The creeper is widespread throughout most of the eastern half of the United States through the southern edge of Canada, but absent in Florida, Georgia, and South Carolina. Drainages where it is found include the Interior basin from central Texas to Lake Winnipeg, Canada, and the Canadian Interior basin in the Nelson River from western Ontario to Saskatchewan. In the upper Atlantic drainage it is found in the upper Savannah river system of South Carolina. This species is also found in the St. Lawrence river system and Nova Scotia.
In Michigan this species is widespread throughout river systems in both the upper and lower peninsulas. (Burch, 1975)
Strophitus undulatus is found in a wide range of habitats, from headwaters to pools to larger streams. It is probably more scarce in lower reaches of rivers, and is generally absent from land-locked lakes. (Cummings and Mayer, 1992; van der Schalie, 1938; Watters, 1995)
The creeper is up to 10.2 cm (4 inches) long. Headwater specimens are generally smaller than those found in larger creeks. The shell is elliptical or oval and ranges from being thin to fairly thick in older individuals. The anterior end is broadly rounded and the posterior end is bluntly pointed or truncated. The dorsal margin is rounded and the ventral margin is straight to slightly curved.
Umbos are low and raised only slightly above the hinge line. The beak sculpture has three to five v-shaped ridges.
The periostracum (outer shell layer) is green with rays, and brown to black in older individuals.
On the inner shell, the left valve has a pseudocardinal tooth which is mainly a thickening of the hinge line. The tooth is located under the beak. The right valve has a similar thickening of the hinge line, with the tooth anterior to the beak. Lateral teeth are absent.
The beak cavity is shallow. The nacre is cream colored or salmon in the center and bluish-white on the outer margin.
In Michigan, this species can be confused with the cylindrical papershell or giant floater. The cylindrical papershell in general is more cylindrical. The creeper has a beak sculpture that is more coarse. In general, the creeper generally has a more truncated posterior end than the giant floater. The hinge on the creeper is also generally thicker and has a more concentric beak sculpture. (Cummings and Mayer, 1992; Oesch, 1984; Watters, 1995)
Fertilized eggs are brooded in the marsupia (water tubes) up to 11 months, where they develop into larvae, called glochidia. The glochidia are then released into the water where they must attach to the gill filaments and/or general body surface of the host fish. After attachment, epithelial tissue from the host fish grows over and encapsulates a glochidium, usually within a few hours. The glochidia then metamorphoses into a juvenile mussel within a few days or weeks. After metamorphosis, the juvenile is sloughed off as a free-living organism. Juveniles are found in the substrate where they develop into adults. (Arey, 1921; Lefevre and Curtis, 1910; Oesch, 1984)
Increasing water temperatures stimulates male mussels to produce sperm and release it into the water column, where it is taken up by nearby females.
Age to sexual maturity for this species is unknown. Unionids are gonochoristic (sexes are separate) and viviparous. The glochidia, which are the larval stage of the mussels, are released live from the female after they are fully developed.
In general, gametogenesis in unionids is initiated by increasing water temperatures. The general life cycle of a unionid, includes open fertilization. Males release sperm into the water, which is taken in by the females through their respiratory current. The eggs are internally fertilized in the suprabranchial chambers, then pass into water tubes of the gills, where they develop into glochidia.
Strophitus undulatus is a long-term brooder. Gravid females were observed on the Huron River from late July to the end of May. Glochidia are likely released at the end of May. (Lefevre and Curtis, 1912; van der Schalie, 1938; Watters, 1995)
Females brood fertilized eggs in their marsupial pouch. The fertilized eggs develop into glochidia. There is no parental investment after the female releases the glochidia.
The age of mussels can be determined by looking at annual rings on the shell. However, no demographic data on this species has been recorded.
Mussels in general are rather sedentary, although they may move in response to changing water levels and conditions. Although not thoroughly documented, the mussels may vertically migrate to release glochidia and spawn. (Oesch, 1984)
The middle lobe of the mantle edge has most of a bivalve's sensory organs. Paired statocysts, which are fluid filled chambers with a solid granule or pellet (a statolity) are in the mussel's foot. The statocysts help the mussel with georeception, or orientation.
Mussels are heterothermic, and therefore are sensitive and responsive to temperature.
