Labyrinthus dunkeri ( Pfeiffer, 1852 )

Cuezzo, Maria Gabriela, 2006, On a new species of Isomeria Beck and redescription of species of Labyrinthus Beck from South America (Gastropoda: Stylommatophora: Camaenidae), Zootaxa 1221, pp. 1-23 : 4-8

Labyrinthus dunkeri ( Pfeiffer, 1852)

Figures 1–14

Helix dunkeri Pfeiffer, 1852: 156 .

Description: Shell: ( Fig. 1 ) As described by Solem (1966).

Pallial Organs: ( Figs 2, 3 ) Pulmonary roof with few veins becoming more abundant, ramified near mantle collar ( Figs 2, 3 ). Proximal portion of pulmonary roof not extending beyond top of kidney. Dark pigmented spots more abundant in distal portion of pulmonary roof ( Fig. 3 ). Main pulmonary vein splitting into two main branches before reaching mantle collar. Many other minor veins running transversally to main veins. Kidney narrow, long, extending about 60% of pulmonary roof; secondary ureter closed from top of pulmonary roof to mantle collar, running parallel to rectum, ureteric interramus triangular, deeply excavated.

Reproductive system ( Figs 4–8 ; 32–33): Ovotestis consisting of single group of small digitiform acini located between second and third whorls, embedded in digestive gland ( Fig. 4 ); hermaphroditic duct thin, long, convoluted, forming in middle portion, swollen vesicula seminalis. Fertilization pouch­spermathecal complex (FPSC) not evident outside albumen gland, hermaphroditic duct folded over itself, penetrating at distal portion of albumen gland, bean­shaped, continuous with spermoviduct ( Figs 4 , 5 ). Oviducal portion of spermoviduct organized into transversal folds over entire length. Prostatic zone continuing distally into long, vas deferens, descending parallel to vagina towards peni­oviducal angle. Vas deferens attached by connective tissue to junction of penis with oviduct. Ascending branch of vas deferens running parallel to penial complex, inserting in proximal epiphallus. Free oviduct a quarter of length of bursa copulatrix duct ( Fig. 6 ). Natural position of free oviduct forming angle with vagina, bursa copulatrix duct continuous with free oviduct. Bursa copulatrix running parallel to spermoviduct until distal portion of albumen gland ( Fig. 5 ). Bursa copulatrix and spermoviduct wrapped together by thin connective tissue. Bursa copulatrix sac elongated, oval, naturally reflexed over duct ( Figs 5, 6 ). Inner structure of vagina consisting of thin parallel longitudinal folds, becoming thicker, deeper, with zigzag pattern. Distal portion of vagina more swollen than proximal part ( Fig. 5 ). Vagina without hooked denticles. Penial complex composed by flagellum, epiphallus, penis ( Figs 5, 7 ). Flagellum short, diameter decreasing towards proximal portion. Internally, flagellar pilaster with dorsal groove ending level where vas deferens enters epiphallus through papilla. Second longitudinal pilaster continuous within epiphallus. Epiphallus cylindrical, elongated with thick muscular walls. Internal structure consisting of thick medial pilaster with wrinkled surface without pustules. Internal pilasters running through entire epiphallus­flagellum length. Vas deferens inserting in proximal epiphallus below flagellum­epiphallus junction. Penis thick, reflexed over epiphallus, tightly packed with muscular fibers ( Fig. 7 ). Penial sheath muscular, cylindrical, with upper proximal, lower distal borders well delimited ( Figs 5, 7 ). Penis retractor becoming thicker before inserting at penis­epiphallus junction. Internal structure of penis consisting of longitudinal, parallel ridges running through entire penis length. Ridges thicker with zigzag pattern at proximal portion, overlapped in part by penial sheath ( Fig. 8 ). White small, fragile denticles with basal oval plate of about 300 m in length and long hook ( Figs 32, 33 ). Denticles regularly distributed on top of zigzag ridges in proximal penis, absent in distal portion of penis ( Fig. 8 ). Verge absent.

Digestive system ( Figs 9–12 ): Jaw arcuate, apparently smooth without ribs. Thin transversal striae deeper than other perpendicular ones in jaw surface visible in SEM. Central tooth of radula unicuspid, lateral teeth unicuspid ( Fig. 9 ) becoming bicuspids at level of N° 14, mesocone well developed ( Fig. 10 ). First marginal teeth tricuspid ( Fig. 11 ) close to margins of radula, marginal teeth become pluricuspis, wider ( Fig. 12 ). Buccal mass muscular, spherical; esophagus cylindrical, open dorsally. Esophagus wall thick with inner longitudinal, parallel ridges. Two long salivary glands opening through thin ducts into dorsal portion of buccal mass at sides of esophageal opening. Esophageal crop walls thin, transparent without inner special sculpture. Stomach receiving anterior and posterior ducts of digestive gland; anterior opening into concavity between esophageal crop and intestine, posterior duct opening in parietal portion of stomach. Two internal typhlosoles arising from point of insertion of digestive gland ducts, one, longer, beginning at opening of anterior duct, running into proximal intestine. Intestine running along columelar side of visceral mass, turning down under anterior portion of gastric crop, then forming periaortic loop before finishing in rectum. Rectum closed along its entire length before opening into anus, running parallel to kidney, ending at mantle collar.

