Pyrgulopsis madridensis Perez, 2022

Perez, Kathryn E., Hutchins, Benjamin T., Solis, Megan & Schwartz, Benjamin F., 2022, New species of Pyrgulopsis Call & Pilsbry, 1886 (Mollusca: Caenogastropoda Hydrobiidae) from two Chihuahuan Desert springs, Zootaxa 5213 (1), pp. 64-74 : 69-72

Pyrgulopsis madridensis Perez , sp. nov.

urn:lsid:zoobank.org:act:F22BFC52-391E-41FB-877C-D27360C1FFE3

Figs. 4A–H , 5A–D , 6A–D .

Diagnosis. A low-conical to trochoform snail with visible growth lines on teleoconch. Aperture ovate and usually separated from body whorl in adults with a distinct groove. Mantle tissue pigmented gray-black or unpigmented. Sharply pointed median cusp of lateral radular teeth. Penial lobe much shorter than filament, with large terminal gland and numerous large penial glands on the lobe.

Types. Holotype ANSP A492826 , paratypes ANSP A492828 , all from Madrid Falls , Presidio County, Texas.

Type locality. Madrid Falls , Big Bend Ranch State Park, 29.37975 W, -103.88411 N, Presidio County, TX

Additional materials examined. ANSP A492830 , South Fork , Crawford-Smith Canyon , Big Bend Ranch State Park, 29.39205 W, -103.87243 N, Presidio County, TX .

Etymology. We use the specific epithet “ madridensis ” reflecting the type locality, a spectacular waterfall in desert west Texas.

Remarks. We propose the common name “Madrid Falls springsnail”.

Description. Shell low-conical to ovate-conic, pale to light brown in color ( Fig. 4A–C ; 5A–B ). In life, the shell usually appears partially or completely black in color due to the shell being covered in dark-colored biofilm. The spire is relatively short with convex to slightly shouldered whorls. Whorls with a distinct suture. Protoconch with the initial portion lightly punctate ( Fig. 5C–D ). Teleoconch with strong growth lines. Aperture ovate, angled above, sometimes appressed to body whorl, but usually slightly separated with a distinct groove or gap between aperture and previous whorl. Peristome complete, inner lip sometimes nearly straight, slightly reflected in the columellar portion and outer lip. Outer lip simple, slightly prosocline. Umbilicus narrow.

Average shell measurements for n = 15 adult individuals from Madrid Falls: shell height = 1.73 mm (SD = 0.20), shell width = 1.41 mm (SD = 0.12), body whorl width = 1.21 mm (SD = 0.11), aperture height = 0.95 mm (SD = 0.08), aperture width = 0.85 mm (SD = 0.10), number of whorls = 3.47 (SD = 0.27). Average shell measurements for n = 15 adult individuals from Crawford-Smith Canyon: shell height = 2.14 mm (SD = 0.27), shell width = 1.53 mm (SD = 0.13), body whorl width = 1.30 mm (SD = 0.13), aperture height = 1.05 mm (SD = 0.08), aperture width = 0.93 mm (SD = 0.10), number of whorls = 3.98 (SD = 0.06).

Operculum ( Fig. 4G, H ) narrowly ovate, flat, light amber, except for pale narrow fringe; eccentric nucleus, paucispiral growth pattern.Attachment scar distinct and ending with gap before columellar edge. Attachment region callus moderately thick. Growth lines distinct, simple. Outer margin thin but with raised ridge along inner margin between nucleus and columellar edge. Pale, outer margin wider on the rest of the operculum.

Central radular tooth ( Fig. 6A–B, D ) with moderately to deeply indented dorsal edge; lateral cusps 4–6; central cusp sharply pointed, considerably broader and 2X longer than lateral cusps, basal cusps narrowly elongate, straight, with slight buttress at base. Basal process medium width, broadly v-shaped; basal sockets deep. Lateral tooth face tall, rectangular, with broad neck and inner wing; central cusp large, wide, and blade-like, lateral cusps 3 (inner) and 3 (outer); on one individual, a few of the central cusps of the lateral tooth at the end of the radula were notched at tip; large, blunt basal projection and outer wing long and broad with distinct ridge along outer edge. Inner marginal teeth having 16-18 cusps; fourth cusp from outer edge enlarged. Outer marginal teeth ( Fig. 6C ) rounded and spoonlike, with a narrow neck, inner edge with a long wing and with 12-20 on the outer surface and ~20 small cusps on the inner surface pointed but small.

