Overview

Comprehensive Description

At hot vents only. The life habit of the adult is semiepibiotic on bare basalt, living in cracks and crevices from which hydrothermal fluids emanate; early life history stages are often encountered living within basaltic rubble associated with such warm cracks and crevices. The presence of this species is correlated with elevated levels of hydrogen sulphide. The soft tissue is coloured dark red when retrieved living due to the presence of intracellular hemoglobin. The thick and large gills contain sulfur oxidizing chemoautotrophic symbionts. The large rugose foot is often seen protruding when the clams are viewed in life position.
  • BOSS K. & R. TURNER (1980) Malacologia 20: 161-194.

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Distribution

Entire Northern East Pacific Rise and Southern East Pacific Rise: 21°N to 22°S; Galapagos Spreading Center. ARP A. J., CHILDRESS J.J. & C.J. FISHER (1984) Physiol. l Zool. 57: 648-662.
  • BOSS K. & R. TURNER (1980) Malacologia 20: 161-194.

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Physical Description

Morphology

Boss and Turner (1980) described the anatomy of the species. Below is a summary of their observations:

Mantle: Pedal aperture large. Middle mantle fold with short papillae. Short, separate incurrent and excurrent siphons formed by fusion of the inner mantle folds.

Foot: Large, with byssal groove and gland, but no byssal threads produced by adult specimens.

Gills: Large, flat (non-plicate), with inner and outer demibranchs displaying both lamellae. Formed by filaments of identical morphology (homorhabdic).

Digestive tract: Labial palps very small. Rectum passes through the pericardial cavity and the ventricle of the heart.

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Shell very large, variable, oval to elongate-oval in outline, inequilateral and equivalve, usually without gape; valves white, entirely aragonitic; periostracum present, but frequently eroded away on older portions of shell; umbos prosogyrous, sometimes partially enrolled; lunule and escutcheon variable, present or absent; ligament external, opisthodetic, and parivincular; foot strong and rugose, with byssal gland.
  • BOSS K. & R. TURNER (1980) Malacologia 20: 161-194.

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Size

Shell length up to 263 mm.
  • BOSS K. & R. TURNER (1980) Malacologia 20: 161-194.

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Diagnostic Description

Shell white, brittle, elongate-ovate, with the right and left valves equal in size, outline and inflation (equivalve). Umbones at the anterior third, with the beaks poorly defined. Periostracum brown, dehiscent (absent from the older portions of the shell). External sculpture of irregular commarginal growth increments generally restricted to the margins of the shell flank. Internal surface and margins smooth. Pallial sinus absent. Ventral surface of the hinge plate with a series of small scars. Ligament external, supported by nymphal ridges, extending along most of the postero-dorsal margin of the shell. Hinge teeth represented by irregular cardinals; lateral teeth absent.

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Ecology

Habitat

Depth range based on 21 specimens in 1 taxon.
Water temperature and chemistry ranges based on 21 samples.

Environmental ranges
  Depth range (m): 2451 - 2632.5
  Temperature range (°C): 1.823 - 2.075
  Nitrate (umol/L): 35.653 - 41.112
  Salinity (PPS): 34.663 - 34.674
  Oxygen (ml/l): 2.461 - 3.601
  Phosphate (umol/l): 2.483 - 2.812
  Silicate (umol/l): 126.871 - 161.139

Graphical representation

Depth range (m): 2451 - 2632.5

Temperature range (°C): 1.823 - 2.075

Nitrate (umol/L): 35.653 - 41.112

Salinity (PPS): 34.663 - 34.674

Oxygen (ml/l): 2.461 - 3.601

Phosphate (umol/l): 2.483 - 2.812

Silicate (umol/l): 126.871 - 161.139
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

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Molecular Biology and Genetics

Molecular Biology

Barcode data: Calyptogena magnifica

The following is a representative barcode sequence, the centroid of all available sequences for this species.


There are 12 barcode sequences available from BOLD and GenBank.  Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.  See the BOLD taxonomy browser for more complete information about this specimen and other sequences.

