Zospeum isselianum Pollonera, 1887

Jochum, Adrienne, Slapnik, Rajko, Klussmann-Kolb, Annette, Pall-Gergely, Barna, Kampschulte, Marian, Martels, Gunhild, Vrabec, Marko, Claudia Nesselhauf, & Weigand, Alexander M., 2015, Groping through the black box of variability: An integrative taxonomic and nomenclatural re-evaluation of Zospeumisselianum Pollonera, 1887 and allied species using new imaging technology (Nano-CT, SEM), conchological, histological and molecular data (Ellobioidea, Carychiidae), Subterranean Biology 16, pp. 123-165 : 134-138

Taxon classification Animalia Pulmonata Ellobiidae

Zospeum isselianum Pollonera, 1887 Figures 2B−F, 8A−F, 9A− F

Zospeum alpestre - Bourguignat 1856 [non Carychium alpestre Freyer, 1855]

Zospeum isselianum Pollonera, 1887

Zospeum alpestre - Stossich 1899 [non Carychium alpestre Freyer, 1855]

Zospeum alpestre - Giusti and Pezzoli 1982 [non Carychium alpestre Freyer, 1855]

Data regarding the original type material.

The two syntypes of Zospeum isselianum were collected in debris of the Natisone River in the northeastern Italian region of Friuli ( Pollonera 1887). Pollonera remarked that A. Tellini collected the debris far north of the town of Cividale and that the specimens could only have originated from the upper, mountainous part of the Natisone valley, namely, the right tributary of the Isonzo River. The Natisone ( Nadiža) flows from the Slovenian side of the Julian Prealps and courses the Slovenian-Italian border crossing into Eastern Friuli. Currently, the only known type material consists of a single shell (MZUT M3232) labeled “cotypus” from the Pollonera collection housed in the Museo Regionale di Scienze Naturali Sezione di Zoologia, Torino, Italy (Fig. 2A). Since this specimen (MZUT M3232) is unrecognizable due to Bynesian decay (also called "Bynes disease"), a granular efflorescence of the shell due to a physicochemical reaction involving acetate/formate compound salts and water, which largely erodes the shells ( Callomon and Rosenberg 2012, Cavallari et al. 2014), it is no longer taxonomically informative. Moreover, since it cannot maintain nomenclatural stability ( ICZN 2014, Art. 75.5), we propose the designation of a neotype (CSR SASA 37013) from the assumed type locality. Material of Zospeum isselianum selected for the neotype here was collected in Turjeva jama, located on the right bank of the Natisone ( Nadiža) River by the village of Robič in the municipality of Kobarid, Slovenia. Geographically, this cave is most likely the source of the two shells initially presented to Arturo Issel and later dedicated to him in 1887 by Pollonera.

Original differential diagnosis ( Pollonera 1887).

"This species just resembles Zospeum obesum Schmidt, Zospeum alpestre Freyer (pars), and Zospeum nyctozoilum Bourg. From the first it differs because it lacks an obsolete columellar fold, because it has the umbilicus more open, the peristome less swollen, and the apex not acute. From the second it differs because it has the umbilicus less cramped, the apex less acute (indeed mammillatus), the sutures deeper and it has the last lap with a lower development. From the third it differs because the right margin is a little arched (not reflected) and it has the umbilicus more open (Issel)" ( Pollonera 1887, translated from Italian by Massimo Prodan and Floriana Umani 2014).

Material examined.

Neotype (CSR SASA 37013/37013a) (Fig. 8A−E). Conspecifics (BOLD-ID: BARCA121-10, ACCESSION NR: HQ171594) ( Weigand et al. 2011)), SMF 341636 (Fig. 2B−F), NMBE 532009 (Fig. 8F): Turjeva jama, Robič, Kobarid, Julian Alps, Slovenia, 46.2435°N, 13.5046°E, alt. ca. 253 m, air temp. in cave 9.3° C, June 1, 2013. Leg. Rajko Slapnik.

Diagnosis.

Shell minute, transparent when fresh, conical with entire, half-roundish and more or less thickened peristome; parietal lamella; columella non-introrse, secondary columellar dilatation just above umbilical indentation; columellar lamella inclinate.

Description.

Measurements of neotype specimen CSR SASA 37013 (Fig. 8A−E): shell height 1.56 mm, shell diameter 1.07 mm, peristome width 0.75 mm, peristome height 0.84 mm.

