Pyrgulopsis milleri, Hershler, Robert & Liu, Hsiu-Ping, 2010

Hershler, Robert & Liu, Hsiu-Ping, 2010, Two new, possibly threatened species of Pyrgulopsis (Gastropoda: Hydrobiidae) from southwestern California, Zootaxa 2343, pp. 1-17 : 10-15

Pyrgulopsis milleri sp. nov.

( Figs 6–8 )

Types. Holotype ( Fig. 6 A), SBMNH 83651, creek 0.7 mile (1.13 km) east of Pierpoint Spring on (California) Hwy 190, approximately 15.6 miles (25.1 km) east of Springville, Tule River drainage, Tulare County, California, Walter B. Miller, 1/viii/1964. Paratypes, SBMNH 74688, USNM 1132568 (from same lot, 211 + 6 dry shells, respectively).

Etymology. In honor of deceased zoologist Walter B. Miller, an intrepid collector of western North American nonmarine mollusks ( Hochberg & Roth 2001) who first discovered this novelty in 1964.

Referred material. CALIFORNIA. Tulare County: SBMNH 74687, Pierpoint Spring, 6.5 miles (10.46 km) east of Tule River power house, 353028 E, 4000829 N (approximate coordinates), Walter B. Miller, 31/ vii/1964. USNM 905257, ibid., Robert Hershler, 26/vi/2000. SBMNH 74540, spring along Hwy 190 7 miles (11.23 km) east of Tule hydroelectric plant, Walter B. Miller, 25/i/1963.

Diagnosis. A medium-sized species having ovate- to narrow-conic shell with weakly convex whorls. Penis usually alobate; filament medium length; penial ornament usually consisting of a small ventral gland.

Description. Shell ( Fig. 6 A–D) ovate- or narrow-conic, height about 2.5–4.0 mm; whorls 4.25–5.25. Periostracum tan, thin, often covered with dark deposits. Protoconch ( Fig. 6 E) near planispiral, 1.3–1.5 whorls, diameter about 380 µm, surface weakly wrinkled near apex ( Fig. 6 F), otherwise smooth. Teleoconch whorls weakly convex, sometimes narrowly shouldered, last 0.25 whorl rarely slightly loosened; sculpture of collabral growth lines. Aperture ovate, angled adapically. Inner lip complete, usually adnate, slightly thickened internally; columellar shelf absent; outer lip thin, weakly prosocline. Umbilicus narrow.

Operculum ( Fig. 6 G) thin, flat, light amber, multispiral with eccentric nucleus; last quarter whorl frilled on outer side; inner side ( Fig. 6 H–I) having attachment scar border slightly thickened almost all around. Radula taenioglossate ( Fig. 7 A), having about 55 well-formed rows of teeth. Central teeth ( Fig. 7 B) about 28 µm wide, cutting edge concave; lateral cusps 3–6; central cusp large, U-shaped; basal cusp 1, small; basal tongue V-shaped, about as long as lateral margins. Lateral tooth ( Fig. 7 C) face rectangular, angled; central cusp large, U-shaped; lateral cusps 2–4 (inner), 3–5 (outer); outer wing medium width, straight, about 200% length of cutting edge; basal tongue well developed. Inner marginal teeth ( Fig. 7 D) having 17–21 cusps. Outer marginal teeth ( Fig. 7 E–F) having 19–28 cusps; inner edge having long, rectangular wing. Radula data were from USNM 905257.

Head-foot generally pale. Snout usually pale, but sometimes light to dark brown. Pallial roof, visceral coil dark brown or black. Ctenidium well developed, positioned a little in front of pericardium; ctenidial filaments about 20, broadly triangular. Osphradium narrow, positioned slightly posterior to middle of ctenidium. Prostate gland large, bean-shaped, with about 40% of length in pallial roof. Anterior vas deferens opening from ventral edge of prostate gland a little in front of posterior pallial wall, section of duct on columellar muscle straight. Penis ( Fig. 8 A–C) medium-sized, base rectangular, inner edge smooth; filament short or medium length, tapering, slightly oblique; lobe usually absent, nub-like when present ( Fig. 8 C). Terminal gland (observed in one specimen) small, ovate, positioned on ventral surface of lobe. Ventral gland small, ovate, centrally positioned, borne on raised swelling. Penial duct narrow, nearly straight. Penis entirely pale or with filament variably pigmented by black granules. Female glandular oviduct and associated structures shown in Figure 8 D–F. Coiled oviduct a small, proximally kinked, posterior-oblique loop. Bursa copulatrix small, narrowly ovate, horizontal, about 50% overlapped by albumen gland. Bursal duct about as long as bursa, medium width, opening from distal edge, partly embedded in albumen gland. Seminal receptacle small, pouch-shaped, positioned along ventral edge of proximal bursal duct; duct short. Albumen gland a little shorter than capsule gland, having very short pallial section. Capsule gland composed of a single tissue section. Genital aperture a terminal slit.

