Carychium belizeense 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 : 100-102

Carychium belizeense Jochum & Weigand sp. n. Figures 11, 12

Weigand et al., 2013: 3, Fig. 1 40|C10; Seq. ID: BARCA BARCA135-12; BARCA136-12.

Material.

Holotype (NMBE 549923/1 ex AJC 1588): Belize, Maya Mountains, Toledo District, Forest Hill, Bladen Nature Reserve; N16.557167, W-88.707833, alt. c. 404 m, in wet depressions between layers of moist leaves; 12 July 2012; leg. Dan Dourson.

Paratypes: locus typicus: 8 shells (NMBE 549924/8 ex AJC 1588) (2 CT-scanned) and 5 specimens in alcohol (NMBE 549925/5 ex AJC 1589); 5 shells (SMF 341639 ex AJC 1589); 4 shells (UF 489972 ex AJC 1589); 4 shells (CM 155815 ex AJC 1589); 6 specimens in alcohol (ANSP A24823 ex AJC 1588); data as the holotype.

Diagnosis.

Shell c. 1.75 mm in height, elongate-pupiform with an elliptical-shaped aperture, pellucid, thick peristome with a columellar-basal apertural barrier and a pronounced parietal denticle. Although it bears one more whorl than C. costaricanum , it is smaller than this species but larger than C. mexicanum . Internally, C. belizeense has a highly sinuate, tightly coiled, two-tiered columellar configuration.

Description.

Measurements are provided in Table 2. Shell minute, elongate-pupiform, transparent when fresh, robust, with about 4-5 highly convex whorls and a deeply incised suture; with irregular striations or blunt growth lines on the body whorl. Protoconch bulbous. Teleoconch is irregularly smooth with course texture and vague indentations disrupting the overall glossy sheen. Peristome elliptical and thick, only slightly higher than wide, closely adhering to spire, taking up about one third of the shell height, moderately reflected, projecting beyond shell (Fig. 11C, K) and curved back in profile view (Fig. 11D, L). Columellar margin has a large callus and an acute entering fold above. Parietal denticle thick, downward projecting, prominently visible from the umbilical perspective (Fig. 11E, G). Columella two-tiered with two, sinuous, thin, tightly coiled lamellae culminating in the thick parietal denticle (Fig. 12 A–D). In dorsal perspective, the columellar lamella slants directly diagonal with its thickest part at the bottom end and projecting moderately from the columella (Fig. 12 E–F). Remarkable is the side perspective with aperture facing right (Fig. 12 I–J), whereby the columellar lamella takes on a strongly curved tongue-like form directly over the dense, blister-like second lamella of the two-tiered columellar apparatus. The base of the columella spindle is short and obliquely set. The high degree of sinuosity and tight coiling of the two-tiered lamella is remarkable for this species.

Differential diagnosis.

Differs from C. hardiei sp. n. by its generally more robust and fatter shell, greater degree of whorl convexity and general reduction of distinct striation on the teleoconch. In side view aperture-left profile, the peristome of C. belizeense is practically sheer with the convexity of the body whorl whereby in C. hardiei , the body whorl projects c. 1/6 beyond the rim of the peristome. The columellar callus on the inner edge of the peristome of C. belizeense is much more prominent than in C. hardiei as is the remarkably thick and prominent parietal denticle. Internally, by the highly sinuate, tightly coiled two-tiered columellar configuration versus the singular and simple, moderately sinuate lamellar configuration of C. hardiei ; from C. floridanum by the increased convexity of the body whorl giving the impression of a fatter shell, by the decreased concentration of callus in the interior part of the outermost peristome rim causing less an alabaster-like appearance in the side view, aperture-facing-left perspective. Internally, by the highly sinuate, tightly coiled, two-tiered columellar configuration versus the singular and sinuate lamellar configuration of C. floridanum ; differs from C. mexicanum by the more elongate shell and the possession of an additional whorl, by the uneven roundish, flat expanse of the peristome onto the body whorl whereby, in C. mexicanum , this feature seems to vary from a straight seam on the surface of the body whorl (Fig. 8A) to a fully-callused expansive peristome with a straight seam as in C. costaricanum (Figs 2F, 8I). The parieto-columellar callus is more pronounced in both C. mexicanum and C. costaricanum . Internally, the highly sinuate, tightly coiled, two-tiered columellar configuration of C. belizeense is greatly elaborate (Fig. 12 C–D) compared to the less complex, and smoother sinuosity of the lamellar configurations of C. mexicanum and C. costaricanum (Fig. 9). In C. mexicanum , the narrow lamella unfolds mid-way from within the penultimate whorl position into a moderate tongue-like projection (Fig. 9E, G), maintaining a slightly thickened S-shaped sinuous form when turning the shell from dorsal (Fig. 9 E–G) to aperture-right perspective (Fig. 9I), whereby for C. costaricanum , the lamella is wider at its source in the penultimate whorl, descending smoothly without elaboration. The parietal denticle in C. belizeense is stronger and larger than in both C. mexicanum and C. costaricanum . Carychium jardineanum is conchologically distinct from C. hardiei in that it is more tapered, more elongated and slender in form, clearly ribbed and bears one additional whorl.

DNA barcode data can clearly delineate Carychium belizeense sp. n. from all other North and Central American taxa, demonstrating its lowest K2P genetic distance of 3.9 % to C. costaricanum and C. jardineanum (Fig. 3), respectively.

Etymology.

The new species is named after Belize, the Central American country of origin.

Distribution.

Only known from the type locality.

Ecology.

Tropical rainforest and karst geology of the eastern slopes of the Mayan Mountain Divide ( Dourson and Caldwell 2017).

Conservation.

Carychium belizeense sp. n. is so far only known from the Bladen Nature Reserve (BNR). Since it was found abundantly and is considered "a fairly common species where it is found living between layers of moist leaves" (Dan Dourson pers. comm.) it is likely not immediately threatened on the highly protected Bladen Nature Reserve. Still, on a global scale, its current distribution is probably limited to the 400-square km comprising the BNR and thus, it constitutes an Endangered narrow range endemic (EN B1) in conjunction with the Guidelines for the IUCN Red List (IUCN Standards and petitions Subcommittee 2014). Since the Bladen Nature Reserve is a major conservation priority in Belize, we are confident C. belizeense sp. n. is thriving well because of this protection.

Remarks.

The primary upper columellar lamella is incredibly thin, almost like gauze at the line of flexure where it projects away from the columella (Fig. 12 A–B). Two scans were necessary to interpret the correct position and fragility of this structure (one slightly damaged in the process). The high extent of sinuosity is remarkable for this species.

In their upcoming publication, Daniel C. Dourson and Ronald S. Caldwell (2017) mention "in the first few whorls, there are minute spiral papillae (beads) which can only be seen under high magnification" (Dan Dourson pers. comm. 2013). In our CT scans, we cannot detect this feature. If pitting on the protoconch is meant here, and only detectable via SEM, this is a common character known throughout the Carychiidae ( Burch and Schrader van Devender 1978, Bank and Gittenberger 1985, Jochum 2011) and not unique to this species.

Internally, Carychium belizeense is conchologically quite different from all other North American and Central American species hitherto described. In shape and shell robustness, it lies between C. mexicanum and C. costaricanum . Carychium jardineanum is conchologically distinct from C. belizeanum in that it is more tapered, elongate and slender in form, clearly ribbed and bears an additional whorl.