Chlamydoconcha orcutti

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).

• Biogeographic Regions
• pacific ocean pacific ocean
  • native 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.

• Habitat Regions
• temperate temperate
• saltwater or marine saltwater or marine

• Aquatic Biomes
• benthic benthic
• coastal coastal

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.

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.

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!

• Other Physical Features
• ectothermic ectothermic
• heterothermic heterothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• female larger
• sexes shaped differently

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.

• Development - Life Cycle
• metamorphosis 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.

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.

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.

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

• 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.

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.

• Key Behaviors
• sedentary sedentary

Communication and Perception

The pheromone organ described above is suggested to be secretory and might be used to attract and guide males.

• Communication Channels
• chemical chemical

• Other Communication Modes
• pheromones pheromones

• Perception Channels
• chemical 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.

• Primary Diet
• planktivore planktivore

• Animal Foods
• zooplankton zooplankton

• Other Foods
• detritus detritus

• Foraging Behavior
• filter-feeding 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.

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.

Additional Links

Encyclopedia of Life

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.