Endothyrella plectostoma (Benson, 1836)

Pall-Gergely, Barna, Budha, Prem B., Naggs, Fred, Backeljau, Thierry & Asami, Takahiro, 2015, Review of the genus Endothyrella Zilch, 1960 with description of five new species (Gastropoda, Pulmonata, Plectopylidae), ZooKeys 529, pp. 1-70 : 37-41

Taxon classification Animalia Pulmonata Plectopylidae

Endothyrella plectostoma (Benson, 1836) Figures 6D, 13 A–B, 19 E–F, 20 D–E, 22A, 22 D–F, 26

Endothyrella plectostoma 1836 Helix (Helicodonta) plectostoma Benson: Journal of the Asiatic Society of Bengal, 5: 351. [not specified. "North-East Frontier of Bengal" (in the title)].

Endothyrella plectostoma 1848 Helix plectostoma , - Pfeiffer, Martini & Chemnitz, 1(12): 367, Plate 64, figs 19-21.

Endothyrella plectostoma 1854 Helix plectostoma , - Reeve: Conchologia Iconica 7, species 782.

Endothyrella plectostoma 1860 Helix plectostoma , - Benson: The Annals and Magazine of Natural History, 3 (5): 247.

Endothyrella plectostoma 1865 Helix plectostoma , - W. Blanford: Journal of the Asiatic Society of Bengal 34 (2): 94. ["...the Himalayan and Khasi Helix plectostoma , Bens. abounded south of the town of Bassein in several places, Pyema Khyoung, Long Island, &c. It was also found by Captain Ingram in Arakan, near Tongoop."].

Endothyrella plectostoma 1872 Helix (Plectopylis) plectostoma , - Hanley & Theobald: Conchologia Indica …: 7, Plate 13, fig. 2. ["Darjiling and Khasia Hills"].

Endothyrella plectostoma 1875 Plectopylis plectostoma , - Godwin-Austen: Proceedings of the Zoological Society of London: 612-613, Plate 73, figs 2-2a. (1874, part IV, published in 1875; see Duncan 1937).

Endothyrella plectostoma 1878 Helix (Plectopylis) plectostoma , - Nevill: Hand list of Mollusca in the Indian Museum …: 1: 71. [ “Nágá Hills", "Bassein, &c., Pegu", “Sylhet”, "Arakan Hills", "Khasi Hills", “Darjeeling”].

Endothyrella plectostoma 1887 Helix (Plectopylis) plectostoma , - Tryon: Manual of Conchology …, 2 (3): 160-161, Plate 34, figs 69-70.

Endothyrella plectostoma 1894 Plectopylis plectostoma , - Pilsbry: Manual of Conchology..., 2 (9): 146.

Endothyrella plectostoma 1897b Plectopylis plectostoma , - Gude: Science Gossip, 3: 274-275, figs 39 a– 7c. [ “Darjeeling”, "Burma- Bassein and Arakan; Assam - Sylhet, Khasia and Naga Hills", "Dafla Hills in Assam"].

Endothyrella plectostoma 1899c Plectopylis (Endothyra) plectostoma , - Gude: Science Gossip, 6: 148, 149.

Endothyrella plectostoma 1899d Plectopylis (Endothyra) plectostoma , - Gude: Science Gossip, 6: 175, 177.

Endothyrella plectostoma 1914b Plectopylis (Endothyra) plectostoma , - Gude: The Fauna of British India …: 72, 73, 75, 81-83, figs 31 a–c. ["Naga Hills", "Dafla Hills, Khasi Hills", "Burma: Arakan Hills", “Tongoop”, "Bassein: Pegu", “Sylhet”, "Sikkim: Darjeeling"].

Endothyrella plectostoma 1922 Plectopylis (Endothyra) plectostoma , - Ehrmann: Sitzungsberichte der Naturforschender Gesellschaft zu Leipzig, 45-48: 8-10.

