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anadromous—ascending
rivers from the sea for breeding
anterior
end—the shorter end of the shell as measured
from the umbo to the margin. In a live animal, the foot extends from this
end, and this end is usually embedded in the substrate
beak cavity—a
cavity that extends into the beak, usually under the pseudocardinal teeth
(Oesch 1995)
biramous—having
two branches
bradytictic—species
with females gravid for long periods, usually becoming gravid in late
summer or early fall and remaining gravid through the spring or early
summer
branchial septa—a
dividing membrane within the gills or associated structures
demibranchs—one-half
of one of the paired gills of a freshwater bivalve (Parmalee and Bogan
1998)
dendritic—resembling
a tree in structure
dorsal margin—the
margin of the shell with the umbo, hinge, and ligament
endemic—restricted
or peculiar to a locality or region
elliptical—oval
elongate—stretched
out
excurrent aperture—an
opening of the mantle at the posterior end of the mussel which expels
water, wastes, glochidia or sperm; may be tube-like; above incurrent aperture
extant—in
reference to a population, present as live individuals in a particular
area
extirpated—in
reference to a population, no longer present as live individuals in a
particular area
fish host—a
species of fish parasitized by the glochidia of a mussel species
foot—a
muscular part of the body used for movement on or within the substrate;
extends from antero-ventral shell area
glochidia—the
parasitic life stage of a freshwater mussel
gravid—condition
when glochidia or young mussels are present in the gills
growth rests—a
ridge formed during an intermediate stage of growth when this area was
the edge of the shell (Clarke 1981)
hermaphroditic—an
individual that has both male and female sexual organs (Clarke 1981).
hinge line—the
dorsal edge where the two valves of a shell meet; connected by the hinge
ligament
incurrent aperture—an
opening of the mantle at the posterior end of the mussel which brings
water and other resources into the body of the mussel; may be tube-like;
below excurrent aperture
interdental projection—a
"tooth" that juts out from the interdentum
interdentum—the
area between the pseudocardinal and lateral teeth
iridescent—a
play of colors producing rainbow effects (as in a soap bubble)
lateral teeth—the
long blade-like structures along the hinge line of each valve and closest
to the posterior end of the shell
left valve—the
shell half on the left side when the hinge is facing up and the anterior
end is directed forward (away from you)
mantle—the
folds or lobes of the body wall of a mollusk that lines the shell and
bears shell-secreting glands; the number of lobes or folds varies by species.
marsupium—structures
for enclosing or carrying eggs or young
nacre—the
inner surface of the shell
obovate—ovate
with the narrower end basal
pallial line—a
linear impression on the inner surface of the shell, parallel to the ventral
margin, the line of attachment of the mantle muscles.
papillae—small
finger-like sensory projections associated with the outer margins of the
apertures, and in some species, associated with the outer margins of the
mantle.
periostracum—the
external surface of the shell
plications—parallel
ridges
posterior end—the
longer end of the shell as measured from the umbo to the margin. In a
live animal, the siphons extend from this end.
posterior ridge—a
ridge along the external surface of the shell extending from the umbo
to the posterio-ventral margin.
pseudocardinal
teeth—the compact, often triangular, tooth like structures along
the hinge line of each valve and closest to the anterior end of the shell.
rays—streaks
or lines of color on the external surface of the shell.
right valve—the
right half of the shell when the hinge is facing up and the anterior end
is directed forward (away from you)
sexually dimorphic—a
condition in which males and females of the same species are morphologically
different, usually indicated in unionoids by an expanded posterior marsupial
area in the female in contrast to a more pointed or bluntly rounded area
in the male. (Parmalee and Bogan 1998)
shell—the
hard outer covering of the mussel.
subovate—less
than ovate
suprabranchial
chamber—the dorsal portion of the gills
tachytictic—species
with females gravid for short periods, usually late spring or early summer
teeth—the
structures along the hinge line on the inner surface of the shell that
serve to lock the two valves together when the animal closes its shell.
terminus—an
extreme point or element
trapezoidal—a
four sided form having only two sides parallel
umbo—the
raised part at the dorsal margin of each valve, an external structure
valves—one
of the two halves of the shell
vestigial—a
structure that is less fully developed compared with closely related forms
ventral margin—the
bottom edge of the shell, opposite the hinge line
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