Shell measurements (mean + standard deviation in parentheses): height 3.00–4.00 mm (3.42+0.35), width 2.00– 2.50 mm (2.17+0.12), body whorl height 2.25–2.75 mm (2.45+0.15), body whorl width 1.70–2.19 mm (1.87+0.13), aperture height 1.36–1.61 mm (1.46+0.07), aperture width 1.15–1.41 mm (1.25+0.06), shell width/height 0.58–0.69 (0.64+0.03), body whorl height/shell height 0.67–0.76 (0.72+0.02), aperture height/ shell height 0.39–0.47 (0.43+0.02) (paratypes, SBMNH 74688, n = 30). Height 2.91–3.46 mm (3.12+0.14), width 1.77–2.16 mm (1.97+0.08), body whorl height 2.10–2.57 mm (2.30+0.10), body whorl width 1.52–1.80 mm (1.65+0.07), aperture height 1.23–1.57 mm (1.39+0.07), aperture width 1.08–1.31 mm (1.16+0.06), shell width/height 0.57–0.66 (0.63+0.02), body whorl height/shell height 0.68–0.77 (0.74+0.02), aperture height/ shell height 0.39–0.48 (0.45+0.02) (SBMNH 74687, n = 30).

Measurements of holotype: height, 3.70 mm, width 2.36 mm, body whorl height 2.67 mm, body whorl width 2.01 mm, aperture height 1.59 mm, aperture width 1.39 mm, shell width/height 0.64, body whorl height/shell height 0.72, aperture height/shell height 0.43, 5.0 whorls.

Distribution, habitat and conservation status. Pyrgulopsis milleri is known only from its type locality area, which consists of spring-fed waters along a very short (ca. 1.0 km) reach of the South Fork of the Middle Fork Tule River drainage. Pierpoint Spring spills down a rock face into a ditch right alongside Hwy 190; part of its flow issues from a pipe (see Jenkins & Jenkins 1995:153 for a photograph of this spring). The first author collected P. milleri from aquatic vegetation in this ditch; density was low. There is no information on the habitat and current status of the other two populations which Miller sampled during the early 1960’s. (The first author did not attempt to access these sites during his brief visit to the area in 2000.)

Pyrgulopsis milleri is distributed within a parcel of patented (private) land that is nested within the Giant Sequoia National Monument (Sequoia National Forest). This species currently has no protection and may be threatened by the diversion of Pierpoint Spring, physical disturbance (e.g., trampling, pollution) associated with the frequent use of this spring as a drinking water supply by travelers on CA Highway 190 ( Jenkins & Jenkins 1995:153), and the planned local widening of this road (CDOT 2009).

Remarks. Pyrgulopsis milleri differs from closely similar P. stearnsiana , which ranges into the lower portion of the Tule River basin (Hershler unpublished), in its broader central cusps on the central radular teeth, shorter pallial section of the albumen gland, greater overlap of the bursa copulatrix by the albumen gland, absence of a bend or loop in the anterior vas deferens, presence of a ventral gland on the penis and absence (except in one specimen) of a terminal gland. Pyrgulospis milleri was most similar to P. stearnsiana from the Santa Clara River basin (21AA) in its mtCOI sequences (2.8% divergence) and differed from other specimens of this species by 3.3–8.4%. Thus, as with P. castaicensis (described above), both morphological and genetic evidence indicate that this snail is a new species.

Based on the road distances provided by Miller we infer that Pierpoint Spring is the well known (unnamed) spring that is shown on USGS maps along the north side of Hwy 190 about 0.6 km east of the Pierpoint Springs Resort and 1.6 km east of Camp Nelson.

Figures

FIGURE 6. P. milleri sp. nov. A – D. Shells. Scale = 1.0 mm. A. Holotype, SBMNH 83651. B – C. Paratypes, SBMNH 74688. D. SBMNH 74687. E. Shell apex, SBMNH 74688. Scale = 100 µm. F. Close-up of protoconch sculpture, SBMNH 74688. Scale = 100 µm. G – I. Opercula, USNM 90527. Scale = 500 µm. G. Outer side. H – I. Inner side, showing variation in thickening of attachment scar margin.

FIGURE 7. P. milleri sp. nov., USNM 90527, scales = 10 µm. A. Portion of radula ribbon. B. Central radular teeth. C. Lateral tooth. D. Inner marginal teeth. E – F. Outer marginal teeth. Wg = wing.

FIGURE 8. P. milleri sp. nov., USNM 90527. Scale = 0.5 mm. A – C. Penis. A. Dorsal surface. B – C. Ventral surface, showing ventral and terminal glands. D. Female glandular oviduct and associated structures (viewed from the left side). E. Bursa copulatrix and its duct. F. Seminal receptacle and its duct. Ag = albumen gland, Bu = bursa copulatrix, Cd = common duct of seminal receptacle and coiled oviduct, Cg = capsule gland, Co = coiled oviduct, Dbu = bursal duct, Ga = genital aperture, Pd = penial duct, Pf = penial filament, Pl = penial lobe, Pw = posterior wall of pallial cavity, Sr = seminal receptacle, Tg = terminal gland, Vc = ventral channel, Vg = ventral gland.