WATER POLLUTION CONTROL RESEARCH SERIES * 18050 ELDO3/72
BIOTA OF FRESHWATER
ECOSYSTEMS
Identification
Manual
FRESHWATER
SPHAERIACEAN CLAMS
(MOLLUSCA: PELECYPODA)
OF NORTH
AMERICA
U.S. ENVIRONMENTAL PROTECTION AGENCY
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Biota of Freshwater Ecosystems
Identification Manual No. 3
FRESHWATER SPHAERIACEAN CLAMS (MOLLUSCA:PELECYPODA) OF NORTH AMERICA
by
J. B. Burch
Museum of Zoology
The University of Michigan
Ann Arbor, Michigan 48104
for the
ENVIRONMENTAL PROTECTION AGENCY
Project * 18050 EL'D
Contract # 14-12-894
March 1972
For sale by 'the Superintendent of Documents, U.S. Government Printing Office
Washington, D.C. 20402 - Price $2.50
Stock Number 5501-0367
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EPA Review Notice
This report has been reviewed by the Environ-
mental Protection Agency and approved for pub-
lication. Approval does not signify that the
contents necessarily reflect the views and
policies of the EPA, nor does mention of trade
names or commercial products constitute endorse-
ment or recommendation for use.
WATER POLLUTION CONTROL RESEARCH SERIES
The Water Pollution Control Research Series describes the
results and progress in the control and abatement of pollution
in our Nation's waters. They provide a central source of
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Inquiries pertaining to Water Pollution Control Research
Reports should be directed to the Chief, Publications Branch
(Water), Research Information Division, R&M, Environmental
Protection Agency, Washington, DC 20460.
11
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FOREWORD
"Freshwater Sphaeriacean Clams (Mollusca:Pelecypoda) of
North America" is the third of a series of identification
manuals for selected taxa of invertebrates occurring in
freshwater systems. These documents prepared by the Oceano-
graphy and Limnology Program, Smithsonian Institution for
the Environmental Protection Agency will contribute toward
improving the quality of the data upon which environmental
decisions are based.
Additional manuals will include, but not necessarily be
limited to, freshwater representatives of the following
groups: amphipod crustaceans (Gammaridae), branchiuran
crustaceans (Argulus], isopod crustaceans (Asellidae),
decapod crayfish crustaceans (Astacidae), leeches (Hirudinea),
freshwater planarians (Turbellaria), polychaete worms
(Polychaeta) and aquatic dryopoid beetles (Dryopoidea).
111
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ABSTRACT
Bivalved mollusks of the superfamily Sphaeriacea (Order Heterodonta)
are represented in North America by 34 native and four apparently
introduced species of the cosmopolitan freshwater family Sphaeriidae
and by one introduced species (Corbioula manitensis) of the Afro-
Oriental family Corbiculidae. The North American Sphaeriidae include
three genera: Sphaeriwn with 12 species, Pisiditm with 25 species,
and Eupeva with one species. The genera Sphaevivem and Pisidiwn are
world-wide in distribution and occur in all North American states and
provinces. Eupera is restricted to the Western Hemisphere: northern
South America, Central America and the southern Coastal Plain of
eastern North America.
Although characters of soft anatomy are used in taxonomy of the
Sphaeriacea, especially in the classification at the generic level and
above, all taxa can be identified readily by characters of the shells,
and such shell characters are particularly important in distinguishing
the species. The main feature of this publication is an illustrated
taxonomic key using shell characters for identification of the 39
species of North American Sphaeriacea.
v
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CONTENTS
Section Page
I Introduction 1
Collection, Preservation and Identification 3
II Species List and Ranges 5
III Key to the North American Sphaeriacea 9
IV Acknowledgements 23
V References 25
VI Glossary 27
VII Index to Scientific Names 31
vn
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FIGURES
Page
1 Hinge teeth terminology 2
2 Equipment for collecting Sphaeriacea 4
3 Cofbicula manilensis 9
4 Beak positions in Sphaeriidae 9
5 Eupera cubensi,s, Sphaemum si-mile 1"
6 Sphaeriian str-i-atinum^ S. fabate 1®
7 S. transversum, S. partumeiwn H
8 S. lacustre, S. rhomboidewn H
9 S. corneion, S. patella 12
10 S. securisj S. nitidum 12
ii 5. ocaidentale, S. lacustre ^
12 Pisidiitin dubi-wn, P. arrm.'iaum 13
13 P. dubiwn, P. armicwn 14
14 P. adamsi, P. -idahoense 14
15 P. fallax, P. m-Lliwn 15
16 P. -insi-gne, P. ultrconontamMn 15
17 P. conventus, P. eruc-iatwn 16
18 P. cruo-Latiffn, P. aomppessum 16
19 P. compression 16
20 P. punctiferwn, P. punotatwn 17
21 P. n-tt'idim 17
22 P. equilatevale, P. variabile 18
23 P. ferrugineum, P. casertanwn 18
24 P. ferrug'ineum, P. oasevtanwn 19
25 Pisidium, cusps of lateral teeth PII 19
26 P. walkerij P. subtruncatian 19
27 P. rotundatum, P. venti"icosiun 20
28 P. rotundatum, P. ventriooswn 20
29 P-is'id'iwn, anterior and dorsal margins 20
30 P. lilljeborg-i 21
31 Pisidium, dorsal margins 21
32 Pisidiwn, beaks 21
33 P-is-id-ium, AI cusps of lateral teeth 21
34 P. henslowanwn, P. supinian 22
Vlll
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SECTION I
INTRODUCTION
The Sphaeriacea are represented in North America b> 38 species of the
family Sphaeriidae (four of which are apparently introduced), and by
one introduced species of the Afro-Oriental family Corbiculidae.