Tentacles pale with scattered patches of pigmentation on dorsal surface. Snout dark gray-black, light colored on distal edge. Foot darkly pigmented on part of anterior surface, and light colored beneath. Opercular lobe black along anterior edge with pigment patches elsewhere. Neck pigmented along edges, pale below. In some individuals visceral coil and pallial roof both darkly pigmented, purplish-black. In others, dark purplish pigment occurs in large patch near entrance to mantle cavity, then sparsely on rest of body.

Ctenidium occupies a small portion of the pallial cavity, at anterior end filaments triangular, broader than high, with central portion of filaments elongate, roughly triangular, both tall and wide at the base, ~15. Osphradium elongate, long, opposite posterior end to middle of ctenidium, anterior end simple.

Digestive gland occupies most of first two whorls, with highly convoluted intestine leading to stomach. Stomach as expected for Pyrgulopsis with ~ equally sized chambers. Rectum straight with anus near edge of mantle.

Testes sac-like lobe, elongate bean-shaped prostate. Penis large ( Fig. 4E, F ); filament medium length, fingerlike, rounded, tapered at distal tip; lobe shorter than filament, broad. Penial gland covers the length of the filament, distal to the body, does not appear bifurcate. Dorsal gland 1 (Dg1) robust, broad, almost separate from base of proximal end of the penis base, visible both dorsally and ventrally; Dg2 slightly curved, situated vertically, crossing penial lobe; Dg3 smaller positioned near inner base of lobe; several smaller glands run alongside Dg2. Terminal gland very large, appearing to cover terminal portion of penial lobe, visible on both dorsal and ventral sides of lobe. Ventral gland wide and prominent, near base of lobe. Filament with line of moderately dark internal pigment, appearing ventrally, and pigmental patches scattered on ventral surface.

Capsule and albumen gland similar in size, albumen gland tapered, elongate. Most (2/3) of albumen gland ahead of pallial wall. Capsule gland divided into two sections. Genital aperture near terminal end of capsule gland with small vestibule. Coiled oviduct a long, large loop. Seminal receptacle small elongate sac that narrows near insertion with common duct of seminal receptacle and coiled oviduct.

Figures

FIGURE 4. Shells and anatomical features of Pyrgulopsis madridensis sp. nov. A–C. holotype, Madrid Falls Spring, ANSP A492826. D.Animals with shell removed to show variation in pigmentation. E–F. Penial anatomy illustrating glandular features. Pf=Penial filament, Tg=terminal gland, Tl=terminal lobe, Vg=ventral gland, Dp=penial gland, Dg1=dorsal gland 1, Dg2=dorsal gland 2, Dg3=dorsal gland 3. E. Penis, dorsal surface (yellow color due to Bouin’s solution). F. Penis, ventral surface. G. Operculum, outer surface. H. Operculum, inner surface. Scale bars A–F = 100 µm; G–H = 200 µm.

FIGURE 5. Scanning electron micrographs of Pyrgulopsis madridensis sp. nov. ANSP A492829 & A492830. Shells (A–B) and protoconch (C–D). A, C, D images of individuals from Madrid Falls. B. Shell of individual from Crawford-Smith Canyon. Scale bars A–B = 500 µm; C = 100 µm; D = 20 µm.

FIGURE 6. Scanning electron micrographs of radula of Pyrgulopsis madridensis sp. nov. Individuals in A, C were from Madrid Falls and B, D from Crawford-Smith Canyon. A = portion of radular ribbon; B = portion of radular ribbon; C = portion of radular ribbon; D = lateral teeth, inner and outer marginal teeth. Scale bars = 10 µm.