Calyptogena magnifica

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.

Communication Channels: chemical

Perception Channels: infrared/heat ; tactile ; chemical

This species is not under any protection status.

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

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.

Development - Life Cycle: metamorphosis ; indeterminate growth

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

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.

Positive Impacts: research and education

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.

Mutualist Species:

• sulfur-metabolizing bacteria

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.

Other Foods: microbes

Foraging Behavior: filter-feeding

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.

Biogeographic Regions: pacific ocean (Native )

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.

Average depth: 2000 m.

Habitat Regions: saltwater or marine

Aquatic Biomes: oceanic vent

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.

Average lifespan
Status: wild: 25 years.

Typical lifespan
Status: wild: 3.5 to 25 years.

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.

Range length: 10 to 26 cm.

Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry

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.

Known Predators:

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

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.

Mating System: polygynandrous (promiscuous)

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.

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.

Key Reproductive Features: year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal )

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.

Parental Investment: pre-fertilization (Provisioning)

Calyptogena magnifica – Veneroida būrio dvigeldžių moliuskų rūšis. Gyvena vandenynų dugne, 2500 m gylyje, prie karštųjų versmių.

Užauga iki 30 cm ilgio ir yra kur kas didesnė už giminingas rūšis. Kiautas porcelianiškai baltas. Virškinimo sistema pakitusi. Minta žiaunose gyvenančių ir sierą oksiduojančių bakterijų tiekiama energija. Dėl sieros oksidacijos nuo moliusko sklinda nemalonus kvapas. Organizmo vidus ryškiai raudonas dėl hemoglobino, kuris greičiausiai palengvina deguonies įsisavinimą.