Carychium hardiei 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 : 99-100

Carychium hardiei Jochum & Weigand sp. n. Figures 4, 5

Weigand et al., 2013: 3, Fig. 1 37|C9; Seq. ID: BARCA038-10, BARCA039-10, BARCA040-10

Material.

Holotype (NMBE 549920/1 ex AJC 1444): USA, Georgia, Flovilla, Butts County, Indian Springs State Park; N 33.242367 W -83.92035; under moist leaf litter in drainage basin; 5 April 2010; leg. Adrienne Jochum.

Paratypes: locus typicus 8 shells (NMBE 549921/8 ex AJC 1444); 8 specimens in alcohol (NMBE 549922/8 ex AJC 1444); 8 shells (SMF 341638 ex AJC 1444); 7 shells (ANSP 467825 ex AJC 1444); 7 shells (CM 155814 ex AJC 1444); 6 shells (UF 489973 ex AJC 1444); 24 shells previously preserved in formalin and dried (AJC 1445); data as the holotype.

Diagnosis.

Shell ca. 1.75 mm in height, transparent, elongate-pupiform with an entire, elliptical-oblique, moderately thickened peristome, including a small, deeply set parietal denticle and a slight columellar-basal callus.

Description

(material from type locality). Measurements of holotype and paratypes are provided in Table 2.

Shell minute, elongate-pupiform, pellucid when fresh, opaque shiny when older. Aperture elliptical-oblique, somewhat higher than wide, taking up less than one third the shell height, outer lip moderately reflected, thin above, increasingly thickened on its outermost extension by a heavy deposit of callus upon its surface and inner edge; columellar margin has a callus and an acute entering fold above. Whorls convex, moderately rounded, ranging from 4.8-5.4 in number. Suture deep. Protoconch bulbous. Teleoconch sculpture consists of weak, irregular oblique striae. Maximum width of body whorl extends 1/6 beyond the rim of the peristome in side view facing left (Fig. 4D, L). Palatal rim appears alabaster-like. In profile view facing left, the peristome of the mature shell gently curves in at the upper edge, expands moderately and then bends gently back at the base of the shell in alignment with the central axis (Fig. 4D, L). A small, deeply set, parietal denticle is almost centrally positioned on the parietal face (Fig. 4A, I). The tiny, deeply set parietal denticle is partially visible in umbilical view (Fig. 5G). Internally, from the dorsal and aperture-facing-right perspectives, the columella bears a single, simple elongate lamella beginning one third the distance from the top of the penultimate whorl (Fig. 5 B–C, F), which elaborates into a characteristic, broadly winged, tongue-like structure in aperture-facing-left position (Fig. 5D). In ventral perspective, the lamella is slightly sinuate, whereby the first thickened flexure directed upward is in alignment with the columellar axis (Fig. 5A). The lamella culminates at the base of the gently twisted columella as a small, deeply set, well-formed, non-sinuous denticle. The base of the columella spindle (portion under the tongue-like lamella) is moderately long and dilated by the final manifestation of the columellar lamella forming the parietal denticle (Fig. 5 E–F).

Differential diagnosis.

Differs from Carychium floridanum G.H. Clapp, 1918 (Figs 6-7) by the more bulbous protoconch, the thinner, less rounded and less swollen peristome, the enhanced elaboration of sinuosity and thickness of the columellar lamella (interior ventral view) and the downward projection of the lamella in tongue-like form, the presence of the parietal denticle in umbilical view and the reduced size of the deeply-set parietal denticle; from C. mexicanum (RBINS 10591.2, "Texolo Falls, V. Cruz [Veracruz], Mexico" ( Pilsbry 1948)) (Figs 2 A–E, 8-9) by its larger and more tapered shell, the thinner, less swollen peristome, the first flexure of the sinuate lamella synchronal with the shell axis as seen in the interior ventral view, the more elaborate configuration of the columellar lamella (in side view-left perspective) and the tininess of the parietal denticle; in C. costaricanum (RBINS 10591.1), "San José Plateau Costa Rica" (E. von Martens 1898) (Figs 2 F–I, 9), the shell is more robust with increased roundness of the whorls, the aperture is markedly more auriform, the peristome is greatly thickened (swollen) and rounder with a thick columellar-basal callus in the inner left-hand corner, the columellar lamella is simple and smooth without wing-like elaboration, the parietal denticle is thick and less finely defined as in C. hardiei .

