Plagiodontes weyenberghii (Doering, 1877)

Pizá, Julia & Cazzaniga, Néstor J., 2012, Barrels and pagodas: clarifying the identity and variability of two nominal taxa of carinated land snails in the genus Plagiodontes (Gastropoda: Orthalicidae: Odontostominae), Journal of Natural History 46 (7 - 8), pp. 383-410 : 390-393

Plagiodontes weyenberghii ( Doering, 1877 [“1875”])

Bulimus (Plagiodontes) weyenberghii Doering, 1877 [“1875”], p. 241; Doering 1878 [“1876”]: 322.

Bulimus (Plagiodontes) weyemberghii: Doering 1877 [“1875”], p. 241; Doering 1878 [“1876”]: 322 (lapsus calami); Kobelt 1878. p. 133.

Bulimus weyenberghii: Kobelt 1880, p. 289 ; Breure 1974, p. 126.

Odontostomus (Plagiodontes) weyenberghi: Pilsbry 1901, p. 100 –101; Holmberg 1912, p. 25–26; Parodiz 1939, p. 728.

Odontostomus (Plagiodontes) weyemberghi: Parodiz 1943 [“1942”], p. 340.

Cyclodontina (Plagiodontes) weyemberghi: Parodiz 1957, p. 28 .

Plagiodontes weyenberghi: Hylton-Scott 1965, p. 24 .

Scalarinella (Plagiodontes) weyemberghi: Zilch 1971, p. 199 .

Plagiodontes weyemberghi: Fernández 1973, p. 154 .

Odontostomus weyemberghii: Breure 1974, p. 126 .

Plagiodontes weyemberghii: Breure and Schouten 1985, p. 17 ; Cuezzo and Dragh 1995, p.196.

Odontostomus weyemberghi: Richardson 1993, p. 52 .

Diagnosis

Cylindrical to pagoda-shaped by the presence of a sutural keel, brownish shell of medium size, with a short, wide and obtuse apex. Protoconch and teleoconch sculptures forming a transition area. Teleoconch sculpture with strong axial ribs and minor undulated axial striae in between. Aperture with an expanded and slightly reflected peristome. Pallial complex moderately vascularized. Free portion of the fertilization pouch–spermathecal complex long and straight. Bursa copulatrix duct markedly swollen distally. The penial papilla has an accessory lobe slightly shorter than the papilla. Vagina with a medial longitudinal depression.

Type series

Holotype, SMF 9354 28.44 mm long, 14.35 mm wide ( Figure 1 ); four paratypes, SMF 9355 .

Type locality

Chancaní, Sierra de Pocho. Córdoba province, Argentina.

Distribution

Endemic to Sierra de Pocho , north-western Córdoba province .

Description

Shell ( Figures 1 , 2 , 6 ). Cylindrical to pagoda-shaped, rimate, solid, light-brown to brown. 20.14–28.5 mm long by 10.25–13 mm wide. It has 6.25 to 8.25 flattened whorls, almost straight, with a suprasutural carina of variable development. Spire cylindrical trapezoid in shape, occupying 29–45% of shell length. The apex is a short and obtuse cone. Aperture subvertical, ovate, 9.29–13.24 mm long by 7.14–10.39 mm wide with a widely expanded and reflected peristome in adult specimens.

Protoconch and teleoconch sculpture ( Figure 7 A–D). Protoconch of 2 to 2.5 whorls with conspicuous axial ribs, crossed by spiral lines less marked with an internal depression in most specimens ( Figure 7A,C ). Protoconch-teleoconch boundary not well defined, forming a transition area ( Figure 7A,B ). Teleoconch with strong, straight axial ribs with minor undulated spiral elements in the intercostal space ( Figure 7B,D ).

Apertural lamellae and folds ( Figures 1 , 2 ). The studied specimens had 9 to 13 apertural lamellae and folds (mode = 11) similar to those of the remaining Plagiodontes species ( Pizá and Cazzaniga 2003, 2009; Cazzaniga et al. 2005; Pizá et al. 2006). Angular fold joined to the parietal lamella; a supracolumellar denticle present in 50% of the specimens. Frequencies of lower palatal folds distributed as shown in Figure 8 .

Pallial complex ( Figure 9 ). General arrangement similar to that already described for other Plagiodontes species ( Pizá and Cazzaniga 2009, 2010), 30 and 35 mm long in the studied specimens. The pericardium, 4.73 and 4.76 mm long, occupied 52 and 60% of the kidney length. The kidney, triangular in shape, occupied 20 and 30% of the pallial complex length. The ureteric pore opened at the level of the midpoint of the kidney in one specimen and above it in the other. Pulmonary vein 19 and 25.7 mm long; the afferent marginal vein branched near the midpoint of the pulmonary vein. The vascularization was conspicuous in the adrectal area and weaker in the area between the pulmonary vein and the marginal afferent vein. Marginal vein poorly vascularized. The mantle collar included a spongy pallial gland and some dents corresponding to the position of the apertural lamellae and folds.

