Provisional Key to the Mussels of Allen County

By Warren W. Pryor

Draft 3, 26 February 2008

(replaces draft 2, 18 February 2008)

(replaces draft 1, 7 February 2008)

Introduction

I began to develop this document by eliminating from Fisher’s (2007) Indiana-wide key, those species not having been previously observed in Allen County (Pryor, 2005). I then included two Allen County species that did not appear in Fisher’s key, namely, Fusconaia subrotunda and Epioblasma obliquata. Unnecessary questions were then eliminated. Species descriptions found in Parmalee & Bogan (1998), Sietman (2003) and Grabarkiewicz & Crail (2006) provided key characteristics to supplement those in Fisher (2007) to create the set of Brief Species Descriptions that appear below.

The intended users of this provisional key are students at the University of Saint Francis and other interested parties, who wish to participate in field work on mussel ecology. It should be considered a work-in-progress; thus, suggestions and comments are invited.

Testing the Key with Real People

Rosie Morman used Draft 1 to identify 11 mussel specimens on 14 February.

Rosie Morman and Jackie Ehlerding used Draft 2, and Amy Roberts used Draft 1 on 21 February, to identify more than 27 specimens. A summary of which species have been keyed-out successfully appears below:

Species (bold = specimens available in drawers) (italics = specimens available in lab) (* = presently unavailable)	ID numbers that have been successfully keyed-out
Actinonaias ligamentina
Alasmidonta marginata	5792, 5775, 5785, 5786, 5780, 5776
Amblema plicata
Anodontoides ferussacianus *
Cyclonaias tuberculata	5789
Ellipsaria lineolata *
Elliptio dilatata
Epioblasma obliquata (female) *
Epioblasma obliquata (male) *
Fusconaia flava
Fusconaia subrotunda *
Lampsilis cardium
Lampsilis fasciola *
Lampsilis siliquoidea
Lasmigona complanata
Lasmigona compressa *
Lasmigona costata
Leptodea fragilis	5769, 5764, 5773, 5763
Ligumia recta
Ligumia subrotunda *
Obovaria subrotunda
Pleurobema clava *
Pleurobema sintoxia *
Potamilus alatus	5774
Ptychobranchus fasciolaris *
Pyganodon grandis	5788
Quadrula cylindrica *
Quadrula nodulata *
Quadrula pustulosa (lacking pustules)	5778
Quadrula pustulosa (with pustules)	5794, 5795, 5787
Quadrula quadrula
Strophitus undulatus *
Toxolasma lividus (female) *
Toxolasma lividus (male) *
Toxolasma parvus *
Truncilla donaciformis *
Truncilla truncata	5777, 5790, 5797, 5779, 5781, 5793, 5791
Utterbackia imbecillis
Villosa fabalis *
Villosa iris

Jackie discovered a problem with the key that needs to be addressed, when she was working with #5779. This specimen lacked rays, which presented a problem at Question 44. Its resolution is remains outstanding.

Rosie found that Question 23 was ambiguous in Draft 2, and so attempted to discriminate Quadrula pustulosa (with pustules) from Cyclonaias tuberculata based upon the size of the pseudocardinal teeth. To this end, she measured several specimens of each, and the data was entered into Excel by Jackie. Warren performed the statistical analysis.

It turned out that the mean relative pseudocardinal tooth height significantly differed (p < 0.001, t-test) for shells of Quadrula pustulosa (mean TH/SL = 0.134, SD = 0.029, n = 9) and Cyclonaias tuberculata (mean TH/SL = 0.185, SD = 0.016, n = 8). Based upon these data, 95% confidence intervals pseudocardinal tooth height standardized to shell length (TH/SL) for these two species are thus:

• Quadrula pustulosa 0.115 to 0.153

• Cyclonaias tuberculata 0.174 to 0.196

The midpoint between the high value for Q. pustulosa and the low value for C. tuberculata is 0.164, which was used to revise Question 23 in Draft 3 of the Key.

