Animal Diversity Web

Ge­o­graphic Range

Chlamy­do­con­cha or­cutti is found along the west coast of North Amer­ica (East­ern Pa­cific), from north­ern Cal­i­for­nia (Shell Beach, Sonoma Co. (38.4°N)), south to Punta San Pablo, Baja Cal­i­for­nia Sur (27.2°N). (Carl­ton, 1979; Coan, et al., 2000)

• Biogeographic Regions
• pacific ocean
  • native

Habi­tat

This species oc­curs near shore, from the in­ter­tidal zone to 40m depth. It was nor­mally found under rocks, crawl­ing or an­chored by byssal threads. Some­times it can also be found within kelp hold­fasts. (Carl­ton, 1979; Coan, et al., 2000)

• Habitat Regions
• temperate
• saltwater or marine

• Aquatic Biomes
• benthic
• coastal

• Range depth

  0 to 40 m

  0.00 to 131.23 ft

Phys­i­cal De­scrip­tion

Chlamy­do­con­cha or­cutti is one of the most pe­cu­liar look­ing clams, com­monly known as the “naked clam”. In large adults (see re­pro­duc­tion sec­tion for more in­for­ma­tion about dwarf males) the shells are highly re­duced and com­pletely em­bed­ded in the en­larged, translu­cent white man­tle. The shells grow mostly an­te­ri­orly and have lit­tle pos­te­rior growth, re­sult­ing in an elon­gated, lance­o­late shape. The prodis­so­conch (rudi­men­tary lar­val shell) is often clearly de­mar­cated. (Mor­ton, 1981)

The man­tle is greatly thick­ened and fused, form­ing an “en­ve­lope” that en­closes the shells. The an­te­rior man­tle open­ing acts as the in­halant path­way for the an­i­mal and a pos­te­rior siphon forms the ex­ha­lent open­ing. The dor­sal-lat­eral sur­face of the man­tle ex­hibits many white papil­lae that are re­tractable into pits. The papil­lae have var­i­ous spher­i­cal in­clu­sions that act as se­cre­tory tubules. Those papil­lae may have a chem­i­cal de­fense func­tion pro­tect­ing the an­i­mal from its preda­tors. A group of unique papil­lae also ex­ists be­hind the an­te­rior man­tle open­ing, form­ing an anemone-like disc struc­ture known as the pheromone organ. (Mor­ton, 1981; Rouse, 2011)

Chlamy­do­con­cha or­cutti has a very large and mus­cu­lar foot that en­ables it to crawl around very ac­tively; to­gether with the thick­ened man­tle, they give this an­i­mal an ap­pear­ance of a sea slug rather than a clam. Rouse, 2011 is a video of two live spec­i­mens in cap­tiv­ity– have a look for your­self! (Rouse, 2011)

• Other Physical Features
• ectothermic
• heterothermic
• bilateral symmetry

• Sexual Dimorphism
• female larger
• sexes shaped differently

• Range length

  4 to 13.5 mm

  0.16 to 0.53 in

De­vel­op­ment

The fer­til­ized eggs are brooded in man­tle cav­i­ties of fe­males, then re­leased as veliger lar­vae. No de­tailed stud­ies have been done on the de­vel­op­ment of this species. How­ever, stud­ies on species from the same su­per­fam­ily show that early cleav­age to lar­val re­lease may take 12-29 days, or even up to 2 months. The veligers feed on the plank­ton and meta­mor­pho­sis into ju­ve­niles. (Jes­persen and Lützen, 2006)

• Development - Life Cycle
• metamorphosis

Re­pro­duc­tion

Chlamy­do­con­cha or­cutti has two very dif­fer­ent adult body forms. Large in­di­vid­u­als as de­scribed above are typ­i­cally her­maph­ro­ditic. They pos­sess both fe­male and male re­pro­duc­tive or­gans and both can be func­tional, al­though some­times one sex may be much more de­vel­oped than the other. How­ever, tiny sex­u­ally ma­ture “dwarf” males are often pre­sent. They are sig­nif­i­cantly smaller than the large her­maph­ro­ditic adults and can­not live by them­selves. Dwarf males are typ­i­cally found in­side man­tle cav­i­ties of large in­di­vid­u­als, at­tached by byssal threads. Their shells have promi­nent prodis­so­conchs and are also cov­ered with ex­tended man­tle tis­sue. (Mor­ton, 1981)

Chlamy­do­con­cha or­cutti is a protan­dric se­quen­tial her­maph­ro­dite. In the pres­ence of large con­specifics, plank­tonic larva may meta­mor­phose di­rectly into dwarf male forms, but this is not a per­ma­nent stage. If en­vi­ron­men­tal con­di­tions allow, dwarf males can sub­se­quently de­velop into large her­maph­ro­ditic body form. The evol­lu­tion of dwarf male morphs may rep­re­sent adap­ta­tion to small pop­u­la­tion sizes and iso­lated dis­tri­b­u­tions. (Mor­ton, 1981; Ó Foighil, 1985)

Dwarf males or her­maph­ro­ditic large adults re­lease sper­ma­to­zoa that are taken up by the in­cur­rent siphon of the egg-pro­duc­ing part­ner. The eggs are fer­til­ized and in­cu­bated in the suprabranchial cham­ber of the fe­male/her­maph­ro­dite. (Mor­ton, 1981)

