Animal Diversity Web

Ge­o­graphic Range

The deer toe is found through­out the Mis­sis­sippi river sys­tem and in the the St. Lawrence sys­tem. Its range ex­tends from west­ern Penn­syl­va­nia to Michi­gan and Min­nesota, south though east­ern Iowa, east­ern Kansas, east­ern Texas, through Louisiana, Al­abama and Ten­nessee.

In the lower penin­sula in west­ern Michi­gan, T. trun­cata is found in the Grand River sys­tem, the Kala­ma­zoo and Black and St. Joseph (Lake Michi­gan) Rivers. In the south­east­ern part of the state it is found in Lake Erie and trib­u­taries, in­clud­ing the Belle, Black, Huron, and Raisin Rivers. (Burch, 1975)

• Biogeographic Regions
• nearctic
  • native

Habi­tat

In Michi­gan, Trun­cilla trun­cata is gen­er­ally found in Lake Erie or the lower stretches of rivers. In gen­eral it is found in lakes and medium to large rivers, usu­ally in mud, sand and/or gravel. (Cum­mings and Mayer, 1992; van der Schalie, 1938; Wat­ters, 1995)

• Habitat Regions
• freshwater

• Aquatic Biomes
• rivers and streams

Phys­i­cal De­scrip­tion

The deer­toe is up to 5.1 cm (2 inches) long , and is tri­an­gu­lar, mod­er­ately in­flated, and fairly thick. The an­te­rior end is uni­formly rounded, the pos­te­rior end bluntly pointed or trun­cated. The dor­sal mar­gin is rounded. The ven­tral mar­gin is broadly rounded, and straight to con­cave to­ward the pos­te­rior end. A shal­low sul­cus is an­te­rior to the pos­te­rior ridge, which is sharply an­gled and promi­nent. Fe­males and males are not as eas­ily dis­tin­guished as other mem­bers of the sub­fam­ily Lamp­sili­nae.

Umbos are promi­nent and raised slightly above the hinge line. The beak sculp­ture is fine, with three to five dou­ble-looped ridges.

The pe­rios­tracum (outer shell layer) is yel­low, green, to yel­low-brown. Usu­ally nu­mer­ous green rays are pre­sent, vary­ing in widths and shape. Rays may be fine bro­ken lines or V-shaped zigzag mark­ings. Older spec­i­mens tend to be more brown.

On the inner shell, the left valve has two pseudo­car­di­nal teeth, which are tall, rough, notched and com­pressed. The two lat­eral teeth are slightly curved, short and stri­ated. The right valve has one erect, tri­an­gu­lar, notched pseudo­car­di­nal tooth. An­te­rior to this tooth is a smaller (lamel­lar) tooth. The one lat­eral tooth is arched, high and stri­ated.

The beak cav­ity is shal­low. Al­though the nacre is white, oc­ca­sion­ally it is has a pink or salmon tint and is iri­des­cent at the pos­te­rior end.

In Michi­gan, this species can be con­fused with the fawns­foot. The fawns­foot is more elon­gated and has a smoother dor­sal ridge. (Cum­mings and Mayer, 1992; Oesch, 1984; Wat­ters, 1995)

• Other Physical Features
• ectothermic
• heterothermic
• bilateral symmetry

• Sexual Dimorphism
• sexes shaped differently

• Range length

  5.1 (high) cm

  2.01 (high) in

De­vel­op­ment

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)

• Development - Life Cycle
• metamorphosis

Re­pro­duc­tion

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.

Trun­cilla trun­cata is a long-term brooder. In the Huron River, it was ravid from early Au­gust to early July. After it re­leases its glochidia in early July, it likely spawns. (Lefevre and Cur­tis, 1912; van der Schalie, 1938; Wat­ters, 1995)

• Key Reproductive Features
• seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• fertilization
  • internal
• viviparous

• Breeding interval

  The deertoe breeds once in the warmer months of the year.

• Breeding season

  In Michigan, the breeding season is probably mid-July to early August.

• Average gestation period

  10 months

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.

• Parental Investment
• pre-fertilization
  • provisioning
• pre-hatching/birth
  • provisioning
    • female

Lifes­pan/Longevity

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.

Be­hav­ior

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)

• Key Behaviors
• parasite
• motile
• sedentary

Com­mu­ni­ca­tion and Per­cep­tion

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. Man­tle flaps in the lamp­si­lines are mod­i­fied to at­tract po­ten­tial fish hosts. How the deer­toe at­tracts and if it rec­og­nizes its fish host is un­known.

