Overview

Overview

Ellipse (Venustaconcha ellipsiformis), a mussel presently listed as Threatened in Wisconsin. This species prefers shallow, flowing, clean small streams with stable substrate in the eastern and southern part of the state. It has also been recorded from localized populations in the western part of the state. The host fish are mostly small stream species including the rainbow darter, Johnny darter and mottled sculpin.

State status

Status and Natural Heritage Inventory documented occurrences in Wisconsin

The table below provides information about the protected status - both state and federal - and the rank (S and G Ranks) for Ellipse (Venustaconcha ellipsiformis). See the Working List Key for more information about abbreviations. Counties shaded blue have documented occurrences for this species in the Wisconsin Natural Heritage Inventory database. The map is provided as a general reference of where occurrences of this species meet NHI data standards and is not meant as a comprehensive map of all observations.

Note: Species recently added to the NHI Working List may temporarily have blank occurrence maps.

Species guidance

Note: a species guidance document is not available at this time. Information below was compiled from publication PUB-ER-085-99 (now out-of-print).

Identification: Shell is elliptical, heavy and rough having a sharp crease near the posterior ridge. The outside of the shell is greenish-yellow with numerous wavy, continuous rays of dark green. Pseudocardinal and lateral teeth are heavy. Umbro sculpture consists of three or four fine double looped concentric ridges. The nacre is bluish-white to white. The ellipse is small, up to 89 mm (3.5 inches) long.

Habitat: Inhabits small to medium sized streams with good current, in shallow water, on sand or gravel bottoms.

State Distribution: Occurs in the following rivers in Wisconsin: Ashippun, Bark, Crawfish, Manitowac, Meeme, Milwaukee, Mukwonago, Mullet, Oconomowoc, Pigeon, south fork of the Popple, Rock, Sugar, and Yellow. Also found in Cedar Creek, Jericho Creek, O'Neil Creek, Sugar Creek. This species may yet be found in rivers for which only historical records now exist. Refer to the species map.

Phenology: Breeding occurs in late summer and fall but glochidia are not shed until the late spring or early summer of the next year. The host fish are darters.

Management Guidelines: Because it inhabits small streams and headwaters, this mussel is particularly vulnerable to siltation and pollution from runoff. Habitat protection and water quality improvements would benefit this species. Increased development along waterways in southeast Wisconsin is of particular concern for the continued existence of the species.

Other resources

Links to additional Ellipse information

• Michigan Natural Features Inventory [PDF exit DNR]
• MN Department of Natural Resources [exit DNR]
• Illinois Natural History Survey [exit DNR]

Other links related to mussels and clams

• NatureServe Explorer
• Illinois Natural History Survey [exit DNR]
• The Field Museum [exit DNR]
• Conchologists of America [exit DNR]
• EPA Biological Criteria [exit DNR]
• Milwaukee Public Museum: Mathiak Collection of Freshwater Mussels of Wisconsin [exit DNR]

Photos/Video

No additional photos are available for Ellipse at this time. Please consider donating a photo to the Natural Heritage Conservation program.