The abundance of Aplysia gliagrana depends on Ca2+ and/or Na+ concentrations in sea water.
The glial cells surrounding the identified giant nerve cell bodies R2 or LP1 of Aplysia punctata were studied by quantitative electron microscopy. They contain specific, electron-dense but non-osmiophilic membrane-bound granules, approximately 0.3 microns in diameter, called gliagrana. Similar glial granules are more often found in marine than in freshwater molluscs, possibly because they represent a calcium store used to compensate excess Na+ in the extracellular milieu of marine species and to regulate perineuronal calcium concentration. In agreement with this hypothesis, the abundance of gliagrana (= number of glial granules per microns 2) is found to be higher in animals adapted to low Ca2+ artificial sea water than in animals kept in high Ca2+ (or low Na+) conditions. This finding is not observed after 1 week but after 2 weeks of adaptation.
Keicher
E
E
Cytologie Expérimentale, Université de Nice-Sophia Antipolis, France.
Maggio
K
K
Hernandez-Nicaise
M L
ML
Nicaise
G
G
D000818:Animals; D001048:Aplysia / Q000737:chemistry / Q000502:physiology* / Q000648:ultrastructure; D002118:Calcium / Q000032:analysis / Q000502:physiology*; D003594:Cytoplasmic Granules / Q000737:chemistry; D006458:Hemolymph / Q000737:chemistry; D008854:Microscopy, Electron; D009457:Neuroglia / Q000502:physiology* / Q000648:ultrastructure; D009994:Osmolar Concentration; D012621:Seasons; D012623:Seawater / Q000737:chemistry*; D012964:Sodium / Q000032:analysis / Q000502:physiology*
D012964:Sodium; D002118:Calcium