Illinois Natural History Survey - University of Illinois

Apalone mutica (Le Sueur, 1827) -- Smooth Softshell

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Key Characters: Anterior edge of carapace lacking spines or tubercles; snout with rounded tip; nostrils lacking horizontal septal projections.

Similar Species: Spiny Softshell. See Key to Illinois Turtles for help with identification.

Subspecies: Two subspecies are currently recognized, Gulf Coast Smooth Softshell, A. m. calvata (Webb, 1959) and Midland Smooth Softshell, A. m. mutica. Only the latter is found in Illinois.

Description: Medium-sized (up to 28 cm CL) turtle with tan, brown, or olive carapace with light posterior border. Carapace irregularly patterned with small dark spots or dashes that expand into blotches or mottling in large females. Plastron white to cream. Paired, dark-bordered, white stripes extend across snout to eyes. A similar but expanded pair of stripes extend posteriorly from eyes onto the neck. Feet neither strongly streaked nor patterned. Male smaller than female and has a larger, thicker tail with vent opening beyond rear edge of carapace.

Habitat: Rivers and large streams having sand substrate, bars, and banks. Unusual in lakes.

Natural History: Males and juveniles congregate in sandy shallows to bury in the substrate and bask along exposed banks. Female is more solitary, wanders more, and utilizes deeper water than male. Relatively nonagressive. The diet includes a variety of animal foods but especially aquatic insects. Female lays multiple clutches of 6 to 26 round, brittle-shelled eggs (ca. 22 mm diameter) in sand banks or bars from late May into July.

Distribution Notes: Although restricted to rivers with sandy bottoms and frequent sandbars, the Smooth Softshell is absent from the apparently suitable rivers of Kankakee and Iroquois counties.

Status: Endangered. Populations appear to be declining in much of the state. Agricultural runoff, siltation, and pollution are probable causes.

Etymology: Apalone - apo (Greek) meaning separate; alone (Anglo-Saxon) meaning solitary; or apalos (Greek) meaning soft, tender; mutica - mutilus (Latin) meaning shortened, docked

Original Description: Le Sueur, C.A. 1827. Note sur deux especes de tortues du genre Trionyx Gff. St. H. Mem. Mus. Hist. Natur., Paris. Vol. 15.

Type Specimen: Syntypes. 5 specimens, MNHN 564, 4143, 7977, 8813, and 8814.  8813 designated lectotype by Webb (1962. University of Kansas Publications. Museum of Natural History. Lawrence. 13 (10): 429-611).

Type Locality: "Newharmony, sur le Wabash" [=New Harmony, Wabash River, Posey County, IN]

Original Name: Trionyx muticus Le Sueur, 1827

Nomenclatural History: Also referred to as Amyda mutica in older literature.



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