Spixia pyriformis ( Pilsbry 1901 )

Oroño, Eugenia Salas, 2007, Taxonomic review of the Spixia pyriformis species complex (Gastropoda: Pulmonata: Odontostominae), Zootaxa 1498, pp. 1-25 : 15-19

Spixia pyriformis ( Pilsbry 1901)

( Figures 27 –39)

Odontostomus (Spixia) pyriformis Pilsbry, 1901: 72 . nom. nov. pro Bulimus (Odontostomus) doeringii Kobelt, 1882 . Odontostomus (Spixia) pyriformis Parodiz, 1942a: 216 .

Scalarinella (Spixia) pyriformis Zilch, 1971: 202 .

Spixia pyriformis Fernández, 1973: 136 .

Lectotype: SMF 171579.

Type locality: Argentina, Córdoba, Sierras de Córdoba.

Shell: pyriform, 8 1/2 whorls, first ones slightly convex, turret shaped, last two whorls convex of abrupt growth ( Fig. 27 ). Shell deeply umbilicated. Shell light brownish to whitish homogeneous; usually with no periostracum. Protoconch with slim axial ribs ( Fig. 28 ). Spaces between each rib smooth ( Fig. 29 ). Teleoconch sculptured with axial oblique wrinkles interrupted by thin spiral grooves well marked in shell coinciding with not continuous periostracal spiral rows. Triangular lamellae inserted at regular intervals on spiral rows ( Fig. 30–31 ). Without periostracum the sculpture is a quadrangular grillwork similar to S. martensii ( Fig. 32–33 ). Aperture ovate, 1/3 of shell total length ( Fig. 27 ). Peristome expanded. Parietal callus prominent, of continuous development. Union between palatal and parietal wall origins a pronounced incision. Aperture with one tooth and four lamellae well developed. Parietal lamella tall, with both sides concave and perpendicularly from peristome. Columellar lamellae wide, concave, with pronounced margin, close to palatal lamella border. Basal lamella tall with both sides concave, slightly oblique from peristome. Palatal lamella perpendicular to peristome with superior border curved to basal side. Suprapalatal tooth 1/3 shorter than palatal lamella, always present.

Shell Measurements: FML 461 (n=5): H: 11.7–17.6 (Median: 15); D maj: 9.45–9.9 (Median: 9.65); H ap: 7.15–8 (Median: 7.5); D ap: 5–5 (Median: 5); Ang sp: 54º–65º (61.6º); Ang max: 114º–123.5º (Median: 120º). FML 825 (n=7): H: 19–22.3 (Median: 20.6); D maj: 9.8–10 (Median: 9.9); H ap: 8–9 (Median: 8.3); D ap: 5.3–6 (Median: 5.5); Ang sp: 43º–54º (Median: 48.6º); Ang max: 119º–132º (Median: 124.2º). FML 14793 (n=12): H: 17–25 (Median: 21.6); D maj: 9.4–11 (Median: 10.15); H ap: 7.5–9.8 (Median: 8.7); D ap: 4.7–6.5 (Median: 5.7); Ang sp: 39º–55º (Median: 50.8º); Ang max: 114º–140º (Median: 122.4º). FML 14794 (n=10): H: 9–20 (Median: 15); D maj: 6.2–10.5 (Median: 8.03); H ap: 5.3–8.5 (Median: 6.5); D ap: 3.8–6 (Median: 4.8). Ang sp: 40º–65º (Median: 52.8º); Ang max: 105º–125º (Median: 112.8º).

Digestive System: Jaw ( Fig. 34 ) arcuate formed by 14 rectangular imbricate plaques and four central plaques, two of them half wide than two other ones ( Fig. 35 ). Radula similar to S. doellojuradoi , 1 central tooth tricuspid, lateral teeth bicuspid, marginal teeth tricuspid.

Pallial System: Similar to S. doellojuradoi . Large kidney 1/3 to 1/5 of pulmonary roof length. Pallial gland prominent, with dark pigmentation, slightly arcuate. Tissue which divides pallial gland from mantle collar is tighter than in S. doellojuradoi .

Reproductive System ( Fig. 36 ): Ovotestis within second whorl consisting of five, fan shaped groups of acini. Each acinus ramified, digitiform, light orange homogeneous. Albumen gland yellowish, inside third body whorl. Fertilization pouch with wide base and narrow to hermaphroditic duct connection, externally sculptured with fine longitudinal lines. Bursa copulatrix duct same length than spermoviduct. Oviduct wide in its distal portion. Flagellum short, 1/2 of epiphallus length. Epiphallus wider in diameter than flagellum, 1/3 of penis length. Penis long, tubular, penial area I is twice the length than in S. doellojuradoi . Penial gland small, rounded. Inner wall of area I with fine, irregular folds. Penial area II internally sculptured with an area with grillwork of circles, the diameter of circles is bigger and they are more separated from each other than in S. doellojuradoi ( Fig. 37 ). Presence of a pilaster extending from penial area II to IV, formed by short lamellae irregular in shape, pilaster running in central or lateral portion of area II. Penial area III with enlarged undulated pustules located diagonally. Penial area IV with numerous pustules, of irregular distribution. Area V pustules becoming less numerous, longitudinal folds, semi undulated are present to atrium ( Fig. 38 ). Retractor muscle inserted at proximal portion of penial area II. Vas deferens stacked to retractor muscle on the insertion point of retractor muscle, running parallel to epiphallus. Penial sheath short, overlapping distal penis.

Habitat: Spixia pyriformis lives among roots and basal portions of small shrubs.

