Endangered Resources Program Species Information
Ellipse (Venustaconcha ellipsiformis)
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Overview
Species 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.
Status and NHI Documented Occurrences in Wisconsin
The table below provides information about the protected status (State and Federal Status) and the rank (S and G Ranks) for Ellipse (Venustaconcha ellipsiformis). See the Working List Key for more information about the abbreviations used. Counties shaded blue have documented occurrences for this species in the Wisconsin Natural Heritage Inventory database. For invertebrates, dots depict locations from the "Invertebrate Atlas," a database with occurrences of rare and common aquatic and select terrestrial invertebrate species found in Wisconsin and adjacent areas. While the invertebrate atlas is a quality assured database, not all records have been verified. The map is provided as a general reference of where this species has been found to date and is not meant as a range map.
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Detailed Information
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 Guidance: 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.
Information compiled from publication PUB-ER-085-99 (now out-of-print).
Photos
No additional photos are available for Ellipse at this time.
Related Links
Links to Additional Ellipse Information
- Michigan Natural Features Inventory [Exit DNR]
- MN Department of Natural Resources [Exit DNR]
- Illinois Natural History Survey [Exit DNR]
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