The Sphaeriidae is one of the truly cosmopolitan families of freshwater
mollusks. Its members are the "pea", "pill" or "fingernail clams", and
at least one of its many species can be found in almost any body of
freshwater. Until recently the classification of these obscure bivalves
seemed hopelessly confused because of the plethora of names based on
nearly every minor form of shell variation (e.g., see "Synonymy" in
Herrington, 1962, p 52-54).
The Sphaeriidae as recognized here contain four genera: Sphaeviwn3 Pisi-
diwn} Byssanodonta and Eupeva. Byssanodonta3 characterized by an
entirely smooth hinge and the total absence of teeth, is limited in
distribution to South America. EupeTa3 like Sphaeriwn and P-isi.diwn3
has an articulating hinge with cardinal and lateral teeth, but differs
from those two genera by having only one cardinal tooth in each valve.
In addition, Eupera exhibits several distinctive differences in soft
anatomy from both Sphaeriim and Pis£dittmf and each of the latter two
genera are also quite distinct in soft anatomy. These differences have
been considered basic enough to warrant separate subfamilies for each
of the three genera occurring in North America (Heard, 1965a). Their
diagnostic characters are given below.
Subfamily Sphaeriinae Baker, 1927
Branchial and anal siphons are both present and partially fused
together (for the greater part of their length in the subgenus
Musculiwn; only at their bases in Spha.evi.wn s. s.) ; embryos
develop in each anterior gill in several thin-walled longitudinal
sacs; byssal gland absent.
Subfamily Euperinae Heard, 1965
Branchial and anal siphons are both present and typically well-
separated for their entire length; each embryo develops in an
individual spherical marsupial covering between the inner and
outer lamellae of the anterior gills; byssal gland present and
functional.
Subfamily Pisidiinae Baker, 1927
The anal siphon is present, but the branchial siphon is absent
(subgenus Neopisid-ium') or represented by a slit in the mantle
(subgenera Pisidiwn s.s. and Cyolocalyx); embryos develop in
each anterior gill in a thick-walled sac containing individual
chambers for the embryos; byssal gland absent.
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Sphaerium and Pisidiim are cosmopolitan genera, and each contains many
species. In North America there are 12 species of Sphaerium and 25
species of Pisidiim. Besides the characters of soft anatomy listed
above, the two genera can be readily distinguished by their shells.
The posterior end of the shell is longer than the anterior end in
Sphaeriim., while just the reverse is true for Pisidium. (The anterior
end of the shell covers the foot, and the posterior end of the shell
surrounds the siphons. The anterior end of an empty shell can be dis-
tinguished by first determining which is the right and which is the
left valve. The right valve contains only one cardinal tooth and two
pairs of lateral teeth (Fig. 1). Conversely, the left valve has two
cardinal teeth, but only two lateral teeth.)
Cardinal tooth (C 3)
Beak
Anterior outer
lateral (A m)
Ligament
Anterior end
Anterior inner
lateral (A I)
Cusp
Hinge
RIGHT VALVE
Posterior outer
lateral (P m)
\—Cusp
\ Posterior inner
\~lateral (P I)
Ligament
Beak
Posterior
lateral (P
Cusp
Posterior
end
.C 4
Cardinal teeth
Anterior lateral (A n)
Cusp
Hinge
LEFT VALVE
Fig. 1 Hinge teeth terminology.
Eupera is represented in North Ajnerica (north of Mexico) by only one
species, E. eubensis, which is sporadically distributed in the
Coastal Plain from southern Texas to central North Carolina.
The key which follows is based on the one I prepared (without illus-
trations) for a revision of the Sphaeriidae of North America by
Herrington (1962). The present key is illustrated and contains
several modifications, including the addition of three more species
of Pisidiwn} and the genera Eupera and Corbicula.
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COLLECTION, PRESERVATION AND IDENTIFICATION
Some equipment especially useful for collecting Sphaeriacea is shown
in Fig. 2: a dip-net, drag dredge and sorting sieve. In addition, a
round-pointed shovel and a 10- to 12-quart pail is recommended. When
collecting on a soft bottom in shallow water (two feet or less), the
shovel can be used to skim the surface of the bottom. The material
obtained is then washed in the sieve. By nearly submerging the sieve
in water, tipping and moving it slowly, most of the fine debris lighter
than the specimens can be removed.
If the water depth exceeds two feet, or the bottom is very soft, the
dipnet is more useful than the shovel. The dredge is used for depths
greater than five feet, usually being dragged behind a rowboat, and
the contents emptied into a tub in the boat.
Specimens to be used for anatomical study should be narcotized, i.e.,
relaxed in a life-like position and to such an extent that they do not
contract when placed in fixative. One of the most common methods of
narcotization is to add several menthol crystals to the shallow water
vessel containing the specimens. However, a variety of other reagents
can be used (see Runham, Isarankura and Smith, 1965), some with better
results, some worse, depending on the species of mollusk.
Fixatives most commonly employed with freshwater mollusks are 65-75%
ethyl alcohol or neutralized formalin. Formalin-alcohol-acetic acid
and Bouin's fluid are also used, but since their acids dissolve the
carbonates of the mollusk shell, fixation time should be carefully
regulated if it is necessary to save the shell.
Freshwater mollusks are generally preserved in 60-70% ethyl alcohol,
although neutralized 4% formalin or 1% propylene phenoxetol may also
be used.
