Gudeodiscus (Gudeodiscus) fischeri (Gude, 1901)

Pall-Gergely, Barna, Hunyadi, Andras, Ablett, Jonathan, Lương, Hao Văn, Fred Naggs, & Asami, Takahiro, 2015, Systematics of the family Plectopylidae in Vietnam with additional information on Chinese taxa (Gastropoda, Pulmonata, Stylommatophora), ZooKeys 473, pp. 1-118 : 13-17

Taxon classification Animalia Stylommatophora Plectopylidae

Gudeodiscus (Gudeodiscus) fischeri (Gude, 1901) Figures 2E, 3 A–C, 9 P–Q, 15 H–R, 17, 18, 28D, 29D, 29J, 30E, 31D, 34 M–O

Plectopylis Fischeri Gude 1901a, Journal de Conchyliologie, 49: 204-205., Figs 4 a–e, Plate 6, Figs 4 a–c. ["Environs de Bac-Kan"].

Plectopylis tenuis Gude 1901a, syn. n., Journal de Conchyliologie, 49: 202-204, 205., Figs 3 a–e, Plate 6, Figs 3 a–c. ["Cho-Ra (le type); environs de Bac-Khan; environs de Cho Moi"].

Plectopylis Fischeri , - Dautzenberg & Fischer 1905b, Journal de Conchyliologie, 53: 360. ["Ha Giang"].

Plectopylis tenuis , - Gude 1909, Proceedings of the Malacological Society of London, 8: 215, 216.

Gudeodiscus fischeri , - Páll-Gergely & Hunyadi 2013, Archiv für Molluskenkunde, 142 (1): 8.

Gudeodiscus tenuis , - Páll-Gergely & Hunyadi 2013, Archiv für Molluskenkunde, 142 (1): 8.

Types examined.

Tonkin, Environs de Bac-Kan, leg. Messager, MNHN 24579 (holotype of fischeri , Figure 3B); Tonkin, Cho-Ra, leg. Messager, MNHN 24587 (holotype of tenuis , Figure 3C).

Museum material examined.

Tonkin, Bac-Kan, NHMUK 1908.12.21.144/1; Tonkin, environs de Bac-Kan, leg. Messager, (n. 28), RBINS/2; Tonkin, Ha-Giang, leg. Messager, RBINS/5; Ha Giang, leg. Mansuy, coll. M. H. Fischer, MNHN-IM-2012-2241/12 adult, 1jb; Ha Giang, coll. Mansuy, MNHN-IM-2012-2257/5; Tonkin, leg. Messager, MNHN-IM-2012-2390/1; Cho-Ra, leg. Messager, MNHN-IM-2012-2477/1; Bac-Kan, leg. Messager, MNHN-IM-2012-2466/3; Tonkin, Cho Rah, ex Rolle, USNM 207813/2 (" tenuis "); Nga-Son, leg. Messager, MNHN-IM-2012-2233/2 (" tenuis "); Nga-Son, leg. Messager, MNHN-IM-2012-2253/2 (" tenuis "); Tonkin, coll. Denis, 1946, MNHN-IM-2012-2338/3 (" tenuis "); Cho-Ra, leg. Messager, MNHN-IM-2012-2361/1 (" tenuis "); Tonkin, Bac-Kan, coll. Rolle, NHMW 71640/O/14028/1.

New material examined.

