Tag Archives: microsnails

Gastrocopta contracta

Gastrocopta contracta, Bruce Peninsula National Park, Ontario

Gastrocopta contracta, Bruce Peninsula National Park, Ontario. Shell 2.7 mm.

I have to admit a fasciation with the Gastrocopta, a.k.a. “Snaggletooths”. The genus seems so foreign to me, and in a way it is. Here in British Columbia, there seems to be just one species, G. holzingeri, and it is rare! The pattern in Canada is that Ontario has the most Gastrocopta species (seconded by Quebec), with decreasing numbers of species east and west of Central Canada.

Seen here is Gastrocopta contracta, the Bottleneck Snaggletooth, known from Manitoba to at least western Quebec. Insofar as Gastrocopta go, this species is very distinctive. The conical spire and narrowed last whorl that is produced into a projecting, vaguely triangular aperture are diagnostic. The “folds” (aka, plicae, lamellae, denticles, etc. … whatever terminology you use) within the aperture give the appearance of almost blocking the opening, and hence the name.

The pale colour of Gastrocopta shells is so not widespread in Canadian micro-snails (in older literature: having the colour of “spermaceti” — a waxy substance in the head of whales according to Wikipedia),*  But, shells of this and other species often are plastered with dirt and debris, making them almost unrecognizable as snails, such as the well-camouflaged G. tappaniana in a photo in a previous post.

*This is a case where old descriptions use terminology that no longer has as much meaning as it once did, since when was the time you came across a jar (did it come in jars?) of spermaceti to compare with snails’ colour?

Myriad snails

Collecting, screening, and picking through samples of leaf litter can be an effective means of finding the most minute of land snails. As part of a research project funding in part by the Ottawa Field-Naturalists’ Club, in August/September 2016 fieldwork that used this technique was undertaken.

I’m working on sorting samples into species now, having just finished picking snails out of the litter samples. As an example of what can be found at a species-rich site, here’s a photo of part of the unsorted material.

Unsorted microsnails. Seen here, Helicodiscus parallelus (centre, pale snail), Paravitrea multidentata (to the left of Helicodiscus), Strobilops labyrinthicus (other large snails), Carychium exile (pale, slender snails),and Gastrocopta pentodon (toothy snail in hiding), and several other species. For scale, the central snail, Helicodiscus parallelus is 2.1 mm in maximum diameter.

This sample came from Morris Island Conservation Area, at the north edge of Ottawa.

Fourteen species were collected, including: Carychium exile, Columella edentula, Discus catskillensis, Euconulus polygyratus, Gastrocopta pentodon, Helicodiscus parallelus, Nesovitrea binneyana, Paravitrea multidentata, Punctum minutissimum, Striatura exigua, S. milium,  Strobilops aenus, S. labyrinthicus, and Zonitoides arboreus In all, 293 specimens were recovered from the sample; with the most common species, C. exile, represented by 134 specimens (46% of the total).

Re-collected was Strobilops aeneus, a rare species that was previously found at this site and documented here: notes.on.mollus.ca and Check List journal.