Distribution: Argentina, Salta Province, Metán department. Area of distribution of the present species is part of the Chaco biogeographic area in Argentina delimited by Morrone (2006).

Remarks: Spixia pyriformis shows a high degree of variability in its shell morphology and especially in its size ( Fig. 27 ). Smaller specimens were found mostly in places of high altitude (900–1100 m) being absent at lower altitudes. Larger specimens were found between 700–1100 m although at altitudes higher than 900 m these forms were less abundant. Although high shell variability is registered, the specimens collected belonged to the same species. In smaller specimens, the parietal callus is prominent but slightly concave in at its medial portion. The periostracal sculpture is simpler than in S. martensii and S. tucumanensis without a clearly present net pattern. When the periostracum is lost, mostly in old shells, only axial wrinkles are distinguished between the spiral rows. Lamellae are similar in its morphology to the ones present in the other species of the complex, but are generally lost in adult specimens when the periostracum is lost or abraded. The sculpture of periostracum with the presence of rows and lamellae was never mentioned in previous works, possibly due to the fact that the descriptions where based only on old adult shells. Concerning the pallial system, the length of pulmonary roof is variable and the pallial gland is more prominent and has darker pigmentation than in the rest of the species complex. The tissue between the pallial gland and the mantle collar is tighter than in S. doellojuradoi . In the genital system, the fertilization pouch-spermathecal complex has the same longitudinal sculpture as in S. doellojuradoi and different from two other species. Concerning the phallic complex, the penial gland is small and rounded, similar to S. martensii and different from the two other species. The sculpture of the penial inner wall differs from the rest of the species especially in penial areas II, III and IV. Areas I and V, as it was previously stated, are similar in the four species. Spixia pyriformis is similar to S. doellojuradoi in area II differing in the general arrangement of the circular grillwork. The circles are larger in diameter and less tightly apprised with each other. Area II is not comparable to the other species because of the different structures present in those. The penial area III is shorter than in the rest of the species, with enlarged undulated pustules located diagonally. In penial area IV, the pustules are bigger and more lobed than in S. tucumanensis . The lamellas of the pilaster that extends from penial area II to penial area IV are similar in shape to S. martensii and S. tucumanensis .

Pilsbry (1901) stated that the type locality of Spixia pyriformis is “Sierra de Cordoba”, however, as in the case for the other species, this information is vague. The present species is only represented in museums by material collected in Cerro Colorado, Salta Province. The only specimen found in Tucumán by R. Shreiter in 1917 was erroneously classified as S. pyriformis but it belongs to S. tucumanensis , as it was previously pointed out by Hylton Scott (1948). It is very surprising that the species has never been collected in Córdoba after Doering and that also in Cordoba there is a locality called Cerro Colorado that could have probably been mistaken by the Cerro Colorado in Salta where the species is very abundant. Further collections will have to be done before this is confirmed.

Specimen record: FML 461 (DM): Salta, Metan dept. Cerro Colorado, M.I. Hylton Scott leg. FML 761 (DM): Salta, Metan dept. Cerro Colorado, west hillside, M.I. Hylton Scott leg. FML 825 (DM): Salta, Metan dept. Cerro Colorado, 650–750 m, 22/02/1964, W.Weyrauch leg. FML 14793 (AM): Salta, Metan dept. Cerro Colorado, west hillside on the road to Pala Pala, 776 m, 25º 36’ 44’’S 64º 29’ 48’’ W, 15/12/2005, E. Salas Oroño leg. FML 14794 (AM): Salta, Metan dept. Cerro Colorrado, peak of mountain, 1134 m 25º 36’ 46’’S 64º 28’ 25’’W, 15/12/2005, E. Salas Oroño leg. FML 14795 (AM): Salta, Metan dept. Cerro Colorrado, Filo, near Pala Pala, 946 m, 25º 36’ 34’’S 64º 29’ 7.8’’W, 15/12/2005, E. Salas Oroño leg.

Figures

FIGURE 27. Spixia pyriformis. Size variation of shells, scale bar: 10 mm.

FIGURES 28 – 31. Spixia pyriformis. 28. General view of protoconch showing axial ribs, scale bar: 100 Μm. 29: Protoconch sculpture between ribs, scale bar: 10 Μm. 30. Dorsal view from protoconch to seventh whorl showing general sculpture of shell, scale bar: 1 mm. 31. Seventh whorl, periostracum with spiral rows and lamellae, scale bar: 100 Μm.

FIGURES 32 – 35. Spixia pyriformis. 32. Seventh whorl, detail of spiral rows, scale bar: 100 Μm. 33. Sculpture of body whorl without periostracum, scale bar: 1 mm. 34. Jaw, general view, scale bar: 100 Μm. 35. Jaw, central plaque, scale bar: 10 Μm.

FIGURES 36 – 38. Spixia pyriformis. 36. Reproductive system dissected out, scale bar: 5 mm. 37. Detail of widening area II and part of area III sculpture, scale bar: 2 mm. 38. Phallic complex inner wall, scale bar: 5 mm. Abbreviations: A: atrium; Ag: albumen gland; Bc: bursa copulatrix; Bcd: bursa copulatrix duct; Ca: constriction area; Ep: epiphallus; F: flagellum; Hd: hermaphroditic duct; Lf: longitudinal folds; Ov: oviduct; P: penis; Pg: penial gland; Pi: pilaster; Piw: penis inner wall; Pr: prostate; Ps: penial sheath; Pw: penis wall; Rm: retractor muscle; I: proximal portion; II: widening area; III: proximal medial portion; IV: distal medial portion; V: distal portion.