Wollastonia jessicae jessicae De Mattia, Neiber & Groh

Mattia, Willy De, Neiber, Marco T. & Groh, Klaus, 2018, Revision of the genus-group Hystricella R. T. Lowe, 1855 from Porto Santo (Madeira Archipelago), with descriptions of new recent and fossil taxa (Gastropoda, Helicoidea, Geomitridae), ZooKeys 732, pp. 1-125 : 44-50

Wollastonia jessicae jessicae De Mattia, Neiber & Groh sp. n. Figs 147-149

Type material.

NMWC Z.2016.013.00001, holotype, from loc. typ., leg. W. De Mattia & J. Macor, May 25 2015, NMWC Z.2016.013.00002/4 PT, SMF 348934/4 PT, NHMW 112140/3 PT, CKG/3 PT, CMN/7 PT, CWDM/23 PT, from loc. typ., leg. W. De Mattia & J. Macor, May 24 2015; FW 11154/10 PT, CMN/10 PT, ZMH 131207, 10 PT, hill E of Ribeira Santo Antonio and W of Vale do Touro, upper edge of the S slope, 33°03'47"N / 16°19'41"W, 40 m, leg. F. Walther, Apr. 5 2017; CKG/5 PT, CJG/2 PT, Vale do Touro, under stones, 33°03'51"N / 16°19'26"W, 45 m, leg. J. Gerber, K. Groh & J. Hemmen, Aug. 16 1985. Fossil: CKG/2 PT, Vale do Touro, Quaternary slope deposits, 33°03'47"N / 16°19'26"W, 25 m, leg. J. Gerber, K. Groh & J. Hemmen, Aug. 16 1985. GNM 72-13.386/1 PT, Portela, 500 m SW, in the road cutting, Quaternary muds, 33°03'54"N / 16°19'12"W, 95 m, leg. H. W. Waldén, Feb. 13 1972; ANSP H 11920/7 PT [with 8 spms of H. aucta ], Vale do Touro, Quaternary slope deposits, 33°03'47"N / 16°19'26"W, 25 m, leg. J. Gerber, K. Groh & J. Hemmen, Aug. 16 1985; ANSP H 11773/2 PT [with 3 Caseolus compactus ], Vale do Touro, under stones, 33°03'51"N / 16°19'26"W, 45 m, leg. J. Gerber, K. Groh & J. Hemmen, Aug. 16 1985.

Locus typicus.

Upper edge of the S slope of hill E of Ribeira Santo Antonio and W of Vale do Touro, under stones in grassland, 33°03'47"N / 16°19'41"W, 40 m.

Diagnosis.

Small Wollastonia species, with a conical shell and two keels on the body whorl, the lower more distinct than the upper; granulation relatively fine and scattered; internal walls of penis with one to three well-developed, irregular pleats.

Etymology.

Named after the wife of the first author, Mrs. Jessica Macor from Trieste, Italy, as a token of gratitude for her assistance and companionship during the collecting activities.

Description of shell.

The shell is dextral and hairless. Its shape is scalariform, with deep sutures and rather flattened whorls. The protoconch is from yellowish to dark brown with 1.5 to 2.5 whorls. It is almost smooth along the first whorl and shows fine radial striae in its remaining whorls. The teleoconch has from 3.3 to 3.8 rapidly increasing whorls. It is usually dark brown with brick red and/or dark violet shades in colour, but also yellowish specimens with light reddish shades are found. The darker areas of the shell are mottled with more or less light brown to whitish areas, usually placed longitudinally and slightly slanting. The body whorl has two well-developed keels. The lower one is stronger and more distinct than the upper one. Both keels are usually whitish and contrasting from the rest of the body whorl. No banding pattern is visible along the upper whorls. On the lower part of the last whorl one principal, but rather narrow, dark (reddish to dark brown) band is usually present. A second light and indistinct band is sometimes present just below the keel. The area around the umbilicus is usually the lightest in colour. The external surface has strong, clearly visible, irregularly spaced, growth lines. Tubercles are present all over the teleoconch. They are usually large and rather widely scattered, whitish in colour and arranged somewhat obliquely, following the course of the growth lines. The larger tubercles are somewhat denser along the keel(s) of the last whorls, letting the keel(s) appear like a rough chord. The last whorl is usually large, with a contribution of 60% of the total shell height and descending near the aperture. The umbilicus is open but very narrow, either concentric or eccentric, and it measures approximately 10% of the maximum shell diameter. The aperture is elliptical with a faint thickening along the columellar portion of the stoma. Sometimes this thickening can also extend as far the parietal side of the aperture. The peristome is continuous and reflected (see Figs 147-149).

Measurements.

D 4.8 ± 0.3 mm (range 4.4-5.2 mm); H 3.3 ± 0.3 mm (range 3.0-3.9 mm); FW 2.3 ± 0.1 mm (range 2.2-2.4 mm); PA 58.2 ± 7.4° (range 50.0-68.0°); DU 0.7 ± 0.05 mm (range 0.6-0.8 mm); NT 23 ± 12 (range 9-37); NW 5.6 ± 0.4 (range 5.0-5.9) (n = 40). Ratio D/H 1.5; ratio FW/H 0.7.

Body.