20090519B Tuyên Quang Province, Hàm Yên District, Yên Phú Commune, Đồng Tiến, Thống Nhất, ca 70 m, 22°08.673'N, 104°58.634'E, leg. Ohara, K., 19.05.2009., OK/12, PGB/3; 20090515C Bắc Kạn Province, Ba Bể District, Ba Bể Nat. Park, Khâu Kum, ca 185 m, 22°26.465'N, 105°36.642'E, leg. Ohara, K., 15.05.2009., OK/8, PGB/2; 20081113C Hà Giang Province, Hà Giang Town, Ngọc Đường Commune, Bản Cườm (= Cườm Village), ca 110 m, 22°51.180'N, 105°01.075'E, leg. Ohara, K., 13.11.2008., OK/1, PGB/1; Vn10-118 Hà Giang Province, Tâm Village, ca. 7-8 km SE of Hà Giang (between Vị Xuyên and Bản Hãm = “Hãm Village"), 22°48.019'N, 105°00.888'E, leg. Hemmen, Ch. & J., 16.10.2010., PGB/2; Vn11-138 Tuyên Quang Province, near Tôn Hông, road #185 from Tuyên Quang to Vĩnh Lộc (formerly Chiêm Hóa) (NE of Tuyên Quang), leg. Hemmen, Ch. & J., 19.03.2011., HE/1, PGB/1 (anatomically examined, see Figures 17, 28D, 29J, 31D, 34 M–O); Vn10-120 Hà Giang Province, ca. 9.8 km from Hà Giang to Tam Sơn (formerly Quản Bạ), left side off road, 22°52.907'N, 104°59.885'E, leg. Hemmen, Ch. & J., 17.10.2010., PGB/3; 2012/56 Hà Giang Province, Hà Giang 7 km towards Tam Sơn, left side of the road nr. 4C, 100 m, 22°51.650'N, 105°00.768'E, leg. Hunyadi, A., 03.06.2012., HA/4; 2012/57 Hà Giang Province, Hà Giang 9.8 km towards Tam Sơn, left side of the road 4C, 120 m, 22°52.881'N, 104°59.927'E, leg. Hunyadi, A., 03.06.2012., HA/20+7jb, PGB/2; Vn11-179 Tuyên Quang Province, ca. 5.5 km E of Chương Dương (left bank of Lô River), leg. Hemmen, Ch. & J., 30.09.2011., HE/2; 20090517A Bắc Kạn Province, Ba Bể District, Ba Bể Nat. Park, along the trekking road, near guest house, 205 m, 22°25.049'N, 105°37.699'E, leg. Ohara, K., 17.05.2009., OK/8, PGB/2 (" tenuis ", anatomically examined, see Figure 29D); Vn10-28A Bắc Kạn Province, ca 1 km from Ba Bể Nat. Park, headquarters to Ba Bể Lake, 22°24.829'N, 105°37.652'E, leg. Hemmen, Ch. & J., 20.10.2010., PGB/6 (" tenuis "); Vn09-26 Bắc Kạn Province, Ba Bể Nat. Park, near bungalows (at Park Headquarters), leg. Hemmen, Ch. & J., 17.10.2009., HE/2 (" tenuis "); 2011/91 Bắc Kạn Province, Ba Bể Nat. Park, path starting from the bungalows 500 m, 240 m, 22°25.072'N, 105°37.941'E, leg. Hunyadi, A., 17.11.2011., HA/11+5jb, PGB/2 (" tenuis "); 2011/96 Bắc Kạn Province, Ba Bể Nat. Park, Thẳm Kịt Cave 2 km from the look-out tower, 335 m, 22°24.686'N, 105°37.710'E, leg. Hunyadi, A., 19.11.2011., HA/29+3jb, PGB/2 (" tenuis ", anatomically examined, see Figure 18); 2011/97 Bắc Kạn Province, Ba Bể Nat. Park, Thẳm Kịt Cave 1 km from the look-out tower, no GPS data, leg. Hunyadi, A., 19.11.2011., HA/8+4jb (" tenuis ").

Diagnosis.

Shell small to medium-sized, with smooth basal and usually finely ribbed apical surface (in some populations also smooth and glossy, see Figure 2E); shell usually flat, or with very slightly elevated spire, or only the protoconch is elevated from the dorsal surface; callus and apertural fold (if present) weak (Figures 9 P–Q). Parietal wall with two lamellae (the anterior is exceptionally dissolved into small denticles); middle palatal plicae oblique, depressed Z or L-shaped, they are free or sometimes connected to each other (Figures 15 H–N).

Measurements

(in mm): D = 16.6-18.6, H = 7-7.9 (n=3, Vn10-120); D = 12.1-12.4, H = 4.8-5.3 (n=3, 20090519B); D = 15.5-15.9, H = 7.1-7.2. (n=2, 20090515C); D = 14.6, H = 7.4-7.6. (n=2, 2011/91); D = 12.9-14.7, H = 6.4-7.3 (n=6, Vn10-28A).

Differential diagnosis.

