THE ROLE OF ULTRASTRUCTURE AND PHYSIOLOGICAL DIFFERENTIATION OF EPITHELIA IN AMINO ACID UPTAKE BY THE BLOODWORM, GLYCERA

¹ Developmental and Cell Biology, University of California, Irvine, California 92664

1. The epidermis of Glycera consists of interdigitating columnar cells and mucus secreting goblet cells. Both types of cells are covered by a collagenous cuticle, 1 to 12 µm thick.

2. The cuticle is made up of layers of orthogonally arranged tubules in an amorphous matrix. Individual tubules measures 0.1 to 0.3 µm in diameter and are composed of collagen fibers about 5 nm thick.

3. Microvilli extending from the columnar epithelial cells into the cuticle increase the surface area of these cells about 13 times.

4. The peritoneum which covers the coelomic surface of the body wall is composed of one to several layers of flattened cells. Irregular cytoplasmic projections double the surface area.

5. Glycera whole animals take up eight different amino acids by saturable systems. The K_t values range from 2 x 10^-4 to 2 x 10^-3 moles/liter, which fall in the upper range of reported K^t values for marine invertebrates.

6. Influx of amino acids occurs across both surfaces of isolated pieces of body wall. The kinetic characteristics of transport across the epidermis are similar to those of the whole worms.

7. Both the ultrastructure and the physiological differentiation of the epithelial cells are shown to be important in the transport of amino acids across Glycera body wall.