''Calyptogena magnifica'' is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...

of giant white

clam Clam is a common name for several kinds of bivalve molluscs. The word is often applied only to those that are edible and live as infauna, spending most of their lives halfway buried in the sand of the seafloor or riverbeds. Clams have two shel ...

found clustered around

hydrothermal vent A hydrothermal vent is a fissure on the seabed from which geothermally heated water discharges. They are commonly found near volcanically active places, areas where tectonic plates are moving apart at mid-ocean ridges, ocean basins, and hotspo ...

s at abyssal depths in the Pacific Ocean.

Description

The

systematics Biological systematics is the study of the diversification of living forms, both past and present, and the relationships among living things through time. Relationships are visualized as evolutionary trees (synonyms: cladograms, phylogenetic t ...

of the family Vesicomyidae is unclear because of the small number of specimens collected, the variability between specimens of the same species and their wide dispersal in isolated, deep water locations. The morphology of ''Calyptogena magnifica'' resembles another member of the genus, '' Calyptogena elongata'', the type locality of which is several hundred miles further north. ''C elongata'' is only known from three small specimens and the size of mature individuals is unknown. The two valves of ''Calyptogena magnifica'' are oval or slightly kidney-shaped and about two times as long as they are high. The umbones are towards the anterior end of the valve and the growth rings are most noticeable near the margins. The shell material is thick and the exterior is white and usually chalky in appearance. The

periostracum The periostracum ( ) is a thin, organic coating (or "skin") that is the outermost layer of the shell of many shelled animals, including molluscs and brachiopods. Among molluscs, it is primarily seen in snails and clams, i.e. in gastropods ...

is yellowish brown, wrinkled and loose. The ligament is external and there are several U-shaped cardinal hinge teeth on each valve. The largest specimen so far collected has a valve length of . The mantle is an iridescent purplish pink and there is a large pink protrudible foot divided into two portions. The two separate siphons are short and do not extend beyond the edge of the valves. The pallial sinus is small. The

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they ar ...

s are large and thick and the visceral mass is red due to the

haemoglobin Hemoglobin (haemoglobin BrE) (from the Greek word αἷμα, ''haîma'' 'blood' + Latin ''globus'' 'ball, sphere' + ''-in'') (), abbreviated Hb or Hgb, is the iron-containing oxygen-transport metalloprotein present in red blood cells (erythrocyte ...

in the blood.

Distribution

''Calyptogena magnifica'' was first described by Kenneth Boss and

Ruth Turner Ruth Dixon Turner (1914 – April 30, 2000) was a pioneering U.S. marine biologist and malacologist. She was the world's expert on Teredinidae or shipworms, a taxonomic family of wood-boring bivalve mollusks which severely damage wooden mari ...

of Harvard's

Museum of Comparative Zoology A museum ( ; plural museums or, rarely, musea) is a building or institution that cares for and displays a collection of artifacts and other objects of artistic, cultural, historical, or scientific importance. Many public museums make thes ...

, in 1980, following its discovery during research dives by the submersible vehicle

DSV Alvin ''Alvin'' (DSV-2) is a crewed deep-ocean research submersible owned by the United States Navy and operated by the Woods Hole Oceanographic Institution (WHOI) in Woods Hole, Massachusetts. The vehicle was built by General Mills' Electronics Gro ...

to the floor of the Pacific Ocean in 1977 and 1979. The location of the thermal vent where it was found was approximately west of

Punta Mita Punta Mita is a private peninsula that is home to the Four Seasons Punta Mita, St. Regis Punta Mita, and 16 sub-communities. Punta Mita is located on the north end of Banderas Bay in the Mexican state of Nayarit, about north of Puerto Valla ...

, Mexico at a depth of . Further deep water exploration shows that it is present at other thermal vents on the

East Pacific Rise The East Pacific Rise is a mid-ocean rise (termed an oceanic rise and not a mid-ocean ridge due to its higher rate of spreading that results in less elevation increase and more regular terrain), a divergent tectonic plate boundary located alon ...

between 21°N and 22°S as well as in the Galapagos Rift. In some locations it is plentiful while in other, apparently suitable habitats, it is not present at all.Deep-Sea Vent Clams
Monterey Bay Aquarium Research Institute. Retrieved 2012-04-15.

Biology

''Calyptogena magnifica'' is assumed to burrow and it is thought the divided foot may be specially adapted for insertion into cracks in hard substrates or among mussels (''

Bathymodiolus thermophilus ''Bathymodiolus thermophilus'' is a species of large, deep water mussel, a marine bivalve mollusc in the family Mytilidae, the true mussels. The species was discovered at abyssal depths when submersible vehicles such as DSV Alvin began explorin ...

''). The animal can move around on the sea floor with its muscular foot and usually takes up a vertical position rather than lying flat. ''Calyptogena magnifica'' is specially adapted to life round hydrothermal vents by the chemosymbiotic bacteria it harbours in its gills which oxidize

hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The under ...

seeping from the vents. The clam absorbs nutrients produced by these bacteria rather than photosynthetically derived products and no longer has guts.Hydrothermal vents
Deep Ocean. Retrieved 2012-04-15. Little is known of the reproduction and life cycle of ''Calyptogena magnifica'' but examination of specimens brought up from the deep showed numerous large

oocyte An oocyte (, ), oöcyte, or ovocyte is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in a female fetus in the ovary during female gametogenesis. The female ...

s with yolks in various stages of development among the visceral mass. Researchers thought this might mean that the clam had poor dispersal abilities but a study using rDNA analysis showed that larvae did in fact disperse to other vents throughout its range. Hydrothermal vents emit hot, sulfur-rich water for several years and then cease to flow. This results in the death of the community surrounding them, and for the continuing existence of their species, there is a need for the larvae of these animals to have dispersed to other existing vents and for them to exploit new vents when they open up.

Ecology

''Calyptogena magnifica'' was found near thermal vents in the deep sea floor where it was part of a rich benthic community. There were considerable numbers of empty shells and a few live individuals in the small area studied. The clams were lodged in crevices among a large number of mussels and some large galatheid crabs were observed walking over the bed of bivalves.

Shrimp Shrimp are crustaceans (a form of shellfish) with elongated bodies and a primarily swimming mode of locomotion – most commonly Caridea and Dendrobranchiata of the decapod order, although some crustaceans outside of this order are ref ...

s and

octopus An octopus ( : octopuses or octopodes, see below for variants) is a soft-bodied, eight- limbed mollusc of the order Octopoda (, ). The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttlefish, ...

es were also observed in the vicinity.

References

{{Taxonbar, from=Q5024690 Vesicomyidae Animals living on hydrothermal vents Molluscs described in 1980 Chemosynthetic symbiosis