Osmotic and ionic concentration of the egg capsule fluid of Crepidula fornicata in relation to embryonic development |
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Authors: | A N Maeda-Martínez |
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Institution: | (1) Centro de Investigaciones Biológicas del Noroeste (CIBNOR), Mar Bermejo 195, Col. Playa Palo de Santa Rita, La Paz, BCS, 23090, Mexico |
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Abstract: | Osmotic pressure and major ions (Cl−, Na+, Mg2+, Ca2+) of the egg capsule fluid in the slipper limpet Crepidula fornicata were investigated in relation to embryonic development. Calcium permeability of the capsule wall was studied at oviposition,
by dipping freshly laid egg capsules in 45Ca as a tracer. This study also determined total calcium content of the embryos at different developmental stages. Osmolarity
and major ion concentrations in egg capsule fluid were higher than seawater at uncleaved and trochophore stages, and then
dropped to the same level as sea water at veliger stage. Concentrations of Cl− and Na+ were relatively high at oviposition, peaked at trochophore stage, and finally dropped close to concentrations of seawater
at hatching. In contrast, concentrations of Mg2+ and Ca2+ decreased steadily during capsular development. Radiotracer permeability experiments in freshly laid egg capsules confirmed
that the capsule wall is impermeable to this ion at that stage. However, because of the dissolution of the inner layer of
the wall during the final part of capsular development, the wall becomes permeable to calcium and probably to the rest of
the major ions studied. |
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