Page 111 - The Freshwater Mussels of Oklahoma

Partial Synonymy:
Quadrula heros (Say, 1829), Simpson 1914; Isely 1925
Megalonaias gigantea (Barnes, 1823), Murray and Leonard 1962; Valentine
and Stansbery 1971; Johnson 1980; Branson 1982
Megalonaias nervosa (Rafinesque, 1820), Oesch 1984; Turgeon and others
1988; Vidrine 1993; Watters 1995; Howells and others 1996
Description:
“Shell long rhomboid or long quadrate [sic.], subinflated to inflated, solid,
inequilateral; posterior ridge usually full, rounded; beaks rather full and high, their
sculpture strong, doubly looped or zigzag ridges; dorsal line straight or lightly curved;
anterior end rounded, generally angled above; base line straight or a little curved;
posterior end almost squarely or somewhat obliquely truncate and angled above where it
joins the low dorsal wing, rounded below; surface with uneven, concentric sculpture, all
except where it joins the low dorsal wing, rounded below; surface with uneven,
concentric sculpture, all except the anterior basal part, more or less covered with oblique
folds and nodules. The earlier growth is usually densely covered with subradial or
chevron-shaped, nodulous plications; frequently the sculpture in front is decidedly
nodulous; epidermis brownish or blackish; pseudocardinals elevated, radial, radially
striate; laterals straight or slightly curved; muscle scars large, the anterior ones with
rough nacreous matter; beak cavities deep, compressed; nacre whitish, often blotched
with lurid color, much thinner and iridescent behind; pallial line remote” (Simpson 1914,
p 825).
Hosts for Glochidia:
American Eel, Black Bullhead, Black Crappie, Bluegill, Bowfin, Brown
Bullhead, Channel Catfish, Freshwater Drum, Gizzard Shad, Green Sunfish, Tadpole
Madtom, White Bass, White Crappie (Watters, 1994).
Comments:
Our largest species.

Table 19. Summary of M. nervosa shell characters.

Maximum
H/L Range Mean H/L Length W/L Range Mean W/L
Location N (%) (%) (mm) (%) (%)
Arkansas River System
Verdigris River 3 64.2-72.0 68.5 175 29.7-38.3 33.1
Neosho River 8 64.2-74.2 69.7 214 32.3-38.8 35.6
Caney River 1 66.7 - 153 34.0 -
Red River System
Muddy Boggy River 12 64.7-72.7 68.9 173 34.5-42.0 38.2
Kiamichi River 5 62.8-74.5 68.6 157 35.9-41.0 37.9
Little River 3 68.8-70.0 69.2 144 40.0-42.0 41.2

General Distributon:
Mississippi River drainage, Great Lakes drainage and Gulf of Mexico drainages
from northern Mexico to Alabama.

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