CoTb-icula and many of the species of Sphaerium can be identified
easily without any magnification, or at most only a simple hand lens
is needed. But to identify most species of Pis-idiim3 a stereoscopic
microscope with high magnification is necessary.
Fine forceps are needed to manipulate specimens and, because of the
fragile nature of many pisidia shells, a small brush is also useful.
Herrington (1961) recommends using tweezers made from a 3/4 x 6 inch
celluloid strip bent around a 3/4 inch square block of wood.
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Fig. 2. a - Dip-net, made from round iron, a broom handle, and
a piece of burlap; b - sieve, made from a wooden box, brass wire
screening, and cord and screweye; c drag dredge made from
galvanized iron, two burlap potato sacks, a piece of wire, and
some sash cord. From Herrington (1961).
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SECTION II
SPECIES LIST AND RANGES
The geographical distributions given below are rather general ones,
because many of the species have very wide ranges. For more detailed
lists of distributions and localities, see Sinclair and Isom (1961,
1963), Herrington (1962), Heard (1963, 1965) and Clarke (in press). For
additional details of taxonomy see Kuiper (1962, 1965), Herrington
(1965) and Heard (1966, 1969).
Family CORBICULIDAE
CoTbiaula manilensis (Philippi, 1844). Introduced from east Asia and
first noticed in Washington State in 1938. Since then it has
spread south to California and across the United States to Florida,
and in the Mississippi River system it has spread from Louisiana
and Mississippi north to the upper Ohio River.
Family SPHAERIIDAE
Genus Sphaeriwri Scopoli, 1777
Sub genus Sphaer-iwm s.s.
Sphaeriim ooTcneim (Linnaeus, 1758). Apparently introduced from Europe.
It has been reported from several localities in southern Ontario,
and in the United States from Lake Champlain (New York) and Lake
Erie (Ohio).
Sphae-rium fdbale Prime, 1851. In Canada it occurs in southern Ontario.
In the eastern United States this species is distributed from New
York south to Georgia and Alabama. In the midwest it is found in
Ohio, Michigan and Illinois.
Sphaerlum niti-dum Clessin, 1876. Holarctic in distribution. In the
Western Hemisphere it occurs from northern Canada south to north-
ern United States, where it extends from northern Maine west to
Washington and the Aleutian Islands. This species has been
reported from all the Great Lakes except Lake Erie. In the Rocky
Mountains it extends south to Utah.
Sphaeriwn oooidentale Prime, 1853. Sporadically distributed; in
Canada from New Brunswick to southeastern Manitoba, and in the
United States in all the northern states, south to Florida in the
east and to Utah and Colorado in the west.
Sphaerium patella (Gould, 1850). Western United States: Washington,
Oregon, Idaho and California.
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Sphaerium rhorriboideum (Say, 1822). Southern Canada from New Brunswick
to British Columbia; northern United States from Maine and
Pennsylvania to Idaho.
Sphaerium striatinum (Lamarck, 1818). In Canada from New Brunswick
northwest to Great Slave Lake and the Upper Yukon River; throughout
the United States and south into Mexico and Central America (Panama).
Sphaerium simile (Say, 1816). Southern Canada from New Brunswick to
northern and central British Columbia, south to Virginia, Iowa and
Wyoming.
Subgenus Musculium Link, 1807
Sphaerium (Musculium) lacustre (Miiller, 1774). From the tree-line in
Canada and Alaska south, throughout Canada and the United States
(except the southwestern states). Also found in Hawaii, Central and
South America, Australasia and Eurasia.
Sphaerium (Musculium) partumeium (Say, 1822). In southern Canada from
New Brunswick to Saskatchewan. It is found throughout the United
States.
Sphaerium (Musculium) securis Prime, 1851. In Canada from Nova Scotia
west to British Columbia and southwestern Northern Territories. It
is recorded from most of the United States except the southwestern
states.
Sphaerium (Musculium) transversum (Say, 1829). North America from
southwestern Northwest Territories, the Canadian provinces and United
States east of the Rocky Mountains, south to Florida, Texas and
Mexico.
Genus Eupera Bourguignat, 1854
Eupera eubensis (Prime, 1865). Atlantic Coastal Plain from southern Texas
to central North Carolina. Also found in Central America and north-
ern South America.
Genus Pisidium Pfeiffer, 1821
Subgenus Pisidium s.s.
Pisidium amnicum (Miiller, 1774). Eurasia and Africa. Introduced into
North America and found mainly around the eastern Great Lakes and the
St. Lawrence River. Also reported from Pennsylvania, New Jersey and
Lake Champlain.
Pisidium dubium (Say, 1816). North America east of the Mississippi River
from southern Ontario to Florida.
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Pisidium iddhoense Roper, 1890. Southern Canada and the Great Lakes
region of the United States west to the Aleutian Islands, British
Columbia, Washington and California.
Subgenus Cyelocalyx Dall, 1903
Pisidium (Cyclooalyx) adamsi Prime, 1852. In Canada from Nova Scotia
west to Saskatchewan. Reported from nearly all of the United States
east of the Rocky Mountains except for the southcentral states.
Pisidium (Cyclooalyx) easertanum (Poli, 1795). Nearly cosmopolitan in
distribution. It has been reliably recorded from all of the United
States except Hawaii, Kentucky and North Dakota.
Pisidiwn (Cyclocalyx) comppessum Prime, 1852. Found throughout most of
Canada and the United States, and into Mexico.
Pisidiwn (Cyelocalyx) equilaterale Prime, 1852. Southeastern Canada to
eastern Lake Superior, south to Virginia, Pennsylvania and Illinois.
