Idiopyrgus eowynae, Salvador & Bichuette, 2024

Salvador, Rodrigo Brincalepe & Bichuette, Maria Elina, 2024, Idiopyrgus Pilsbry, 1911 (Gastropoda, Tomichiidae): a relict genus radiating into subterranean environments, Zoosystematics and Evolution 100 (4), pp. 1543-1556 : 1543-1556

Idiopyrgus eowynae sp. nov.

Fig. 4

Type material.

LES 29795 (holotype), LES 29796 (4 paratypes), LES 29797 (2 dark morphs paratype), MNRJ 37168 (3 paratypes), MZSP 168419 (3 paratypes). All specimens collected on 10. ix. 2021 (M. E. Bichuette & J. E. Gallão leg.); all paratypes from type locality (except dark morphs, which are from the same cave but from the entrance zone) .

Type locality.

Brazil, Bahia state, Carinhanha municipality, Gruna do Pedro Cassiano (“ Pedro Cassiano Cave ”), 13°47'48.0"S, 43°54'50.0"W.

Etymology.

The species is named in honour of Éowyn, from J. R. R. Tolkien’s “ The Lord of the Rings. ” Éowyn exemplifies courage, resilience, and resistance against darkness, both internal and external, standing against Gríma Wormtongue and the Witch-king of Angmar.

Diagnosis.

Shell conical to turriform and relatively tall in comparison to congeners. Body whorl is translucent yellow; previous whorls are slightly darker and brownish. Teleoconch sculpture consisting of few (4–7) radial rows of thorn-like hairs on the apical portion of whorl and a multitude of fine irregular spiral lines below them, reaching all the way to the umbilicus. Aperture large, rounded.

Description.

Shell conical to turriform, 5–5 ¼ whorls, 4.5–4.6 mm high, ~ 2.7 mm wide. Colour pale beige or yellowish on body whorl, but slightly darker and brownish on earlier whorls; body whorl translucent; early whorls typically with flaked off periostracum. Protoconch of 1 ¼ whorl, rounded, smooth (Fig. 4 G, I ). Suture deep. Whorls increasing uniformly in width but more rapidly in height. Teleoconch sculptured by minute triangular thorn-like ‘ periostracal hairs’ arranged in equidistantly spaced spiral rows (4 to 7 rows) and restricted to apical portion of body whorl (Fig. 4 A – D, H ). Below the rows of periostracal hairs, there is a multitude of fine, irregular spiral lines, reaching all the way to the umbilicus (Fig. 4 H ). Periostracal hairs can be worn out in older specimens (Fig. 4 C, D ), particularly in the early whorls. Peristome complete, not covering penultimate whorl, expanded, wider in abapical region, narrower in columellar region, of same colour as body whorl or slightly whiter. Aperture rounded, with light apical angulation, but with smooth, rounded contour. Umbilicus rimate, nearly closed. Operculum oval, paucispiral; corneous, thin, and translucent, of same colour as body whorl. Soft body completely white in colour.

Dark morph (Fig. 4 E, F ) differs from the above-described typical morph by having a black shell with thicker walls, in which the teleoconch sculpture is nearly invisible: a few remnants of the spiral rows of hairs are visible in the adapical portion of the whorls; traces of the sculpture can also be seen through the shell wall of the aperture (Fig. 4 E ).

Distribution.

Known only from type locality (Fig. 1 ), the twilight and dark (aphotic) zones of the cave (typical morph) and at the cave entrance (dark morph).

Remarks.

Idiopyrgus eowynae sp. nov. can be easily distinguished from most of its congeners (including the type species I. souleyetianus ) by its much wider shell and the presence of teleoconch sculpture. It closely resembles I. meriadoci sp. nov. (see below) and I. umbraticola . It differs from I. meriadoci sp. nov. by a much larger size and larger number of whorls, as well as by having a different teleoconch sculpture, which includes periostracal hairs. Conchologically, I. eowynae sp. nov. is most similar to I. umbraticola comb. nov., from which it can be distinguished by its smaller size (~ 4.5 mm vs. ~ 5.0 mm in I. umbraticola ), higher whorls with a more strongly convex outline, a larger and rounder aperture, and by having a different teleoconch sculpture. In I. eowynae sp. nov., there are few spiral rows of the triangular thorn-like hairs, restricted to the apical portion of the whorl, and which are then replaced by irregular spiral lines that continue towards the umbilicus (also visible in juveniles). In I. umbraticola , there is a larger number of rows of hairs, stretching the median portion of the whorl; the spiral lines are absent. Notably, a dark morph has also been observed in I. adamanteus Salvador, Silva & Bichuette, 2022, and I. cf. walkeri Pilsbry, 1924 ( Salvador et al. 2022 a).

Except for the existence of two morphs (typical and black), there is little variation in shell shape, form, and proportions among the presently available specimens of I. eowynae sp. nov. (Fig. 4 A – F ). Notably, the sequences of the COI barcoding gene fragment of the two morphs were 100 % identical, while the sequences of both morphs had a pairwise identity of around 90 % in relation to I. adamanteus and I. minor . According to the results of the phylogenetic analysis (Fig. 3 ), I. eowynae sp. nov. is sister to I. adamanteus ; both species together are sister to I. minor .

Figures

Figure 1. Distribution map of Idiopyrgus spp. (and Spiripockia punctata) in caves of the state of Minas Gerais and Bahia, Brazil.

Figure 3. Bayesian inference phylogenetic tree based on concatenated but unlinked markers, highlighting the family Tomichiidae and showing the position of the new species in the genus Idiopyrgus and its relationship to its congeners. Posterior probabilities are shown on the nodes. Scale bar is substitutions per site.

Figure 4. Idiopyrgus eowynae sp. nov. A, B. Holotype LES 29795; . C. Paratype (typical morph) # 1 LES 29796; D. Paratype (typical morph) # 2 LES 29796; E, F. Paratype (dark morph) LES 29797; G. Paratype (typical morph) # 3 LES 29796, juvenile, showing the protoconch in greater detail as well as the sculpture of the first teleoconch whorls; H. Detail of the body whorl of holotype in dorsal view, showing the teleoconch sculpture, in particular the multitude of spiral lines; I. Paratype # 3 in apical view, showing the protoconch.