Unionids in general may have some form of chemical reception to recognize fish hosts. How the creeper recognizes its fish host is not known.
Glochidia respond to both touch, light and some chemical cues. In general, when touched or a fluid is introduced, they will respond by clamping shut. (Arey, 1921; Brusca and Brusca, 2003; Watters, 1995)
In general, unionids are filter feeders. The mussels use cilia to pump water into the incurrent siphon where food is caught in a mucus lining in the demibranchs. Particles are sorted by the labial palps and then directed to the mouth. Mussels have been cultured on algae, but they may also ingest bacteria, protozoans and other organic particles.
The parasitic glochidial stage absorbs blood and nutrients from hosts after attachment. Mantle cells within the glochidia feed off of the host’s tissue through phagocytocis. (Watters, 1995)
Unionids in general are preyed on by muskrats, raccoons, minks, otters, and some birds. Juveniles are probably also fed upon by freshwater drum, sheepshead, lake sturgeon, spotted suckers, redhorses, and pumpkinseeds.
Unionid mortality and reproduction is affected by unionicolid mites and monogenic trematodes feeding on gill and mantle tissue. Parasitic chironomid larvae may destroy up to half the mussel gill. (Cummings and Mayer, 1992; Watters, 1995)
Fish hosts are determined by looking at both lab metamorphosis and natural infestations. Looking at both is necessary, as lab transformations from glochidia to juvenile may occur, but the mussel may not actually infect a particular species in a natural situation. Natural infestations may also be found, but glochidia will attach to almost any fish, including those that are not suitable hosts. Lab transformations involve isolating one particular fish species and introducing glochidia either into the fish tank or directly inoculating the fish gills with glochidia. Tanks are monitored and if juveniles are later found the fish species is considered a suitable host.
Strophitus undulatus glochidia are unique in that they may metamorphose without the use of a fish host. However, the glochidia have also metamorphosed on several species of fish in lab trials. No natural infestations on fish have been recorded. Species of fish that the S. undulatus glochidia have metamorphosed on include: channel catfish, black bullhead, yellow bullhead, burbot, plains killifish, bluegill, pumpkinseed, black crappie, white crappie, green sunfish, rock bass, smallmouth bass, largemouth bass, common shiner, common stoneroller, river chub, creek chub, blacknose dace, longnose dace, northern redbelly dace, bluntnose minnow, fathead minnow, spotfin shiner, sand shiner, spottail shiner, central mudminnow, banded darter, fantail darter, rainbow darter, Iowa darter, johnny darter, slenderhead darter, logperch, blackside darter, yellow perch, walleye and brook stickleback. (Hillegass and Hove, 1997; Hove, et al., 1997; van Snik Gray, et al., 1999; Watters, et al., 1998)
Creeper glochidia have been found on: channel catfish, black bullhead, yellow bullhead, burbot, plains killifish, bluegill, pumpkinseed, black crappie, white crappie, green sunfish, rock bass, smallmouth bass, largemouth bass, common shiner, common stoneroller, river chub, creek chub, blacknose dace, longnose dace, northern redbelly dace, bluntnose minnow, fathead minnow, spotfin shiner, sand shiner, spottail shiner, central mudminnow, banded darter, fantail darter, rainbow darter, Iowa darter, johnny darter, slenderhead darter, logperch, blackside darter, yellow perch, walleye and brook stickleback.
Mussels are ecological indicators. Their presence in a water body usually indicates good water quality.
There are no significant negative impacts of mussels on humans.
Strophitus undulatus is synonomous (same species, but with a former different name) with S. rugosus.
Renee Sherman Mulcrone (author).
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
uses smells or other chemicals to communicate
an animal that mainly eats decomposed plants and/or animals
particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
union of egg and spermatozoan
a method of feeding where small food particles are filtered from the surrounding water by various mechanisms. Used mainly by aquatic invertebrates, especially plankton, but also by baleen whales.
mainly lives in water that is not salty.
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
fertilization takes place within the female's body
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death
photosynthetic or plant constituent of plankton; mainly unicellular algae. (Compare to zooplankton.)
an animal that mainly eats plankton
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
breeding is confined to a particular season
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
movements of a hard surface that are produced by animals as signals to others
uses sight to communicate
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
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