A - B - C - D - E - F - G - H - I - J - L - M - N - O - P - Q - R - S - T - U - V

A

ad hoc - to establish for a specific purpose or situation

algae - a large group of primarily aquatic plants that usually contain chlorophyll but lack the true roots, stems, and leaves that are characteristic of more complex plants

anatomy - the structure of a plant or animal

anterior end - the shorter end of the shell as measured from the umbo; also considered the front end

aquatic ecosystems - basic ecological unit composed of living and non-living elements interacting in an aqueous environment

B

beak - the raised part of the dorsal margin of the shell; also called the umbo

beak cavity - the depression or pocket on the inside of each valve leading into the beak

beak sculpture - the raised loops, ridges, or bumps on the umbo

benthic - the bottom of a river, lake, or ocean where the water meets the surface of the accumulated sediments

bivalve - a mollusk with a shell that consists of two symmetrical valves

brail or crow foot drag bar - an approximately 8' foot long piece of wood or metal with chains hanging down.  At the end of each chain are several 4-pronged hooks with knobs on each prong (like small grappling hooks).  As the bar is dragged along the bottom of the river, mussels close on the hooks, thus allowing collection of large numbers of mussels without diving.

brood pouch or marsupium - portion of female mussel's gill where larvae develop into glochidia

byssal thread - one or more fibers secreted from a gland in juvenile mussels. Allows attachment to a substrate such as large sand grains, rocks, or even other mussels, thereby anchoring the mussel and preventing it from being swept away by current. In zebra mussels, the adults maintain their byssal threads which allows them to attach to hard substrates (rocks, shells, boats, docks, etc.).

C

calcium carbonate - the primary mineral that comprises the shell of a mollusk

channelization - the straightening and/or deepening of a river channel

chevron - a V-shaped marking

clam - common name frequently used to refer to certain freshwater bivalves (i.e., fingernail clams and the Asiatic clam). Differs from a mussel in that anterior and posterior lateral and cardinal teeth are present

clammer or sheller - a person who harvests mussels

compressed - flattened or pressed together laterally

concentric - having a common center

conglutinate - a number of glochidia bound together with mucus

contaminant - an impurity in the environment that may be toxic to sensitive organisms

cultured pearl - a pearl that was purposely developed through human intervention

D

digestive tract - the series of animal tissues that physically and chemically transform food for assimilation

distal - away from the center or origin

diversity - the total number of species that occupy an area

dorsal - referring to the top part of the shell where the hinge is located

E

ecosystem - an interdependent group of plants and animals and the physical environment where they exist

elliptical - having the form of an ellipse, or oval

elongate - long or extended

endangered - a species faced with the danger of extinction

extinct - a species that no longer exists

extirpated - a species that has been eliminated from a particular area, but still exists somewhere else

exotic - from another part of the world; foreign

extinction - the processes that cause all members of a species to die

extracted - removed from

F

fauna - a collective group animals, particularly those of a certain region or time

G

glochidia - term for freshwater mussel larvae that possess little or no automotive abilities that are ready to be released from the female mussel and usually attach to a vertebrate host for continued life cycle development

glochidium - the larva of a freshwater mussel (Superfamily Unionoidea) that generally lives as a temporary parasite on a host fish; a mussel larva that is microscopic, many species require a fish as a host for development to a juvenile

growth lines - darkened lines on the surface of the shell indicating periods of rest during growth

H

harvest - the take or consumption of a renewable natural resource by humans

hermaphrodite - an animal or plant having both male and female reproductive organs

hinge - the joint of the shell of a bivalve mollusk

host fish - one or more species of fish whose tissues and body fluids meet the developmental needs of a particular mussel species during its parasitic glochidial life stage

I

impoundment - a man-made reservoir built from what was once part of a free-flowing river

inflated - swollen or expanded

interdentum - a flattened area between the pseudocardinal and lateral teeth

introduced - brought in and established in a new place or surroundings

iridescent - exhibiting rainbow colors

J

juvenile -the life history stage after the larval stage but before the adult stage

L

larvae - the embryonic life-cycle stages that follow the fertilization of an egg of a metamorphic animal

lateral teeth - the elongated teeth along the hinge line of the shell of a bivalve mollusk

larva - the newly hatched, immature form of an animal that undergoes metamorphosis, differing markedly in form or appearance from the adult

left valve - the left half of the shell when the dorsal edge or hinge is facing up and the anterior end is directed forward (away from the collector)

ligament - a group of tough, fibrous tissues that are attached to the shell of a bivalve mollusk and which expand and contract to open and close the shell

locomotion - the self-propelled movement of an organism from one location to another