Provisional Key

1. Presence of teeth.

   1. The shell lacks teeth. (go to 2)

   2. The shell has teeth. (go to 6)

2. Umbo position

   1. The umbo does not extend above the hinge line (Utterbackia imbecillis).

   2. The umbo does extend above the hinge line (go to 4).

4. Beak sculpture

   1. The beak sculpture is double-looped (Pyganodon grandis).

   2. The beak sculpture is not double-looped (go to 5).

5. Beak sculpture and hinge line

   1. The beak sculpture consists of 3 to 4 heavy bars. The hinge line is somewhat thickened and is slightly curved (Strophitus undulatus).

   2. The beak sculpture is a couple of very fine ridges. The hinge line is not thickened or curved (Anodontoides ferussacianus).

6. Lateral teeth

   1. The lateral teeth are absent or are poorly developed (go to 10).

   2. The lateral teeth are well-developed (go to 12).

10. Wing

    1. A dorsal wing is present (Lasmigona complanata).

    2. A dorsal wing is lacking (go to 11).

11. Posterior ridge sculpture and shape

    1. Many prominent ridges appear along the flattened posterior ridge (Lasmigona costata).

    2. Several fine ridges are found along a severely sloped posterior ridge (Alasmidonta marginata).

12. Pustules and ridges

    1. The exterior is prominently marked with either pustules or ridges (go to 13).

    2. The exterior lacks both pustules and ridges (go to 24).

13. Pustules and ridges

    1. The exterior is prominently marked with ridges (go to 61).

    2. The exterior is prominently marked with pustules (go to 16).

16. Profile shape

1. (SH/SL) < 0.640 (Quadrula cylindrica).

2. (SH/SL) > 0.640 (go to 17).

16. Pustule arrangement

1. Pustules are arranged into one or more distinct rows (go to 20).

2. Pustules are randomly distributed over most of the exterior (go to 23).

20. Pustules and ridges

1. There is a prominent sulcus running between the rows of pustules (Quadrula quadrula).

2. No sulcus runs between the rows of pustules (Quadrula nodulata).

23. Rays on periostracum

1. The pseudocardinal teeth are medium-sized (TH/SL < 0.164). A single, large green ray extends from the umbo toward the center. The nacre is white (Quadrula pustulosa).

2. The pseudocardinal teeth are huge (TH/SL > 0.164). The periostracum lacks rays. The nacre is purple (Cyclonaias tuberculata).

24. Wing

1. A dorsal wing is present (go to 26).

2. A dorsal wing is lacking (go to 27)

26. Nacre color

1. The nacre is purple, and the pseudocardinal teeth are pointed and erect (Potamilus alatus).

2. The nacre color ranges from white to pinkish-white. The pseudocardinal teeth are very small (Leptodea fragilis).

27. Profile shape

1. (SH/SL) < 0.640 (go to 64).

2. (SH/SL) > 0.640 (go to 44).

44. Rays on periostracum

1. One or more prominent green or brown rays appear on the periostracum (go to 45).

2. Rays are lacking from the periostracum (go to 52).

45. Profile shape

1. The profile shape is triangular (go to 46).

2. The profile shape is circular (go to 50).

46. Posterior ridge

1. The posterior ridge is not sharply angled (go to 62).

2. The posterior ridge is sharply angled (go to 47).

47. Pseudocardinal teeth

1. The pseudocardinal teeth are massive (Ellipsaria lineolata).

2. The pseudocardinal teeth are of moderate size (Truncilla truncata).

50. Rays on periostracum

1. Many uniformly thin, wavy green rays appear on the periostracum (Lampsilis fasciola).

2. Many green waves of various widths appear on the periostracum (Lampsilis cardium).

3. A single broad, broken green ray extends from the umbo toward the center (Quadrula pustulosa).

52. Umbo position

1. The umbo is centrally located along the hinge line (Obovaria subrotunda).

2. The umbo is not centrally located along the hinge line (go to 54).

54. Sulcus

1. A distinct sulcus is located anterior to the posterior ridge (Fusconaia flava).

2. No sulcus is present (go to 78).

61. Ridge number and size

1. Six or more very small ridges per shell are present (Epioblasma obliquata, female).

2. Five or fewer very large ridges per shell are present (Amblema plicata).

62. Lateral teeth

1. The lateral teeth are long and thin (Pleurobema clava).

2. The lateral teeth are short and thick (Epioblasma obliquata, male).

64. Profile shape

1. (SH/SL) < 0.600 (go to 70).

