Tag: Gastrodontidae

• Patulastra? (Punctum?) pugetensis Dall 1895: 130.
• Radiodiscus hubrichti B.A. Branson 1975: 47, fig. 1a–c.

Identification. Shell subdiscoid, with very low, domed spire. Suture deep. Whorls c. 3½, last slightly descending in adults. Periphery rounded, medial. Width of last whorl c. 2× penultimate whorl. Aperture subrotund, edentulous. Lip thin, simple. Protoconch with close, strong spiral threads. Teleoconch with colabral thin-edged riblets, with spiral threads between, including on base. Umbilicus c. ¼ of shell width. Width to 1.8 mm (wider than high). Shell thin, pale yellowish grey, corneous.

Animal translucent white, with head and tentacles grey and a small black spot over the lung.

Comparison. There is no other snail quite like this species in BC. The pale colour of the shell and intricate microsculpture (not well shown in the photograph) are distinctive among BC microsnails.

Habitat. This species inhabits moist forests where it lives in leaf litter and under woody debris.

Geographic range. In BC, S. pugetensis occurs along the whole coast where it is common. It also is in the southern interior, including the Kootenays, where it is known from a few, scattered records (Ovaska et al. 2020) and the valley of the North Thompson River (Forsyth 2001).

Striatura pugetensis occurs from south-eastern Alaska south to Isla Guadalupe, Baja California, Mexico (Pilsbry 1927; Smith et al. 1990) and east to Glacier National Park, northwestern Montana (Berry 1919). This species was said to also occur in the Hawaiian Islands, on Kauai (Baker 1941), but see Remarks.

Etymology. Striatura: derived from the Latin striatus, furrowed + the –ura suffix to form a noun from an adjective; the gender is feminine. Pugetensis (Latin), of Puget Sound, or the more general region.

Remarks. This species was first described as new by Dall (1895) from material collected at Seattle, Washington by the amateur conchologist P.B. Randolph (see Punctum randolphii). Berry (1919) first recognized this species as a Striatura, and Baker (1928) later placed the species in the subgenus Pseudohyalina. While specimens from northwest Montana were said by Berry (1919: 492) to be “larger and flatter and coarser in appearance, slightly approaching in some respects the giant southern meridionalis Pilsbry and Ferriss [1906]”, Pilsbry (1946) considered these to be typical of S. pugetensis.

By misplacing the heading for the subgenus Striatura s.s., Pilsbry (1946) wrongly indicated that this species belongs in that subgenus, but he corrected this in the following part of his monograph (Pilsbry 1948: 1102).

Specimens from Kauai were identified by Baker (1941) as S. pugetensis, but his figured specimen (pl. 60, figs 1–3) shows a shell with a higher spire and slightly different form than shells from BC (and presumably Puget Sound) material, and one suspects that it is not the same species; the Hawaiian archipelago also has several endemic Striatura species (Baker 1941), so it seems likely that Hawaiian “S. pugetensis”is yet another endemic species, not S. pugetensis.

Radiodiscus hubrichti B.A. Branson, 1975, which was described from the Olympic Peninsula (Branson 1975), was recognized by Solem (1977a, b) as a synonym of S. pugetensis.

If following the classification of Schileyko (2003), who diverged from other authors in treating Pseudohyalina as a full genus, this species would be Pseudohyalina pugetensis (Dall, 1895).

References

Baker HB (1928) Mexican mollusks collected for Dr. Bryant Walker in 1926, I. Occasional Papers of the Museum of Zoology, University of Michigan 193: 64 pp., pl. 6.

Baker HB (1941) Zonitid snails from Pacific Islands, parts 3 and 4. 3. Genera other than Microcystinae. 4. Distribution and indexes. Bernice P Bishop Museum, Bulletin 166: 203–370, pls 43–65. https://babel.hathitrust.org/cgi/pt?id=mdp.39015069709080

Berry SS (1919) Mollusca of Glacier National Park, Montana. Proceedings of The Academy of Natural Sciences of Philadelphia 1919: 195–205, pls 9, 10. https://www.jstor.org/stable/4063842

Branson BA (1975) Radiodiscus hubrichti (Pulmonata: Endodontidae) new species from the Olympic Peninsula, Washington. The Nautilus 89: 47–48. https://www.biodiversitylibrary.org/page/16319395

Dall WH (1895) New species of land shells from Puget Sound. The Nautilus 8: 129–130. https://www.biodiversitylibrary.org/page/27055682

Forsyth RG (2001) A note on the distribution of Striatura pugetensis in British Columbia. The Festivus 33: 57–58. https://www.biodiversitylibrary.org/page/50507922

Ovaska K, Sopuck L, Heron J (2019 [2020]) Surveys for terrestrial gastropods in the Kootenay region of British Columbia, with new records and range extensions. The Canadian Field-Naturalist 133: 221–234. https://doi.org/10.22621/cfn.v133i3.2287

Pilsbry HA (1927) Expedition to Guadalupe Island, Mexico, in 1922. Land and freshwater mollusks. Proceedings of the California Academy of Sciences (4th Series) 16: 159–203, pls 6–12. https://www.biodiversitylibrary.org/page/3174272

Pilsbry HA (1946) Land Mollusca of North America (north of Mexico), vol. II, part 1. The Academy of Natural Sciences of Philadelphia, Monographs 3: frontispiece + i–vi + 1–520.

