INDICATOR GRADIENT PATTERNS IN OÖCYTES AND EARLY DEVELOPMENTAL STAGES OF ECHINODERMS: A REEXAMINATION

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Abstract
The paper concerns that aspect of redox indicator pattern in early echinoderm development which is made directly visible by intracellular formation of indophenol from p-aminodimethyl aniline and [alpha]-naphthol in very low concns. and by intracellular oxidation of redox dyes, reduced in external solution by minute, non-toxic quantities of sodium hydrosulfite. The indophenol reaction and dye oxidation are catalyzed by one or more intracellular oxidases. With progress in use of redox indicators it has been found that the very slight gradient differentials of early developmental stages become more distinctly visible by intracellular oxidation than by intracellular reduction after staining by oxidized dyes. The echinoids, Strongylocentrotus purpuratus and Dendraster excentricus and the starfish, Patiria miniata were used as material. A gradient pattern has been made directly visible from early oocyte to larval stages. The evidence indicates that the gradient of the early oocyte becomes the polar gradient of the egg and later stages. Position of the nucleus in the early o3cyte is somewhat variable, but as oocyte growth progresses, it usually comes to lie near the pole of most rapid intracellular oxidation, the polar bodies form there and this becomes the apical (animal) pole of later stages. The ventrodorsal gradient becomes visible later, but is doubtless present before it becomes distinguishable. Other gradients appear in later larval development. In conclusion, certain points in the experiments of Pease on determination of ventrodorsality in Dendraster by a gradient of various external agents are briefly discussed.