2. (SH/SL) > 0.600 (go to 65).

65. Periostracum rays

1. Distinct rays are present on the periostracum (go to 67).

2. Rays are lacking on the periostracum (Toxolasma lividus, male).

67. Periostracum rays

1. The rays are broken and v-shaped (Truncilla donaciformis).

2. The rays are unbroken (Actinonaias ligamentina).

70. Periostracum rays

1. Rays are lacking on the periostracum (go to 71).

2. Distinct rays are present on the periostracum (go to 72).

71. Profile shape

1. (SH/SL) < 0.450 (Ligumia recta).

2. (SH/SL) > 0.450 (go to 75).

72. Shape and width of lateral teeth

1. The lateral teeth are thin and straight (Villosa iris).

2. The lateral teeth are wide or curved (go to 73).

73. Pseudocardinal teeth

1. The pseudocardinal teeth are large (go to 76).

2. The pseudocardinal teeth are small and erect (go to 74).

74. Posterior margin

1. The posterior margin is blunt (Lampsilis siliquoidea).

2. The posterior margin is sharply pointed (Ligumia subrostrata).

75. Nacre color

1. The nacre color ranges from bluish-white to salmon (Toxolasma parvus).

2. The nacre color is purple (Elliptio dilatata).

76. Beak sculpture

1. The beak sculpture is prominently double-looped (go to 77).

2. The beak sculpture consists of indistinct, wavy ridges (Ptychobranchus fasciolaris).

77. Shape and length of lateral teeth

1. The lateral teeth are short and heavy (Villosa fabalis).

2. The lateral teeth are long and slightly curved (Lasmigona compressa).

78. Nacre color

1. The nacre color ranges from white to pink (go to 79).

2. The nacre is deep purple (Toxolasma lividus).

79. Beak cavity

1. The beak cavity is very shallow (Pleurobema sintoxia).

2. The beak cavity is deep and somewhat compressed (Fusconaia subrotunda).

Brief Species Descriptions

Actinonaias ligamentina

This shell has relatively large, thick pseudocardinal teeth, and lateral teeth. The outer surface lacks pustules and ridges. There is no wing. The profile shape is elliptical (SH/SL between 0.621 and 0.631). The beak cavity is moderately deep. The periostracum is yellow with broad, green, unbroken rays.

Alasmidonta marginata

This shell has pseudocardinal teeth, but lateral teeth are missing. The profile shape is elongate (SH/SL between 0.561 and 0.579). There is no wing. There are several fine ridges along a severely sloped posterior ridge. The shells are laterally inflated.

Amblema plicata

This shell has pseudocardinal and lateral teeth. The exterior surface has prominent, large ridges numbering about three on each side (three on the right shell, and three on the left shell). The profile shape is circular (SH/SL between 0.714 and 0.740).

Anodontoides ferussacianus

This shell lacks both pseudocardinal and lateral teeth. The umbo extends above the hinge line. Beak sculpture is a couple of very fine ridges. The profile shape is circular (SH/SL between 0.768 and 0.796). The hinge line is not thickened or curved.

Cyclonaias tuberculata

This shell has well-developed pseudocardinal teeth and lateral teeth. Its profile shape is circular (SH/SL between 0.848 and 0.864). The exterior is covered with randomly distributed pustules. The periostracum lacks rays. The nacre is purple.