• Key Reproductive Features
• sequential hermaphrodite
  • protandrous
• sexual
• fertilization
  • internal
• ovoviviparous

Chlamy­do­con­cha or­cutti are brood­ers, i.e., fer­til­ized eggs and de­vel­op­ing em­bryos are pro­tected in­side the man­tle cav­ity until they are re­leased as free-liv­ing plank­tonic lar­vae. (Mor­ton, 1981)

• Parental Investment
• pre-hatching/birth
  • protecting
    • female

Lifes­pan/Longevity

Most Chlamy­do­con­cha or­cutti adult in­di­vid­u­als were ob­served in fall and win­ter (Au­gust to Jan­u­ary, oc­ca­sion­ally in April), with pop­u­la­tion peaks about Oc­to­ber. Lifes­pan of this species is not de­ter­mined, but the clam could prob­a­bly live for sev­eral years. (Carl­ton, 1979; Mor­ton, 1981)

Be­hav­ior

Chlamy­do­con­cha or­cutti nor­mally at­taches to the bot­tom of rocks, how­ever when de­tached, it can crawl and move ac­tively with it's large, mus­cu­lar foot. (Mor­ton, 1981)

• Key Behaviors
• sedentary

Com­mu­ni­ca­tion and Per­cep­tion

The pheromone organ de­scribed above is sug­gested to be se­cre­tory and might be used to at­tract and guide males. (Bernard, 1897; Mor­ton, 1981)

• Communication Channels
• chemical

• Other Communication Modes
• pheromones

• Perception Channels
• chemical

Food Habits

Chlamy­do­con­cha or­cutti is a sus­pen­sion feeder, it gath­ers food par­ti­cles from the water col­umn by pass­ing cur­rent through its cteni­dia (“gills”). Fil­tered ma­te­r­ial trav­els within food grooves to the mouth. (Mor­ton, 1981)

• Primary Diet
• planktivore

• Animal Foods
• zooplankton

• Other Foods
• detritus

• Foraging Behavior
• filter-feeding

Pre­da­tion

Spe­cific preda­tors of Chlamy­do­con­cha or­cutti are not iden­ti­fied, but it could be po­ten­tially be pre­dated by a spec­trum of ben­thic preda­tors if they can have ac­cess to it. Chlamy­do­con­cha or­cutti nor­mally hides under rocks; papil­lae on the man­tle of the clam are likely to be chem­i­cal de­fen­sive or­gans that pro­tect the an­i­mal from its preda­tors. (Mor­ton, 1981)

Ecosys­tem Roles

Very lit­tle is known about the ecol­ogy of this species, or its eco­log­i­cal re­la­tion­ships with other species.

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

There are no known pos­i­tive ef­fects of Chlamy­do­con­cha or­cutti on hu­mans.

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

There are no known ad­verse ef­fects of Chlamy­do­con­cha or­cutti on hu­mans.

Con­ser­va­tion Sta­tus

Very lit­tle is known about the pop­u­la­tion sta­tus of this species. It does not re­ceive any spe­cial legal pro­tec­tion.

• IUCN Red List

  Not Evaluated

• US Federal List

  No special status

• CITES

  No special status

Con­trib­u­tors

Jingchun Li (au­thor), Spe­cial Pro­jects, George Ham­mond (ed­i­tor), An­i­mal Di­ver­sity Web Staff.

Ref­er­ences

Bernard, F. 1897. Note prélim­i­naire sur Chlamy­do­con­cha Or­cutti Dall, Lamel­li­branche à co­quille in­terne. Bul­letin du Muséum d'His­toire Na­turelle, 3: 65-67.

Carl­ton, J. 1979. Chlamy­do­con­cha or­cutti Dall: re­view and dis­tri­b­u­tion of a lit­tle-known bi­valve. Veliger, 21: 375-378.

Coan, E., P. Valen­tich-Scott, F. Bernard. 2000. Bi­valve Seashells of West­ern North Amer­ica. Santa Bar­bara: Santa Bar­bara Musuem.

Jes­persen, Å., J. Lützen. 2006. Re­pro­duc­tion and sperm struc­ture in Ga­le­om­mati­dae (Bi­valvia, Ga­le­om­ma­toidea). Zoomor­phol­ogy, 125: 157-173.

Mor­ton, B. 1981. The bi­ol­ogy and func­tional mor­phol­ogy of Chlamy­do­con­cha or­cutti with a dis­cus­sion on the tax­o­nomic sta­tus of the Chlamy­do­con­chacea (Mol­lusca: Bi­valvia). Jour­nal of Zo­ol­ogy, Lon­don, 195: 81–121.

Rouse, G. 2011. "Chlamy­do­con­cha" (On-line). Ac­cessed Au­gust 19, 2011 at http://​www.​youtube.​com/​watch?​v=Kr7m_​OSzwV8.

Ó Foighil, D. 1985. Form, func­tion and ori­gin of tem­po­rary dwarf males in Pseudopy­thina rugifera (Car­pen­ter, 1864) (Bi­valvia: Ga­le­om­mat­acea). Veliger, 27: 245–252.