Endothyrella plectostoma 1960 Plectopylis (Endothyrella) plectostoma , - Zilch: Handbuch der Paläozoologie, 6 (2): fig. 2092.

Types:.

Darjeeling, coll. MacAndrew ex coll. Benson, UMZC 102160 (7 syntypes of plectostoma ); Darjeeling, coll. MacAndrew ex coll. Benson, UMZC 102155 (1 syntype of plectostoma , Figure 13A); Bengal, coll. MacAndrew ex coll. Benson, UMZC 102156 (3 syntypes of plectostoma ).

Additional material examined.

Indien, Khasi Hills, ex coll. Oberwimmer, NHMSB 122805-122810/5; India, Meghalaya, Khasi Hills, Altonaer Museum, ZMH 45909/4; Assam, coll. Steenberg, ZMUC-GAS-1812/2; Naraindher, Cachar, Ede, coll. Godwin-Austen, NHMUK 1903.7.1.1666/15 (several of them are juveniles); Darjiling, coll. W. Blanford, NHMUK 1860.6.27.10/2; India, NHMUK 20150169/1; Teria Ghat, NHMUK 1888.12.4.1536-1540/5; Pegu, coll. Godwin-Austen, NHMUK 1909.3.15.92/7; Naga Hills, coll. Godwin-Austen, NHMUK 1903.7.1.760/3; Pegu, Arakan, NHMUK 1903.7.1.758/3; Arakan, coll. W. Blanford, NHMUK 1909.3.15.60/3; Assam, Khasi Hills, coll. Salisbury ex coll. Beddome, NHMUK20150170/3; Lhota Naga, coll. Chennell, NHMUK 1903.7.1.759/10; Saddia, E Assam, coll. Godwin-Austen, NHMUK 1903.7.1.761/8; Picholanulla, Durrang, Assam, coll. Godwin-Austen, NHMUK 1903.7.1.763/1; Khasi Hills, coll. W. Blanford, NHMUK 1906.2.2.356.1-3 (3 shells; mixed sample with Endothyrella sowerbyi : 1906.2.2.356.4); Arakan, coll. W. Blanford, NHMUK 1906.2.2.355/4; India, NHMUK 20150171 (6 specimens); Darjiling, NHMUK 1906.2.2.142/1 (mixed sample with Endothyrella blanda ); Shiroifurar, Lahupa Naga, coll. Godwin-Austen, NHMUK 1903.6.1.762/1; India, NHMUK 71.9.23.206/3; no data, coll. W. Blanford, NHMUK 20150172/2; Munipur valley, Bishenpur, west side, NHMUK 20150173/25 (several of them are juvenile shells); N. Cachar, coll. Godwin-Austen, NHMUK 20150174/2; Teria Ghat, coll. Godwin-Austen, NHMUK 20150175/1; Cherra, Khasi Hills, Assam, coll. Godwin-Austen, NHMUK 20150176/25; Dunsiri valley, coll. Godwin-Austen, NHMUK 20150177/4; Khasi Hills, coll. Godwin-Austen, NHMUK 20150178/68; Garo Hills, NHMUK leg. W. Robert, coll. Godwin-Austen, NHMUK 20150179/27; Burma, Bassein, coll. Benson 1863, NHMUK 1954.6.2.287/1; Khasi Hills, NHMUK 20150180/1 (mixed sample with Endothyrella tricarinata : NHMUK 20150181); Khasi Hills, NHMUK 20150182/3; Burroi Gorge, NHMUK 20150183/2; label not readable, NHMUK 20150185/7; Burrali, NHMUK 20150186/10; Khasi Hills, coll. Godwin-Austen, NHMUK 20150187/65; Khasi Hills, coll. W. Blanford, NHMUK 20150188/3; W. Khasi Hills, coll. Godwin-Austen, NHMUK 20150189/1; N. Khasi, coll. Godwin-Austen, NHMUK 20150190 (more than 100 shells); Khasi Hills, coll. Kennard, NHMUK/20150195/2 (mixed sample with Endothyrella tricarinata ); Manipur, station 36, Godwin Austen Collection. NHMUK 20150191/87; Manipur, station 48, Godwin Austen Collection. NHMUK 20150192/58; Manipur, station 54, Godwin Austen Collection. NHMUK 20150193/119; Manipur, station 54, Godwin Austen Collection. NHMUK 20150194/89; Indien, leg. Stoliczka, coll. Oberwimmer, NHMW 71640/O/415 (2 shells; mixed sample with Endothyrella sowerbyi : NHMW 109252); Khasi Hills, leg. Stoliczka, 1870, NHMW 92588/3; Viaggio in Birmania (= trip to Burma), Shweego, coll. Fea, 1885-1889, NHMW 20034/4; Shwegoo, Birmania, leg. Mission L. Fea 1885-1889, MNHN 2012-27053/3; Khasi Hills, Himalaya, India, coll. Rušnov ex coll. Blume, NHMW 71770/R/13 (2 adult, 1 juv. shells); Ostindien, Pegu, leg. Stoliczka, coll. Edlauer, 477, NHMW 75000/E/4770 (1 shell; mixed sample with Endothyrella sowerbyi : NHMW 109253); Darjeeling, Himalaya, India, coll. Rušnov ex coll. Blume, NHMW 71770/R/14 (1 adult, 1 juv. shells; mixed sample with Endothyrella sowerbyi : NHMW 71770/R/15); Ostind., coll. Gerstenbrandt, NHMW 83901/G/2745 (2 shells); Pegu, ex coll. Hauer, NHMW 21617/4; Assam, coll. Landauer, NHMW 92594/2; Khasi Hills, Pegu (2 different label were found in the sample), coll. Stoliczka, NHMW 92591/41 (one of them is probably a juvenile Endothyrella tricarinata ); Khasi, leg. Stoliczka, 1880, NHMW 92592/7; Khasi Hills, leg. Stoliczka, 1880, NHMW 92593/2 (mixed sample with Endothyrella sowerbyi : NHMW 109254 and Endothyrella blanda : NHMW 109255); East India, leg. Bernardi, Altonaer Museum, coll. O. Semper, ZMH 45908/1; Siam, Altonaer Museum, ZMH 45910/2; Birma, Moulmein, Hinterindien, coll. Krüper 1928, ex coll. Oberwimmer, SMF 118090/2 (mixed sample with Endothyrella sowerbyi : SMF 346406); Darjeeling, Himalaya, coll. Jetschin ex coll. Oberwimmer 1899, SMF 118088/1 (mixed sample with Endothyrella sowerbyi : SMF 346407); Khasi Hills, coll. Bosch, ex coll. Rolle, SMF 172072/1 (mixed sample with Endothyrella sowerbyi : SMF 346408); S-Shan Staaten, Ywathit, Prov. Karenni, a. mittleren Salwen, leg. Michelitz, SMF 150108/3; Indien, coll. Jetschin ex coll. Oberwimmer 1899, SMF 118089/2; Indien, Darjeeling, (alte Schau-sammlung), coll. Kobelt, SMF 150109/2; Khasi-Berge, coll. C. R. Boettger 1904, SMF 118091/1 (Fig. 13B); Assam, coll. Bosch, ex coll. Rolle, SMF 172071/4; Indien, Khasi-Hills, coll. Webb 1928, SMF 150086/2; Indien, Katschar, coll. Möllendorff, Orig. Handb. Pal. Fig. 2092; SMF 150106/4; Goramarah (Ghoramara), Chittagong, coll. Foulon 1936, MNHN 2012-27045/2; no locality, coll. Jousseaume, MNHN 2012-27050/3; no locality, coll. Jousseaume, MNHN 2012-27049/50.