Material examined: COLOMBIA: FMNH 163709, Cesar Department, Sierra Perijá, El Roncon, 10–12 Km East of Becerril, 9°42'N, 73°11'W, 200– 300 m.; 16 September, 1969. Borys Malkin Coll. FMNH 173867 Cesar Department, Sierra de Perija, El Eocon, 10–12 km east of Becerril, 17 September 1969. B. Malkin Coll. AMNH 39705, Colombia.

Remarks: In species of Labyrinthus and Caracolus Montfort, 1810 , in which the jaw morphology was studied, it was reported as smooth or oxygnath ( Wurtz 1955). However, in L. dunkeri , the jaw showed incipient vertical ribs, and could not be consider as oxygnath. The morphology of the jaw in the rest of Labyrinthus species should be carefully examined to check if it really can be consider smooth and if this character can be used to diagnose the genus. The oxygnath condition is a character that has been used as unique of the American Belogona Euadenia (= Cepoliinae) ( Pilsbry 1894). However, this kind of jaw is also present in some Camaenidae and Sphincterochilidae among the Helicoidea ( Hausdorf 1998, Cuezzo 2003). The rest of the Helicoidean groups have an odontognath jaw ( Hausdorf 1998). The length of the hooked penis denticles and the absence of denticles in the vagina clearly separates L. dunkeri from the remaining species of Labyrinthus in which soft anatomy is known. The hooks on the dorsal portion of the denticles in L. dunkeri are more than twice the length than those in other species of Labyrinthus .

Figures

FIGURES 1 – 4: Labyrinthus dunkeri. 1: Diagram of shell morphology, scale bar = 5 mm. 2: Position of pallial organs before dissection, shell excluded, scale bar = 5 mm. Abbreviations: mc: mantle collar; p: pericardium; ag: albumen gland; go: genital orifice; f: foot; l: lung; r: rectum; k: kidney; t: ocular tentacle. 3: Ventral view of the general morphology of dissected out pallial organs, scale bar = 5 mm. Abbreviations: p: pericardium; i: intestine; k: kidney; pu: primary ureter; su: secondary ureter. 4: Position of genital system before dissection, shell excluded, dorsal view. Abbreviations: ag: albumen gland; bc: bursa copulatrix; dg: digestive gland; hd: hermaphroditic duct; e: epiphallus; f: flagellum; ag: albumen gland; dg: digestive gland; o: ovotestis; p: penis; pr: penis retractor muscle; s: spermoviduct; t: ocular tentacle; ps: penis sheath.

FIGURES 5 – 8: Labyrinthus dunkeri. 5: Reproductive system dissected out, ovotestis and part of the hermaphroditic duct excluded, scale bar = 1 cm. Abbreviations: bc: bursa copulatrix; hd: hermaphroditic duct; e: epiphallus; f: flagellum; ag: albumen gland; p: penis; pr: penis retractor muscle; s: spermoviduct; v: vagina; vd: vas deferens; ps: penis sheath. 6: Detail of spermoviduct and bursa copulatrix in ventral view. Abbreviations: bcd: duct of bursa copulatrix; fo: free oviduct; pro: prostate; ut: female portion of spermoviduct; v: vagina. 7: Detail of penis complex in ventral view, scale bar = 1 cm. Abbreviations: e: epiphallus; vd: vas deferens. 8: Inner structure of penis, scale bar = 5 mm. Abbreviations: d: denticles; go: genital orifice; v: vagina; ps: penis sheath.

FIGURES 9 – 12: Labyrinthus dunkeri. 9: Central tooth with two lateral teeth, scale bar = 10 m. 10: Lateral teeth Nro. 8 – 10 to the right of central tooth, scale bar = 10 m. 11: Same row than in fig. 10, showing the change from lateral Nro. 14 bicuspid to marginal tricuspid, scale bar = 10 m. 12: Marginal teeth near radular margin, scale bar = 10 m.

FIGURES 13 – 16: Labyrinthus subplanatus. 13: Morphology of shell aperture. 14: General morphology of reproductive system in ventral view, ovotestis not figured, scale bar = 5 mm. Abbreviations: ag: albumen gland; bc: bursa copulatrix; f: flagellum; fo: free oviduct; go: genital opening; hd: hermaphroditic duct; p: penis; s: spermoviduct; v: vagina; ps: penis sheath. 15: Detail of penial complex, dorsal view, scale bar = 5 mm. Abbreviations: f: flagellum; p: penis; pr: penis retractor muscle; vd: vas deferens; ps: penis sheath. 16: Inner structure of penial complex, scale bar = 2 mm. Abbreviations: a: atrium; d: denticles; e: epiphallus; f: flagellum; p: penis; pi: pilaster; pr: penis retractor muscle; vd: vas deferens; ps: penis sheath.

FIGURES 32 – 35. 32, 33: Labyrinthus dunkeri. 32: Lateral view of a denticle from penis wall showing the long hook, scale bar = 100 m. 33: Dorsal view of a hooked denticle from inner penis wall. Basal plate is partly covered by soft tissue, scale bar = 100 m. 34, 35: L. tarapotoensis. 34: Dorso­lateral view of a hooked denticle from inner penis wall, scale bar = 100 m. 35: Lateral view of other denticle from penis wall, scale bar = 100 m.