A review of Gongylonema spp. (Nematoda: Gongylonematidae) in North American rodents with description of a new species from the cotton rat, Sigmodon hispidus (Mammalia: Cricetidae)

Gongylonema archboldi n. sp. (Nematoda: Gongylonematidae) is described from tunnels in the gastric mucosa of the stomach of the cotton rat (Sigmodon hispidus) from Highlands County, Florida, U.S.A. Measurements are also given for specimens from cotton mice (Peromyscus gossypinus), oldfield mice (Peromyscus polionotus), Florida mice (Podomys floridanus), and golden mice (Ochrotomys nuttalli) from the same locality. Additional specimens were collected from the cotton rat and the rice rat (Oryzomys palustris) from Berry Island, San Patricio County, Texas. The new species is differentiated from congeners by a combination of the following characters: length of the left spicule, length and shape of the gubernaculum, distribution of cuticular bosses, length of esophagus, and distance of the vulva from the posterior end. The status of the genus Gongylonema in North American rodents is reviewed.


Introduction
Nematodes of the genus Gongylonema Molin, 1857 (Spirurida: Gongylonematidae) dwell in the epithelial mucosa of the mouth, esophagus, and stomach of mammals and birds. Although there has been no comprehensive taxonomic review of the genus since Yamaguti (1961), there are currently about 47 species recognized, 10 of which parasitize birds and 37 mammals. Of the 37 mammalian species, 15 are found in rodents. Only 5 species have been recorded in North American rodents: Gongylonema neoplasticum (Fibiger & Ditlevsen, 1914); Gongylonema pulchrum Molin, 1857; Gongylonema dipodomysis Kruidenier & Peebles, 1958; Gongylonema peromysci Kruidenier & Peebles, 1958;and Gongylonema mysciphilia Frandsen & Grundmann, 1961. Table 1 lists North American records from rodents for these 5 species, as well as records of Gongylonema not identified to species. Experimental infections and infections in zoo animals are not included. Between 1972 and1973, an unidentified species of Gongylonema was found in cotton rats, Sigmodon hispidus Say & Ord, in southern Florida, as well as in 4 other species of cricetid mice (Kinsella, 1974(Kinsella, , 1991Forrester, 1992). More recently, the same species was found in cotton rats and rice rats, Oryzomys palustris (Harlan) in eastern Texas. This paper describes this new species and reviews other species found in North America.

Material and methods
Some hosts infected with Gongylonema were collected by JMK in Sherman live traps between October, 1972 andAugust, 1973 at Archbold Biological Station (ABS), Highlands County, Florida, U.S.A. The remaining hosts were collected in Sherman live traps between June and August, 2015 by WCP on Berry Island, San Patricio County, Texas. Names of hosts follow Wilson & Reeder (2005). Nematodes were teased from the gastric mucosa using fine forceps, killed in glacial acetic acid, and preserved in 70% ethanol with 5% glycerine. Specimens were cleared and studied in temporary mounts of lacto-phenol and then returned to the preservative. Drawings were made with the aid of a drawing tube. Some specimens were dried using the critical point method, examined via Scanning Electron Microscopy (SEM) (JEOL JSV 6360 LV, Tokyo, Japan), and photographed.
All measurements are in microns unless otherwise specified. Type and paratype specimens were deposited in the National Parasite Collection in the United States National Museum (USNM), Smithsonian Institute, Washington D.C., U.S.A. Vouchers from Texas collections were deposited in the Harold W. Manter Laboratory (HWML) at the University of Nebraska, Lincoln, Nebraska, U.S.A..

Results
A total of 5 of 22 (23%) cotton rats at ABS were infected with 1 to 15 (mean 6.0) specimens of Gongylonema. Because of the difficulty of teasing them from epithelial tunnels, only a few females were recovered intact. Infections of the same species were found in 12 of 86 (14%) cotton mice, Peromyscus gossypinus (LeConte); 4 of 41 (9.8%) oldfield mice, Peromyscus polionotus (Wagner); 15 of 102 (15%) Florida mice, Podomys floridanus (Chapman); and 2 of 18 (11%) golden mice, Ochrotomys nuttalli (Harlan) from ABS. In addition to being lower in prevalence, infections in the 4 species of mice were lower in average intensity and females tended to be less gravid.
In 2015, additional specimens were collected from 3 of 4 (75%) cotton rats and 1 of 4 (25%) rice rats, Oryzomys palustris (Harlan) from Berry Island in San Patricio County, Texas. Gravid worms were found in both hosts. These specimens matched the Florida material in all respects except for a longer left spicule length, which we attribute to geographic variation.
Although we believe that all of the specimens reported here represent the same species, in order to be conservative, the following description is based only on specimens from cotton rats from Florida. Measurements from the other Florida hosts are given in Table 2.
Description. With characteristics of the genus. Long filiform worms with prominent cuticular bosses at the anterior end, more numerous in the female than the male ( Fig. 1A, 1B lateral constrictions opposite 2 large, lateral amphids. Three triangular teeth, 1 dorsal and 2 subventral on each side of mouth opening with a circle of 4 small papillae surrounding mouth opening. Two prominent lateral alae beginning at level of base of pharynx and extending to near the anus in both sexes (Fig 2C).