Endothyrella blanda (Gude, 1898)

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 : 23-25

Taxon classification Animalia Pulmonata Plectopylidae

Endothyrella blanda (Gude, 1898) Figures 17 B–C, 18, 19 A–B, 20 A–C

Endothyrella blanda 1898 Plectopylis blanda Gude: Science Gossip, 4: 264, figs 70 a–f. ["Naga Hills, Assam"]

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

Endothyrella blanda 1899d Plectopylis (Endothyra) blanda , - Gude: Science Gossip, 6: 175, 176.

Endothyrella blanda 1900 Plectopylis blanda , - Gude: The Journal of Malacology, 7: 34-35, figs 11 a–f.

Endothyrella blanda 1914b Plectopylis (Endothyra) blanda , - Gude: The Fauna of British India …: 73, 77-78, figs 28 a–f.

Types.

Naga Hills, NHMUK 1922.8.29.41., coll. Godwin-Austen (holotype, Figure 17B).

Additional material examined.

Richila Peak, Sikkim, India, coll. Ottó, L., MMGY 66425/2; Darjeeling, India, West Bengal, Darjeeling, North Point 900-1400 m asl., under stones in forest clearings, coll. Topál, 1967. HNHM 98849/2; Damsang, coll. Godwin-Austen, NHMUK 20150133/26; Rissetchu, Sikkim, coll. Godwin-Austen, NHMUK 20150135/8; Rissetchu & Richila Peak, W. Bhutan, coll. Godwin-Austen, NHMUK 20150136/33 (several of these are juvenile shells); Sikhim, Nampok, coll. Godwin-Austen, NHMUK 20150137/28; Richila Peak, Sikkim, coll. Godwin-Austen, NHMUK 20150138/102; Risset-Chu, Sikkim, NHMUK 20150139/309; Sikhim, NHMUK 20150140/8 (there is a label with the number “749”); Sikhim, coll. Beddome ex coll. Godwin-Austen, NHMUK 1912.4.16.318/1 (large variety); Sikhim, Rinkpo valley, NHMUK 1906.1.1.752/1; Sikkim, Rechila Peak, coll. W. Robert, NHMUK 1903.7.1.28/1; Sikhim, NHMUK 20150141/8; Sikkim, Rarhichu, coll. Godwin-Austen, NHMUK 20120110/1 (labelled as hanleyi ?); Sikhim, Rarhichu, NHMUK 20150143/35 (mixed sample with Endothyrella minor ); Darjiling, NHMUK 1906.2.2.142/5 (mixed sample with Endothyrella plectostoma ); Rarhichu, NHMUK 20150134/49; Khasi Hills, leg. Stoliczka, 1880, NHMW 109255/3 (mixed sample with Endothyrella plectostoma : NHMW 92593 and Endothyrella sowerbyi : NHMW 109254).

Diagnosis.

Shell tiny to very small, sinistral, with narrow umbilicus, conical dorsal surface and 7 rows of hairs; callus weak but present; palatal plicae divided, posterior fractions denticle-like; anterior fractions horizontal, straight; lamella straight or very slightly S-shaped, with posterior denticles above and below, and with a lower and an upper plica close to the sutures; lower plica sometimes short, sometimes very long, and reaches the peristome.

Measurements

(in mm): D: 4.9-5.7, H: 2.8-3.3 (n = 3, NHMUK 20150134).

Differential diagnosis.

See under Endothyrella macromphalus , Endothyrella minor , Endothyrella robustistriata sp. n. and Endothyrella williamsoni and Table 5.

Description of the genitalia

(Figure 18): Two specimens were anatomically examined. Collection data: Silchar Cachar, F. Ede, coll. Godwin-Austen, NHMUK 1903.7.1.502. Both specimens had several embryos developing in the uterus.

The left ommatophoral retractor passes between penis and vagina. Atrium short, penis long, rather cylindrical, but slowly tapers towards the proximal end; opening the penis was very difficult, not only because of its size, but also due to the age of the speci men; the internal morphology could hardly be seen, although parallel folds forming “pockets” were visible; a little thickening was found near the posterior end of the penis, this could be interpreted as a penial caecum. The slender and relatively long retractor muscle inserts on the proximal end of the penis, slightly in proximal direction from the caecum; epiphallus also slender, slightly longer than the penis; vas deferens long and slim; vagina shorter than the penis and epiphallus combined, it is very thick, with a well-developed vaginal bulb; several short muscle fibres attach the vagina to the body wall and diaphragm; both the gametolytic sac and the diverticulum are very long and slim, although the gametolytic sac is somewhat thickened.

Radula

(Figures 19 A–B): Radula elongated, but not very slender, central tooth present, laterals approximately 6, standing in straight lines (perpendicular to the central column); marginals approximately 14, although it is difficult to distinguish which are laterals and which are marginals; marginals are placed in oblique rows; central tooth wide-based triangular, smaller than the endocone of the first lateral, but much larger than the ectocone; laterals bicuspid, endo- and ectocones are triangular; marginals usually tricuspid (the endocone has two cusps), but some of the marginals are tetracuspid (both the endocone and the ectocone have two cusps); all cusps pointed, the incision between the innermost two cusps is deep.

Distribution.

Most museum samples have been collected in the Sikkim area. Gude received the holotype from Godwin-Austen, and it was said to be collected in the Naga Hills, approximately 600 km from Sikkim. The anatomically examined specimens have been collected from Silchar Cachar, which is located at least 500 km from Sikkim, but not far from the Naga Hills. If the samples from the Naga Hills and from Silchar are correctly labelled, we may expect that the species is widely distributed throughout north-eastern India (see also Figure 11).