Pilsbry HA (1948) Land Mollusca of North America (north of Mexico), vol. II, part 2. The Academy of Natural Sciences of Philadelphia, Monographs 3: i–xlvii + 521–1113.

Smith AG, Miller WB, Christensen CC, Roth B (1990) Land Mollusca of Baja California, Mexico. Proceedings of the California Academy of Sciences (4th Series) 47: 95–158. https://www.biodiversitylibrary.org/page/15776117

Solem A (1977a) Radiodiscus hubrichti Branson, 1975, a synonym of Striatura pugetensis (Dall, 1895) (Pulmonata: Zonitidae). The Nautilus 91: 146–148. https://www.biodiversitylibrary.org/page/8273672

Solem A (1977b) Shell microsculpture in Striatura, Punctum, Radiodiscus, and Planogyra (Pulmonata). The Nautilus 91: 149–155. https://www.biodiversitylibrary.org/page/8273675

• Helix nitidula Draparnaud [1805]: 117.
• Other synonyms in Europe.

Identification. Shell flattened, subdiscoid, with low rounded spire. Whorls 3½–4½, convex; whorls rapidly enlarging; in apical view, last whorl decidedly broader than penultimate whorl. Periphery rounded, medial. Protoconch smooth. Teleoconch smoothish with inconspicuous fine spiral striae that cross minute colabral striae to form a microscopically reticulate sculpture. Aperture subovate, moderately oblique, edentulous, wider than high. Lip thin, simple. Umbilicus relatively wide, c. 1/4.5 of shell width. Shell thin, nearly opaque, with a waxy lustre (not glossy); reddish amber-brown but with milky-whitish area around umbilicus. Width to c. 6–11 mm (wider than high).

Animal dark bluish grey, paler on sides and tail; sole pale. Tentacles blue-black.

Comparison. Shells of Oxychilus are glossier and without the minute reticulate sculpture of A. nitidula. Under strong magnification, the shell of A. nitidula has microscopic spiral striae that are absent in Oxychilus shells. Under strong magnification, the shell of A. nitidula has microscopic spiral striae that are absent in Oxychilus shells. Zonitoides species are also similar, but spiral striae in Z. arboreus are much weaker, scarcely visible with standard magnification, and spiral striae are absent in in Z. nitidus.

Geographic range. This species is introduced to BC, where it is known from Metro Vancouver (Forsyth et al. 2001). Although Dall (1905) reported “Retinella nitidula” from Great Slave Lake, NWT, this seems likely in error (Forsyth et al. 2001) for, perhaps, Zonitoides nitidus, which he listed from the same locality. Strangely, it remains unknown from elsewhere in North America, although presumably it may have just been overlooked. Aegopinella nitidula is native to Western Europe, from southern Scandinavia to the Iberian Peninsula, and there are scattered occurrences in Eastern Europe, east to Ukraine (Welter-Schultes 2012).

Habitat. In BC, A. nitidula is a synanthrope, living in mature, unkempt gardens and places where garden waste is dumped, such as vacant lots and roadside areas. In lives in leaf litter and under dead wood, dense vegetation such as ivy, stones, and garbage.

Biology. A. nitidula is omnivorous, eating mostly dead plant material but also preying on small snails and slugs, earthworms, and other small invertebrates. This species has a biennial life cycle, maturing and breeding in the summer following its second winter (Mordan 1978).

Etymology. Aegopinella is derived from the land-snail genus Aegopis and the Latin diminutive suffix –ella; Aegopis may mean “goat meadow” (Forsyth 2004), but this is not certain. The gender is feminine. The species epithet is derived from nitidus is Latin, meaning shining, with the diminutive suffix –ula added.

Remarks. See Welter-Schultes (2012) regarding the availability of the name Helix nitidula Draparnaud, 1805.

References

• Dall WH (1905) Land and fresh water mollusks. Doubleday, Page and Co., New York, New York, USA, 1–171, pp.
• Draparnaud J-P-R ([1805]) Histoire naturelle des Mollusques terrestres et fluviatiles de France, ouvrage posthume. Louis Colas, Paris, 164 pp., 13 pls. pp. https://doi.org/10.5962/bhl.title.12856
• Forsyth RG, Hutchinson JMC, Reise H (2001) Aegopinella nitidula (Draparnaud, 1805) (Gastropoda: Zonitidae) in British Columbia—first confirmed North American record. American Malacological Bulletin 16: 65–69.
• Mordan PB (1978) The life cycle of Aegopinella nitidula (Draparnaud) (Pulmonata: Zonitidae) at Monks Wood. Journal of Conchology 29: 247–252.
• Welter-Schultes F (2012) European Non-marine Molluscs, a Guide for Species Identification. Bestimmungsbuch für europäische Land- und Süsswassermollusken. Planet Poster Editions, Göttingen, [3] + 679 + [78] pp.