Tryonia peregrina Hershler, Liu & Landye, 2011, sp. nov.
Creators: name: Hershler, Robert
name: Liu, Hsiu-Ping
name: Landye, Jerry
Publisher: name: Zenodo
Year: 2011
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Littorinimorpha
Hydrobiidae
Tryonia
Tryonia peregrina

description: Tryonia peregrina sp. nov.
(Figs 3, 4 A–D, H–I, M– O, 5A)
Tryonia sp.— Williams et al. 1985: 50 (reference to Yepomera populations). Tryonia n. sp. 1.— Hershler et al. 2005: 1757 (COI sequences).
Types. Holotype, USNM 874032, Ojo Vareleño, 2.4 km northwest of Casas Grandes, Chihuahua, 30º24'1.95" N, 107º59'7.8" W, leg. J.J.L. and P. Hines, 16/ix/1990. Paratypes (from same lot), USNM 1153677.
Etymology. The species name is derived from the Latin adjective peregrinus, meaning wandering, and refers to the distribution of this species in the Río Casas Grandes (interior) and Río Papigochic (Pacific) drainages.
Referred material. CHIHUAHUA. USNM 892114, topotypes, leg. R.H and J.J.L., 6/xii/1998. USNM 873288, USNM 873299, spring on east side of Yepomera, 29º3'19.55" N, 107º50'33.82" W, leg. J.J.L., 15/iv/1973. USNM 1138233, ibid., leg. J.J.L., 11/iii/2010. USNM 873197, spring on west side of creek in northwest part of Yepomera, 29º3'55" N, 107º51'29" W (estimated), leg. J.J.L., 10/xi/1980. USNM 873269, spring run at Rancho El Ojito, 29º3'58" N, 107º51'13" W (estimated), leg. J.J.L., 16/iv/1973.
Diagnosis. Shell medium-sized, conic; penis having two distal papillae on the inner edge and a basal papilla both on the inner and outer edges. Differs from T. zaragozae (described next), which is the only other congener that is distributed in the Río Casas Grandes or Río Papigochic drainages, in its more convex and weaker sculptured teleoconch whorls, more rounded adapical end of the shell aperture, umbilicate shell, and smooth inner side of operculum. Differs from T. hertleini (Drake, 1956), an apparently extinct species (Hershler 2001) which was distributed near the terminus of the Río Casas Grandes drainage (Fig. 1, locality 1), in its larger size (4.08 vs. 3.08 mm mean shell height, t-test, t=-5.916, df = 8.3, P <0.01; n=5 for T. hertleini), larger size and number of cusps on the inner marginal radular teeth, smaller basal papilla on the inner edge of the penis, and in having a papilla on the outer edge of the penis.
Description. Shell (Fig. 4 A–D) up to 5.9 mm tall, large females having 4.75–7.5 whorls, spire height 150–200% width of shell, male shells smaller than those of females. Teleoconch whorls medium to highly convex, evenly rounded with impressed sutures. Aperture usually rounded, sometimes weakly angled adapically. Parietal lip complete, adnate or slightly disjunct, umbilicus narrow. Outer lip usually orthocline, sometimes weakly opisthocline, sometimes weakly sinuate. Sculpture of strong growth lines and weak spiral threads. Periostracum dark brown.
Shell measurements (mean in parentheses): height 3.45–4.80 mm (4.08), width 1.56–1.90 mm (1.71), body whorl height 1.83–2.29 mm (2.06), body whorl width 1.46–1.82 mm (1.64), aperture height 1.06–1.29 mm (1.18), aperture width 0.86–1.06 mm (0.94), total number of whorls 5.75–6.50 (6.12) (USNM 1153677, n = 13).
Measurements of holotype: height 3.94 mm, width 1.57 mm, body whorl height 1.96 mm, body whorl width 1.51 mm, aperture height 0.92 mm, aperture width 0.40 mm, 6.25 whorls.
Inner and outer sides of operculum smooth (Fig. 4 H-I). Radula (Fig. 4 M-O): dorsal edge of central teeth concave, basal tongue rounded or V-shaped, median cusps elongate, distally pointed, parallel-sided proximally, lateral cusps four–six, basal cusps one–three, usually two (innermost larger; Fig. 4 N). Lateral teeth having two–three cusps on inner and four–five cusps on outer side, length of outer wing about 200% width of cutting edge, central cusp pointed or hoe-shaped (Fig. 4 O). Inner marginal teeth with 21–33 cusps, outer marginal teeth with 29–42 cusps. Radula data are from USNM 873288, USNM 1153677.
Animal darkly pigmented. Penis (Fig. 5 A) having two distal and one basal papillae on inner edge and a slightly enlarged basal papilla on outer edge (40 of 46 specimens from two samples); one specimen differed in having a single distal papilla on inner edge, one specimen had three distal papillae along the inner edge, and three specimens lacked a papilla on the outer edge. Basal papilla along inner edge often small. Distal bulb of penis expanded laterally on inner side, black; stylet small. Penial duct undulating along most of length. Penial data are from USNM 873299, USNM 1153677.
Distribution and habitat. Tryonia peregrina is distributed in a single locality in both the Río Casas Grandes and Río Papigochic drainages (Fig. 1, localities 2–3). The type locality, Ojo Vareleño, consists of numerous small springs that form a large cienega (Fig. 6 A). Some of these springs have been developed for domestic water usage while others have been diverted into an earthen canal that courses southwest towards Casas Grandes. Tryonia peregrina was found in intermediate elevation springs within the cienega (in detritus) and in the canal; snails were especially abundant in the latter at a small ranch, Chulavista, about 1.0 km downflow from the spring sources. A Tryonia -like species, Eremopyrgus elegans Hershler et al., 2002b is distributed in the upper portion of this cienega (Hershler et al. 2002b). The water temperature of these habitats is about 27°C. Tryonia peregrina is also distributed in a large spring on the east side of Yepomera (Fig. 6 B) that is referred to locally as El Ojo de Yepomera (Miller et al. 2005). In 1973 this snail was found in both the walled headspring (on rocks) and in the outflow (on rocks and on the bases of aquatic vegetation). The site was re-visited in 1998, when the headspring was being developed into a new domestic water system, and T. peregrina was not found. However, in 2010 it was abundant (in sand and aquatic vegetation) in the (19°C) outflow; the status of the population in the headspring, which has been transformed into a large pond, is uncertain. In 1973 T. peregrina was also found in a small (17°C) spring brook at Rancho El Ojito on the north side of Yepomera, and in an oxbow cienega on the northwest side of the village. Snails were not found at these sites during several subsequent visits to the area; the spring at Rancho El Ojito was dry or capped when visited in 1998.
Remarks. Tryonia peregrina was delineated in the Bayesian analysis as a well supported lineage (Fig. 2). The two populations of this species are closely similar in all morphological details; their haplotypes differed by 0.17–0.5%.
description: Published as part of Hershler, Robert, Liu, Hsiu-Ping & Landye, Jerry, 2011, New species and records of springsnails (Caenogastropoda: Cochliopidae: Tryonia) from the Chihuahuan Desert (Mexico and United States), an imperiled biodiversity hotspot, pp. 1-32 in Zootaxa 3001 on pages 7-9, DOI: 10.5281/zenodo.278442