GGAGTTTTAGGAGAT---AGTCATTTGTACCAGGTAGTGGTTACTGCACATGGTTTGTTGATGATTTTCTTCTTAGTAATGCCGATGATGATTGGGGGTTTTGGGAATTGATTAGTACCTTTAATG---TTGCAAATTCCTGATATGGCTTTTCCACGGATGAATAATTTAAGATTTTGGTTAATACCTAGGTCGGTTTTAATGCTTCTTGGCTCTGCTTATGTAGAGAGTGGGGCAGGTACTGGTTGAACTATTTATCCCCCATTGTCTAGTATTATAGGGCATGCTGGTCCATCTGTAGATTTT---GTAATTTTGTCTCTTCATTTAGGTGGCGTGTCTTCTATTTTGGCTTCAATTAATTTTGTTGTTACTTCTCTTTGTATGCGTGTTGAAGCTTTATCGTTATTGCGTGTGACTATGTTTGTTTGATGTGTTGCTGTCACTGGATTTTTACTGATTATTGCTATACCTGTCTTGGCTGGGAGA---TTAACAATACTATTAACTGATCGTAATTTTAATACTAGTTTTTTTGATCCTGCTGGGTTGGGGGATCCTATTCTCTTTGGGCATTTGGTTTGATTTTTTGGACACCCTGAGGTTTATATTTTGATTTTACCTGGATTTGGGATTATTTCCCACGTGATTAAAGTTGGGAGGAGAAAGCTT---GAATTGTTTGGAAAAGTTCCTATAATTTATGCTGTTTTATCTATTGGATTTTTAGGGTTTATTGTTTGG
-- end --

Download FASTA File
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Statistics of barcoding coverage: Calyptogena magnifica

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 12
Specimens with Barcodes: 12
Species With Barcodes: 1
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Source: Barcode of Life Data Systems (BOLD)

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Wikipedia

Calyptogena magnifica

Calyptogena magnifica is a species of giant white clam found clustered around hydrothermal vents at abyssal depths in the Pacific Ocean.

Contents

Description

The systematics 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.[2]

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 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 263 millimetres (10.4 in). 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 gills are large and thick and the visceral mass is red due to the haemoglobin in the blood.[2]

Distribution

Calyptogena magnifica was first described by Kenneth Boss and Ruth Turner of Harvard's Museum of Comparative Zoology, in 1980, following its discovery during research dives by the submersible vehicle DSV Alvin to the floor of the Pacific Ocean in 1977 and 1979. The location of the thermal vent where it was found was approximately 200 miles (320 km) west of Punta Mita, Mexico at a depth of 2,645 metres (8,678 ft).[2] Further deep water exploration shows that it is present at other thermal vents on the East Pacific Rise 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.[3]

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). The animal can move around on the sea floor with its muscular foot and usually takes up a vertical position rather than lying flat.[2]

Calyptogena magnifica is specially adapted to life round hydrothermal vents by the chemosymbiotic bacteria it harbours in its gills which oxidize hydrogen sulfide seeping from the vents. The clam absorbs nutrients produced by these bacteria rather than photosynthetically derived products and no longer has guts.[4]

Little is known of the reproduction and life cycle of Calyptogena magnifica but examination of specimens brought up from the deep showed numerous large oocytes with yolks in various stages of development among the visceral mass.[2] 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.[3] 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.[4]

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. Shrimps and octopuses were also observed in the vicinity.[2]

References

  1. ^ Tran, Bastien (2010). "Calyptogena magnifica Boss & Turner, 1980". World Register of Marine Species. http://www.marinespecies.org/aphia.php?p=taxdetails&id=464366. Retrieved 2012-04-14.
  2. ^ a b c d e f Boss, K. J.; Turner, R. D. (1980). "The giant white clam from the Galapagos Rift, Calyptogena magnifica species novum". Malacologia 20 (1): 161–194. 
  3. ^ a b Deep-Sea Vent Clams Monterey Bay Aquarium Research Institute. Retrieved 2012-04-15.
  4. ^ a b Hydrothermal vents Deep Ocean. Retrieved 2012-04-15.
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