Ellipsaria lineolata

This thick, heavy shell has large pseudocardinal and lateral teeth. The exterior surface lacks pustules and ridges There is no wing. The profile shape is triangular. The posterior ridge is sharply angled. The periostracum is marked with green/brown rays. (SH/SL between 0.684 and 0.850).

Elliptio dilatata

This shell has pseudocardinal and lateral teeth. The exterior lacks pustules and ridges. There is no dorsal wing. The profile shape is elliptical (SH/SL between 0.510 and 0.524). Beak sculpture is a couple of thick, raised ridges. The periostracum is dark green, brown, or black, and is marked with only faint rays. The nacre is usually purple.

Epioblasma obliquata (female)

This shell has pseudocardial and lateral teeth. The exterior surface has ten or more very small ridges. The profile shape is circular (SH/SL between 0.734 and 0.802).

Epioblasma obliquata (male)

This shell has both pseudocardinal teeth and short, thick lateral teeth. The exterior lacks prominent pustules and ridges. There is no dorsal wing. The profile shape is triangular (SH/SL between 0.734 and 0.802). The periostracum is marked with many fine, wavy, green rays. The posterior ridge is not sharply angled.

Fusconaia flava

This shell has pseudocardinal and lateral teeth. The exterior lacks ridges and pustules. There is no wing. The profile shape is circular (SH/SL between 0.723 and 0.743). The umbo is not centrally located along the hinge line. There is a sulcus located anterior to the posterior ridge. The periostracum lacks prominent rays.

Fusconaia subrotunda

This shell has both pseudocardinal and lateral teeth. The exterior lacks prominent pustules and ridges. There is no dorsal wing. The profile shape is generally elliptical (SH/SL between 0.730 and 0.732). The periostracum is nearly black, and lacks rays. “Beak sculpture consists of a few subnodular ridges or wrinkles,” (Parmalee & Bogan, 1998). The pseudocardinal teeth are about ¾ as wide as the lateral teeth are long. The umbo is not centrally located along the hinge line. “The beak cavity is deep and somewhat compressed,” (Parmalee & Bogan, 1998).

Lampsilis cardium

This shell has both pseudocardinal and lateral teeth. The exterior lacks prominent ridges and pustules. There is no dorsal wing. The profile shape is circular (SH/SL between 0.648 and 0.700). The periostracum has many green rays of various widths.

Lampsilis fasciola

This shell has pseudocardinal and lateral teeth. The exterior lacks prominent pustules and ridges. There is no dorsal wing. The profile shape is circular (SH/SL between 0.819 and 0.915). The green rays on the periostracum are numerous and uniformly thin and wavy.

Lampsilis siliquoidea

This shell has small, erect pseudocardinal teeth, and slightly curved, thin lateral teeth. The exterior lacks prominent pustules and ridges. There is no dorsal wing. Its profile shape is elongate (SH/SL between 0.584 and 0.598). The periostracum is marked with green rays. The posterior margin is blunt.

Lasmigona complanata

This shell has pseudocardinal teeth, but true lateral teeth are missing. The profile shape is circular (SH/SL between 0.688 and 0.718). A dorsal wing is present.

Lasmigona compressa

This shell has well-developed, flattened pseudocardinal teeth, and slightly curved lateral teeth. The exterior lacks pustules and ridges. There is no dorsal wing. The profile shape is elongate (SH/SL between 0.566 and 0.590). The, “periostracum is green with yellow rays,” (Eddy & Hodson, 1950). The nacre is white, often with salmon or purple in the beak cavity. The beak sculpture is double-looped, and the umbo is nearly flush with the hinge line (Grabarkiewicz & Crail, 2006).

Lasmigona costata

This shell has pseudocardinal teeth, but lateral teeth are absent. The profile shape is elongate (SH/SL between 0.530 and 0.546). There is no dorsal wing. There are many prominent ridges along the flattened posterior ridge.

Leptodea fragilis

This shell has small pseudocardinal teeth and well-developed lateral teeth. The exterior lacks prominent ridges and pustules. The profile shape is circular (SH/SL between 0.648 and 0.660). There is a small dorsal wing. The nacre is white to pinkish-white.