M

mantle - a tissue lining the inside of a mussel shell that encloses the viscera and secretes new shell material from its edges for continued shell growth

marsupium - the portion of the gills of a female mussel that contain glochidia

metamorphosis - a marked change in the form or structure of an animal occurring after birth or hatching (verb. metamorphose)

micrometer - a metric unit of linear measurement equivalent to one-thousandth of a millimeter or one-millionth of a meter, it is the common dimension used to measure the length of glochidia and juvenile mussels

midden - an accumulation of visually dead mussel shells that suggests a prior living community

mollusk - a member of the phylum Mollusca, a group of marine and freshwater invertebrates with soft tissues that are protected by a hard shell composed of one or more parts

mortality - death

mussel - a marine or freshwater species with an elongated shell; common name frequently used to refer to freshwater mussels. Differs from a clam in that either anterior or posterior lateral teeth are present, but not both.

mussel bed - a dense, natural aggregation of mussels which can support a diverse variety of benthic fauna

N

nacre - the inner-most layer of shell that often has a pearl-like appearance

naiad - a freshwater mussel

navigation channel - an artificially maintained waterway that ensures a minimum water depth to allow unimpeded passage for a variety of vessels

nuclei - the central core of an object that forms the basis for its future development

nucleus -  the center around which things are formed.  Beads made from the shell of freshwater mussels are used as the center around which oysters lay nacre to form a cultured pearl

O

oblong - having the shape of or resembling a rectangle or ellipse

opalescent - exhibiting a milky iridescence like that of an opal

ovate - egg-shaped

ovisac - membranous capsule containing glochidia

overexploitation - excessive consumption of a renewable natural resource at a rate that cannot be maintained due to a dwindling reproductive population

P

pallial line - a linear depression on the inside of the shell

parasite - an organism that grows, feeds, and is sheltered on or in a different organism (host) while contributing nothing to the survival of the host

parasitic - characteristic of an organism that grows, feeds, and is sheltered on or in a different organism (the host) while contributing nothing to the survival of the host

periostracum - the outside layer or covering of the shell

plankton - microscopic aquatic plants and animals that depend chiefly upon currents for their movements

planktonic - exhibiting movements characteristic of plankton

plications - folds

pollywogging - wading in the water to find mussels

posterior end - the longer end of the shell as measured from the umbo; also considered the back end; also the end with the siphons, usually sticking above the stream bottom

posterior ridge - the ridge on the back half of the valve running from the umbo to the posterior ventral edge

posterior slope - the area along the dorsal part of the shell between the posterior ridges of the valves

propagate - human supervised plant or animal breeding

pseudocardinal teeth - the triangular, often serrated, teeth located on the anterior-dorsal part of the shell

pustule - a bump or raised knob on the outside surface of the shell

Q

quadrate - square

R

right valve - the right half of the shell when the dorsal edge or hinge is facing up and the anterior end is directed forward (away from the collector)

S

secretion - a non-waste substance that is derived and released from tissue cells for a specific purpose

sedentary - a lifestyle characterized by little or no movement, thus remaining in one area

sediments - a complex mixture of materials transported by flowing water that eventually settles and accumulates

serrated - notched or grooved

shell margin - the circumference of a valve outline when laid flat; also known as the edge

sheller - see clammer

sheen - a glistening brightness

siltation - deposition of fine mineral particles (silt) on the beds of streams or lakes

solid - thick or heavy

spawn - to deposit sperm or eggs into the water

species - a group of biologically distinct organisms that are self-perpetuating

striated - marked with lines or grooves

substrate - soil on the river's bottom

sulcus - a shallow depression or furrow on the outside surface of the shell

T

threatened - a species likely to become endangered

toxic - harmful, poisonous, deadly

transform - metamorphosis in which a parasitic glochidia matures physiologically and releases itself from the host fish to live independently as a juvenile mussel

translocate - to displace or cause to move from one location to another

truncate - having the end shortened or squared off

tubercle - a small mineralized lump or nodule that protrudes on the outer surface of the shell

U

umbo - the inflated dorsal part of the shell; also called the beak

unionid - refers to freshwater mussels in the order Unionoida. “Unio” is latin for pearls.

V

valve - one of the two halves of the shell of a bivalve mollusk

veligers - term for the planktonic larvae of the zebra mussel

ventral - referring to the bottom edge of the shell