Calyptogena magnifica

Geographic Range

Discovered in 1977, the vesicomyid clam Calyptogena magnifica populates the deep-sea hydrothermal vent areas of the East Pacific Rise and the Galapagos Rift. Only a handful of scientists have studied this species, and it has yet to be found elsewhere. (Boss and Turner, 1980; Terwilliger, et al., 1983; Van Dover, 2000)

Habitat

Calyptogena magnifica thrives in the lush areas surrounding hydrothermal vents. Using the foot and byssal threads as an anchor, these organisms pack, or clump, themselves in the crevices of basalt on the ocean floor. These clumps are termed “clambakes.” Within the cracks, there is a low flow of warm, carbon dioxide and hydrogen sulfide rich vent water, no sunlight, over a thousand atmospheres of pressure, and a temperature of about 10-15 degrees Celsius (C). The visceral mass of the animal experiences a temperature of about 2-4 degrees C, due to its location above the foot. The siphons of the clam are used to tap into the ambient oxygen and carbon dioxide above the valves. Population density increases with increasing concentrations of hydrogen sulfide. (Boss and Turner, 1980; Cary and Giovannoni, 1993; Powell and Somero, 1986)

  • Average depth
    2000 m
    6561.68 ft

Physical Description

Calyptogena magnifica is a heterodont bivalve that can reach 26 cm in length. The valves are white and fairly elliptical in shape, and individuals grow an average of 4 cm per year. This species has the basic bivalvian body plan, with a few unique features. Most notable are the communities of sulfur-oxidizing chemolithotrophic bacterial symbionts within the gills and other tissues. The bacteria produce organic carbon and nitrogen, which serve as nutrition for the clam. As a result, the digestive system and labial palps of the bivalve are extremely reduced, and the foot and gills are highly vascularized to better facilitate gas exchange and hydrogen sulfide uptake. The visceral mass is a conspicuous red color due to intracellular hemoglobin, and the circulatory system is about 44% of the clam’s weight. (Boss and Turner, 1980; Jones, 1983; Powell and Somero, 1986; Terwilliger, et al., 1983)

  • Range length
    10 to 26 cm
    3.94 to 10.24 in

Development

Calyptogena magnifica larvae are lecithotrophic, and nonplanktonic. Larvae are free-swimming and rely solely on their stored yolk reserves for energy. Once contacting a substrate, the larvae metamorphoses into the adult form. This species has indeterminate growth, as the shell of the bivalve grows in annual, evident increments. (Cary and Giovannoni, 1993; Jones, 1983; Van Dover, 2000)

Reproduction

Once sexually mature, Calyptogena magnifica gametes are released into the environment continuously and in small numbers by all individuals. Egg cells range from 105-195 micrometers, and the heads of sperm cells are about 3 micrometers in diameter. Fertilization results from any successful union of an egg cell and a sperm cell. Therefore, mating is random and results in high gene flow and genetic variability. (Berg, 1985; Boss and Turner, 1980)

Calyptogena magnifica is a sessile bivalve species. Sexes are separate (dioecious) and fertilization is external and non-specific. Once clams are greater than 6 cm in length (between 1 and 4 years old) they begin maturing sexually, and by 9-10 cm long they are considered ripe. The gonads then start filling, and complete sexual maturity is reached at 12-14 cm. Since environmental stimuli are largely absent, spawning is continuous and takes place between the ages of 3 and 15. Thus, breeding occurs year round. Large clams remain almost fully ripe, as only a small proportion of gametes are released at any one time. Although dispersal distance is limited, this species has no problem effectively dispersing gametes from individuals throughout its range. (Berg, 1985; Van Dover, 2000)

  • Breeding interval
    Calyptogena magnifica spawns year round.
  • Range age at sexual or reproductive maturity (female)
    1 to 4 years
  • Range age at sexual or reproductive maturity (male)
    1 to 4 years

Due to the newness of vent invertebrate studies, very little is known about the degree of parental involvement in Calyptogena magnifica. The yolk reserves of the lecithotrophic larvae are the only known maternal support the offspring receive. (Berg, 1985; Cary and Giovannoni, 1993; Van Dover, 2000)

  • Parental Investment
  • pre-fertilization
    • provisioning

Lifespan/Longevity

Calyptogena magnifica individuals can survive anywhere from 3.5 to approximately 25 years. The hydrothermal vents where they anchor themselves last only tens of years, so strong colonization abilities are favored over longevity since adults are non-motile. The shell of the bivalve grows in annual increments, which makes it possible to determine the age. (Jones, 1983; Van Dover, 2000)

  • Average lifespan
    Status: wild
    25 years
  • Typical lifespan
    Status: wild
    3.5 to 25 years