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)

• Communication Channels
• chemical

• Perception Channels
• visual
• tactile
• vibrations
• chemical

Food Habits

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. (Arey, 1921; Meglitsch and Schram, 1991; Wat­ters, 1995)

• Primary Diet
• planktivore
• detritivore

• Plant Foods
• algae
• phytoplankton

• Other Foods
• detritus
• microbes

• Foraging Behavior
• filter-feeding

Pre­da­tion

Union­ids in gen­eral are preyed upon 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)

• Known Predators

  • muskrat, Ondatra zibethicus
  • mink, Neovison vison
  • raccoon Procyon lotor
  • otter, Lontra canadensis
  • turtles, Testudines
  • hellbenders, Cryptobranchus
  • freshwater drum, Aplodinotus grunniens
  • sheepshead, Archosargus probatocephalus
  • lake sturgeon, Acipenser fulvescens
  • shortnosed sturgeon, Acipenser brevirostrum
  • spotted suckers, Minytrema melanops
  • common red-horse, Moxostoma
  • catfish, Siluriformes
  • pumpkinseed, Lepomis gibbosus

Ecosys­tem Roles

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.

Lab tri­als have not been con­ducted to de­ter­mine the deer toe's fish host. Nat­ural in­fes­ta­tions were ob­served for fresh­wa­ter drum and sauger, but meta­mor­pho­sis has not been ob­served on ei­ther species. (Wil­son, 1916)

• Ecosystem Impact
• parasite

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

Mus­sels are eco­log­i­cal in­di­ca­tors. Their pres­ence in a water body usu­ally in­di­cates good water qual­ity.

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

There are no sig­nif­i­cant neg­a­tive im­pacts of mus­sels on hu­mans.

Con­ser­va­tion Sta­tus

Trun­cilla donaci­formis is not cur­rently con­sid­ered for con­ser­va­tion sta­tus lists.

• IUCN Red List

  No special status

• US Federal List

  No special status

• CITES

  No special status

Con­trib­u­tors

Renee Sher­man Mul­crone (au­thor).

Ref­er­ences

Arey, L. 1921. An ex­per­i­men­tal study on glochidia and the fac­tors un­der­ly­ing en­cyst­ment. J. Exp. Zool., 33: 463-499.

Br­usca, R., G. Br­usca. 2003. In­ver­te­brates. Sun­der­land, Mass­a­chu­setts: Sin­auer As­so­ci­ates, Inc..

Burch, J. 1975. Fresh­wa­ter unionacean clams (Mol­lusca: Pele­cy­poda) of North Amer­ica. Ham­burg, Michi­gan: Mala­co­log­i­cal Pub­li­ca­tions.

Cum­mings, K., C. Mayer. 1992. Field guide to fresh­wa­ter mus­sels of the Mid­west. Cham­paign, Illi­nois: Illi­nois Nat­ural His­tory Sur­vey Man­ual 5. Ac­cessed Au­gust 25, 2005 at http://​www.​inhs.​uiuc.​edu/​cbd/​collections/​mollusk/​fieldguide.​html.

Lefevre, G., W. Cur­tis. 1912. Ex­per­i­ments in the ar­ti­fi­cial prop­a­ga­tion of fresh-wa­ter mus­sels. Proc. In­ter­nat. Fish­ery Con­gress, Wash­ing­ton. Bull. Bur. Fish­eries, 28: 617-626.

Lefevre, G., W. Cur­tis. 1910. Re­pro­duc­tion and par­a­sitism in the Union­idae. J. Expt. Biol., 9: 79-115.

Meglitsch, P., F. Schram. 1991. In­ver­te­brate Zo­ol­ogy, Third Edi­tion. New York, NY: Ox­ford Uni­ver­sity Press, Inc.

Oesch, R. 1984. Mis­souri na­iades, a guide to the mus­sels of Mis­souri. Jef­fer­son City, Mis­souri: Mis­souri De­part­ment of Con­ser­va­tion.

Wat­ters, G. 1995. A guide to the fresh­wa­ter mus­sels of Ohio. Colum­bus, Ohio: Ohio De­part­ment of Nat­ural Re­sources.

Wil­son, C. 1916. Cope­pod par­a­sites of fresh-wa­ter fishes and their eco­nomic re­la­tions to mus­sel glochidia. Bul­letin of the Bu­reau of Fish­eries, 34: 333-374.

van der Schalie, H. 1938. The naiad fauna of the Huron River, in south­east­ern Michi­gan. Mis­cel­la­neous Pub­li­ca­tions of the Mu­seum of Zo­ol­ogy, Uni­ver­sity of Michi­gan, 40: 1-83.