OXYGEN CONSUMPTION IN ANTERIOR VERSUS POSTERIOR EMBRYONIC SHIELD OF FUNDULUS HETEROCLITUS

¹ Duke University Marine Laboratory, Beaufort, North Carolina, and the Belle W. Baruch Coastal Research Institute, Columbia, South Carolina

1. Experiments were designed to determine whether measurable differences in respiration exist between the anterior and posterior embryonic shield of the gastrula of Fundulus heteroclitus.

2. Anterior and posterior embryonic shields were carefully excised from embryos of early gastrula, late gastrula, and post-blastopore-closure stages. Using Cartesian diver microrespirometers (10 to 13 µl), oxygen consumption of each individual explant was measured at 25° C over a period of two to two and one-half hours.

3. Oxygen consumption data, expressed as µl O₂ per hour per µg dry weight 10^-3, for the two embryonic shield regions at the three stages of development are compared.

4. Posterior shield was found to exhibit a significantly higher rate of O₂ uptake than anterior embryonic shield at all three stages of development.

5. Oxygen uptake appears to increase in the posterior shield as development proceeds from early gastrula to closure of the blastopore; anterior shield exhibits a concomitant decrease.

6. The results are discussed in light of what is known about cell movements, cell proliferation, cell interactions, and cell differentiation in the teleost embryo and are compared with similar experiments on amphibian embryos.