Measurements of conspecifics from Turjeva jama are provided in Table 3 (based on neotype and conspecifics of neotype). Shells minute (Table 5), variable in height (1.05-1.63 mm), conical with about 5 whorls, regularly coiled, suture deep, whorls convex, more or less shouldered; aperture semicircular, peristome closely adhering to spire (Fig. 2D), thickened, higher than wide, taking up to ca. 35% of shell height; umbilicus closed, shallow depression; contact between the columellar edge of peristome and last whorl moderately long (0.34-0.59 mm); non-expressed parietal lamella in aperture continues only in traces within shell; parietal plica present or absent (Fig. 8F); penultimate whorl “sinks” into ultimate whorl at upper junction of peristome and penultimate whorl in profile perspective (Fig. 2D); columella twisted but non-introrse, slender, secondary columellar dilatation at base; columellar lamella inclinate, extended (Fig. 8A−D); secondary columellar dilatation equal to ½ distance of maximal upper columellar lamella extension; protoconch with pattern of spiral interconnected pits separated by zones of non-pitted bands (Fig. 9D−E); teleoconch with tightly spaced irregular spiral striae of densely interconnected pits (Fig. 9B, C, F); broader spiral bands interrupt finer rows of pitted striae (Fig. 9B).

Differential diagnosis

(Figs 10, 11). Differs greatest from congeners here in columellar apparatus and surface microstructure; differs from Zospeum sp. ( Konečka zijalka) by the more slender columella, secondary columellar dilatation equal to ½ distance of maximal upper columellar lamella extension, columellar lamella inclinate, extended; Zospeum cf. amoenum ( Potočka zijalka) lacks columellar lamella, columella straight cylindrical (Fig. 10J); from Zospeum kupitzense by the planar less inclinate orientation of columellar lamella (Fig. 10A−F), less pronounced parietal lamella than in Zospeum kupitzense ( Ložekarjeva zijalka) (Fig. 10E); from Zospeum alpestre ( Kamniška jama) by the more slender columella, secondary columellar dilatation at base, columellar base of Zospeum alpestre clavate inflated, moderately attenuate (Fig. 10G); irregular striation of tightly interconnected pits of upper teleoconch differs from regular impressed wavy bands on teleoconch of Zospeum kupitzense (Fig. 9I−L); differs from rather regularly spaced rows of interconnected pits on teleoconch of Zospeum amoenum ( Ihanščica cave). The differential diagnosis of genetic data is presented with the respective BOLD-ID numbers in Table 2.

Distribution.

Although we question past distribution records (Fig. 1, Table 1), Zospeum isselianum likely occurs within a narrow radius encompassing the Southeastern Alpine region of contiguous cave and river systems of northeastern Italy, southern Austria, Slovenia and northwest Croatia ( Bole 1974, Maier and Bole 1975, Mildner 1976, Slapnik 1991, 1994, Slapnik and Ozimec 2004).

Ecology.

Live Zospeum isselianum were found in Turjeva jama on mud and muddy walls at the end of the cave and adjacent to the central pit located in the middle of the cave. Bats were seen in the vicinity of the collection site.

Conservation.

In the caves sampled for this study, empty shells were sparsely found in sediment and live individuals sparsely populated certain cave walls during the summer season. These findings suggest that Zospeum isselianum occurred there for more than one season, and that these populations are/were not immediately threatened. Still, on a global scale, its distribution is fragmented and likely limited to far less than 312 caves within a radius of 20,000 km2. In conjunction with the categories for the IUCN Red List ( IUCN Standards and Petitions Subcommittee 2014), it can be considered a taxon of Least Concern (LC) since Zospeum isselianum is (potentially) known from many sites and these populations seem to be rather stable. Habitat disturbance through human agency poses the greatest threat.

Remarks.

This species shows a wide range of variability in the shell. The parietal lamella with its nondescript shape and configuration has been considered characteristic ( Bole 1974, Slapnik 1991). The size and shape of the shell and aperture in conjunction with the visible parietal lamella indicate the very close relationship with Zospeum alpestre (see Bole 1974) and with Zospeum amoenum (see Slapnik 1991) in eastern Slovenia. The columella differs from congeners in this study by the presence of a secondary columellar dilatation at the base and an inclinate, extended columellar lamella. Superficial microstructure on the protoconch consists of spirally arranged pits interspersed by medium to wide zones of smooth non-pitted bands. The teleoconch shows a deep suture and irregular rows of tightly interconnected pits. Sometimes microscopic white chalky bands above and below the suture can be seen.