The head and the neck are usually grey. The sides and the posterior upper section of the foot are whitish. The pigmented ommatophoral retractor muscles are visible through the skin of the back of the cephalic area. The foot is white and the sole is longitudinally divided into three areas. The central area is smooth, whereas the two lateral areas are equipped with bands of muscles that are roughly arranged in a chevron pattern. The mantle border is grey to dark grey, with five more or less developed lobes. The ratio of the lateral to the dorsal lobes varies from specimen to specimen, also in the same population. In some specimens, one of these lobes (either lateral or dorsal) may be totally missing. The walls of the pallial cavity are colourless, without any stripes or spots. A strong pulmonary vein is visible. The jaw is odonthognatous and is very variable in shape, ranging from almost straight to markedly arched. There are many smooth transverse ridges, ranging from 18 to 22 in number. The right ommatophoral retractor is independent from both penis and vagina.

Genital anatomy.

The general arrangement of the genitalia is semi-diaulic monotrematic. A convoluted to almost straight hermaphrodite duct arises from a multi-lobated gonad. The albumen gland is long and thin and is connected to an approximately twice as long sperm-oviduct that consists of a prostatic and a uterine portion. The prostatic part extends into a thin vas deferens, which is approximately as long as the sperm-oviduct and terminates in the penial complex. The distal portion of the uterine part extends into the free oviduct, turning into a vagina at the level of the duct of the bursa copulatrix. The free oviduct can be as long as, or slightly shorter than the vagina. The duct of the bursa copulatrix is usually thin, approximately as long as the penis and uniform in diameter. It ends into a variable, oval to roundish, bursa copulatrix. The transition area between the duct and the bursa itself is usually sharply delimited, with the duct abruptly widening and turning into the bursa. The spermatophore is unknown. One tuft of digitiform glands arises from the proximal part of the vagina. There are usually two glands that are approximately equally long and very rarely branched. A short and thin vaginal appendix arises from the vagina’s wall, just distal of the glandular tuft. Very smooth, rather wide and little elevated, irregularly spaced pleats run longitudinally along the inner surface of the vagina, reaching into the genital atrium as far as the genital orifice. The atrium is usually long and thin. Its internal walls have large and soft pleats running longitudinally as far the genital orifice. The penial complex consists of a flagellum, an epiphallus (which extends from the insertion of the vas deferens to the penial retractor muscle) and a penis, which inserts into the atrium. The penial flagellum is short, remarkably cylindrical and with a blunt apex. It is usually as long as the epiphallus. Its internal walls are completely smooth. The epiphallus is usually short and its internal walls present 2 to 4 longitudinal, smooth pleats that are only slightly elevated. The retractor muscle is not very large, but strong, usually as long as the flagellum + epiphallus together. The penis lacks any muscular or glandular sheath. It is thick-walled and approximately three times longer than the flagellum. It is usually slightly swollen in its distal part near the genital atrium. The inner walls of the penis usually have one to three irregular, spaced pleats, which run longitudinally and reach the genital atrium. These pleats can be connected by small “bridge-like” pleats. In some specimens, the section where the penial papilla is located is detectable from the outside by virtue of a fine circular swelling corresponding to the origin of the papilla itself. The penial papilla is usually very variable in dimensions (measuring from 10% to 50% of the total penial length) and conical in shape. It has smooth external walls, with the opening emerging apically. The channel of the penial papilla is thin and narrow. The inner lumen of the penial papilla is occupied by a spongy and sturdy tissue, which directly connects with the walls of the epiphallus. The longitudinal section of the penial papilla shows that its walls are the continuation of the penial walls that abruptly bend inward (see Figs 150-157).

Distribution.

Wollastonia jessicae jessicae sp. n. is found only along the southern slope of a hill east of Ribeira Santo Antonio and west of Vale do Touro, just east of the town of Vila Baleira, along the road leading to the new harbour. The distribution is shown in Fig. 158.

Ecology.

Wollastonia jessicae jessicae sp. n. is commonly found under volcanic rocks scattered on grassland in open fields that are more or less sloping. The specimens aestivate on the lower surfaces of the rocks, frequently forming clusters of individuals attached one to another.

Comparison and comments.

At first glance W. jessicae jessicae sp. n. can be confused with H. bicarinata because of the overall similarity of their shell’s shape (i.e. granulated surface with the last whorl with two keels). This is probably the reason why the new species has been overlooked until now. Nevertheless, a closer look reveals differences such as the much coarser granulation on the surface of H. bicarinata .

W. jessicae jessicae sp. n. (as for W. jessicae monticola sp. n. described in the following section) always shows a finer granulation, having smaller and more scattered tubercles. With regard to genital anatomy, W. jessicae jessicae sp. n. has internal walls of the penis with one to three irregular and well-spaced strong pleats, which run longitudinally and reach the genital atrium, whereas H. bicarinata has at least some large and smooth folds. Our phylogenetic analysis clearly show that the two species are not closely related, i.e. they were placed in two well-separated clades. This further corroborates, aside from morphology, its status as a distinct species.

Status and conservation.

The subspecies has a very limited distribution area of less than 1 km2 (Fig. 158) close to a village and population size is probably rather low. Habitat quality is inferred to be declining and potential and ongoing threats to the subspecies include, in our opinion, urbanization, tourism, goat grazing and quarrying. Therefore, the species is considered here to be Critically Endangered (CR B1a, b(iii), 2a, b(iii)).