Zospeum simplex Inäbnit, Jochum & Neubert, 2021

Jochum, Adrienne, Michalik, Peter, Inäbnit, Thomas, Kneubühler, Jeannette, Slapnik, Rajko, Vrabec, Marko, Schilthuizen, Menno & Ruthensteiner, Bernhard, 2024, 3 D X-ray microscopy (Micro-CT) and SEM reveal Zospeum troglobalcanicum Absolon, 1916 and allied species from the Western Balkans (Ellobioidea: Carychiidae), European Journal of Taxonomy 926, pp. 1-62 : 48-51

Zospeum simplex Inäbnit, Jochum & Neubert, 2021

Figs 18–19

Original diagnosis

Shell usually ca 1.3 mm in height, transparent, conical, peristome thickened, roundish, with a differentiated parietal shield, lamellae not present.

Type material

Holotype

BOSNIA AND HERZEGOVINA • municipality of Tomislavgrad, Gornji Brišnik, Jama Dobravljevac ; 43.6347° N, 17.2328° E; 25 Aug. 2019; R. Slapnik and J. Valentinčič leg.; NMBE 568060 (ex RSC 3760).

Other material examined (via Micro-CT and SEM)

BOSNIA AND HERZEGOVINA • 2 specs ( Fig. 18 , MicroCT); same collection data as for holotype; NHMW-MO-113642 (ex RSC 3760) • 2 specs ( Fig. 19 , SEM); same collection data as for holotype; SMF 349425 (ex RSC 3760) .

Emended diagnosis considering Micro-CT and SEM Data

Shell ca 1.4 mm and 5½–6 whorls; conical with narrow spire; peristome bears slight indentation at upper junction of parietal and palatal sides; low, hump-like callus on the inner columellar side of peristome; teleoconch with dense rows of microscopic, radially aligned, elongated pits; medium-sized columella with either two weak, loosely coiled low incomplete lamellae or a single incomplete lamella.

Enhanced description with Micro-CT and SEM Data

MEASUREMENTS (N = 2). sh: 1.40–1.41 mm; sw: 0.93–0.96 mm; ah: 0.57 mm; aw: 0.61–0.62 mm; hlw: 0.83–0.84 mm; SA: 56.46–59.45 deg., NHMW-MO-113642 (ex RSC 3760).

Shell ca 1.4 mm, conical, with 5½–6 regularly coiled, convex whorls with height of last whorl slightly greater than half of shell height; spire angle narrow; protoconch bulbous with microstructure of dense pitting and some irregular raised bands extending to the suture; the second and third whorls bear rows of interrupted dashes of radial pitting; teleoconch sculpture includes blunt irregular growth lines and weak radial banding on all whorls; density of blunt striations varies, showing a tendency towards costateness at the suture zones; high magnification of shell surface (5 μm) shows tiny pinpoint perforations; aperture reniform, wider than high; peristome slightly oblique on columellar side with a low, hump-like thickening on the inner columellar side ( Fig. 18A ), palatal side narrowly reflected with low ribbing extending some distance beyond the lip; parietal shield well defined, long and angular, with a slight indentation at upper parietal and palatal junction; upper rim of peristome recedes ca 1 / 5 the width of the penultimate whorl (aperture facing left) ( Fig. 18E ); columella centrally aligned and slender; a low lamella is present under penultimate whorl (aperture facing right) ( Fig. 18B ) which then turns into either two incomplete loosely coiled low lamellae (dorsal view) ( Fig. 18D ) or constitutes one well pronounced one ( Fig. 18J ); ventral side with small, umbilical depression with no puckering; columellar side of peristome arches slightly over and oblique to umbilical depression, alignment of last 1/4 whorl somewhat compact ( Fig. 18F ).

Remarks

Differs from Z. troglobalcanicum in that it bears at least one additional or ½ whorl; the upper parietal and palatal junction has a slight indentation in contrast to a well-defined notch; protoconch is more bulbous and somewhat elevated; the shell spire angle is narrower than that of Z. troglobalcanicum but within the spectrum of the narrowest spire measurements of two shells of Z. constrictum Jochum & Ruthensteiner sp. nov. (57.5–59.2 deg.); width of the shell is narrower than that of Z. troglobalcanicum ; the low, hump-like thickening of callus (not a denticle) a short distance inside the columellar side of the peristome is so far distinctive for this species.

When compared to its molecularly closest congener, Z. kolbae Jochum, Inäbnit, Kneubühler & Ruthensteiner sp. nov., Z. simplex Inäbnit, Jochum & Neubert, 2021 shows a significantly lower apertural height of an almost equal width with that of Z. kolbae as well as a narrower spire angle than that of Z. kolbae . Shell height shows more range in Z. kolbae than in Z. simplex .

Though Z. simplex Inäbnit, Jochum & Neubert, 2021 resembles Z. amplioscutum Jochum & Ruthensteiner sp. nov., it differs by its reduced extension onto the body whorl and less heavily callused parietal shield. Z. simplex is larger, has a narrower spire angle and a markedly less textured teleoconch in comparison to that of Z. amplioscutum . Zospeum simplex does not have a second lamella on the columella (aperture facing right) ( Fig. 18B ) but rather, weak ripples of a potential double one ( Fig. 18D ) or a stronger, incomplete single one in dorsal view ( Fig. 18J ). The narrow columella ( Fig. 9C–D ) and the elongation of the last whorl further beyond the umbilical depression (ventral side) additionally differentiate Z. amplioscutum from Z. simplex .

The incidence of the one solid lamella versus the two incomplete low lamellae occurred in one of the two shells scanned. In sync with Inäbnit et al. (2021), the shell height:shell width ratio is the most effective way to differentiate Z. simplex Inäbnit, Jochum & Neubert, 2021 from morphs of Z. troglobalcanicum . The low, hump-like callus on the inner columellar side of the peristome is consistent in the three shells from the type locality.

Figures

Fig. 18. 3D visualizations of Micro-CT data of Zospeum simplex Inäbnit, Jochum & Neubert, 2021, (NMHW-MO-113642 ex RSC 3760) from Dobravljevac jama, Gornji Brišnik, Bosnia and Herzegovina. A–F. Specimen 1 (spm1). A. Aperture view. B. Aperture facing right view. C. Apical view. D. Dorsal view. E. Aperture facing left view. F. Ventral view. G–L. Specimen 2 (spm2). Same perspectives as Specimen 1.

Fig. 19. Zospeum simplex Inäbnit, Jochum & Neubert, 2021, (SMF 349425) Scanning Electron Microscopy images. A. Protoconch and upper teleoconch showing microstructure of superficial pitting. B. Close up view of pitting microstructure. C. Last whorl with axial ribbing extending beyond peristome lip. D. Close up view of second whorl showing rows of interrupted dashes of radial pitting. E. Growth lines and radial banding on teleoconch. F. Close up view of growth lines and shell microstructure.

Fig. 9. Zospeum amplioscutum Jochum & Ruthensteiner sp. nov., (NHMW Mol.Coll.Edlauer 19.069) with sample labels. A. Light microscopic images of paratype (NHMW Mol.Coll.Edlauer 19.069), apertural and dorsal views.B. Light microscopic images of holotype (NHMW Mol.Coll.Edlauer 19.069), aperture and dorsal views. C–H. 3D visualizations of X-ray Micro-CT data of holotype (NHMW Mol. Coll.Edlauer 19.069). C. Aperture view. D. Aperture facing right view. E. Apical view. F. Dorsal view. G. Aperture facing left view. H. Ventral view showing coiling projecting high up on shell and peristome oblique to umbilicus.