Gudeodiscus cyrtochilus is smaller than Gudeodiscus fischeri , it has a narrower umbilicus, more regularly growing whorls (the last whorl is only slightly wider than the penultimate one), a shorter lower horizontal parietal plica and no apertural fold. The Chinese Gudeodiscus multispira and Gudeodiscus soosi are also smaller, have a greater number of densely-coiled whorls and at the position of the anterior lamella there are usually 2-4 clearly separated denticles (see also Remarks). In some populations of Gudeodiscus multispira the denticles are missing so that only the posterior lamella is present. Gudeodiscus yunnanensis has no anterior lamella, just a curved single lamella (homologous with the posterior lamella). Gudeodiscus eroessi never has an apertural fold and its anterior lamella is dissolved into small denticles, or missing. Gudeodiscus infralevis and Gudeodiscus suprafilaris have a more elevated spire, narrower umbilicus and rather straight, horizontal, parallel plicae.

Intraspecific diversity.

The variability is quite large in terms of shell size and shape, sculpture, strength of the callus and apertural fold and the formation of parietal plicae and lamellae. The combination of weak callus and apertural fold and the “nautiliform” shape helps in the identification of the species. See also Table 7.

Description of the genitalia.

Two specimens were dissected, belonging to two different populations: “Specimen1” Tuyên Quang Province, near Tôn Hông, road #185 from Tuyên Quang to Vĩnh Lộc (formerly Chiêm Hóa) (NE of Tuyên Quang), leg. Hemmen, Ch. & J., 19.03.2011. (specimen without embryos in the uterus, but with calcareous hooks inside the penis, Figure 17, 31D); “Specimen2” Bắc Kạn Province, Ba Bể Nat. Park, Thẳm Kịt Cave 2 km from the look-out tower, 335 m, 22°24.686'N, 105°37.710'E, leg. Hunyadi, A., 19.11.2011. (typical Plectopylis tenuis ; with a developing embryo in the uterus, Figure 18).

The penis is a cylindrical tube with several longitudinal, parallel folds on the inner wall; there are pockets formed by some of these folds; in the wall of the opened penis the series of pockets are arranged along a bell-shaped line (Figure 28D); there were calcareous hooks within the pockets of “Specimen1”; the base of the hooks were elongated, they lay within the pockets, whereas the tip portion projects out of the pockets (Figure 30E); epiphallus as long as the penis, with few parallel folds in the lumen (Figure 29D); distal portion of the penis and the proximal part of the epiphallus are connected with weak membrane; more closely to the genital opening these two organs are more stronger connected; penial caecum tapers toward the end, it is about a quarter as long as the penis; its inner wall with irregular folds arranged in longitudinal lines, with calcareous granules in between (mainly at the distal end); retractor muscle attaching on the apical part of the penial caecum is approximately as long as the caecum; there is an additional retractor muscle on the proximal part of the penis. Vagina is thickened and forms a "vaginal bulb", which is attached to the body wall with several thin ligaments; inner wall of the vaginal bulb and the distal part of the vagina with well-developed, longitudinal, serrulate folds (Figure 31D); stem of the gametolytic sac is long and slim; it is attached hardly to the spermoviduct; diverticulum well-developed, free; the diverticulum of the specimen from the Ba Bể Nat. Park contained three long, slightly C-shaped spermatophores; the proximal side of the spermatophores were damaged, thus they might have been connected; spermoviductus slim and long.

Besides the presence or absence of embryos and calcareous penial hooks between the two specimens the only notable difference is the longer retractor muscle in “Specimen2” than in “Specimen1”, but the taxonomic value of this character is unknown.

Radula.

See Table 6 and Figures 34 M–O.

Distribution

(see Figure 41): Gudeodiscus fischeri is known from Hà Giang, Tuyên Quang and Bắc Kạn Provinces.

Remarks.

Some samples from the Ba Bể Nat. Park (Vn10-28A, 20090517A, 2011/91, 2011/96) are identical with the type specimen of Plectopylis tenuis described from Cho Ra (see Figure 39). This town is situated approximately 7 km from the locality of our recent material. Some 3 km north of our tenuis localities there is a population (20090515C) which agrees with tenuis in every shell character except that the anterior parietal lamella and the lower horizontal plica are connected (typical in fischeri ). Since no other shell characters are known to be different between tenuis and fischeri , and other populations of fischeri show relatively large variability in terms of several shell characters, we synonymize Plectopylis tenuis with Plectopylis fischeri .

The shells collected 9.8 km north of Hà Giang are relatively large and thick-walled, have the anterior lamella dissolved into 3-4 denticles, and have strong apertural denticle and callus (Figures 3A, 15 L–M). The shells collected at Đồng Tiến are small and very glossy in appearance (Figure 2E).