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Organs of elephant-ear mussels and other mussels are usually tentacle mechanoreceptors or chemoreceptors. The osphradium, a clump of cells below the posterior adductor muscle, may also help with chemical sensitivity or in measuring the water's turbidity. Other sense organs, located mainly on the edge of their mantle, are involved with touch, chemical sense, and balance (statocysts). However, they are poorly developed.
In a way, females communicate with host fish during the development of their offspring. Some may cluster their larvae together in a way that attracts fish searching for food in order to give the offspring a better chance to attach to the fins or gills.
Communication Channels: visual ; tactile ; chemical
Perception Channels: polarized light ; tactile ; chemical
Elephant-ear mussels have endangered status in Minnesota, Missouri and Wisconsin, and considered threatened in Illinois.
CITES: no special status
State of Michigan List: no special status
The development of mussels like elephant-ears is fairly complex. Once an egg has been fertilized inside a female, it transforms into a larval stage, called a glochidium. The glochidia develop into juveniles while attached to host fish. Juveniles are a small form of adults and begin to grow when they break free from the host and fall to the substrate. The mantle of their shells works to produce new shell material that is continually added to the last. The umbo is the oldest part of the shell, and layers of shell are added to it.
Development - Life Cycle: metamorphosis
There are no known negative economic effects of elephant-ear mussels.
Mussels in general may remove unwanted toxins from the water as they filter feed. Their presence or absence can provide an indication of the health of the water system for their own species and others. Studying mussels like elephant-ears provides a better understanding of aquatic life systems and how they adapt. Mussels do not get cancer, and studies may be beneficial to combat this disease. Mussels were used to make tools by native Americans and were likely a food source as well. Thicker-shelled unionids were harvested for the button industry in the 20th century, and more recently are harvested for the pearl industry.
Positive Impacts: body parts are source of valuable material; research and education
When a number of elephant-ear mussels live close together, they can form mussel beds which provide important habitat for some fish and aquatic worms or insects. They also clean the water around them while filter feeding, giving other organisms more a more habitable environment. During reproduction, elephant-ear mussels use skipjack herring (Alosa chrysochloris) as a host for their larvae. Although the mussel larvae live on herring gills for nutrients until they mature to the next stage of development, they do not harm the fish in the process.
The introduction of zebra mussels (Dreissena polymorpha) brought an exotic parasite to elephant-ear mussels Elliptio crassidens and their habitat. Zebra mussels reproduce very quickly, much faster than native species, and in greater numbers. Along with taking up native mussel habitat, zebra mussels also attach hard surfaces, such as the shells of elephant-ear or other mussel species, hindering their natural behaviors and physiology.
Ecosystem Impact: creates habitat; parasite
Species Used as Host:
Commensal/Parasitic Species:
Like other mussels, elephant-ear mussels are filter feeders. Water and food particles are collected by hair-like cilia pulling water through ostia (pores) and into their gills. Food is trapped in a structure called the gill filament and motion from cilia move the food in a string of mucous toward the digestive system. They may feed on bacteria, protozoans, algae, plankton.
Animal Foods: zooplankton
Plant Foods: algae; phytoplankton
Other Foods: detritus ; microbes
Foraging Behavior: filter-feeding
Primary Diet: planktivore
Elliptio crassidens has a wide range in the U.S. in midwestern, eastern and some southern states and a portion of Canada. In the U.S., it inhabits the Escambia and Apalachicola River drainages in the Florida panhandle, Alabama, Florida, Georgia, Illinois, Indiana, Kentucky, Louisiana, Minnesota, Mississippi, Missouri, Ohio, Tennessee, Virginia, West Virginia and Wisconsin. In Canada, it is found in Quebec and Ontario. This species is thought to be completely lost from Iowa, Oklahoma and Pennsylvania.
Biogeographic Regions: nearctic (Native )
Elephant-ear mussels live in mud, sand, gravel and rocky substrates (commonly limestone). They inhabit waters with moderate to swift currents in large creeks, rivers, or sometimes channels.
Average depth: 0.5 - 3.0 m.
Habitat Regions: temperate ; freshwater
Aquatic Biomes: benthic ; rivers and streams
Other Habitat Features: riparian
Mussels in general can be very long-lived, from 20 to even 100 years. There are no specific longevity data for elephant-ear mussels.
