DEPOSITION AND BINDING OF CALCIUM AND MAGNESIUM IN EGG CAPSULES OF RAJA-ERINACEA MITCHILL DURING FORMATION AND TANNING IN UTERO

The possibility that oviparous elasmobranchs deposit minerals in their egg capsules during formation in the nidamental gland or tanning in utero was investigated. The results of mineral measurements on egg capsules of Raja erinacea Mitchill at various stages of formation and tanning established that calcium and magnesium are integral components of the egg capsule. The bulk of the calcium and a portion of the magnesium present in oviposited capsules derive from maternal sources and are deposited in the capsular material during formation in the nidamental gland. Subsequent binding of these minerals is is concomitant with tanning of the capsule while in the uterine portion of the oviduct, suggesting that they participate in the sclerotization of the matrix. Magnesium contents increase five-fold while the capsule is in the urogenital sinus before oviposition. These observations demonstrate that oviparous elasmobranchs, like many oviparous terrestrial vertebrates, deposit minerals in their egg shells.