Freshwater Mussels Pacific Northwest - The Xerces Society

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The Crooked River is home to populations of western ridged mussels. photo: Dennis Frates 36 Western Ridged Mussel Gonidea angulata (Lea, 1838) Description 15,18 Size: Up to five inches Shape: Obovate to trapezoidal. Slightly laterally compressed. The shell has an angular ridge that runs from the beak to the basal part of the posterior margin; this ridge may be less angular in specimens living in slow-moving water. The ventral margin is usually straight. The shell is heavier than that of all other native species. Periostracum: Color yellowish-brown to brown or black. No shell rays or sculpturing on the shell. Lateral Teeth: Absent. Pseudocardinal Teeth: The right valve has one small tooth and the left valve has either one small tooth or none at all. The teeth are small and compressed, sometimes hard to distinguish. Nacre: Usually white, but sometimes salmon-colored in fresh specimens and pale blue toward the posterior margin and beak cavity. Range Also known as the Rocky Mountain ridged mussel, this species is widely distributed west of the Continental Divide from California to British Colum- Freshwater Mussels of the Pacific Northwest
A. B. C. Western Ridged Mussel A. External shell (left valve), B. Internal shell (right valve), C. Hinge (right valve) bia 21,30,99 . It is found east to Idaho and Nevada, and in the northern part of its range it is mainly distributed east of the Cascades but also occurs on the west side 30 . There is a historical record from the Columbia River in western Montana, although this record is problematic because the Columbia River is Freshwater Mussels of the Pacific Northwest 37
Page 1 and 2: Freshwater Mussels of the Pacific N
Page 3 and 4: Freshwater Mussels of the Pacific N
Page 5 and 6: CONTENTS Introduction to Freshwater
Page 7 and 8: Introduction to Freshwater Mussels
Page 9 and 10: foot illustration: Ethan Nedeau gil
Page 11 and 12: Underwater view of western ridged m
Page 13 and 14: that live in flowing water may inha
Page 15 and 16: of glaciers, dispersal barriers, cl
Page 17 and 18: Freshwater mussels have been greatl
Page 19 and 20: Warning about collecting mussels! S
Page 21 and 22: Identification Field Guide The purp
Page 23 and 24: Anodonta Taxonomy It would be misle
Page 25 and 26: Anodonta General Account Variation
Page 27 and 28: Anodonta grow rapidly, often reachi
Page 29 and 30: Anodonta Clade 1 California Floater
Page 31 and 32: and east to western Wyoming, easter
Page 33 and 34: A. C. Internal and external valves
Page 35 and 36: The Yukon floater is found in lakes
Page 37 and 38: Small wooded creeks often have abun
Page 39 and 40: tion for this distribution is headw
Page 41: unknown. Native hosts with which mu
Page 45 and 46: Conservation G. angulata have disap
Page 47 and 48: ies, especially in shallow water. A
Page 49 and 50: Literature Cited 1. Anthony, J.L.,
Page 51 and 52: 30. Frest, T. J. and E. J. Johannes
Page 53 and 54: 59. Mackie, G.L. 1991. Biology of t
Page 55 and 56: 90. Stagliano, D.M., G.M. Stephens,
Page 57: 118. Ziuganov, V., E.S. Miguel, R.J

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