Pisidium (Cyelocalyx) fallax Sterki, 1890. Distributed sporadically
from Great Slave Lake, Alberta and western James Bay south through
southern Canada and northern United States from Washington to New
Jersey. Also recorded from Alabama.
Pisidium (Cyelocalyx) ferrugineum Prime, 1852. Found in most of Canada
and distributed south to the northern United States from Washington
and Utah to New Jersey.
Pisidium (Cyelocalyx) henslowanum (Sheppard, 1825). Reported from sev-
eral localities in the eastern Great Lakes region. Apparently
introduced into North America, probably from Europe.
Pisidium (Cyelocalyx) lilljeborgi Clessin, 1886. Northern Canada and
Alaska south throughout Canada and the northern United States, and
in the Rocky Mountains south to Colorado, Utah and California.
Pisidium (Cycloealyx) milium Held, 1836. Aleutian islands and Great
Slave Lake, south to British Columbia, James Bay, Prince Edward
Island and Maine, and south in the Rocky Mountains to Utah and
Colorado.
Pisidium (Cyelocalyx) nitidum Jenyns, 1832. In most parts of the conti-
nental United States except Alaska, and in all Canadian provinces
except Nova Scotia. Also in Mexico, Eurasia and North Africa.
Pisidium (Cyelocalyx) rotundatum Prime, 1851. Northern Canada to the
northern United States from Maine to Washington, south in the Rocky
Mountains to Mexico; Oklahoma.
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Pisidiwn (Cyolooalyx) subtrunaatwn Malam, 1855. Northern and central
Canada to the northern United States from New York to Montana, and
south in the Rocky Mountains to Colorado and California.
Pisidiwn (Cyolooalyx) supinwn Schmidt, 1850. Found at several localities
in the eastern Great Lakes region. Apparently an introduced species,
probably from Europe.
Pisidiwn (Cyolocalyx) ultramontanwn Prime, 1865. Known only from several
localities in southwestern Oregon and northern California.
Pisidiwn (Cyolooalyx) varidbile Prime, 1852. Found throughout Canada and
the United States.
Pisidiwn (Cyolooalyx) ventricoswn Prime, 1851. Northern Canada to the
northern United States from Maine to Washington, south in the Rocky
Mountains to Mexico.
Pisidiwn (Cyolooalyx) walkeri Sterki, 1895. Northern Canada south to
Virginia and Arizona.
Subgenus Neopisidiwn Odhner, 1921
Pisidiwn (Neopisidiwn) oonventus Clessin, 1877. Holarctic, usually in
arctic, subarctic or alpine lakes. Found in many localities in
Canada, in several of the Great Lakes, and in Alaska, Washington,
Montana, Wisconsin and New York.
Pisidiwn (Neopisidiwn) oruciatwn Sterki, 1895. Central Great Lakes region
of the United States and southern Ontario.
Pisidiwn (Neopisidiwn) insigne Gabb, 1868. Southern Ontario and British
Columbia in Canada. In the northern United States from Maine to
Washington, south in the Rocky Mountains to the southern border states.
Pisidiwn (Neopisidiwn) punotatwn Sterki, 1895. Southern Canada and the
Great Lakes region of the United States south to Ohio, Pennsylvania,
Virginia and Tennessee.
Pisidiwn (Neopisidiwn) punotifemm Guppy, 1867. In the United States found
only in Florida and Texas. Additional distribution: Mexico, Central
America and Caribbean islands.
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SECTION III
KEY TO THE NORTH AMERICAN SPHAERIACEA
All scale lines in figures are marked off in mm.
Hinge of shell with serrated lateral teeth (Fig. 3a,b).,
Corbiculidae: Corbioula man-ilensis
Hinge of shell with smooth lateral teeth. Sphaeriidae 2
a b
Fig. 3. Covbiaula manilens-is. a - Hinge; b - External view of left valve.
2 (1) Beaks of shell anterior, or if subcentral, on the anterior side of
center (Fig. 4a) . Sphaerium^ Eupera 3
Beaks of shell posterior, or if subcentral, on the posterior side
of center (Fig. 4b) . Pisidium 18
Fig. 4. Sphaeriidae, beak positions as seen from left side of shell.
a - Beaks anterior; b - Beaks posterior.
3 (2) Shell with two cardinal teeth in one valve, and one in the
opposing valve; shell without mottling 4
Shell with only one cardinal tooth in each valve; shell usually
mottled (Fig. 5a): Eupera aubensi-s
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Fig. 5. Sphaeriidae, left valves, a - Eupera oubensis; b - Sphaerium
simile.
4 (3) Shell sculptured with coarse striae or relatively widely spaced
striae (8 or less per mm in the middle of the shell) 5
Shell sculptured with fine striae or relatively narrowly spaced
striae (12 or more striae per mm in the middle of the shell).?
5 (4) Striae evenly spaced (Fig. 5b): S. simile
Striae not evenly spaced 6
6 (5) Surface even, except for rest marks and striae; shell inflated;
striae not weaker in region of the beaks (Fig. 6a) :
S. stviatinum
Surface uneven; shell compressed; striae weaker in region of
the beaks (Fig. 6b): S. fdbale
a
Fig. 6. Sphaeriwn, left valves, a - S. striatinum; b - S. fabate
10
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7 (4) Adult shell large, more than 8 nun in length 8
Adult shell smaller, less than 8 mm in length 13
8 (7) Beaks prominent, distinctly raised above the dorsal margin 9
Beaks not prominent, only very slightly raised above the dorsal
margin 11
9 (8) Shell long in outline, height 3/4 or less of the length
(Fig. 7a): S. transverswn
Shell higher in outline, height 7/8 or more of the length 10
10 (9) Dorsal margin rather straight, posterior end more or less at
right angles to the dorsal margin; striae very fine (Fig.
