Georissa filiasaulae Haase & Schilthuizen, 2007

Zacaery Khalik, Mohd, P. Hendriks, Kasper, J. Vermeulen, Jaap & Menno Schilthuizen,, 2019, Conchological and molecular analysis of the " non-scaly " Bornean Georissa with descriptions of three new species (Gastropoda, Neritimorpha, Hydrocenidae), ZooKeys 840, pp. 35-86 : 58-59

Georissa filiasaulae Haase & Schilthuizen, 2007 Figure 13 A–K

Georissa filiasaulae Haase & Schilthuizen, 2007: 216, figs 2 A–B and 2E; Clements et al. 2006: 736; Clements et al. 2008: Appendix D; Schilthuizen et al. 2012; Khalik et al. 2018.

Type locality.

Malaysia, Sabah, Sepulut valley, Interior province, Batu Sanaron (04°42.05'N, 116°36.01'E).

Type material.

Holotype (Holotype by original designation). Malaysia, Sabah, Sepulut valley, Interior province, Batu Sanaron (04°42.05'N, 116°36.01'E): BOR/MOL 3795. Paratypes. Malaysia, Sabah, Sepulut valley, Interior province, Batu Sanaron (04°42.05'N, 116°36.01'E): BOR/MOL 3491 (7); ZMB 107143-107149 (7) (not seen).

Other material.

Batu Sanaron, Interior province, Sepulut valley, Sabah: BOR/MOL 532, BOR/MOL 3405. Batu Pungiton, Interior province, Sepulut valley, Sabah Batu Pungiton, Sabah (04°42.41'N, 116°36.04'E): BOR/MOL 12768 (Fig. 13).

Description.

Protoconch. Colour: white. Sculpture: a mix of rounded, ellipsoidal to irregular sculptural shape. Mesh width: 2.5-20 µm. Teleoconch. Colour: white. First whorl: convex. Subsequent whorls: convex, shell shape slender to broad. Suture: clearly impressed. Shoulder: slightly extended, regularly spaced nodules. Number of whorls: 2 ½– 3. SH: 1.21-1.68 mm. SW: 1.67-1.68 mm. SI: 1.08-1.27. Shell sculpture. Radial sculpture: absent, weak to strong growth lines. Spiral sculpture: present, rather weak and thin, densely spaced on the first whorl, the ribbing appears immediately after the protoconch, sometimes distorted/discontinuous by the growth lines, superficially smooth on the later whorls. Aperture. Shape: rounded to semi-elliptic, straight to slightly convex parietal side, palatal side rounded, palatal edge partially contiguous with the body whorl and parietal side, basal side convex. AH: 0.67- 0.79 mm. AW: 0.69-0.83 mm. AI: 0.93-0.97.

Diagnosis.

Georissa filiasaulae has weak, thin, and densely arranged spiral sculpture with nodular structure on the shoulder. The shell colour and thickness are most similar to G. corrugata , which has white and partially transparent shell.

Distribution.

Georissa filiasaulae is a cave specialist, known from the cave system of Batu Sanaron and Batu Tinahas in the Sepulut valley. Schilthuizen et al. (2012) studied the population genetics of G. filiasaulae and its sister species, G. saulae . They found narrow hybrid zones between the two species in cave entrances.

Molecular analysis.

ML and Bayesian analyses of G. filiasaulae (16S: n = 3; CO1: n = 3) show that G. filiasaulae form one clade with 98% BS and 100% PP. The sister group is the G. saulae population from Pungiton ( G. saulae is paraphyletic).

Discussion.

Georissa filiasaulae is one of the two known Bornean Georissa that is troglobitic. Khalik et al. (2018) described G. silaburensis , another species of Bornean Georissa from the “scaly” group as a possible troglobite from Gunung Silabur, Serian, Sarawak. Georissa filiasaulae differs from G. saulae by the absence of any scale-like sculpture, reduced shell pigmentation, and relatively larger shell size and broader shell shape. Population genetic studies suggest that the hybrid zone between the two is restricted to a narrow region at the cave entrances, rendering the two species as independent evolutionary units. Therefore, considering them as separate species is warranted ( Schilthuizen 2000).