DNA barcode data can clearly delineate Carychium hardiei sp. n. from all other North and Central American taxa, demonstrating its lowest K2P genetic distance of 5.4 % to C. exile (Fig. 3). For comparison, the genetic distances between individuals of the two widely distributed European species Carychium minimum O. F. Müller, 1774 and Carychium tridentatum (Risso, 1826), for which the most sophisticated DNA bar code dataset exists (with more than 270,000 pairwise estimates), are always ≥ 4.3 %, and within-species K2P genetic distances not above 3.4 % ( Weigand et al. 2014).

Etymology.

The new species is named after the American chemical engineer, naturalist, field biologist and long-time friend of the first author, Frank Hardie of South Carolina. Frank’s tireless hours in the field contributed substantially to the Carychium dataset encompassed in Weigand et al. (2011, 2013) as well as to the burgeoning dataset of our ongoing investigation of the Carychiidae . Without his dedication and perseverance in the field, the genus Carychium would be remarkably poorer for it. In accordance with Mr. Hardie’s heritage in the southeastern USA, we gratefully dedicate Carychium hardiei from the American southeastern State of Georgia in his name.

Distribution.

This species is only known from the type locality at Indian Springs State Park, ca. 90 km south of Atlanta, Georgia. The drainage basin where these individuals were collected was located proximate to the park entrance and adjacent to the latrine complex (Fig. 10). It remains questionable whether any of the so-called C. mexicanum distributions included in Hubricht (1985) for the southeastern United States include C. hardiei sp. n. Moreover, Hubricht (1985) explicitly states that faunistic surveys were largely lacking in the State of Georgia and thus, the existence of C. hardiei sp. n. could well have been overlooked completely.

Ecology.

Mixed deciduous leaf litter.

Conservation.

In the drainage basin where this species was found (see above), live individuals occurred in relative abundance, suggesting that C. hardiei has optimum ecological conditions to survive there. Still, on a global scale, its current distribution may be limited to the 2.14 square kilometres of woodland in the middle of Georgia, regarded as Indian Springs since 1825 and as a "State Forest Park" since 1927. In conjunction with the Guidelines for the IUCN Red List (IUCN Standards and petitions Subcommittee 2014) it likely constitutes a Critically Endangered narrow range endemic (CR B1). Habitat disturbance by pollution and human encroachment via tourism or urban development may pose the greatest threat.

Remarks.

In a subsequent study of the degrees of morphological variation observed in Carychium exiguum var. mexicanum Pilsbry, 1891, Pilsbry (1948) introduced the description " Carychium exile mexicanum " to make a point while comparing the variations of Carychium exile H.C. Lea, 1842 forms collected in Texas with those from the southern extension of the Carychium exiguum var. mexicanum range. This temporary and awkward nomenclatural construction was subsequently used by Weigand et al. (2013) when these authors assessed their material, overlooking Pilsbry’s (1948) momentarily useful, but erroneous nomenclatural construction in naming the respective morphospecies for the evolutionary lineages C1 and C4 from northern Georgia, Alabama and northern Florida. Regarding C. hardiei sp. n. and our investigations of C. mexicanum here, Pilsbry’s (1948) considerations were very insightful and are still relevant considering his broader observation of southern forms (diversity) in what we now see, using cutting-edge methods, as taxonomically unrecognized species. For Carychium exiguum var. mexicanum , Pilsbry (1948) concluded "It is the tropical representative of the exile stock and probably to be considered a southern subspecies of that, intergrading with it in Texas."

Since Pilsbry’s (1891) initial description of " Carychium exiguum var. mexicanum " from "Orizaba, Mexico", the distribution of Carychium mexicanum has up to now, spanned across the southern United States from Georgia and Florida west to Texas ( Hubricht 1985), and south to Guatemala ( Thompson 2011). However, in context of Weigand et al.'s (2013) recent molecular investigation (based on COI, 16S and H3) and our use of CT scans to assess shell morphology here, we are clearly dealing with separate species. Moreover, this work not only corroborates Pilsbry’s astute morphological observations, but also, shows that what he considered as subspecies were indeed different entities we now consider separate lineages quite distinct from the “true” C. mexicanum collected in Mexico.