Diagnosis.

A very small, sinistral species with very narrow umbilicus, conical dorsal surface, and hairs standing in five rows on the body whorl; palatal plicae more or less straight, the 4th and 5th divided; lamella slightly curved, with short lower and long upper elongation in anterior direction; there are two denticles posteriorly, one above and one below.

Measurements

(in mm): D: 8.1-9, H: 4.6-5.1 (n = 3, SMF 172072).

Differential diagnosis.

Endothyrella plectostoma is similar to Endothyrella affinis and Endothyrella tricarinata in the narrow umbilicus. All other Endothyrella species of similar size have wider umbilicus. Endothyrella plectostoma is usually smaller, darker than Endothyrella affinis , it has a horizontal, relatively long plica anterior to the lamella, and has the periostracal folds arranged on five spiral line. In contrast, Endothyrella affinis lacks the horizontal parietal plica and has four hair rows. Moreover, Endothyrella plectostoma has a narrower umbilicus and more elevated spire than Endothyrella affinis . See also under Endothyrella sowerbyi and Endothyrella tricarinata and Table 5.

Description of the genitalia

(Figures 22A, 22 D–F, 26): Three specimens have been anatomically examined. Collection data: Sikhim, leg. Godwin-Austen, NHMUK 1903.7.1.451. All specimens had 5-6 embryos developing in their uterus. In one specimen no epiphallic differentiation was observed, the vas deferens started from the distal part of the penis (Fig. 22D).

The left ommatophoral retractor passes between penis and vagina. Atrium short; penis relatively short, internally with holes of various sizes; some tiny, rounded calcareous crystals were found in the penis lumen, not directly associated with the holes; this inner structure continued in the epiphallus; penial caecum short, with central thickening; retractor muscle short, it inserts on the proximal end of the penial caecum; epiphallus slightly longer than penis, it enters the proximal penial portion laterally; vas deferens long and slender; vagina approximately as long as the penis, but thicker, curved centrally; vagina with several thick and relatively long muscle fibres attaching it to the body wall and to the diaphragm, especially at its curved portion; vagina internally with longitudinal folds, which are rather sharp, elevated at the curved area of the vagina, and low elsewhere; the gametolytic sac and the diverticulum are aligned in parallel; the gametolytic sac is slightly thicker and shorter; a relatively long part of the spermoviduct was visible distal to the thickened uterus with the developing embryos; the embryo sac contained no visible calcareous granules, which were reported in other plectopylid species ( Páll-Gergely and Hunyadi 2013, Páll-Gergely and Asami 2014); albumen gland conspicuously small. The latter trait is largely dependent on the period of the life cycle of the dissected specimen. In the present case, however, three specimens were anatomically examined and all specimens had a small albumen gland.

Radula

(Figure 19 E–F): Radula elongated, but not very slender, central tooth present, laterals 8, standing in straight lines (perpendicular to the central column); marginals at least 14, staying in oblique rows; central tooth relatively narrow-based triangular, smaller than the endocone of the first lateral, but much larger than the ectocone; laterals bicuspid, endocone oval or narrow-based triangular; marginals tricuspid (the endocone has two cusps); all cusps pointed, the incision between the innermost two cusps is deep; in some cases the three cusps are almost of the same size.

Distribution.

Museum samples are labelled from several locations. This species is probably widely distributed in north-eastern India through south-eastern Bangladesh to Bago, the Arakan Hills and in the Kayah State in Burma (Myanmar) (Figure 7). A sample (ZMH 45910) was collected in “Siam” (= Thailand), which is possible because other samples were collected in Myanmar not far from the Thai Border.

Remarks.

The name " prodigium Benson" probably refers to Endothyrella plectostoma . It is a manuscript name, which was mentioned several times in the literature ( Godwin-Austen 1875, Tryon 1887, Pilsbry 1894, Gude 1899c), but has never been published formally.