Oregon megomphix (Megomphix hemphilli)

Physical description

Taxonomic Note: Oregon Megomphix is in the family Megophicidae.

Ecology and life history

The habitat of the Oregon Megomphix is within moist conifer/hardwood forests up to 3000 feet in elevation in hardwood leaf litter and decaying non-coniferous plant matter under bigleaf maple trees, or beaked hazelnut (Corylus cornuta) bushes, and swordferns, often near rotten logs or stumps. A bigleaf maple component in the tree canopy and an abundance of swordfern on forested slopes and terraces seem characteristic.

This snail species appears to be primarily fossorial, often found on soil under leaf litter or in rodent burrows. The presence of rotten logs seems to be important to local survival. Unusually large or multiple-stemmed bigleaf maples, or clumps of bigleaf maples, seem to provide the most favorable habitat.

Land snails are hermaphroditic and exchange gametes with other conspecific individuals when conditions are favorable, typically in the spring, and then both will lay eggs in damp subsurface situations where the eggs will be relatively safe from predators and desiccation. Land snails do not tend their eggs or young. There is no larval stage and newborn snails look like miniature adults (the innermost part of the shell develops within the egg).

Snails need moisture, so where the habitat dries out, they will estivate in the summer, become active with fall rains, and hibernate when the season turns cold.

Land snails eat plants (living or dead), fungi, fruit, microorganisms, litter, wood, and dead animals.

The Oregon Megomphix seems to be more secretive and photophobic than other Northwest land snails, as no live animals and very few of their shells have been found out in the open; all have been found under the cover of leaf mold or within soft soil or in spaces within rock heaps.

During the summer, snails are found deep in talus accumulations which are adjacent to springs or streams and which serve as refuge sites from desiccation and protection from predators while the snails are immobile. These deep rock refugia also provide the important, environmentally stable sites needed to survive wildfire events and cold winter conditions.

Mollusks which inhabit talus habitats also utilize the surrounding forest areas during moist, cool conditions, ranging out from the refugia provided by the rocks to forage in the adjacent forest floor litter.

Geographic range

This species is known from Olympia southward in foothills of the Cascade and Coast Ranges in conifer/hardwood forests up to 3000 feet in elevation, south through the Willamette Valley, Cascade Range foothills, and Coast Range of Oregon.

For Washington there are 12 records from Thurston, Lewis, and Cowlitz Counties based on 45 specimens (many collected 30 to 120 years ago) that provide seven mappable locations, which are all at low elevations (below 500 feet) in the southwestern part of the state.

It is more widespread in Oregon, known from the Siuslaw, Umpqua, and Willamette National Forests and is suspected to occur in the Mt. Hood, Rogue River, and Siskiyou National Forests, and the Columbia River Gorge National Scenic Area.