Hyperaccumulation of Elements in Marine Organisms

High accumulation of vanadium by a fan worm Pseudopotamilla occelata

Pseudopotamilla occelata belonging to a fan worm (Annelids) live in a shallow water forming a colony. Although it is well-known that ascidians concentrate V in blood cells,I discovered a new V accumulator. A branchial crown composed of many radioles has a high level of V (5,500 μg/g dry). It was found from the application of AEM to the freeze-dried thin section that V is localized in vacuoles of epidermal cells.

The branchial crown of fan worms is used for feeding and gas exchange.

P. occelata

Branchial crown

Light micrograph of a section of radiole

TEM image of the epidermis of a radiole

V distribution in the epidermis by EPMA
（Arrows indicate a deposits of V)

X-ray spectrum of AEM to vacuoles
（A high level of S coexists in vacuoles）

The result of in vivo XAFS analysis shows that the chemical form of V in living states is an aqua complex of V(III) in a sulfuric acid media (V(SO4)(H2O)4-5⁺)

Physiological roles of V in this species and ascidians remains unknown.
When V reaches to vacuoles, V may lose any biological function.

TEM= transmission electron microscopy, EPMA= electron probe microanalysis
AEM= analytical electron microscopy

｜High accumulation of metals by Bryopsis maxima｜High accumulation of vanadium by a fan worm Pseudopotamilla occelata｜
｜ High accumulation of manganese by a giant clam Tridacna squamosa｜
｜High accumulation of manganese by a marine bivalve Cyclosunetta menstrualis｜High accumulaton of iodine by a strawberry conch shell Strombus luhuanus｜
｜ High accumulation of iron by teeth of mollusks｜High accumulation of metals by an octopus Octopus vulgaris｜

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