Micranepsia germana

Micranepsia germana (Gould in A. Binney, 1851)
Pygmy Oregonian

  • Helix germana Gould in A. Binney 1851 in 1851–1852: 156.
  • Polygyra germana vancouverinsulae Pilsbry & Cooke 1922: 38.
Micranepsia germana.

Identification. Shell depressed-globose-heliciform, with low, convexly conical spire. Whorls ca 5, convex, rather closely coiled. Suture well-impressed. Periphery rounded, above middle of last whorl; whorl rather shouldered. Protoconch initially with coarse radial rows of oblong beds. Teleoconch microscopically rugose, matte. Periostracum with rather sparse, long, curved hairs (usually persisting in adults but easily falling off). Last whorl descending slightly to the adult lip. Contraction behind lip and crest preceding it strong. Aperture narrow, crescentic, mostly blocked by dentition (in apertural view). Parietal denticle long, oblique, curved, white. Lip with an inner ridge, expanded but not reflected, thin-edged, strongly contracted behind. Lip thickened within but edentulous. Umbilicus open but very small, partially obscured by the lip. Shell matte, dark brown; parietal denticle white; lip pale tan-whitish. Width to 6.5–8.3 mm (wider than high).

Animal dark grey-brown, with blackish head and tentacles.

Distinguished from species of Cryptomastix by the long, curved palatal tooth and generally hairy shell of adults. Juveniles have longer, thicker periostracal hairs, and have more spire whorls than juveniles Vespericola columbianus of the same size. It is also somewhat similar in appearance to the eastern Euchemotrema species and Stenotrema barbatum.

Habitat. In coastal forests. In leaf litter, under woody debris, and around Sword Ferns, climbing fronds during wet weather.

Global range. British Columbia and south in the USA to Curry County, south-western Oregon (Chace & Chace 1934, Pilsbry 1940).

Canadian range. Coastal British Columbia: Vancouver Island, adjacent mainland coast; Haida Gwaii (Forsyth 2000), and presumably also on the North Coast mainland and islands.

Etymology. Latin, germana, “a sister”. Gould thought it was related to Stenotrema monodon (now S. leaii).

Remarks. This species is usually placed in the genus Cryptomastix. However, I treat Micranepsia as a distinct genus, not a subgenus of Cryptomastix, as the molecular phylogeny of Polygyridae by Perez et al. (2014) has Cryptomastix germana outside of Cryptomastix (sensu stricto) and sister to Vespericola instead. Emberton (1995) had earlier placed Micranepsia as a subgenus of Cryptomastix but suggested that there are sufficient dissimilarities with Cryptomastix sensu stricto to warrant the elevation of Micranepsia to the rank of genus.

Pilsbry & Cooke (1922) and Pilsbry (1940) recognized a subspecies, vancouverinsulae, which was described from Cameron Lake, Vancouver Island, but presumably is exclusively the northern form. This subspecies was characterized as being slightly smaller, with the umbilicus “distinctly perforate”, a shallower furrow behind the baso-palatal lip and less pronounced crest adjacent to it, and sparser periostracal hairs. The status of vancouverinsulae is uncertain. Like many other purported subspecies of land molluscs, little is known about it and the taxon has been largely ignored in the recent literature. If division of the species into subspecies is warranted, all Canadian populations could likely be classified as M. germana vancouverinsulae.