Behavior

Calyptogena magnifica is a sessile and marginally motile organism. Typically its foot is deep in the mud and the siphon extends out toward the overlying water. The foot is highly vascularized and extends; it functions in taking in sulfide and transporting it through the blood to the sulfur-metabolizing bacteria. (Childress, et al., 1993; Hart and Blusztajn, 1998)

Communication and Perception

Calyptogena magnifica has a synchronized but not always consistent release of sperm and eggs. The males detect an increase in water temperature and release sperm through their exhalant siphons. In response, the females release eggs from their exhalant siphons when a threshold of sperm or associated chemicals is detected. However, the water current must be slow for the females to detect the high concentration of chemical cues. If either or both conditions are not met, the females will not release their eggs. The neurotransmitter serotonin is commonly responsible for the stimulation of the release and re-initiation of meiosis in the oocyctes and may be one of the chemical cues responsible for egg release in C. magnifica. Calyptogena magnifica has an inhalant siphon that is used to sense the chemical environment from the incoming flow of water. (Fujikura, et al., 2007; Krylova and Sahling, 2005; Micheli, et al., 2002)

Food Habits

Calyptogena magnifica suspension-feeds on particles rich in nitrogen and lipid compounds present in the hydrothermal fluid. It also receives nutrients through a symbiotic relationship with sulfur-metabolizing bacteria that are located on the outer region of its gill tissue. (Grassle, 1985)

  • Other Foods
  • microbes

Predation

Direct predation of Calyptogena magnifica has been observed by mobile grazers such as small gastropods, amphipods, and crabs. These predators consume newly settled larvae and juveniles. At the same time, indirect predation has also been observed by the removal of bacterial film on rocks by these mobile grazers. Without the bacterial film on rocks, larvae lose the marker that indicates where to settle during development. Large epibenthic predators such as zoarcid fish, Thermarces cerberus, indirectly aid in decreasing the mortality of sessile invertebrates, such as C. magnifica, by feeding on small mobile grazers. Also, the tissue in C. magnifica is considered unpalatable to predators when hydrogen sulfide is released from the sulfide-metabolizing bacterial symbiont on the gill tissue. Once an adult, these clams have a thick shell that provides a structural defense against predators. (Kicklighter, et al., 2004; Micheli, et al., 2002)

  • Known Predators
    • Deep sea vent gastropods
    • Deep sea vent amphipods
    • Brachyuran crab, Bythograea thermidron

Ecosystem Roles

Calyptogena magnifica has a mutualistic relationship with sulfur-metabolizing bacteria located on its gill tissue, foot, and mantle. It depends on these sulfur-metabolizing bacteria to receive its nutrients from the rich hydrogen sulfide environment of the hydrothermal vent. The bacteria located on the outer layer of the foot and mantle also provide peripheral defense by detoxifying the sulfide as soon as it enters the body. High molecular weight factors in the blood bind the sulfide tightly to extract the sulfide from the environment. The sulfide is then transported to the bacterial symbiont via circulation. As a result, low concentration of free sulfide is found in the blood, protecting the aerobic respiration of the organisms from poisoning by sulfide due to its sensitivity to cytochrome-c oxidase and the enzymes involved in carbon fixation in the symbiont. (Powell and Somero, 1986)

Mutualist Species
  • sulfur-metabolizing bacteria

Economic Importance for Humans: Positive

The shells of Calyptogena magnifica can be used to study the thermal and chemical history of hydrothermal vent systems in the mid-ocean ridge and volcanic activity through a time series. By measuring the strontium/calcium ratio and the annual growth rate observed on the shell, the hydrothermal vent temperature can be studied over time and used to evaluate eruptions that may have occurred. Also, its shells are composed of calcium carbonate and will dissolve at a rate dependent on shell mineralogy, shell microstructure, and proximity to hydrothermal vent fluids. The rate of shell dissolution provides information in determining the longevity of hydrothermal vent activity along the rise axis. (Hart and Blusztajn, 1998; Kennish and Lutz, 1999)

  • Positive Impacts
  • research and education

Economic Importance for Humans: Negative

There are no known adverse effects of Calyptogena magnifica on humans.

Conservation Status

This species is not under any protection status.

Contributors

Mary Lee (author), The College of New Jersey, Deanna Tarquinio (author), The College of New Jersey, Keith Pecor (editor), The College of New Jersey, Renee Mulcrone (editor), Special Projects.

Glossary

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

bilateral symmetry

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.

chemical

uses smells or other chemicals to communicate

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

filter-feeding

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.

heterothermic

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.

indeterminate growth

Animals with indeterminate growth continue to grow throughout their lives.

infrared/heat

(as keyword in perception channel section) This animal has a special ability to detect heat from other organisms in its environment.

internal fertilization

fertilization takes place within the female's body

metamorphosis

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.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oceanic vent

Areas of the deep sea floor where continental plates are being pushed apart. Oceanic vents are places where hot sulfur-rich water is released from the ocean floor. An aquatic biome.

