Parasites of Horned Toads (Phrynosoma spp.), with Records from Nevada

Abstract

One hundred and four horned toads, mostly Phrynosoma p. platyrhinos Girard, were collected from six counties within the state of Nevada and examined for helminth parasites. Two species of Nematoda, phrynosoma (Ortlepp, 1922) and Cyrtosomum readi Gambino, 1958, and one adult cestode Diochetos phrynosomatis Harwood, 1932 were collected. In addition, 11 animals harbored tapeworm cysts in their livers. A checklist of endoand ectoparasites of horned toads is presented. This study represents the first published report of helminths of this host from Nevada. Ectoand endoparasites have been extensively reported from homed toads. Endoparasites include primarily helminths (nematodes, cestodes, and acanthocephalans) and protozoa. Virus-like bodies have been also reported (Table I). Records of parasites of these hosts encompass investigations chiefly throughout the deserts of southwestern United States and Mexico. There has been no previous publication concerning parasites of homed toads from Nevada, although two species, comprising four subspecies of horned toads (Phrynosoma douglassii douglassii Bell, d. ornatum Girard, platyrhinos platyrhinos Girard, and p. calidiarum Cope are known to occur here (Schmidt, 1953; Stebbins, 1954). The former two subspecies of horned toads range primarily in the northern part of the state and only d. douglassii (one animal) is included in this study. One hundred and four animals, mostly platyrhinos, were collected from areas of six counties within the state: Clark (77), Lincoln (15), Nye (9), Ormsby (1), Humboldt (1), and White Pine (1). These animals were obtained as kills, by shooting or trapping, and by hand, since they are docile and frequently freeze when approached. As the animals were collected, they were labelled, placed in 10% formalin solution, changed to 70% alcohol, and later examined, employing routine procedures. Four species of helminths were recovered, including two of Cestoda and two of Nematoda. The collection data are given in Table II. A discussion of each parasite follows. Received for publication 12 August 1966. * This work was supported in part by Grant No. 1-1614034 from the Desert Research Institute. NEMATODA phrynosoma (Ortlepp, 1922) (Figs. 1-4) Two species of physalopterids have been described from horned toads. Physaloptera abbreviata Rudolphi, 1819 was reported from Phrynosoma regale Girard (= solare Gray) and/or hernandezi Girard at intervals between 1878-1920 by various authors, including Linstow, Molin, Olssen, Schneider, Seurat, Stiles and Hassall, and Stossich (Stiles and Hassall, 1920). Physaloptera phrynosoma was described from the stomachs of Phrynosoma cornutum Harlan and solare (syn. regale) by Ortlepp (1922). It was reported by Walton (1927) as being present in Leidy's collection, having been taken from P. hernandesi. The species was removed to the genus Schulz in 1927, later partially redescribed by Cobb (1928) and more fully described by Caballero (1937) as Skrjabinoptera (Didelphysoma) phrynosoma Schulz, 1927. In addition to presenting measurements of the worm and a key to three species of Skrjabinoptera, Morgan (1942) concurred with Schulz in considering Physaloptera abbreviata as belonging to the genus Abbreviata Travassos, 1920. In his revision of the physalopterids, Chabaud (1956) retained S. phrynosoma and A. abbreviata (Rudolphi, 1819) and, based upon oral denticulation, discussed and diagrammed features for separating these genera. Yamaguti (1961), on the other hand, included both species in Physaloptera Rudolphi, 1819. phrynosoma is the most commonly found nematode of horned toads (Table I). From Phrynosoma platyrhinos it has been