface. Parasites of water birds Filicollis Liihe, 1911 lb. Cement glands claviform or tubular. Proboscis swollen or not; when swollen, longitudinal rows of hooks cover entire proboscis 2 2a. Genital spines present on at least one sex. Parasites of aquatic birds and mammals --.---... ---Corynosoma Liihe, 1904 (Syn. Chentrosoma Monticelli, 1905, nec Porta, 1906; Echinosoma Porta, 1907, partim.) 2b. Gental spines absent on both sexes ----3 3a. Anterior end of trunk greatly swollen, separated from rest of trunk by conspicuous constriction 4 3b. Anterior trunk not separated from posterior portion by narrow constriction 5 4a. Anterior trunk with 1 field of spines surrounding it. Parasites of Cetacea .....--Bolbosoma Porta, 1908 (Syn. Echinorhynchus Zoega in Miiller, 1776, partim; Bolborhynchus Porta, 1906.)