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

sedentary

remains in the same area

sessile

non-motile; permanently attached at the base.

Attached to substratum and moving little or not at all. Synapomorphy of the Anthozoa

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

year-round breeding

breeding takes place throughout the year

References

Berg, C. 1985. Reproductive strategies of mollusks from abyssal hydrothermal vent communities. Bulletin of the Biological Society of Washington, 6: 185-197.

Boss, K., R. Turner. 1980. The giant white clam from the Galapagos Rift, Calyptogena magnifica species novum. Malacologia, 20(1): 161-194.

Cary, S., S. Giovannoni. 1993. Transovarial inheritance of endosymbiotic bacteria in clams inhabiting deep-sea hydrothermal vents and cold seeps. Proceedings of the National Academy of Sciences of the United States of America, 90: 5695-5699. Accessed October 19, 2012 at http://www.pnas.org/content/90/12/5695.full.pdf+html.

Childress, J., C. Fisher, J. Favuzzi, A. Arp, D. Oros. 1993. The role of a zinc-based, serum-borne sulfide-binding component in the uptake and transport of dissolved sulfide by the chemoautotrophic symbiont-containing clam Calyptogena elongata. The Journal of Experimental Biology, 179: 131-158. Accessed October 20, 2012 at http://jeb.biologists.org/content/179/1/131.short.

Fujikura, K., K. Amaki, J. Barry, Y. Fujiwara, V. Furushima, R. Iwase, H. Yamamoto, T. Maruyama. 2007. Long-term in situ monitoring of spawining behavior and fecundity in Calyptogena spp. Marine Ecology Progress Series, 333: 185-193.

Grassle, J. 1985. Hydrothermal vent animals: distribution and biology. Science, 229(4715): 713-717.

Hart, S., J. Blusztajn. 1998. Clams as recorders of ocean ridge volcanism and hydrothermal vent field activity. Science, 280(5365): 883-886.

Jones, D. 1983. Sclerochronology: reading the record of the molluscan shell. American Scientist, 71(4): 384-391. Accessed October 20, 2012 at http://www.jstor.org/stable/10.2307/27852138.

Kennish, M., R. Lutz. 1999. Calcium carbonate dissolution rates in deep-sea bivalve shells on the East Pacific Rise at 21°N: results of an 8-year in-situ experiment. Palaeogeography, Palaeoclimatology, Palaeoecology, 154(4): 293-299. Accessed October 20, 2012 at http://www.sciencedirect.com/science/article/pii/S0031018299001029.

Kicklighter, C., C. Fisher, M. Hay. 2004. Chemical defense of hydrothermal vent and hydrocarbon seep organisms: a preliminary assessment using shallow-water consumers. Marine Ecology Progress Series, 275: 11-19. Accessed October 20, 2012 at http://smartech.gatech.edu/bitstream/handle/1853/34063/2004_Hay_MEPS_002.pdf?sequence=1.

Krylova, E., H. Sahling. 2005. Recent bivalve molluscs of the genus Calyptogena (Vesicomyidae). Journal of MolluscanStudies, 72(4): 359-395. Accessed October 20, 2012 at http://mollus.oxfordjournals.org/content/72/4/359.full.pdf+html.

Michael, J., R. Lutz. 1999. Calcium carbonate dissolution rates in deep-sea bivalve shells on the East Pacific Rise at 21 deg N: results of an 8-year in-situ experiment. Palaeogeography, Palaeoclimatology, Palaeoecology, 154: 293-299.

Micheli, F., C. Peterson, L. Mullineaux, C. Fisher, S. Mills, G. Sancho, G. Johnson, H. Lenihan. 2002. Predation structures communities at deep-sea hydrothermal vents. Ecological Monographs, 72(3): 365–382. Accessed January 03, 2013 at http://micheli.stanford.edu/pdf/69-Michelietal2002EcolMonog.pdf.

Powell, M., G. Somero. 1986. Adaptations to sulfide by hydrothermal vent animals: sites and mechanisms of detoxification and metabolism. The Biological Bulletin, 171: 274-290. Accessed October 20, 2012 at http://www.biolbull.org/content/171/1/274.full.pdf+html.

Terwilliger, R., N. Terwilliger, A. Arp. 1983. Thermal vent clam (Calyptogena magnifica) hemoglobin. Science, 219(4587): 981-983.

Van Dover, C. 2000. The ecology of deep-sea hydrothermal vents. Princeton, NJ: Princeton University Press.