Pyrgulopsis rubra Perez, 2021

Perez, Kathryn E., Leal, Manuel Spor, Glover, Houston, Chastain, Rebecca T., Hutchins, Benjamin T. & Schwartz, Benjamin, 2021, Two new species of Pyrgulopsis Call & Pilsbry, 1886 (Mollusca: Caenogastropoda: Hydrobiidae) from springs in the Rio Grande watershed in Texas, Zootaxa 5071 (3), pp. 384-402 : 393-396

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Pyrgulopsis rubra Perez

sp. nov.

Pyrgulopsis rubra Perez , sp. nov.

Figs. 8A–F View FIGURE 8 , 9A–F View FIGURE 9 , 10A–E View FIGURE 10 .

Diagnosis. Shell ovate-conic, pale brown with slightly convex whorls. Aperture ovate, usually appressed to body whorl. Mantle tissue pigmented reddish. Rounded median cusp of central radular teeth. Penial gland does not bifurcate at proximal end, terminal gland of the penis extending to ventral and dorsal aspects.

Types. HolotypeANSPA483288,paratypesANSPA483289, all from PaloAmarillo Springs , Presidio County,TX .

Type locality. PaloAmarillo Springs , Big Bend Ranch State Park, 29.50925N,- 104.17158W, Presidio County,TX GoogleMaps .

Etymology. We use the specific epithet “rubra” to refer to both the reddish pigmentation on the tissues of this snail and the red volcanic rock faces in the high canyon walls and surrounding landscape.

Remarks. Among the 30 individuals dissected from this population, only 1 male was observed. Therefore, features of the male anatomy were observed in one individual and should be considered accordingly.

Description. Shell ovate-conic, very pale brown in color, taller spire with slightly convex and shouldered whorls. Protoconch uneroded, mostly smooth with scattered raised granules. Teleoconch with strong growth lines. Aperture ovate, angled above, nearly appressed to body whorl. Peristome complete, inner lip slightly thickened. Outer lip prosocline, simple. Narrowly umbilicate. Average shell measurements for n= 10 adult individuals: shell height= 2.49 mm (SD=0.17), spire height= 0.48 mm (SD=0.08), body whorl height= 2.01 mm (SD=0.13), shell width= 1.84 mm (SD=0.10), body whorl width= 1.34 mm (SD=0.15), aperture height= 1.30 mm (SD=0.05), aperture width= 1.06 mm (SD=0.09), number of whorls=4.20 (SD=0.16).

Operculum ( Fig. 9E, F View FIGURE 9 ) narrowly ovate, flat, light amber, nucleus eccentric and paucispiral. Attachment scar thickened midway to columellar edge. Attachment region callus concentrated near nucleus but with usual extent for the group. Growth lines distinct, but slight, simple. Wide band of thinned outer edges especially along outer margin, without a hint of a ridge, not elevated.

Central radular tooth ( Fig. 9 View FIGURE 9 ) with moderately indented dorsal edge; lateral cusps 5; central cusp rounded, considerably broader, and longer than laterals, basal cusp 1, widely elongate, slightly curved, with moderate, wide dorsal support. Basal process medium width, narrowly v-shaped; basal sockets deep. Lateral tooth face wide; Central cusp narrowly shovel-like, lateral cusps bluntly pointed, 3–4 (inner) and 3–4 (outer); outer wing broad and about same length as cutting edge. Inner marginal teeth having 14–16 cusps which enlarge rapidly beginning with the 5th tooth from the outer edge. Outer marginal teeth having ~13-small, terminal cusps, outermost tooth usually shorter and wider than others, inner edge of tooth margin sometimes with a short wing, near mid-length.

Cephalic tentacles tapered,rounded, nonexpanded, weakly developed eye lobes.Tentacles pale, except for weakly pigmented patch just distal to eye. Some individuals have patch extended into two lines of weak pigment running proximal to eyespot and ending halfway to distal end of tentacle. Snout with dark reddish-brown pigmentation, light colored on distal end. Foot pigmented reddish along anterior portion. Opercular lobe broadly pigmented along anterior portion, with spotty pigment throughout. Neck pale. Pallial roof uniformly dark reddish-brown. Mantle edge of pallial roof without coloration. Visceral coil consistent red pigment, with regular dark reddish-brown patches. Ctenidium occupies nearly the entire length of pallial cavity, filaments broader than high, with filaments elongate, roughly triangular in shape, wider at the base, slightly rounded at tip, ~15. Osphradium broadly ovate, short, opposite near middle of ctenidium, anterior end simple.

Penis large ( Fig. 8D,E View FIGURE 8 ); filament medium length, narrow; lobe half the length of filament, broad. Penial gland covering most of filament, not noticeably bifurcate. Dg1 short, slightly oblique, stretching from just behind penial gland to near base of penis; Dg2 positioned along far left edge, slightly curved proximally toward Dg1; Dg3 very short, positioned at conjunction of lobe and filament. Terminal gland long, transverse, reaching from midpoint of dorsal lobe across outer edge and to near midpoint of ventral lobe. Ventral gland short, vertically aligned. Filament with moderately dark internal pigment.

Capsule gland similar in size to albumen gland. Coiled oviduct a large loop, as large as albumen gland and covering it, with a darkly pigmented stripe. Bursa copulatrix rounded at posterior end, same width as albumen gland, posterior to gland and nearly the same size. Seminal receptacle elongate, slightly curved, larger at the end and narrow near insertion with common duct of seminal receptacle and coiled oviduct, extends nearly to end of albumen gland.

Habitat and Distribution. Palo Amarillo Spring, (89 km SSE of Vasquez Spring) is in a canyon on the SW side of the Big Bend Ranch State Park. The Palo Amarillo Spring population (~ 10 m 2) is found in high concentrations on or just below a vertical igneous bedrock face where a single small spring discharges from a horizontal fracture and flows into a small spring-fed creek in a canyon. Habitat is in a sheet of water flowing down a 2–3 m vertical rock face and through vegetation into an adjacent pool in the canyon. In lower densities on cattail, algae, and on fallen Opuntia sp. pads where spring flows into main pool ( Fig. 11B View FIGURE 11 ). Water temperature was 22.45 °C, pH = 7.85, conductivity = 894.1 (µS/cm), dissolved oxygen = 7.83 mg /L.