Elephant-ear mussels have heavy, thick, triangular shells. The shell is smooth. When they are younger, their outer shells are a reddish-brown with light green rays and vary from brown to black as adults with no rays. The inner shell is purple, although a few have been seen with pink or white. The shape of the shell can be compressed to somewhat inflated with a rounded anterior and more pointed posterior. The dorsal margin has a gentle curve. The ventral margin, although curved in younger mussels, becomes straight as the mussels age.
Other physical features include a low umbo (the oldest part of the shell), beak sculpture with two or three loops parallel to the growth lines (which may or may not be visible as the mussels age), a shallow beak cavity, pseudocardinal teeth, lateral teeth and sharp, prominent posterior ridge. Three well developed pseudocardinal teeth in total are present, two in the left valve and one in the right valve. The lateral teeth are also well developed, but are short, rough and straight.
It is difficult to distinguish between males and females of the species. However, at times a female will have an outer gill that is much thicker than the inner gill, and the outer gill is her brood chamber for developing embryos.
Range length: 15 (high) cm.
Average length: 10 cm.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: sexes alike
Like other freshwater mussels, elephant-ears have muscular foot and adductor muscles as anti-predator adaptations. Their foot can help anchor them into the substrate to prevent them from being taken away by the current or tugged free by an animal attempting to eat it. The adductor muscles help keep their shell closed tightly. Their hard shell also helps them avoid predation by providing a sort of camouflage with the rocks and ground around them and a hard-to-crack outer covering to protect their delicate inner tissues. Common predators include otters (Lontra canadensis), raccoons (Procyon lotor), muskrats (Ondatra zibethicus), herons and egrets (Ardeidae), and various fish (Actinoptergygii).
Known Predators:
Anti-predator Adaptations: cryptic
Elephant ear mussels are "tachytictic", so their breeding season is short. Males fertilize the female eggs by releasing their sperm into the water from a structure called the suprabranchial chamber. If the sperm reaches a nearby female, it is pulled through her incurrent siphon to her outer gills, or brood pouch.
Mating System: polygynandrous (promiscuous)
Once the eggs are fertilized, they develop into the larval, or glochidial stage in the female's outer gills. In this stage, the larvae have only grown to about the size of dust particles. The female may react to the presence of a fish or other external cue and then release the glochidia through an excurrent siphon. The offspring attach to a host's gills or fins with their valves, which develops a protective cyst. After living on fish for several weeks as parasites, the juvenile clams break free and fall to bottom of the river. The juveniles then burrow into the substrate and develop into adult mussels.
Breeding interval: Elephant-ear mussels breed once yearly (or less often).
Breeding season: Elephant-ear mussels breed from April or May to June or July.
Range number of offspring: 100's to 1000's.
Range time to independence: A few weeks to A few months.
Range age at sexual or reproductive maturity (female): 4 to 6 years.
Range age at sexual or reproductive maturity (male): 4 to 6 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal )
Male elephant-ear mussels only release sperm for fertilization and do not have any involvement in their growth or development. After eggs have been fertilized in the female and have grown into the larval glochidia form, the larvae receive nutrients from the mother and may stay in her gills that way for a few weeks to a few months. However, the mother provides no further parental care once they are released to host fish.
Parental Investment: pre-hatching/birth (Provisioning: Female, Protecting: Female)
Elliptio crassidens, the elephant-ear, is a species of freshwater mussel, an aquatic bivalve mollusk in Unionidae, the river-mussel family.
The elephant-ear possesses a thick triangular shell which may be up to six inches long. The outside of the shells is brown or black while the inside is typically light purple. It usually is found in the mud, sand, or fine gravel of large rivers.[3] This mussel is found in the midwestern, eastern, and some southern states of the United States as well as the provinces of Quebec and Ontario in Canada.[4]
Elephant-ears typically breed once a year. Breeding seasons are short, lasting from either April through May or June to July. Both males and females reach sexual maturity at four to six years. Larvae stay in their mother's gills anywhere from a few weeks to a few months. Eventually, the offspring will attach to a host fish's fins or gills. After living parasitically on the host fish for several weeks, juvenile clams break free and fall to bottom of the river where they burrow and develop into adult mussels. The mussels will not likely move more than a few meters from this site throughout their lives. Elephant-ears are filter feeders, consuming primarily bacteria, protozoans, algae, and plankton. Common predators include otters, raccoons, muskrats, herons, egrets, and a variety of fish.[4] Like other mussels, elephant-ears are thought to be long-lived, with lifespans from 20 to as long as 100 years.
