Sequestered calcium triggers oocyte maturation in Chaetopterus.
In order to test the involvement of Ca2+ in maturation and activation of eggs, we have treated Chaetopterus eggs with ionophore A23187 and quercetin, an inhibitor of Ca2+-dependent ATPase. Ionophore A23187 induced rapid germinal vesicle breakdown (GVBD) and activated eggs as evidence by fertilization envelope elevation at a wide range of concentrations. Higher concentrations of A23187 induced GVBD in Ca2+-free artificial sea water, demonstrating the independence of GVBD in Chaetopterus from external Ca2+. At high concentrations of ionophore, eggs became ameboid and underwent the initial phases of differentiation without cleavage. Low concentrations of quercetin induced GVBD with or without external CA2+. This treatment did not activate eggs, but allowed them to be fertilized and undergo some development. The results of these experiments indicate 1) that Ca2+ fluxes regulate GVBD and activation in Chaetopterus, 2) that these fluxes can be internally generated, and 3) that Ca2+ sequestration by Ca2+-dependent ATPase may have a role in maintaining the intact germinal vesicle.
D000845:Annelida / Q000502:physiology*; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D002451:Cell Compartmentation; D005260:Female; D008540:Meiosis / Q000187:drug effects; D009865:Oocytes / Q000502:physiology*; D010063:Ovum / Q000502:physiology*; D011794:Quercetin / Q000494:pharmacology
D000001:Calcimycin; D011794:Quercetin; D002118:Calcium