A method for the demonstration of pores in calcified eggs of vertebrates and invertebrates

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Abstract
Determination of pore number, pore size and pore canal distribution is important in understanding the biology of calcified eggs among vertebrates as well as invertebrates. Various techniques were applied to elucidate pore structure of avian egg shells, including fracturing coupled with scanning electron microscopy and differential histochemical staining of the matrix. The best results reported were from plastic impregnated, etched specimens. The present report is a modification of this latter technique, utilizing a very low viscosity, highly penetrating EM embedding medium. This modification is used in this report of the previously undescribed pores from the egg shells of the giant South American land snail, Strophocheilus oblongus. These eggs, which can be up to 50 mm in length, were recently investigated with respect to the calcium carbonate mineralogy and the matrix biochemistry. (Similar resin was used successfully for the plastic impregnation and ultrathin sectioning of that region of the snail shell where the body muscles insert into the shell columella). This technique, which can be utilized on avian eggs or on any other calcified material in probing for pores, relies on the high penetrating ability of the resin and its easy commercial availability around the world.