7b): S. partumeium
Dorsal margin more rounded, posterior end at a greater angle to
the dorsal margin; striae coaser (Fig. 8aj: S. laoustre
Fig. 7. SphaeTium, left valves, a - S. transverswn; b - S. partwneium.
11 (8) Shell more or less rectangular in outline (Fig. 8b) :S. rhomboi-deum
Shell with more rounded ends 12
b
Fig. 8. Sphaeriwn., left valves, a - S. laoustre; b - S. rhomboideum.
11
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12 (11) Ends of shell rounded in outline (Fig. 9a) : S. eormewn
Ends of shell distinctly tapering toward the beaks (Fig. 9b) :
S. patella
a b
Fig. 9. Sphaeriurrij left valves, a - S. eorneum; B - S. patella.
13 (7) Posterior end nearly at right angles to the dorsal margin 14
Posterior end and dorsal margin rounded or forming an obtuse
angle 15
14 (13) Anterior ventral margin of shell slopes sharply upward; surface
dull; striae coarser (Fig. lOa): S. seauvis
Anterior ventral margin of shell slopes upward, but only
slightly; surface glossy; striae finer (Fig. 7b):S. partwneiwn
15 (13) Striae maintain their spacing and height in the region of the
beaks (Fig. lOb): S. nitidum
Striae fade out in region of beaks 16
a b
Fig. 10. Sphaeriim, left valves, a - S. seouris. b - S. nitidum.
12
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16 (15) Beaks prominent, distinctly raised above the dorsal margin 17
Beaks not prominent, only slightly raised above the dorsal
margin (Fig. 9a): S. aorneum
17 (16) Anterior and posterior ends of shell round; beaks not swollen
(Fig. lla) : s. occidentdle
Posterior end of shell truncate; beaks swollen (Fig. lib):
S. laaustre
Fig. 11. Sphaeriunij left valves, a - S. oacidentale; b -
S. laaustve.
18 (2) Shell large, adults 6 mm or more in length 19
Shell medium or small, adults less than 6 mm in length 22
19 (18) Striae coarser (10 or less per mm) 20
Striae finer (15 or more per mm) . 21
20 (19) Striae fade out in region of beaks; cardinal teeth nearer the
posterior lateral teeth than to the anterior lateral teeth
(Figs 12a, 13a) : Pisidiim dub-Lwn
Striae do not fade out in the region of beaks; cardinal teeth
nearer the anterior lateral teeth than to the posterior lat-
eral teeth (Figs 12b, 13b) : P. comieum
Fig. 12. Pisidium, hinge of right valves, a - P. dubiwn;
b - P. armicum.
13
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a b
Fig. 13. Pisidium,, left valves, a P. dubium; b P. armiown.
21 (19) Shell long in outline, height less than 90% of the length; sur-
face dull (Fig. 14a): P. adamsi
Shell higher in outline, height 90% or more of the length; sur-
face glossy (Fig. 14b): P- idahoense
Fig. 14. Pisidiwn, left valve, a - P. adamsi; b - P. idahoense.
22 (18) Anterior cusp of left valve twisted toward the anterior, and
the corresponding sulcus on the right valve twisted corre-
spondingly (Fig. 15a): P. fallax
Anterior cusp of left valve not twisted, but parallel to the
dorsal margin 23
14
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a b
Fig. 15. Pisidiwn, left valves, a - P. fallax; b - P. miliwn.
23 (22) Ventral aspect of shell very truncate (in end view) (Fig. 15b):
P. miliwn
Shell tapering ventrally 24
24 (23) Hinge long (more than 3/4 the shell length) 25
Hinge short (less than 3/4 the shell length) 36
25 (24) Anterior end terminating in a long blunt point (Fig. 16a):
P. insigne
Anterior end rounded 26
a b
Fig. 16. Pisidiim, left valves, a P. insigne; b - P. ultramontanwn.
26 (25) Shell with heavy ridges which go beyond the beaks; California
and Oregon (Fig. 16b): P. ultmmontanwn
Shell without heavy ridges, or if present, only on the beaks..27
15
-------
27 (26) Cardinal teeth central or subcentral 28
Cardinal teeth near anterior cusps 35
28 (27) Shell shaped like a parallelogram, i.e., the anterior and
posterior ends slope parallel and nearly at the same angle;
found only in cold waters (Fig. 17a): P. oonventus
Anterior and posterior ends slope at different angles, i.e.,
not parallel 29
a b
Fig. 17. Pisidiwn, left valves, a - P. oonventus; b - P. oruciatwn.
29 (28) Shell dull 30
Shell glossy 33
30 (29) Shell with ridges on the beaks 31
Shell without ridges on the beaks 32
31 (30) Beak ridges U-shaped (Figs. 17b, 18a): P. arueiatwn
Beak ridges straight or slightly curved, but not U-shaped
(Figs. 18b, 19): P. compression
Fig. 18. Pisiditm, beak sculpture
a - P. cruc-latim; b - P. aompresswn.
Fig. 19. P. compression,
left valve.
16
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32 (30) Shell medium-sized, up to 3 mm in length; sculptured with very
fine close striae (Fig. 20a) : P. punotifenm
Shell minute, 1.5 mm or less in length; striae prominent and
rather widely spaced (Fig. 20b): P. punctatum
a b
Fig. 20. P-isidium^ left valves, a - P. punotiferwn; b P. punotatum.