Ligumia recta

This shell has both pseudocardinal and lateral teeth. The exterior lacks prominent pustules and ridges. There is no dorsal wing. Its profile shape is very elongate (SH/SL between 0.293 and 0.392). The periostracum is dark green, brown or black, and lacks rays. Beak sculpture is lacking, or is very indistinctly double-looped. The nacre is white, with salmon or purple in the beak cavity.

Ligumia subrostrata

This shell has small, erect pseudocardinal teeth, and slightly curved, well-developed lateral teeth. Its exterior lacks prominent pustules and ridges. There is no dorsal wing. Its profile shape is elongate (SH/SL between 0.426 and 0.505). The periostracum is yellow with green rays. The posterior margin is sharply pointed.

Obovaria subrotunda

This shell has pseudocardinal and lateral teeth. The exterior lacks ridges and pustules. There is no dorsal wing. The profile shape is circular (SH/SL between 0.828 and 0.986). The periostracum lacks prominent rays. The umbo is centrally located along the hinge line.

Pleurobema clava

This shell has pseudocardinal teeth, and long, thin lateral teeth. The exterior lacks prominent ridges and pustules. There is no dorsal wing. The profile shape is triangular (SH/SL between 0.674 and 0.694). The periostracum is marked with, “dark green rays, often interrupted and forming irregular blotches,” (Parmalee & Bogan, 1998). The posterior ridge is not sharply angled.

Pleurobema sintoxia

This shell has pseudocardinal and lateral teeth. The exterior lacks prominent ridges and pustules. There is no dorsal wing. The profile shape is circular (SH/SL about 0.734). The periostracum lacks prominent rays. The umbo is located at the far anterior end of the hinge line. No sulcus is present. The nacre color ranges from white to pink. “The beak cavity is very shallow,” (Parmalee & Bogan, 1998).

Potamilus alatus

This shell has pointed, erect pseudocardinal teeth, and well-developed lateral teeth. The exterior lacks prominent ridges and pustules. There is a large dorsal wing. The nacre is purple. The profile shape is circular (SH/SL between 0.729 and 0.759).

Ptychobranchus fasciolaris

This shell has heavy pseudocardinal teeth and especially wide, robust lateral teeth. The exterior lacks prominent pustules and ridges. There is no dorsal wing. The periostracum is yellow with broad, broken, green rays. The profile is kidney-shaped (SH/SL between 0.533 and 0.554). the beak cavity is very shallow or absent. The, “beak…sculpture consists of several fine, indistinct, wavy ridges (Parmalee & Bogan, 1998).

Pyganodon grandis

This shell lacks both pseudocardinal and lateral teeth. The umbo is elevated above the hinge line. The beak sculpture is double-looped. The profile shape is elongate (SH/SL between 0.550 and 0.568).

Quadrula cylindrica

This shell has pseudocardinal and lateral teeth. The exterior is studded with abundant pustules. The profile shape is elongate (SH/SL between 0.428 and 0.506).

Quadrula nodulata

This shell has pseudocardinal and lateral teeth. The exterior is marked with distinct rows of pustules; however, there is no sulcus between them. The profile shape is circular (SH/SL between 0.849 and 0.851).

Quadrula pustulosa (lacking pustules)

This shell has pseudocardinal and lateral teeth. There is no dorsal wing. The profile shape is circular (SH/SL between 0.837 and 0.845). A broad, green ray extends from the umbo, directed toward the posterior-ventral margin.

Quadrula pustulosa (with pustules)

This shell has pseudocardinal and lateral teeth. The exterior is randomly marked with prominent pustules. The profile shape is circular (SH/SL between 0.837 and 0.845). A broad, green ray extends from the umbo, directed toward the posterior-ventral margin. The nacre is white.