Although widespread, elephant-ears are relatively rare in the Midwest, but are locally abundant in some parts of the Ohio and White rivers of Illinois and Indiana.[5] Elephant-ear mussels are listed as endangered in Minnesota, Missouri, Wisconsin,[4] Ohio[6][7] and Virginia,[8]: 3 and are considered threatened in Illinois.[4]
Elliptio crassidens, the elephant-ear, is a species of freshwater mussel, an aquatic bivalve mollusk in Unionidae, the river-mussel family.
The elephant-ear possesses a thick triangular shell which may be up to six inches long. The outside of the shells is brown or black while the inside is typically light purple. It usually is found in the mud, sand, or fine gravel of large rivers. This mussel is found in the midwestern, eastern, and some southern states of the United States as well as the provinces of Quebec and Ontario in Canada.
Elephant-ears typically breed once a year. Breeding seasons are short, lasting from either April through May or June to July. Both males and females reach sexual maturity at four to six years. Larvae stay in their mother's gills anywhere from a few weeks to a few months. Eventually, the offspring will attach to a host fish's fins or gills. After living parasitically on the host fish for several weeks, juvenile clams break free and fall to bottom of the river where they burrow and develop into adult mussels. The mussels will not likely move more than a few meters from this site throughout their lives. Elephant-ears are filter feeders, consuming primarily bacteria, protozoans, algae, and plankton. Common predators include otters, raccoons, muskrats, herons, egrets, and a variety of fish. Like other mussels, elephant-ears are thought to be long-lived, with lifespans from 20 to as long as 100 years.
Although widespread, elephant-ears are relatively rare in the Midwest, but are locally abundant in some parts of the Ohio and White rivers of Illinois and Indiana. Elephant-ear mussels are listed as endangered in Minnesota, Missouri, Wisconsin, Ohio and Virginia,: 3 and are considered threatened in Illinois.
象耳貝（學名：Elliptio crassidens）是蚌科小方蚌亚科Pleurobemini族之下Elliptio屬的一個淡水雙殼綱軟體動物的物種，生長於北美洲的河流。
象耳貝有一對厚重的三角形外殼，可長達15厘米。殼的外圍棕色或黑色，殼裡淺紫色。常見於大河流的泥灘、沙灘或細礫石灘裡[3]。
本物種分佈於美國中西部、東部及部分南部州份，也見於加拿大安大略省及魁北克省[1][4]。
儘管本物種分佈廣泛，本物種在美國中西部相對比較罕見；但在俄亥俄州部分地區及伊利諾州與印第安納州的白河流域卻比較豐富[5]。在明尼蘇達州、密蘇里州及威斯康星州，本物種被列為受威脅[4][3]。
象耳貝一般每年繁殖一次。繁殖季節短，從4-5月到6-7月。雄性和雌性物種都在出生4到6年後達至性成熟。 幼蟲會逗留於母親的鰓各處，從數星期到數個月不等。然後，幼體會離開母體，尋找宿主並黏附於宿主的鰭或鰓成長。經過在宿主上數星期的寄生生活，幼蚌可回復自由，從宿主身上脫落，落到河床上再挖洞成長。終其一生，象耳貝的移動範圍都不會超過其棲洞的數公尺範圍。象耳貝的寄生階段對牠們的成長至關重要，多項研究都表明淡水蚌類的幼蟲都要寄生在魚類的體表或鰓上，才能發育成為幼貝：1913年，美國爱荷华州基奥卡克的密西西比河上建了一座水電大壩，令到在河中象耳貝幼蟲所寄生的金綠西鯡（亦作墨西哥灣西鯡）的消失，使象耳貝及其他以這種魚寄生的蚌類停止繁殖[6][7][8]。
雖然象耳貝在幼蟲期會寄生在魚上，但成蚌後牠們也是Lophotaspis interiora Ward & Hopkins, 1931的宿主[2]。
象耳貝是濾食者，主要以細菌、原生動物、藻類和浮游生物等較小型的食物[9]為食。常見的捕食者包括水獺、浣熊、麝鼠、鷺、白鷺和各種魚類[4]。 跟其他蚌類一樣，象耳貝的壽命很長，從20年100年不等。
象耳貝（學名：Elliptio crassidens）是蚌科小方蚌亚科Pleurobemini族之下Elliptio屬的一個淡水雙殼綱軟體動物的物種，生長於北美洲的河流。
象耳貝有一對厚重的三角形外殼，可長達15厘米。殼的外圍棕色或黑色，殼裡淺紫色。常見於大河流的泥灘、沙灘或細礫石灘裡。