33 (29) Beaks prominent; moderately striate (less than 30 striae per
mm) 34
Beaks not prominent; finely striate (more than 30 striae per
mm) (Fig. 21): P. nitidum
Fig. 21. Pisidium nit-idum, left valve.
34 (33) Beaks subcentral (Fig. 22a):
Beaks posteriorly placed (Fig. 22b):
P. equ-llatevale
P. vavidbile
17
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Fig. 22. Pisid-iwn, left valves, a - P. equilaterale; b - P.
35 (27) Cusp of All with nearly vertical and parallel sides
(Figs 23a, 24a): P. ferrugineum
Cusp of All may have steeply inclined sides, but not nearly
vertical or parallel (Figs 23b, 24b): P. casertanwn
Fig. 23. Pisidiiuris left valves, a - P. ferrugineum. b - P. aasertanum.
36 (24) PII central, or on proximal side of center (Fig. 25a) 37
PII distal, or on distal side of center (Fig. 25b) 40
18
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Fig. 24. Pisidiujrij cusps of
lateral teeth All. a - P.
ferrug-ineum; b - P. casertonwn.
Fig. 25. Pisidium^ cusps of
of lateral teeth PII. a - cusps
central; b - cusps distal.
37 (36) Surface glossy; finely striate (more than 30 striae per mm)...38
Surface dull; moderately striate (less than 30 striae per mm)
(Fig. 26a): P. walkeri
38 (37) Anterior (proximal) end of sulcus in right valve closed 39
Anterior (proximal) end of sulcus in right valve not closed
(Fig. 26b) : P.
Fig. 26. Pisidiim, left valves, a P. wdlkeri; b P. subtrunoatum.
39 (38) Beaks subcentral; hinge plate between cardinals and All narrow
(Figs 27a, 28a): P. rotundatiffn
Beaks posterior; hinge plate between cardinals and All
relatively wide (Figs 27b, 28b): P. ventriaoswn
19
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a b
Fig. 27. Pisidiwn, left valves, a - P. rotundatwn; b P. ventriaosum.
40 (36) Anterior end joining dorsal margin at an angle (Figs 29a,30):
P. lilljeborg-i,
Anterior end curves gently into the dorsal margin (Fig. 29b)..41
Fig. 28. Pisidium, hinge plates.
a P. rotundation; b.- P. ventri-oosum.
Fig. 29. P-is-idiwn, anterior and
dorsal margins, a - anterior
end joining dorsal margin at an
angle; b - anterior end curves
gently into the dorsal margin.
20
-------
Fig. 30. P. l-illgebovg-i., left valve. Fig. 31. Pi.sidiian3 dorsal margins.
a - almost straight; b- rounded.
41 (40) PII central or on distal side of center; beaks never ridged...42
PII distal; beaks usually ridged 44
42 (41) Dorsal margin anterior of beak almost straight or only faintly
curved (Fig. 31a); beaks not prominent (Figs 23b, 32b):
P. casertanwn
Dorsal margin anterior to beak well rounded (Fig. 31b); beaks
prominent (Fig. 32a) 43
Fig. 32. Pisidium beaks.
inent; b - not prominent,
a -
prom- Fig. 33. AI cusps of lateral teeth
of Pisidium. a - sides steeply
sloped; b - sides gently sloped.
21
-------
43 (42) Beaks subcentral; hinge plate between cardinals and All narrow
(Figs 27a, 28a): P. rotundatwn
Beaks posterior; hinge plate between cardinals and All
relatively wide (Figs 27b, 28b): P. ventricoswn
44 (41) Cusp of AI thin and with steeply sloped sides (Figs 33a, 34a):
P. henslowanum
Cusp of AI thick and with gently sloped sides (Figs 33b, 34b):
P. supinwn
Fig. 34. Pis-id-ium, left valves, a - P. henslowamm; b - P. supinum.
22
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SECTION IV
ACKNOWLEDGEMENTS
Figs 4-11 were drawn by John Tottenham; Figs 3, 13-17, 19-23, 26, 27,
30 and 34 were drawn by Martha Lackey.
23
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SECTION V
REFERENCES
Clarke, Arthur H. in press. The freshwater molluscs of the Canadian
Interior Basin. Malacologia.
Heard, William H. 1963. Survey of the Sphaeriidae (Mollusca:Pelecypoda)
of the southern United States. Proceedings of the Louisiana Academy
of Sciences, 26:102-120.
1965. Comparative life histories of the North American pill clams
(Sphaeriidae•.Pisidium}. Malacologia, 2(3) :381-411.
1965a. Recent Eupera (Pelecypoda:Sphaeriidae) in the United States,
American Midland Naturalist, 74(2):309-317.
1966. Subgeneric classification of Pisidium in North America.
Nautilus, 79 (3):86-89.
1969. Hinge tooth reversals in sphaeriid clams. Nautilus,
82(4):137-144.
Herrington, H.B. 1961. Collecting sphaeriid clams. National Museum of
Canada Bulletin, 183:1-5.
1962. A revision of the Sphaeriidae of North America (Mollusca:
Pelecypoda). Miscellaneous publications. Museum of Zoology,
University of Michigan, No. 118:1-74, pis 1-7.
1965. Corrections of sphaeriid nomenclature. Nautilus, 79(2):
42-45.
Kuiper, J.-G.-J. 1962. Note sur la systematique des pisidies. Journal
de Conahyliologie3 102:53-57.
1965. Familie Pisidiidae. In: "Zoetwatermollusken van Nederland."
Janssen, A.W. en E.F. de Vogel, Den Haag, Pp. 1-19.
