Freshwater Mussels of Florida

Glossary

Glossary accessory denticle – a small, compressed or triangular prominence on the hinge plate anterior or posterior to pseudocardinal teeth. adductor muscle – a large muscle attached internally to shell valves, located dorsally, one each near the anterior and posterior ends of the hinge plate, which serve to draw the two valves together. allopatric – distributional relationship in which the ranges of two species do not overlap . Compare with sympatric. Ambleminae, amblemine – a subfamily of the Unionidae as recognized by Ortmann (1911); typically characterized by well-developed hinge dentition, no mantle modification anterior to the incurrent aperture, marsupia formed by all four or only the outer two gills, glochidia without styliform hooks; type genus Amblema. anadromous – pertaining to the movement of animals from a salt water environment to freshwater for the purpose of spawning. angular – having a corner where two edges meet; not rounded. annulus (annuli, pl.) – a ring; a line in the shell or periostracum, often visible as a dark line in the periostracum, and frequently presumed to be annual in occurrence; sometimes referred to as a growth ring or rest. Anodontinae, anodontine – a subfamily of the Unionidae as recognized by Ortmann (1911); typically characterized by reduced or absent hinge dentition, no mantle modification anterior to the incurrent aperture, marsupia restricted to outer gills, and glochidia with styliform hooks; type genus Anodonta. anteriodorsal – of or relating to the upper portion of the anterior end. anterior – of or relating to the front or forward portion, typically the end nearer the umbo in Unionoida. anterior shell margin – refers herein to the portion of shell lying forward of the umbo extending downward to the ventral margin. anterioventral – of or relating to the lower portion of the anterior end. anthropogenic – of, relating to, or involving the impact of humans on nature. aperture – an opening between opposing mantle membranes (within each valve of a member of Unionoida) through which water is drawn or expelled from the mantle cavity; sometimes erroneously referred to as a siphon. apex – a narrowed or pointed end. apophysis – a small, triangular, downward protruding shell structure on the anterior septum of Mytilopsis valves, which serves as a muscle attachment. aragonite – one of two crystalline forms of calcium carbonate. arborescent – divided distally into multiple branches; treelike in form. arcuate – curved or bent; in the shape of a bow. augmentation – an action to increase the size of an existing population. basin – a stream that empties directly into the marine environment (e.g., Escambia River basin and Econfina Creek basin). Compare with drainage. biangulate – possessing two angles. bifid – divided distally into two approximately equal parts. bifurcate – to divide into two branches or parts. Glossary 420 binomial – a biological name consisting of two terms (genus and species). bioturbation – the disturbance of sediments by organismal activity. Bivalvia – a class of the phylum Mollusca, in which the primary diagnostic characteristic is two opposing valves; formerly Pelecypoda. blackwater – water rich in humic acids and with low nutrient concentrations. brackish – having salinity content intermediate between fresh and sea water. broadcast – to release or scatter in all directions. brood – to maintain eggs, embryos, and/or glochidia in the marsupia. brooding period – the interval during which eggs, embryos, and glochidia are held in the marsupia of unionids; also called gravid period. byssal thread, byssus – a tough, proteinaceous thread used to anchor a bivalve to a hard substrate, secreted by the byssal gland in the base of the foot; often occur in bundles (e.g., Dreissena polymorpha) but are single in Unionoida; not homologous to larval threads of glochidia. calcareous – consisting of or containing calcium carbonate. calyculate – growth variation of the umbo, typical of Musculium born at or near the end of summer, yielding a caplike appearance. captive propagation – production of individuals in an artificial environment. cardinal teeth – hinge teeth positioned between two sets of lateral teeth, which serve to stabilize opposing valves; found in some marine and freshwater families, including Cyrenidae and Sphaeriidae. caruncle – a fleshy protuberance found on the posterioventral mantle margins of female Toxolasma; used to attract glochidial hosts. channelization – the process of straightening and removing obstructions in the course of a stream. chevron – a marking shaped like a wide-angled “V,” usually inverted. chitin, chitinous – hard, amorphous polysaccharide that comprises the covering of some invertebrates; the material forming the ligament of bivalve mollusks. chondrophore – a deep pit or depression on the hinge plate ventral to the umbo. cilium (cilia, pl.) – a small, hairlike process extending from cells, such as those on gills, labial palps, foot, and mantle surfaces, which transports water...