From Wikipedia, the free encyclopedia

A vanadocyte is a specialized type of blood cell found in ascidians (tunicates). These cells are notable for their high levels of vanadium (concentrations 107 higher than that of seawater), which is typically a metabolic poison in other contexts. [1] [2]

Structure and description

Vanadocytes are specialized blood cells found in marine tunicates. These cells are 8-13 μm in size and the cytoplasm contains many acidic globules, termed "vanadophores". [3] These cells are one of several types found in the ascidian circulatory system and are abundant in the blood. [2] [1]

The cells are described as highly distinctive, with little variation between species. They have a circular outline that decays into a rosette form upon desiccation, with several inclusions that almost entirely fill the cell. The cell has a greenish color, varying from dark apple to scarcely perceptible, due to their vanadium complexes. [4] [5]

These green cells are not, as was initially believed, symbiotic zooxanthellae, although ascidians are known to have such symbiotes elsewhere. [5]

Chemistry

Vanadocytes are of interest to biologists and chemists because they contain high levels of vanadium and vacuole of sulfuric acid with acid mass fraction as high as 9 wt%, both of which are typically toxic to living creatures. [5] Additionally, the vanadium complex itself is unstable, found almost exclusively in the air-oxidizable, +3 oxidation state. [4]

Function

The function of vanadocytes is still unclear. [1] It has been proposed that the vanadocyte transports and processes nutrients, contributes to the polysaccharide external tunic, or serves as a defense mechanism. It is unlikely that the vanadium complex serves as an oxygen transport mechanism because it is unable to reversibly bind oxygen. [4]

Research into their utility as anti-biofouling ( allelopathic) mechanisms concluded that the high acidity and high vanadium levels function to significantly reduce epizoic recruitment and predation. [6] [7]

References

  1. ^ a b c Michibata, Hitoshi; Uyama, Taro; Ueki, Tatsuya; Kanamori, Kan (15 March 2002). "Vanadocytes, cells hold the key to resolving the highly selective accumulation and reduction of vanadium in ascidians" (PDF). Microscopy Research and Technique. 56 (6): 421–434. doi: 10.1002/jemt.10042. PMID  11921344. S2CID  15127292.
  2. ^ a b STOECKER, DIANE (December 1978). "Resistance of a Tunicate to Fouling". The Biological Bulletin. 155 (3): 615–626. doi: 10.2307/1540795. JSTOR  1540795.
  3. ^ Botte, L.; Scippa, S.; de Vincentiis, M. (September 1979). "Ultrastructural localization of vanadium in the blood cells of Ascidiacea". Experientia. 35 (9): 1228–1230. doi: 10.1007/BF01963306. PMID  488290. S2CID  33061777.
  4. ^ a b c Carlson, Robert (1975). "Nuclear Magnetic Resonance Spectrum of Living Tunicate Blood Cells and the Structure of the Native Vanadium Chromogen". PNAS. 72 (6): 2217–2221. Bibcode: 1975PNAS...72.2217C. doi: 10.1073/pnas.72.6.2217. JSTOR  64680. PMC  432728. PMID  1056026.
  5. ^ a b c Webb, D.A. (1939). "Observations on the blood of certain ascidians, with special reference to the biochemistry of vanadium". Journal of Experimental Biology. 16 (4): 499–523. doi: 10.1242/jeb.16.4.499. Retrieved 24 June 2019.
  6. ^ Stoecker, Diane (1980). "Relationships between chemical defense and ecology in benthic ascidians". Marine Ecology Progress Series. 3: 257–265. Bibcode: 1980MEPS....3..257S. doi: 10.3354/meps003257.
  7. ^ Stoecker, Diane (1980). "Distribution of acid and vanadium in Rhopalaea birkelandi tokioka". Journal of Experimental Marine Biology and Ecology. 48 (3): 277–281. doi: 10.1016/0022-0981(80)90082-9.
From Wikipedia, the free encyclopedia