Runham, N.W., Isarankura, K. and B.J. Smith. 1965. Methods for
narcotizing and anaesthetizing gastropods. Malaaologia, 2(2):
231-238.
Sinclair, Ralph M. and Billy G. Isom. 1961. "A preliminary report on
the introduced Asiatic clam Corbicula in Tennessee." Tennessee
Stream Pollution Control Board, Tennessee Department of Public
Health, Nashville, Tennessee, 33 pp.
1963. "Further studies on the introduced Asiatic clam Corbicula
in Tennessee." Tennessee Stream Pollution Control Board, Tennessee
Department of Public Health, Nashville, Tennessee, 75 pp.
25
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SECTION VI
GLOSSARY
Anal siphon. The dorsal exhalant tube derived from mantle-margin epithe-
lium and located near the anus at the posterior end of the animal.
Water currents from inside the mantle flow through the anal siphon to
the outside.
Anterior end. The shorter end of the shell (from the beaks) in CoTbioulat
Eupera and Sphaerium; the longer end of the shell in Pisidium. The foot
of the animal is directed toward this end.
Beaks. The raised part on the dorsal margin of the shell. It is formed
by the embryonic shell around which the later shell develops.
Branchial siphon. The ventral inhalant tube derived from mantle-margin
epithelium. It is located at the posterior end of the animal and through
it flows outside water carrying dissolved oxygen, food organisms and male
gametes.
Byssal gland. A gland embedded in the posterior portion of the foot
which secretes adhesive-tipped threads that anchor certain bivalved mol-
lusks to the substratum.
Cardinal teeth. Lamellae on the center of the hinge in the right and
left valves which function to stabilize the two valves against shearing
forces. The opposing cardinal teeth of the two valves fit together in a
complementary fashion. There are usually two cardinal teeth in the left
valve and one in the right; sometimes this order is reversed.
Compressed. Flattened laterally.
Cusps. The highest elevations on the lateral teeth.
Depressed. Flattened dorso-ventrally.
Distal. Farthest from the beaks of the shell in an anterior-posterior
axis.
Dorsal Margin. The upper edge of the shell, including the hinge.
Fingernail clam. Common or vernacular name for a member of the genus
Sphaemum.
Hinge. The stabilizing lamellae (cardinal and lateral teeth) in the
dorsal part of each valve of a pelecypod shell. The opposing single
lamella in the sphaeriacean shell articulates with a pair of complemen-
tary lamellae in the opposing valve.
27
-------
Hinge plate. That part of the dorsal margin of the shell between the
anterior and posterior lateral teeth of each valve, and including the
lateral teeth.
Inflated. Swollen.
Lateral teeth. The elongated lamellae at each end of the hinge-plate.
Left valve. The shell half on the left side when the shell is placed
with the hinge up and the anterior end forward.
Mantle. An extension of the dorsal body wall of mollusks as one or a
pair of folds, which usually secretes a shell and encloses a mantle
cavity, typically containing gills.
Pea clam. Common or vernacular name for a member of the genus Pis-idium
(same as "pill clam").
Pill clam. Common or vernacular name for a member of the genus
Pisidiwn (same as "pea clam") .
Posterior end. The longer end of the shell (from the beaks) in
Corb'iaula, HJupera and Sphaeri.um; the shorter end of the shell in
Pisidiiffn. This is the end from which the siphons extend.
Proximal . Nearest the beaks of the shell in an anterior-posterior axis.
Rest mark. A darker or thicker part of the shell characteristically
formed during a rest period in growth.
Ridge. A wrinkle or raised part on the beaks of some species of
Right valve. The shell half on the right side when the shell is placed
with the hinge up and the anterior end forward.
Serrated. Notched on the edge.
Siphons . Fleshy tubes at the posterior end of bivalved mollusks through
which inhalant and exhalant water passes into and out of the mantle
cavity.
Sphaeriacea. A superfamily of bivalved mollusks (Class Pelecypoda
or Bivalvia, Subclass Lamellibranchia, Order Heterodonta) living in fresh
or brackish water and characterized by a porcelainous shell, round,
triangular or oval in shape, and with cardinal "teeth" or lamellae below
the beaks and usually well-developed lateral "teeth" at each end of the
hinge plate. An external ligament holds the two shell valves together.
The hermaphroditic, ovoviviparous animal contains branchial sacs or spaces
in which the young are brooded.
28
-------
Striae. Concentric raised striations or lines on the exterior surface
of the shell. They may vary from fine to very coarse, the latter
sometimes called ribs.
Subcentral. Not quite central; off-center.
Sulcus. A longitudinal furrow, one usually at each end of the hinge
plate of the right valve, which serves as a socket for the teeth of
the opposing (left) valve.
Teeth. The opposing lamellae on the hinge plates of bivalved mollusks
which serve to stabilize the two valves against shearing forces. In
the Sphaeriacea the central lamellae near the beaks are called cardinal
teeth and the lamellae at each end of the hinge plates are called
lateral teeth.
Truncate. Having the end cut off more or less squarely.
Valve. The single undivided shell of non-pelecypod mollusks, or one of
the opposing halves of the divided shell of a pelecypod mollusk. In
bivalved mollusks the two shell halves are held together by an elastic
ligament.
