Carychium zarzaae Jochum & Weigand

Jochum, Adrienne, Weigand, Alexander M., Bochud, Estee, Inaebnit, Thomas, Doerge, Dorian D., Ruthensteiner, Bernhard, Favre, Adrien, Martels, Gunhild & Kampschulte, Marian, 2017, Three new species of Carychium O. F. Mueller, 1773 from the Southeastern USA, Belize and Panama are described using computer tomography (CT) (Eupulmonata, Ellobioidea, Carychiidae), ZooKeys 675, pp. 97-127 : 102-103

Carychium zarzaae Jochum & Weigand sp. n. Figures 13, 14

Weigand et al., 2013: 3, Fig. 1 49|C13; Seq. ID: BARCA145-12, BARCA146-12, BARCA147-12, BARCA148-12.

Material.

Holotype (NMBE 549926/1 ex AJC ex AJC 1902, slightly damaged): Panama, Chiriquí Province, Boquete, path near Boquete; N8.824767, W-82.495833, on moist stick; 12 June 2011; leg. Eugenia Zarza.

Paratypes: locus typicus: 1 shell (NMBE 549927/1 ex AJC 1902) slightly damaged (CT-scanned) and 1 shell formerly in formol (SMF 341640 ex AJC 1903); 1 shell formerly in formol (CM 155816 ex AJC 1903); data as the holotype.

Diagnosis.

Shell c. 1.72 mm in height, opaque, elongate-pupiform with an entire, elliptically shaped and thickened peristome, with a palatal callus, columellar-basal callus and a moderately sized, parietal denticle.

Description.

Measurements are provided in Table 2. Shell minute, elongate-pupiform, opaque, very thin, with about 4.25 convex whorls and a deeply incised suture; with irregular striations or blunt growth lines on the body whorl. Protoconch bulbous. Teleoconch is smooth with glossy sheen. Peristome elliptical and thickly doubled by callus below the palatal bulge (not denticle), only slightly higher than wide, taking up more than one third of the shell height, moderately reflected and curved back at the base (Fig. 13C, I–K). Columellar margin has a parietal-columellar callus. Parietal denticle deeply set and moderately thick, slightly downward projecting and prominently visible from the umbilical perspective (Fig. 14 F). Internally, C. zarzaae sp. n. has a very thin sinuous lamella starting at the upper third of the penultimate whorl and forming a moderate tongue-like configuration in the body whorl in dorsal perspective (Fig. 14C). Under the sinuous lamella, the elongated columellar spindle twists smoothly, forming the columellar basal callus at its proximal end (Fig. 14 B–C). In dorsal and side-ventral perspectives (Fig. 14 C–D), the columellar lamella forms an oblique, elongated S form with its thickest part forming the rim of the distal portion and projecting moderately from the columella (Fig. 14D).

Differential diagnosis.

Differs from C. hardiei by its very thin shell, rounder whorls and general reduction of marked striation on the teleoconch. In side view aperture-left profile, the body whorl of C. zarzaae projects c. 1/8 beyond the rim of the peristome. The shell of C. zarzaae is smaller and thinner than C. costaricanum and larger and thinner than C. mexicanum . The parietal denticle and the parieto-columellar callus on the peristome of C. zarzaae are not prominent as in C. belizeense (Fig. 11A, E, I) but larger than in C. hardiei (Figs 4A, I, 5A, E) and most similar to those in C. mexicanum (Puebla) (Fig. 8 I–J). The increasing sinuosity of the lamella as it continues into the body whorl in the uppermost part of the penultimate whorl (in the dorsal perspective) of C. zarzaae is similar to that of C. hardiei and not to C. mexicanum nor to C. costaricanum (Fig. 9 G–H). However, in C. zarzaae , the thickness of the lamella and the degree of horizontal lamellar extension is reduced in comparison to this structure in C. hardiei (aperture right and left views Fig. 5 C–D); differs from C. mexicanum by the fatter shell and the reduced parieto-columellar callus seen in some shells from the Puebla C. mexicanum population (Fig. 8 I–J), by the uneven thickness of callus on the peristome at the palatal mid-section and where it curves back at the basal palatal margin; from C. costaricanum by the greatly reduced robustness of the shell and the imbalanced distribution of callus on the peristome. The elongated S-shaped lamella in C. zarzaae is most similar to that in C. mexicanum . The shell of C. zarzaae is homogeneously compact in contrast to the elegantly slender, tapered form of C. jardineanum , which also bears nearly six whorls compared to the 4.25 in Z. zarzaae .

DNA barcode data can clearly delineate Carychium zarzaae sp. n. from all other North and Central American taxa, demonstrating its lowest K2P genetic distance of 4.1 % to C. jardineanum (Fig. 3).

Etymology.

The new species is named after our Mexican colleague and previous coauthor, Eugenia Zarza, who collected the Panamanian material in Weigand et al. (2013) and subsequently, the Mexican material here. Without her perseverance in the field, we could not have molecularly corroborated Pilsbry’s (1948) morphological investigations, nor had enough comparative material to adequately assess C. belizeense . Her field work has opened a new window to Mexican and Central American carychiid diversity and extended the distribution of this genus to its southern-most point in the Western Hemisphere.

Distribution.

Only known from the type locality.

Ecology.

Tropical rainforest.

Conservation.

Carychium zarzaae is only known from Boquete. Consequently, and in conjunction with the Guidelines for the IUCN Red List (IUCN Standards and petitions Subcommittee 2014), it is a Critically Endangered narrow range endemic (CR B1) and as such, warrants immediate conservation priority.

Remarks.

The very thin shell of C. zarzaae contrasts remarkably with the pre-sequence images of the seemingly robust shell of the second Panamanian lineage C12 (Fig. 14), which resembles C. belizeense in peristome formation and C. hardiei in superficial teleoconch striation. Although somewhat hazy in these images, C12 shows a prominently thickened parieto-columellar callus and a thick parietal denticle in congruence with that in C. belizeense . Carychium zarzaae is distinct from this joint Panamanian species. The columellar lamella of C. zarzaae is incredibly thin, almost like ripped gauze at the line of flexure where it projects away from the columella. In our experience, C. zarzaae has the thinnest shell so far encountered within the genus Carychium .