Genital system ( Figures 10–13 ). It followed the general arrangement found in the remaining Plagiodontes species, and presented a general whitish pigmentation. Creamcoloured ovotestis, composed of seven and eight groups of digitiform acini. White and conspicuous fertilization pouch–spermathecal complex, its free portion composed of a long, straight blind sac ( Figure 11A,B ). Albumen gland elongated and whitish. Spermoviduct long, with two circumvolutions in both studied specimens. Vas deferens emerges just above the point where the vagina bifurcates in the free oviduct and the bursa copulatrix duct, and ends in the epiphallus–flagellum boundary after running through the retractor muscle. Bursa copulatrix a round sac, 1.8 and 3 mm in diameter; its duct 25 and 31 mm long and distally swollen ( Figure 10A,B ). Inner surface with straight folds or lamellae. Bifurcation of the vagina in the free oviduct and the bursa copulatrix duct with a marked constriction and a distal widening. Vagina shorter than the penis (penis length / vagina length, 1.48 and 1.74), subcylindrical, thin (vagina length / vagina width 2.10 and 3.75), with a longitudinal medial depression; its inner surface is reticulated by anastomosed lamellae ( Figure 12A,B ).

Penial complex 35 and 38 mm long. The club-shaped penis was 2.5 and 5 times longer than wide, and shorter than the epiphallus (epiphallus length / penis length 1.24 and 1.38). Internal penial papilla with an accessory lobe almost as long as the papilla ( Figure 13A,B ). Inner surface of the penis with longitudinal and undulated pilasters with several branches. Penis sheath short and muscular. Epiphallus with a proximal cylindrical portion with internal thin and straight longitudinal lamellae, and a distal swollen portion, separated by a partition with a hollow minute papilla. The swollen part continued in a cylindrical tube with elevated and anastomosed folds that run into the fleshy penial papilla ( Figure 13B ). Cylindrical flagellum with a longitudinal lamella and two longitudinal parallel thickenings. Epiphallus diameter larger than the flagellum diameter.

Figures

Figure 1. Type material of Plagiodontes weyenberghii weyenberghii (Doering, 1877) housed at the Senckenberg Naturmuseum (Frankfurt am Main, Germany). Upper row: four views of the lectotype; lower row: four paralectotypes.

Figure 2. Shell variability of Plagiodontes weyenberghii weyenberghii (Doering, 1877) and Plagiodontes weyenberghii minor (Parodiz, 1939).

Figure 6. Living snails. (Photographs: Martín A. Carrizo)

Figure 7. Scanning electron micrographs of the protoconch sculpture in Plagiodontes weyenberghii weyenberghii (A–D) and Plagiodontes weyenberghii minor (E–H). (A,B) Protoconch and first teleoconch whorls; (C) close-up of (A) showing spiral lines crossing axial striae and medial depression. (D) Teleoconch sculpture showing waved intercostular lines. (E,F) Protoconch and first teleoconch whorls; (G) close-up of (E) showing spiral lines crossing axial striae. (H) Teleoconch sculpture.

Figure 8. Frequency distribution of the number of lower-palatal folds in Plagiodontes weyenberghii weyenberghii, Plagiodontes weyenberghii minor and Plagiodontes daedaleus.

Figure 9. Pallial complex of Plagiodontes weyenberghii weyenberghii (A,B) and Plagiodontes weyenberghii minor (C,D). Abbreviations: aa, adrectal area; h, heart; k, kidney; mav, marginal afferent vein; mc, mantle collar; mc–d, mantle collar and diaphragm junction; mv, marginal vein; pg, pallial gland; pn, pneumostome; pu, primary ureter; pv, pulmonary vein; r, rectum; su, secondary ureter; up, ureteric pore.

Figure 10. Genital system of Plagiodontes weyenberghii weyenberghii (A,B) and Plagiodontes weyenberghii minor (C,D). Abbreviations: ag, albumen gland; bc, bursa copulatrix; bcd, bursa copulatrix duct; e, epiphallus; f, flagellum; fo, free oviduct; fpsc, fertilization pouchspermathecal complex; ga, genital atrium; hd, hermaphroditic duct; o, ovotestis; p, penis; prm, penis retractor muscle; ps, penial sheath; so, spermoviduct; v, vagina; vd, vas deferens.

Figure 11. Proximal genitalia of Plagiodontes weyenberghii weyenberghii (A,B) and Plagiodontes weyenberghii minor (C,D). Abbreviations: ag, albumen gland; fpsc, fertilization pouchspermathecal complex; hd, hermaphroditic duct; o, ovotestis; so, spermoviduct.

Figure 12. Vaginal internal structure of Plagiodontes weyenberghii weyenberghii (A,B) and Plagiodontes weyenberghii minor (C,D). Abbreviations: bcd, bursa copulatrix duct; fo, free oviduct; ga, genital atrium; gp, genital pore; so, spermoviduct; v, vagina.

Figure 13. Terminal male genitalia of Plagiodontes weyenberghii weyenberghii (A–D) and Plagiodontes weyenberghii minor (E–H). (A,B) Internal structure of penis. (C,D) Internal structure of epiphallus and penial papilla. (E,F) Internal structure of penis. (G,H) Internal structure of epiphallus and penial papilla. Abbreviations: bpe, broadened part of the epiphallus; e, epiphallus; f, flagellum; el, epiphallic lamella; hp, hollow papilla of the epiphallus; pi, pilaster; pp, penial papilla; ppal, penial papilla accessory lobe; prm, penis retractor muscle; vd, vas deferens.