29
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SECTION VII
INDEX TO SCIENTIFIC NAMES
adamsi- (Pisidium (C.)), 7,14
comicum (Pisidium) , 6,13
Byssanodonta3 1
casertanum (Pisidium (C.)), 7,18,21
compression (Pisidium (C.)), 7,16
convertus (Pisidium (N.)), 8,16
Corbioula, 2,3
manilensis, 5,9
Corbiculidae, 5
corneum (Sphaerium), 5,12,13
oruoiatum (Pisidium (N.))3 8,16
oubens-is (Eupera), 2,6,9
Cyolooalyx, 1,7
dubium (Pisisium), 6,13
equilaterale (Pisidium (C.))3 7,17
Eupera, 1,2,6,9
cubensis, 2,6,9
Euperinae, 1
fabate (Sphaerium), 5,10
fallax (Pisidium (C.))3 7,14
ferrugineum (Pisidi-im (C. ) ) 3 7,18
henslowanum (Pisidium (C.))3 7,22
idahoense (Pisiditan)3 7,14
insigne (Pisidium (N.))3 8,15
laeustre (Sphaerium (M. )), 6,11,13
lilljeborgi (Pisidium (C.))3 7,20
manilensis ('Corbicula)3 5,9
milium (Pisidium (C.))3 7,15
Museu~lium3 1,6
Neopisidium3 1,8
nitidum (Pisidium (C.))3 7,17
(Sphaerium), 5,12
ooe-identale (Sphaerium), 5,13
partumeium (Sphaerium (M. ))36)11,12
patella (Sphaeriwn)3 5,12
Pisidiinae, 1
Pisidium3 1,2,3,6,9
amnioum3 6,13
dubium3 6,13
idahoense3 7,14
(Cyaloaalyx) adamsi, 7,14
oasertanum3 7,18,21
eompressum,, 7,16
equilaterale, 7,17
fallax, 7,14
3 7,18
Pisidium (Cyalooalyx) hens~lowanum3
7,22
Iilljeborgi3 7,20
milium, 7,15
nitidum, 7,17
votundatwm, 7,18,22
subtruncatum, 8,19
supinum, 8,22
ultvamontanum, 8,15
variabile, 8,17
ventx>iaosum3 8,19,22
walkevi, 8,19
(Neopisidium) oonventus, 8,16
cruoiatum, 8,16
insigne, 8,15
punatatum, 8,17
punctiferum, 8,17
punotatum (Pisidium (N,)), 8,17
punatiferum (Pisidium (N.)), 8,17
rhomboideum (Sphaerium), 6,11
rotundatum (Pisidium (C.)), 7,18,22
seouris (Sphaerium (M.)), 6,12
simile (Sphaerium). 6,10
Sphaeriidae, 1,5
Sphaeriinae, 1
Sphaerium, 1,2,3,5,9
corneum3 5,12,13
fabale, 5,10
nitidum, 5,12
oooidentale, 5,13
patella, 5,12
rhomboideum, 6,11
simile, 6,10
striatinum, 6,10
(Musoulium) laoustre, 6,11,13
partumeium, 6,11,12
seauris, 6,12
transversum, 6,11
striatinum (Sphaerium), 6,10
subtrunoatum (Pisidium (C,))3 8,19
supinum (Pisidium (C.)), 8,22
transversum (Sphaerium (M.)), 6,11
ultramontanum (Pisidium (C.))3 8,15
variabile (Pisidium (C.)), 8,17
Ventricosum (Pisidium (C.)), 8,19,22
walkeri (Pisidium (C.)), 8,19
31
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SELECTED WATER
RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
1. Report No.
4. Title BIOTA OF FRESHWATER ECOSYSTEMS IDENTIFICATION MANUAL
NO. 3 Freshwater Sphaeriacean Clams (Mollusca:Pelecypoda)
of North America,
7. Author(s) Burch, J. B.
9. Organization Museum Of Zoology,
The University of Michigan,
Ann Arbor, Michigan
12. Sponsoring Organization
15. Supplementary Notes
3. Accession No.
w
5. Report Date
6.
8. Performing Organization
Report No.
10. Project No.
18050 ELD
11. Contract/Grant No.
13. Type of Report and
Period Covered
is. Abstract Bivalved mollusks of the superfamily Sphaeriacea (Order Heterodonta) are
represented in North America by 34 native and four apparently introduced species of
the cosmopolitan freshwater Sphaeriidae and by one introduced species (Corbieulo.
mon-ilensis} of the Afro-Oriental family Corbiculidae. The North American Sphaeriidae
include three genera: Sphaerium with 12 species, Pisidium with 25 species, and Eupera
with one species. The genera Sphaerium and Pis-idiwn are world-wide in distribution
and occur in all North American states and provinces. Eupera is restricted to the
Western Hemisphere: northern South America, Central America arid the southern
Coastal Plain of eastern North America.
Although characters of soft anatomy are used in taxonomy of the Sphaeriacea, especially
in the classification at the generic level and above, all taxa can be identified readily
by characters of the shells, and such shell characters are particularly important in
distinguishing the species. The main feature of this publication is an illustrated
taxonomic key using shell characters for identification of the 39 species of North
American Sphaeriacea.
17a. Descriptors
*Aquatic fauna, *Freshwater, *Mollusks, *Pelecypods, *Clams,
Preservation, Distribution,
nb.identifiers *identification Manual, *Illustrated key, *Sphaeriacea, *North America,
Species List, Collection,
17c. COWRR Field & Group
18. Availability
IDA
19. Security Class.
(Report)
20. Security Class.
(Page)
Abstractor J. B. Burch
21. No. of
Pages
22. Price
Send To:
WATER RESOURCES SCIENTIFIC INFORMATION CENTER
U.S. DEPARTMENT OF THE INTERIOR
WASHINGTON, D. C. 20240
institution The University of Michigan
WRSIC 102 (REV. JUNE 1971)
ft U. S. GOVERNMENT PRINTING OFFICE : 1972 O - 467-103
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