A vanadocyte is a specialized type of blood cell found in ascidians (tunicates). These cells are notable for their high levels of vanadium (concentrations 107 higher than that of seawater), which is typically a metabolic poison in other contexts. [1] [2]

Structure and description

Vanadocytes are specialized blood cells found in marine tunicates. These cells are 8-13 μm in size and the cytoplasm contains many acidic globules, termed "vanadophores". [3] These cells are one of several types found in the ascidian circulatory system and are abundant in the blood. [2] [1]

The cells are described as highly distinctive, with little variation between species. They have a circular outline that decays into a rosette form upon desiccation, with several inclusions that almost entirely fill the cell. The cell has a greenish color, varying from dark apple to scarcely perceptible, due to their vanadium complexes. [4] [5]

These green cells are not, as was initially believed, symbiotic zooxanthellae, although ascidians are known to have such symbiotes elsewhere. [5]

Chemistry

Vanadocytes are of interest to biologists and chemists because they contain high levels of vanadium and vacuole of sulfuric acid with acid mass fraction as high as 9 wt%, both of which are typically toxic to living creatures. [5] Additionally, the vanadium complex itself is unstable, found almost exclusively in the air-oxidizable, +3 oxidation state. [4]

Function

The function of vanadocytes is still unclear. [1] It has been proposed that the vanadocyte transports and processes nutrients, contributes to the polysaccharide external tunic, or serves as a defense mechanism. It is unlikely that the vanadium complex serves as an oxygen transport mechanism because it is unable to reversibly bind oxygen. [4]

Research into their utility as anti-biofouling ( allelopathic) mechanisms concluded that the high acidity and high vanadium levels function to significantly reduce epizoic recruitment and predation. [6] [7]

References

  1. ^ a b c Michibata, Hitoshi; Uyama, Taro; Ueki, Tatsuya; Kanamori, Kan (15 March 2002). "Vanadocytes, cells hold the key to resolving the highly selective accumulation and reduction of vanadium in ascidians" (PDF). Microscopy Research and Technique. 56 (6): 421–434. doi: 10.1002/jemt.10042. PMID  11921344. S2CID  15127292.
  2. ^ a b STOECKER, DIANE (December 1978). "Resistance of a Tunicate to Fouling". The Biological Bulletin. 155 (3): 615–626. doi: 10.2307/1540795. JSTOR  1540795.
  3. ^ Botte, L.; Scippa, S.; de Vincentiis, M. (September 1979). "Ultrastructural localization of vanadium in the blood cells of Ascidiacea". Experientia. 35 (9): 1228–1230. doi: 10.1007/BF01963306. PMID  488290. S2CID  33061777.
  4. ^ a b c Carlson, Robert (1975). "Nuclear Magnetic Resonance Spectrum of Living Tunicate Blood Cells and the Structure of the Native Vanadium Chromogen". PNAS. 72 (6): 2217–2221. Bibcode: 1975PNAS...72.2217C. doi: 10.1073/pnas.72.6.2217. JSTOR  64680. PMC  432728. PMID  1056026.
  5. ^ a b c Webb, D.A. (1939). "Observations on the blood of certain ascidians, with special reference to the biochemistry of vanadium". Journal of Experimental Biology. 16 (4): 499–523. doi: 10.1242/jeb.16.4.499. Retrieved 24 June 2019.
  6. ^ Stoecker, Diane (1980). "Relationships between chemical defense and ecology in benthic ascidians". Marine Ecology Progress Series. 3: 257–265. Bibcode: 1980MEPS....3..257S. doi: 10.3354/meps003257.
  7. ^ Stoecker, Diane (1980). "Distribution of acid and vanadium in Rhopalaea birkelandi tokioka". Journal of Experimental Marine Biology and Ecology. 48 (3): 277–281. doi: 10.1016/0022-0981(80)90082-9.

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