Quadrula quadrula

This shell has pseudocardinal and lateral teeth. The exterior is marked with distinct rows of prominent pustules, between which is a distinct sulcus. The profile shape is circular (SH/SL between 0.755 and 0.835).

Strophitus undulatus

This shell lacks both pseudocardinal and lateral teeth. The umbo extends above the hinge line. Beak sculpture is definitely not double-looped, but rather consists of, “3 – 4 heavy bars,” (Parmalee & Bogan, 1998). The profile shape is elliptical (SH/SL between 0.574 and 0.703).

Toxolasma lividus (female)

This shell has both pseudocardinal and lateral teeth. The exterior lacks prominent pustules and ridges. There is no dorsal wing. The profile shape is circular, and the posterior margin is truncated (SH/SL between 0.641 and 0.653). “The nacre color is usually a deep purple,” (Parmalee & Bogan, 1998). The umbo is not centrally located along the hinge line. No sulcus is present.

Toxolasma lividus (male)

This shell has both pseudocardinal and lateral teeth. The exterior lacks prominent pustules and ridges. There is no dorsal wing. The profile shape is elliptical, with a distinctly pointed posterior margin (SH/SL between 0.601 and 0.640). The periostracum is brown or black, and lacks rays. “The nacre color is usually a deep purple,” (Parmalee & Bogan, 1998).

Toxolasma parvus

This shell has both pseudocardinal and lateral teeth. Its exterior lacks prominent pustules and ridges. There is no dorsal wing. Its profile shape is elongate (SH/SL between 0.522 and 0.562). The periostracum is brown or black, and lacks rays. “The nacre color is bluish white to salmon,” (Parmalee & Bogan, 1998).

Truncilla donaciformis

This shell has pseudocardinal and lateral teeth. The exterior lacks prominent pustules and ridges. There is no dorsal wing. The profile shape is elliptical (SH/SL between 0.625 and 0.633). The umbo is centrally located along the hinge line. The periostracum is marked with green rays which are broken into many v-shapes.

Truncilla truncata

This shell has moderately sized pseudocardinal and lateral teeth. The exterior lacks prominent ridges and pustules. There is no dorsal wing. The profile shape is triangular (SH/SL between 0.709 and 0.715). The periostracum is marked with green rays. The shell is moderately thick. The posterior ridge is sharply angled.

Utterbackia imbecillis

This shell lacks pseudocardinal and lateral teeth. The umbo does not extend above the hinge line. The profile shape is elongate (SH/SL between 0.503 and 0.549).

Villosa fabalis

This shell has low, but well-developed pseudocardinal teeth, and short, heavy lateral teeth. The exterior lacks prominent pustules and ridges. There is no dorsal wing. The profile shape is elongate (SH/SL between 0.540 and 0.556). The periostracum is marked, “with wavy, dark-brown or greenish-brown rays,” (Parmalee & Bogan, 1998). “Beaks are somewhat elevated, having a double-looped, subnodulous sculpture, (Parmalee & Bogan, 1998).

Villosa iris

This shell has pseudocardinal teeth, and straight, thin lateral teeth. The exterior lacks prominent pustules and ridges. There is no dorsal wing. The profile shape is elongate (SH/SL between 0.512 and 0.522). The periostracum is marked with green rays, but not with v-shapes. The umbo is located anteriorly.

Glossary

Anterior.

Beak.

Beak cavity.

Lateral tooth.

Left shell.

Ligament.

Nacre.

Periostracum.

Pseudocardinal tooth.

Posterior.

Pustule.

Ridge.

Right shell.

Shell height.

Shell length.

Shell width.

Umbo.

Wing.

Judging Condition

Live. These shells contain living mussels. They cannot be pried apart with your thumbnails.

Good. The periostracum is at least 75% intact, and the nacre is shiny. Shells that are in good condition and contain at least a little meat (usually bits of adductor mussel still adhering to the nacre) are given the designation “Good-m”.

Fair. Shells whose condition falls between Good and Poor.

Poor. The periostracum is less than 25% intact, and the nacre is dull.